CA1305518C - Three phase fluid flow measuring system - Google Patents
Three phase fluid flow measuring systemInfo
- Publication number
- CA1305518C CA1305518C CA000609751A CA609751A CA1305518C CA 1305518 C CA1305518 C CA 1305518C CA 000609751 A CA000609751 A CA 000609751A CA 609751 A CA609751 A CA 609751A CA 1305518 C CA1305518 C CA 1305518C
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- measuring
- gas
- pressure
- liquid phase
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/26—Oils; viscous liquids; paints; inks
- G01N33/28—Oils, i.e. hydrocarbon liquids
- G01N33/2823—Oils, i.e. hydrocarbon liquids raw oil, drilling fluid or polyphasic mixtures
Abstract
ABSTRACT OF THE DISCLOSURE
A multi-phase fluid flow measuring system for measuring the volumetric fractions of gas, water and oil including a centrifugal separator for conducting primary separation of gas from the liquid phase, a conduit section forming a closed chamber and a piston displaceable into the chamber to measure the increase in pressure of a liquid sample trapped in the chamber in relation to movement of the piston for determining the residual gas content of the liquid phase, a liquid phase flow meter and apparatus for measuring the microwave energy transmissivity through a sample of the liquid phase to determine the volumetric fraction of water and oil in the liquid phase. One embodiment of the system uses two apparatuses for measuring the microwave transmissivity at different pressures of the liquid phase to compare the transmissivity readings as a way of determining the residual gas content in the liquid phase. A method for measuring the residual gas content takes into consideration an increase in pressure in the sample of liquid being measured including elastic stretch of the measuring vessel as a result of the pressure increase, and compressibility of the liquid phase.
A multi-phase fluid flow measuring system for measuring the volumetric fractions of gas, water and oil including a centrifugal separator for conducting primary separation of gas from the liquid phase, a conduit section forming a closed chamber and a piston displaceable into the chamber to measure the increase in pressure of a liquid sample trapped in the chamber in relation to movement of the piston for determining the residual gas content of the liquid phase, a liquid phase flow meter and apparatus for measuring the microwave energy transmissivity through a sample of the liquid phase to determine the volumetric fraction of water and oil in the liquid phase. One embodiment of the system uses two apparatuses for measuring the microwave transmissivity at different pressures of the liquid phase to compare the transmissivity readings as a way of determining the residual gas content in the liquid phase. A method for measuring the residual gas content takes into consideration an increase in pressure in the sample of liquid being measured including elastic stretch of the measuring vessel as a result of the pressure increase, and compressibility of the liquid phase.
Description
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THREE P~SE FLUID FLOW MEASURING SYSTEM
BACKGROUND OF THE INVENTICIN
Field o~ the ïnverltio~
_ The present lnventlon pertalns to a three phase ~luld flow measuring system lncluding a centri~ugal gas-liquid separator, a resldual gas content measurlng apparatus and a meter for determining the proportion of one liquid in another. The system is partlcularly useful for gas-water-oll mixtures being produced from underground reservoirs and the llke.
Back~round Efforts to measure the components of multi-phase fluid mixtures such as the gas-water-oll mixtures which are typIcally produced from oil and gas wells has resulted in the development of ssveral types of flow measuring systems.
For example, U.S. Patent 4,776,210 to Lloyd A. Baillie et al and asslgned to the assignea of the present invention descrlbes a flow measuring system based on measurement of dlfferential pressures and the measurement of the diel trlc constant of tha water-oll mixture separated from the gas fraction of the flowstream. Although this type of system is useful in relatively large steady state flowstreams it is not particularly attractive for use with small intermittent.
flowstreams such as oten result from the productlon of fluids ~rom indlvidual wellsO
In many oll and gas operations lt is import~nt to be able to measure the components of a mult~-phase fluld flowstream produced from each well ln an oil or gas well fleld. Xowever, a system which is adaptabl~ for measuring ths lntermittent and widely varying ranga of the components of a multi-phase fluld stream such as is typically produced by wells in a reservoir which ~s under variou~ stlmulatlon . . . .
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technlques, there ls a need for a relatlvely low cost, slmple yet effective system whlch ls capable of measurlng the volumetric flow of each component of the flowstream for various reasons includlng the ad~ustment of stimulatlon technlques and the allocatlon of ne~ production volumPs to those wells which may be owned by more than one party. It is to this end that the present inventlon has been developed with a vlew to providing an effective, compact and relatively uncompllcated flow measuring system whlch is particularly adapted for measurlng ths components of a gas-water-oil mixture of the type typlcally encountered in the production of underground hydrocarbon reservoirs.
SUMMARY OF THE INVENTION
. . .
The present inventlon provides an improved flow measuring system for measuring multi-phase fluid flow, includlng fluld flow streams of gas-water-hydrocarbon liguid mlxtures including crude oil and natural gasoline liguids produced from underground reservoirs.
In accordance wlth an important aspect of the present invention a system is provided which includes an uncomplicated yet effective centrifugal type gas-llquid separator, an apparatus for measuring the resldual gas content of the-llquld flowstream, an apparatus for measurlng the amount of each liquld ln the liquid mixture separated from the gas and together with flow measur~ng apparatus for measuring the total liquid flow stream and the total gas flowstream after separatlonO
In accordance with another aspect of the present invP.ntlon a multi-phase fluid flow measurlng system is provided which includes in lmproved apparatus and method for measuring the residual gas content in a liquid mixture which has under~one primary gas-liquid separatlo~ processes. ~n particular, the r~sidual gas content measurement device includes a piston whlch dlsplaces a partlcular amount of fluld in a closed chamber wherein the change in pressure in , DP 50-6-1102A ~3~
the chamber and its effect on deflectlon of the structure defining the chamber and the compresslblllty of the llquld is ta~en into conslderation.
The present inventlon still further provldes improved flow measuring systems for measurlng a multi-phase fluid flowstrea~ emanatin~ from a well wherein the flow rate of the fluid flowstream varies conslderably as well as the proportion of the various components of the flowstream varies considerably. Various other features of the respective embodiments of the lnvention described herein will be further appreciated by those skilled in the art upon reading the detailed description which follows in con~unctlon with the drawing.
BRIE~' DESCRIPTION OF THE D~AWING
Figure 1 ls a schematic diagram of a multl-phase fluid flow measurement system in accordance with the present lnvention;
Figure 2 is a schematlc diagram of a residual gas content measurement device for the syst~m of the present lnvention;
Figure 3 is a schematic diagram of a first alternate embodiment of a system ln accordance with the present invention;
Figure 4 is a schematic diagram of a second alternate embodiment of a system in accordance wlth the present lnventlon;
FlgurP 5 is a schematic diagram of a portion of the system of Figure 1 modlfled to provide for separation of residual gas from the llquid mlxture; and Flgure 6 is a schematic dlagram of another embodiment of a componen~ for sep~rating the resldual gas ln the liquld mlxture.
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DESC~IPTION OF PREFE~RED E~BODXMENT~
In the descrlption which follows like parts are generally marked throughout the specif~cation and drawing with the same reference numerals, respectively. The drawlng figures are not necessarily to scals and certaln features are shown ~n schematic form in the interest of clarity and conciseness.
Certain crude oil reservoirs throughout the world produce fluids which comprise basically a mixture of a gas and a llquid mixturs of water and oil. Oil fields that are being stlmulated by gas or water drive, ln particular, may produce widely varying rates of one component of such a three phase mlxture as compar~d with the other components o~
the mixture. It is lmportant ln the development and productlon of at least certain oil flelds to be able to monitor the composition of the fluid flowlng from each well rather than gathering the fluid streams and analyzing the production of several wells collectively. In this regard it is important to be able to have in-circu~t wlth each well production fluid flow conduit a flow measuring system which is relatively compact, structurally slmple and lnexpensive but yet accurate to within a few percent of measurement of the gas content as well as the water and oil content of the liquid mixture in the flowstream.
Fl~ure 1 is a schematlc dlagram of an improved fluid flow measuring system partlcularly adapted for the aforementloned applications, Referriny to Flgure 1 there is lllustrated a fluid flow measuring system 1o which includes a centrlfugal or cyclone type separator of improved construction and which receives ~he inlat flow stre~m from a well or the llke through an inlet conduit 12. The separator lllustrated in Figure 1 ls generally designated by the numeral 14 and comprises a generally cylindrlcal housing or shell 1~ having bottom and top hQad portions 18 and 20.
generally cylindrlcal int~rnal baffle 22 depends from the head portion 20 and forms an annular space ~4 as part of an ,.~ ~, .. . ..................................... .
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interlor chamber 26 deflned by the separator houslng or shell 160 The annular chamber 24 is provlded with a spiral plate baffle 28 whlch ls wound around and secured to the baffle 22 and forms a splral duct 30 whlch opens from ~he chamber 2g lnto the chamber 26.
The splral baffle 28 preferably extends radially to wlthin a fraction of an inch of the side wall 17 of the shell 16 to facllltate assembly and disassembly. The condult 12 opens into the chamber 24 in a tangential manner along the side wall 17 by way of an opening 13.
Accordingly, the fluid mixture entering the separator 14 undergoes a cyclonic or spiral descending flow path through the space 30 whereby the more dense liquld is flung against the wail 17 and trickles down this wall into the chamber 26.
The fluld flowstream entering the chamber 26 at the outlet of the spiral flow path or duct 30 is flowlng in a vortical manner whlch further separates any llquld from thP gas flow stream and the gas then flows upward through a chamber ~` portion 32 fermed wlthin the baffle 22 and through a gas outlet flow conduit 34. The liquld separated from the gas occuples the lower portion of the chamber 26 and the level of liquid in thls portion of the chamber, as indicated by the numeral 27, may be controlled by a level control means il . 38 operable to control a remotely operated flow control valve, not shown, ln the lnlet conduit 12. Residence time of the liquid in the chamber 26 may be controlled t~ allow further separatlon of gas bubbles stlll entrained ln the liquid whereupon the liquid then exits the separator 14 through a flow conduit 40.
It has been determined khat a relatively slmple pressure vessel made of suitable pressure vesse~ grade steel may be constructed ~or bandling flows in the range of 3, 000 barrels of liquld per day mixed with approximately 3,000,000 standard cubic feet of gas per day. A separator having a shell dlameter of approximately 2.0 feet by an overall heiyht of 5.0 feet would occupy a relatively small ~pace at a well site but yet appears to be capable of ef~ectlvely separatlng from 90 to 95~ o~ the gas in the !
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flowstream on a volumetric basis. Moreover, -the structure of the separator 14 is relatively uncomplicated, relying on conventional pressure vessel construction techniques and with a relatively uncomplicated yet effective int:ernal baffle syst:em characterized by -the cylindrical depending baffle 22 and the single spiral plate type baffle 28 which forms -the spiral or helical duct or flow passage 30.
Referring further to Figure 1, the gas separated from the flowstream in the separator 14 is conducted by way of the conduit 34 through a suitable gas flow measuring means such as an orifice me-ter comprising an orifice 42 and a pressure differential measurement device 44.
Conventional gas flow measurement processes and apparatus such as the orifice meter 42 may -thus be used to measure lS the gas content o the flow stream and the gas may be either remixed with the liquid flowstream or conducted -to a suitable gas handling faciliLy, now shown.
The liquid being conducted through the conduit: 40 may, on a steady state basis, be conducted -through a continuing conduit portion 46 having a shutoff valve 48 interposed therein. The conduit 46 is connected to an apparatus, generally designated by the numeral 50, which is adapted -to measure the composition of the liquid mixture utilizing electrical properties such as the dielectric constant of the liquid mixture. In particular, the apparatus 50 includes a housing forming a through flow conduit portion 52 in which a microwave conductor element 54 is disposed in the form of an elongated rod. The apparatus 50 is of a type which measures electromagnetic radiation transmissivity in the microwave frequency range through a combined water-oil liquid mixture for measurement of the water fraction in the liquid mixture. The apparatus 50 is preferably of a type described in Canadian Patent Application No. 549,589 filed October 19, 1987 in the name of Bentley N. Scott and Y. Sam Yang and assigned to the assignee of the present invention. In particular, the apparatus 50 includes an oscillator circuit r~
~3~i5~3 whose operatlng freguency changes ln accerdance wlth the concentratlon of one llquid ln the mlxture ln rslation to the mlxture and the ~reguency change may be affected by the resldual gas content of tha llquid m1xtureO This Prequency change or a change ln the transmlsslvi4y of microwave energy may be rorrelated with the dlelectrlc properties of the fluld mlxture. Slmllar devices of somewhat less accuracy and lacking some of the unlgus featureQ of the apparatus ~0 and also of a known type may be substltuted for $he apparatus 50 for determlning the water and oll fraction of the liquid mixture. For example, a devlce known as a watPr Cut Monitor and available from Halllburton Compasly, Dallas, Texas may be substltuted for the device 50 and for the sake of thls discussion the devlce 50 may comprise such a measurlng apparatus.
The total volumetrlc Plow of the llquid mlxture may also be measured with a conventional Corlolis or positive dlsplacement 10wmeter of a type commercially avallable and generally designated by the numeral 58. The liquid mlxture, after conduction through the flowmeter 58, may be conduct~d further through the conduit 46 to a su~able liguld handllng faclllty for separatlon of the oll from the water, for example.
The separatlon of all o~ the gas from the li~uid mlxture is dlfflcult to obt~in by the separator 14, partlcularly while considering the malntenance of a suitably small slze of the separator whlch does not permit long residen~e time of the primarlly separated liquid ln the chamber 26. Accordlngly, ln order to correct any error~ ln readlngs from the apparatus 50 and meter 58 lt is important to provide furth~r separatlon of gas or to measure the gas content which ls residual in the liquid mixture. An lmportant aspect o~ tha present lnventlo~ is determi nlng the residual gas content of the l~quld mixture so that readings of the ~lowmelter 58 can be correctsd to accourlt for tha gas conte~. In thi~ regard the sy~tem lllustrated in Figure 1 lncludes a r~siau~l gas content~measuring device ~6 which is lnterposed in a branch condult 68 connected to the conduit ..
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46 to form a bypass around the valve 48. The device 66 lncludes an elongated condult 70, see Flgure 2 also, whlch forms an interlor chamber 72 whlch is generally cyllndrical ln configuratlon and devold of any poc:kets or portlons whlch may trap unwanted quantities of gas or llquid. The conduit ls connected at lts oppositle ends to remotely controllable shut off valves 76 and 78. The conduit 70 includes a branch portlon ~0 which lntersects the main portion of the condult 70 and ~ournal~ a reciprocable piston 82 disposed therein and adapted to pro;ect into the chamber 72. The normal retracted positlon of the piston 82 is such that little if any space is provided in the branch conduit portlon 80 for occupancy by fluid and therefore no gas may normally be trapped in the conduit 70 before and durlng pressure tests to determine the resldual gas content of the fluid flow6tream.
The piston 82 ls adapted for control to extend and retract with respect to the chamber 72 by an actuator 84 whlch is operable to be controlled by a suitable controller device 86. The controller devlce 86 is also suitably connected to a pressure transducer 88 to measure the change in pressure in the chamber 72 ln relation to the position of the piston 82. A devi~e which works in some ways slmllar to the resldual gas content measuring device 66 is disclosed ln U.S. Patent 4,329,869 to Toda. Furthermore, the device 66 may also lnclude suitabl~ temperature senslng means 90 for measuring the tempera~ure of the fluid flowlng through the chamber 72 and any change therein resulting from a change ~n pressure of the fluld as influenced by movement of the piston 82.
The system 10 is operable to measure total llquid flow continuously by the flowmeter 58, total gas flow contlnuously by the flowmeter 42 and the percentage of water in oll llquid or vice versa by continuous measuremen~ using the apparatus 50 to measure the transmissivity of mi~rowava radiation. Moreover, these flows may be corrected for the amount o~ residual gas ln the liquld flowstream flowlng DP 50-6-1102A ~ 5~
through the ~ondult 46 by periodlc batch sampllng of a quantlty of liquld wi~h residual gas therein by closing the valve 48 and openlng the valves 76 and 78 long enough to trap a representative sample of llqu:id ln the chamber 72, then simultaneously closlng the valve 76 and 78 and reopening the valve 48 to prevent bui:Ld-up of liquld ln the chamber 26. When a quantity of liguld with some residual gas entralned therein is trapped in the chamber 72 the piston 82 may be stroked to penetrate lnto the chamber 72 a predetermlned distance while measuring the corresponding change ln pressure inside the chamber 72 to detPrmine how much free gas is present in the li~uld stream. For example the followlng equation may be used to determine the gas fraction (fg) when lt is expected that the gas fraction is less than 10% of the total volume of the fluld in the chamber 72:
fg = (A~s)/[ll Pl/P2)(Vs)] (1) wherein~ A equals the cross sPctional area of the piston 82, s equals the plston penetration or stroke lnto the sample ln the chamber 72, Pl ls the sample pressure before the piStoQ activatlon, P2 is the pressure after the piston activatlon and V ls the batch sample volume lncluding th~ liquid and gas.
It may be determlned that the increase ln temperature of the sample for a gas fraction of about 10% or less is lnslgnificant and thus the process is essentially isothermal allowing the use of the ldeal gas laws. ~owever, certain corrections should b~ lncluded for elastlc stretch of the conduit 70 under the effect of the lncreaslng pressure in the chamber 72, the redlssol~ing of some of the gas into the llquid and the compr~ssibility of the liquid. When the piston 82 (of area A) is stroked (by dlstance s) into the sample in th~ chambsr 72, the sample volume i~ decreased by a.~ and the prassure lncreases. Each fluid component ,, ', :' ', . . .
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shrinks~ Conservation of volume lmplies the following about fluid volumes in the cylinder before and after the plston stroke: -dv = V2 - Vs (2) where v2 - fluld volume after the p~ston stroke, dv = fluid volume change = G.VS.dP - A.s, G = an ela~tic stretch factor of the volume of the space 72 dus to stretch or expansion of the condult 70 and dP = P2-Pl.
V2 is the sum of indlvidual component volumes V2 = vo~ + V~' + Vg' (3 where the primes denote shrunken volumes immedlately after the pressure increaseand the notations o, w and g denote oil, water and gas, respectively. Expresslons for each of these terms are llsted below:
Vg' = (fg-fgr).V.[Pl/P2)].~Z2/Zl] (4) Vo' ~ Vw' - (l-fg)~Vs.e b-dP (5) where fgr = gas fractlon re-dissolved due to dP, Zl,Z2 = gas compressibillty factors at Pl and P2, b = li~uid co~pr~ssiblllty coefflcient, and e = constant 2.71828 j The compressibillty factors Zl and Z2 may be obtalned from the Gas Processors Suppliers Assn., Englneering Data Book, Nlnth edition.
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substltutlng ln equatlons 3 and 2, and re~rra~glng, yields the worklng eguations:
[A.s/V~] - dPo (b+a~ - fgr~
fg a ~ ] ( 6 ) in whlch fgr' ls an abbreviation of t~e product of terms ~.[Pl/P2~.tZ2/~13 (7) and in which e b-dP ls approxlmated by 1 - b.dP; slnce b.dP~1.
~ The value of the re-dissolvlng term, fgr, must be less than or equal to fg. ~oreover, fgr ls expected to be much less than fg (say, 1~ of fg) because tbe re-dissolvlng process will be limlted by the finlte gas-llquld lnterf~cial area, and because the pressure increase and measurement wlll be admlnistered qulckly; ln a few seconds. The product of terms, fgr', will therefore llkely be small enough to ignore. Regardless o~ lts sl~e, the effect of fgr' wlll be to sllghtly reduce the pressure lncrease and to ~ause a sllght overestimatlon of gaæ fraction, fg~
As the residual gas content or gas fractlon (fg) of the llquld sample ~pproache~ zero the pressur~ wlll lncrease rapldly lf the plsto~ 82 ls stro~ed when gas conten ls very small. For fg=0 and fgr~0, equatlon (6) ylelds:
: dP ~ (A.s/V~)/(b+G) (8) The piston 82 should not be stroked far lf ga~ con~ent of the fluld ls near zero; otherwlse overpre~suring ths components of the device 66 wlll re~ultO
As the resldual gas content (fg) lncreases, pressure will lncrease relatively slowIy as the plston ~2 i$ 9troked.
In the limlt fgal, fgr=0, lg~orlng ~ because of it~ small relativs value, and equatlo~ ylelds:
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dP/Pl = (Z~l/Zl)/[l-~A.S/vs) ] - 1 ~9) A relatlvely large stroke is needed to produce a measurahle effect on pressure. As the effect becomes measurable, say 1%, the Z2/Zl factor will differ slightly from unlty and it can be expressed as a function of the lnltlal pr~ssure, temperature and the differentlal pressur~ increase.
On the basis of the above the operation of the devlce 66 should be controlled such that the pressure in conduit 70 should not be raised more than a few percent; so as to keep the "re-dlssolving error", (fgr'), as small as possible.
Since the gas fractlon (fg) may be anywhere i~ the 0 to 10%
range, and knowledge of even its approximate value should not be assumedl the piston 82 should be stroked in two stages. For example, initially s~roke the plston ~2 into chamber 72 a very short dlstance so as not to overpressure the valve seals in the event the gas fractlon is near zero.
Then, if the lnitial~pressure lncrease did not exceed 5%, advance the plston 82 untll 596 is achleved and compute the gas fraction ~fg) Yla eguation ~6~.
A resolution of 0.5% in estlmatlng fg vi2 ~quation (5) should be sufflclent for flowmeterlng purposes. For example, fg - 015 + .005. Tests lndicate accuracies of ~ .001. Thus approximate values ~from textbooks) of th~
compressiblllty coeficlent (b~ and the stretch factor (G~
of condui~ 70 can be used in equatlon (6).
.
Moreover, it should also be posslble to measurs the compressibllity of the liquld phase by stroking the piston : 82 until pressure rlse~ by 100 psi or more, and then stroke the piston 82 again until pressure rises by another 100 psi.
This provldes two sets of piston stroke(s) and pressure change (dP) data whlch can be substituted into equatlon (6) to solve simultaneously for ~fg) and compressiblllty ,: ,:
'' '` ' ~ , :
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coefficlent (b~. The value o (b) should then be regarded as the compressibillty of the llquld phase, from which we may solve for oil fractlon (fo~ and water fractlon (fw) as follows:
fo + fw = 1 - fg ( 1 0 ) fo.bo + fw.bw = b (liquid phase compressibllity (ll) coefficient value) from which: b bo(l-fg) fw = - ~12) bw - bo where b,fg = values determined from equat~on (6) and bo,bw = compressibility coefflcients of the oil and water in the sample, respectively.
Values of the compressibillty factors bo and bw can be measured by the piston/cyllnder unit ltself, by periodlcally sampling from layers of oll and water from a small settllng tank.
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A computer controlled linear actuator 84 should have no difficulty in stepping through as many stroking ~tages as might be necessary to measure ga~ fraction and llquid compressibility with reasonable accuracy, Referring now to Flgure 3~ there is illustrated a modlfication of the system illustrated ~n Flgure 1 and whlch is designated by the numeral 100. The ~ystem 100 is simllar to the ~ystem 10 ln essentlally all respects except for the inclusion of a return condult 102 whlch is connected to the conduit 46 and lncludes lnterposed therein a raci.rcula~lng .
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pump 104 and a throttling valve 106. The condult 102 is connected to the separator vessel 14 for recirculating som~
of the liquld flow back to the separator vessel for us ln certain applications of a system in accoidance with the presen~ invention whereln seYere disruptions ln the llquld flow occur or an extremely hlgh percentage of gas ls present. The system 100 may, in fact, be used as a so called well test system for determinlng the exact specifications of a system which would measure the flow rate on a continuous or production basis.
Referrlng to Figure 4, th~re ls illustrated a second alternate embodiment of a system for measuring multl-phase fluld flow rates in accordance wlth the present :Lnvention.
The system illustrated ln Figure 4 ls deslgnated by the numeral 110 and includes a separator vessel 14, a gas flow rate measuring meter 42 lnterposed in a gas outlet cond~it 34 and an outlet conduit 40 for conductlng substantlally gas free liquid from the sep~rator vessel. The conduit 40 is connected to the lnlet of an apparatus 150 ldentical to the apparatus 50 for measuring the fraction of oll in water or vlce versa, the outlet of which ls ln communicatlon by way of a conduit 112 with a flowmeter 58. A second apparatus 250 also identlcal to the apparatus 50 ls provided ln the system 110 in communicatlnn wlth the condult 112 by way of a branch condult 113 and a pressure boostlng pump 114 and is connected to the separator vessel 14 by way of an outlet conduit 116 having a suitable throttiing valve 118 interposed therein.
The arrangement of the system 113 is such that the residual gas content of the llquid flowing through the conduit 40 may be determined by reading the transmlssivity of microwave radiation through th~ apparatus lS0 interposed in ~he conduit 40 and comparing the reading of the apparatus 150 with the readlng taken from the apparatus 250 at a higher pressure as provided by the pump 114. By circulatlng llquid through the condult 40 and the branch conduit 113, ~16 by way o~ th~ pump 114 a comparison of the measurements ' .
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taken by the two appara~uses 150 and 250 can indlcate the resldual gas content ln the llquld flowstream. For example by provi.ding a pump 11~ havlng a sma:Ll capacity of about 5.0 to 10.0 gallons per minute pressure may be boosted for the fluld enterlng the apparatus 250 downstream of the pump to shrink the gas bubbles that may be present in the llquld flow stream and thus the two apparatus~s 150 and 250 will register slightly dlfferen~ xeadlngs of the dlelPctric constants of the fluid flowing therethrough.
The fl~w rates for the respeetive fractlons of oil, water and gas may ~e determ~ned from the following.
Slnce the pressure boost ls small, the ideal gas laws may be used.
fg2 = fgl [ P/ ( P+dP)] (Al) where (fgl,fg2) are volumetric yas fractions ln the apparatus 150 and 250 respectively, P is the pressure in apparatus 150, and dP is the pressure boost achieved in apparatus 250. Equatlon (Al) ls modlfied to account for some of the fre~ gas (fgr) re-dlssolving ln the liquid.
fg2 = fgl [ P/ ( P/ ( P+dP ~ ~ - f~r ( A2 As discussed previously, fgr ls expected to be less than 1%
when dP/P ls on the order of . 05 or less .
The volumetric l~guld fractlons (fP) and gas fractlons (fg) are related as follows (the numerals 1 and 2 re~er to the conditions in the apparatus 150 and 250, respectively?:
ffl ~ fgl = 1 (A3 ~15-. .
ff2 ~ fg2 = 1 ~A4 ) ~f2/~fl - ~ g2)/(1-fgl~
.
~ fgr~Pr.fgl)~ fgl) (A5 J
where Pr = P/ ~ P~dP ) = Pl/P2 .
In apparatus 250, the gas fraction will be lower, and therefore the liquid fraction will be compensatingly higher, than ln apparatus 150 by the factor ff2/ffl. However, the water-to-oll ratio wlll be identical in both apparatus 150 and 250~ Therefore the oil fraction ~ fo) ancl the water fraction (fw) ln apparatus 250 will both be higher by the same factor ff2/ffl (fw) fo2 = fol~ff2/ffl~ (A6) fw2 - fwl~ff2/ffl) (A7) The mixture dielectrlc constants or microwave transmissivity factors (El,E2) regist~red by the two apparatus~s 150 and 250 can ~e expressed ln terms of the oil, water and ga~
dielectric constants (eo,ew,eg) and volumetric fractions (fo~fw~fg) as ollows:
fol~eo + fwl.ew + fgl.eg = ~1 (A8j fo2.eo ~ fw2.ew ~ fg2.eg = ~2 ~A9) These dielectric constants may b~ considered ln terms of the frequency at which the osclllator circults of the apparatu~e~ 150 and 250 operate for a particular mi~ture composition at the respective operating pressures.
Substitutl~g equations ~Al), (A5), ~A6~ and ~A7~ into ~A9 , ~L3 ylelds (ff2/ffl).[fol.eo + fwl.ew] ~ Pr.fgl.eg - fgr.eg = E2 (A10) Comblning equation (A10) with equatlon (~8) yields the solutlon for the gas fractlon (fgl) E2 - El~l+fgr) ~ eg(fgr) fgl = ~ (All) E2 - El(Pl/P2) + ~g(l-Pl/P2) Substitutlng (All ) ln (A~) and utllizing the continulty equation: ;
fol + fwl ~ fgl = 1 ~ Al 2 ) ylelds the following solutlon for oil fractlon (ew - El) + (ew - eg)~fgl fol ~ (A~3) ~ew - eo) The oil volumetrlc flow rate Qo ls obtalned from QO = Q~fol (A143 where Q is the total volumetric flow rate ~rom the flowmeter ~8 ~ eferrlng to Figure ~ there is illustra~ed yet another embodiment of tha present lnve~tion whereln an apparatus 350 is adapted te be lnterposed ln the liquid dlscharge conduit ~0 from the separator vessel 14 ln place of the device 66 ~3~
and the apparatus 50 ln the ~ystem 10, for example. The apparatus 350 ls essentially the same as the apparatus 50 but is also utllized to measure the resldual gas content in the llquld by allowing a quantlty of the llquld to enter the apparatus and reside therein untll the resldual gas fraction separates from ths liquld fraction. In the modificatlon of the inventlon illustrated ln Figure 5 the apparatus 3sO
includes an outer housing or conductor 120 formlng a chamber 122 for receipt of a quantlty of liquid which has undergone primary gas separation. The conduit 120 ls adapted to receive a liquid sample ln the chamber 122 through an inlet valve 124 and discharge a sample through a valve 126 connected to the condult 46 and flowmeter 58 ~see Figure 1).
The center conductor 5,~ extends through the chamber 122 in the same manner as described earlier herein. The condult 120 is arranged generally vertically so that residual gas entrapped ln the liquid sample may separate and collect at the top of the chamber 122 wherein a suitable liquld level sensing device 128 is disposed for determining the liquid level in the chamber 122. Accordingly, a liquid sample may be trapped in the chamber 122 and allowed to reslde a sufficient length o~ time to permit separatlon of the resldual gas. Then readings of the dlelectric strPngth of the liqul~ sample ln the chamber 122 may be made to determine the fraction o~ water and oll and correcting for the now known amount of gas in the chamber 122. By knowing the residual gas content of the liquld ~ample the flowme$er 58 may be corrected for any error~ in reading the flow rate therethrough.
Accordingly, the steps of measuring the flow rates and gas fraction uslng the modifled system of Figure 5 would be to conduct flow through the apparatus 350 to flush a previous sample, isolate a sample ln the chamber 122 by closing the valv~ 124 and 12~ and allowing the residual gas to segregate in the upper part of the chamber 122 and then measure the height of the gas column to determine the -la-"
:~3~
percent by volume of the gas in the sample. The fractlon of water and oll may then be obtalned by taking readings ~f the mlcrowave radiation transmlsslvity or dielectrlc strength of the fluid in the chamber 122. These steps would provide sufficlent lnformatlon regardlng all t.hree components of the multl-phase fluld flowstream.
Flgure 6 illustrates a further modificatlon of the system of Figure 5 whereln an apparatus 50 ls interposed in supply and return branch conduits 130 and 132 which are connected to a column type ~essel 134 ln which the llquid sample is allowed to reslde sufficlently long to allow gas to collect at the top of a chamber 136 as lllustrated.
Sample shut off valves 124 and 126 are interposed in the system to trap the sample of liquld with residual gas interposed therein and liquid may be clrculated through the apparatus 50 by a pump 138 and a suitable mlxing device 140 to assure a homogenous mlxture of liquid to be measured by the apparatus 50. A llquid level sensor 128 is also provided for the sample vessel 134 to determine the percent by volume of the fluld samplP which is liquld and gas, knowing the volume of the chamber 136. The system of ~igure 6 provldes for thoroughly homogenlzing the liquid free of any residual gas to more accurately determlne the oil and water fractlon~
Although preferred embodlments of a system and method for measurlng the volumetric flow rate of a multi-phase fluid flowstream have been disclosed hereln those skilled ln the art will recognlze that various substitutions and modificatlons may be made to the system without departing from the scope and splrit of the lnvention as recited in the appended claims.
What is claimed is:
. , .
THREE P~SE FLUID FLOW MEASURING SYSTEM
BACKGROUND OF THE INVENTICIN
Field o~ the ïnverltio~
_ The present lnventlon pertalns to a three phase ~luld flow measuring system lncluding a centri~ugal gas-liquid separator, a resldual gas content measurlng apparatus and a meter for determining the proportion of one liquid in another. The system is partlcularly useful for gas-water-oll mixtures being produced from underground reservoirs and the llke.
Back~round Efforts to measure the components of multi-phase fluid mixtures such as the gas-water-oll mixtures which are typIcally produced from oil and gas wells has resulted in the development of ssveral types of flow measuring systems.
For example, U.S. Patent 4,776,210 to Lloyd A. Baillie et al and asslgned to the assignea of the present invention descrlbes a flow measuring system based on measurement of dlfferential pressures and the measurement of the diel trlc constant of tha water-oll mixture separated from the gas fraction of the flowstream. Although this type of system is useful in relatively large steady state flowstreams it is not particularly attractive for use with small intermittent.
flowstreams such as oten result from the productlon of fluids ~rom indlvidual wellsO
In many oll and gas operations lt is import~nt to be able to measure the components of a mult~-phase fluld flowstream produced from each well ln an oil or gas well fleld. Xowever, a system which is adaptabl~ for measuring ths lntermittent and widely varying ranga of the components of a multi-phase fluld stream such as is typically produced by wells in a reservoir which ~s under variou~ stlmulatlon . . . .
.
' DP 50-6-1102A ~3~
technlques, there ls a need for a relatlvely low cost, slmple yet effective system whlch ls capable of measurlng the volumetric flow of each component of the flowstream for various reasons includlng the ad~ustment of stimulatlon technlques and the allocatlon of ne~ production volumPs to those wells which may be owned by more than one party. It is to this end that the present inventlon has been developed with a vlew to providing an effective, compact and relatively uncompllcated flow measuring system whlch is particularly adapted for measurlng ths components of a gas-water-oil mixture of the type typlcally encountered in the production of underground hydrocarbon reservoirs.
SUMMARY OF THE INVENTION
. . .
The present inventlon provides an improved flow measuring system for measuring multi-phase fluid flow, includlng fluld flow streams of gas-water-hydrocarbon liguid mlxtures including crude oil and natural gasoline liguids produced from underground reservoirs.
In accordance wlth an important aspect of the present invention a system is provided which includes an uncomplicated yet effective centrifugal type gas-llquid separator, an apparatus for measuring the resldual gas content of the-llquld flowstream, an apparatus for measurlng the amount of each liquld ln the liquid mixture separated from the gas and together with flow measur~ng apparatus for measuring the total liquid flow stream and the total gas flowstream after separatlonO
In accordance with another aspect of the present invP.ntlon a multi-phase fluid flow measurlng system is provided which includes in lmproved apparatus and method for measuring the residual gas content in a liquid mixture which has under~one primary gas-liquid separatlo~ processes. ~n particular, the r~sidual gas content measurement device includes a piston whlch dlsplaces a partlcular amount of fluld in a closed chamber wherein the change in pressure in , DP 50-6-1102A ~3~
the chamber and its effect on deflectlon of the structure defining the chamber and the compresslblllty of the llquld is ta~en into conslderation.
The present inventlon still further provldes improved flow measuring systems for measurlng a multi-phase fluid flowstrea~ emanatin~ from a well wherein the flow rate of the fluid flowstream varies conslderably as well as the proportion of the various components of the flowstream varies considerably. Various other features of the respective embodiments of the lnvention described herein will be further appreciated by those skilled in the art upon reading the detailed description which follows in con~unctlon with the drawing.
BRIE~' DESCRIPTION OF THE D~AWING
Figure 1 ls a schematic diagram of a multl-phase fluid flow measurement system in accordance with the present lnvention;
Figure 2 is a schematlc diagram of a residual gas content measurement device for the syst~m of the present lnvention;
Figure 3 is a schematic diagram of a first alternate embodiment of a system ln accordance with the present invention;
Figure 4 is a schematic diagram of a second alternate embodiment of a system in accordance wlth the present lnventlon;
FlgurP 5 is a schematic diagram of a portion of the system of Figure 1 modlfled to provide for separation of residual gas from the llquid mlxture; and Flgure 6 is a schematic dlagram of another embodiment of a componen~ for sep~rating the resldual gas ln the liquld mlxture.
13~
DESC~IPTION OF PREFE~RED E~BODXMENT~
In the descrlption which follows like parts are generally marked throughout the specif~cation and drawing with the same reference numerals, respectively. The drawlng figures are not necessarily to scals and certaln features are shown ~n schematic form in the interest of clarity and conciseness.
Certain crude oil reservoirs throughout the world produce fluids which comprise basically a mixture of a gas and a llquid mixturs of water and oil. Oil fields that are being stlmulated by gas or water drive, ln particular, may produce widely varying rates of one component of such a three phase mlxture as compar~d with the other components o~
the mixture. It is lmportant ln the development and productlon of at least certain oil flelds to be able to monitor the composition of the fluid flowlng from each well rather than gathering the fluid streams and analyzing the production of several wells collectively. In this regard it is important to be able to have in-circu~t wlth each well production fluid flow conduit a flow measuring system which is relatively compact, structurally slmple and lnexpensive but yet accurate to within a few percent of measurement of the gas content as well as the water and oil content of the liquid mixture in the flowstream.
Fl~ure 1 is a schematlc dlagram of an improved fluid flow measuring system partlcularly adapted for the aforementloned applications, Referriny to Flgure 1 there is lllustrated a fluid flow measuring system 1o which includes a centrlfugal or cyclone type separator of improved construction and which receives ~he inlat flow stre~m from a well or the llke through an inlet conduit 12. The separator lllustrated in Figure 1 ls generally designated by the numeral 14 and comprises a generally cylindrlcal housing or shell 1~ having bottom and top hQad portions 18 and 20.
generally cylindrlcal int~rnal baffle 22 depends from the head portion 20 and forms an annular space ~4 as part of an ,.~ ~, .. . ..................................... .
' DP 50-6-1102A ~3~
interlor chamber 26 deflned by the separator houslng or shell 160 The annular chamber 24 is provlded with a spiral plate baffle 28 whlch ls wound around and secured to the baffle 22 and forms a splral duct 30 whlch opens from ~he chamber 2g lnto the chamber 26.
The splral baffle 28 preferably extends radially to wlthin a fraction of an inch of the side wall 17 of the shell 16 to facllltate assembly and disassembly. The condult 12 opens into the chamber 24 in a tangential manner along the side wall 17 by way of an opening 13.
Accordingly, the fluid mixture entering the separator 14 undergoes a cyclonic or spiral descending flow path through the space 30 whereby the more dense liquld is flung against the wail 17 and trickles down this wall into the chamber 26.
The fluld flowstream entering the chamber 26 at the outlet of the spiral flow path or duct 30 is flowlng in a vortical manner whlch further separates any llquld from thP gas flow stream and the gas then flows upward through a chamber ~` portion 32 fermed wlthin the baffle 22 and through a gas outlet flow conduit 34. The liquld separated from the gas occuples the lower portion of the chamber 26 and the level of liquid in thls portion of the chamber, as indicated by the numeral 27, may be controlled by a level control means il . 38 operable to control a remotely operated flow control valve, not shown, ln the lnlet conduit 12. Residence time of the liquid in the chamber 26 may be controlled t~ allow further separatlon of gas bubbles stlll entrained ln the liquid whereupon the liquid then exits the separator 14 through a flow conduit 40.
It has been determined khat a relatively slmple pressure vessel made of suitable pressure vesse~ grade steel may be constructed ~or bandling flows in the range of 3, 000 barrels of liquld per day mixed with approximately 3,000,000 standard cubic feet of gas per day. A separator having a shell dlameter of approximately 2.0 feet by an overall heiyht of 5.0 feet would occupy a relatively small ~pace at a well site but yet appears to be capable of ef~ectlvely separatlng from 90 to 95~ o~ the gas in the !
':.
`
~3~
flowstream on a volumetric basis. Moreover, -the structure of the separator 14 is relatively uncomplicated, relying on conventional pressure vessel construction techniques and with a relatively uncomplicated yet effective int:ernal baffle syst:em characterized by -the cylindrical depending baffle 22 and the single spiral plate type baffle 28 which forms -the spiral or helical duct or flow passage 30.
Referring further to Figure 1, the gas separated from the flowstream in the separator 14 is conducted by way of the conduit 34 through a suitable gas flow measuring means such as an orifice me-ter comprising an orifice 42 and a pressure differential measurement device 44.
Conventional gas flow measurement processes and apparatus such as the orifice meter 42 may -thus be used to measure lS the gas content o the flow stream and the gas may be either remixed with the liquid flowstream or conducted -to a suitable gas handling faciliLy, now shown.
The liquid being conducted through the conduit: 40 may, on a steady state basis, be conducted -through a continuing conduit portion 46 having a shutoff valve 48 interposed therein. The conduit 46 is connected to an apparatus, generally designated by the numeral 50, which is adapted -to measure the composition of the liquid mixture utilizing electrical properties such as the dielectric constant of the liquid mixture. In particular, the apparatus 50 includes a housing forming a through flow conduit portion 52 in which a microwave conductor element 54 is disposed in the form of an elongated rod. The apparatus 50 is of a type which measures electromagnetic radiation transmissivity in the microwave frequency range through a combined water-oil liquid mixture for measurement of the water fraction in the liquid mixture. The apparatus 50 is preferably of a type described in Canadian Patent Application No. 549,589 filed October 19, 1987 in the name of Bentley N. Scott and Y. Sam Yang and assigned to the assignee of the present invention. In particular, the apparatus 50 includes an oscillator circuit r~
~3~i5~3 whose operatlng freguency changes ln accerdance wlth the concentratlon of one llquid ln the mlxture ln rslation to the mlxture and the ~reguency change may be affected by the resldual gas content of tha llquid m1xtureO This Prequency change or a change ln the transmlsslvi4y of microwave energy may be rorrelated with the dlelectrlc properties of the fluld mlxture. Slmllar devices of somewhat less accuracy and lacking some of the unlgus featureQ of the apparatus ~0 and also of a known type may be substltuted for $he apparatus 50 for determlning the water and oll fraction of the liquid mixture. For example, a devlce known as a watPr Cut Monitor and available from Halllburton Compasly, Dallas, Texas may be substltuted for the device 50 and for the sake of thls discussion the devlce 50 may comprise such a measurlng apparatus.
The total volumetrlc Plow of the llquid mlxture may also be measured with a conventional Corlolis or positive dlsplacement 10wmeter of a type commercially avallable and generally designated by the numeral 58. The liquid mlxture, after conduction through the flowmeter 58, may be conduct~d further through the conduit 46 to a su~able liguld handllng faclllty for separatlon of the oll from the water, for example.
The separatlon of all o~ the gas from the li~uid mlxture is dlfflcult to obt~in by the separator 14, partlcularly while considering the malntenance of a suitably small slze of the separator whlch does not permit long residen~e time of the primarlly separated liquid ln the chamber 26. Accordlngly, ln order to correct any error~ ln readlngs from the apparatus 50 and meter 58 lt is important to provide furth~r separatlon of gas or to measure the gas content which ls residual in the liquid mixture. An lmportant aspect o~ tha present lnventlo~ is determi nlng the residual gas content of the l~quld mixture so that readings of the ~lowmelter 58 can be correctsd to accourlt for tha gas conte~. In thi~ regard the sy~tem lllustrated in Figure 1 lncludes a r~siau~l gas content~measuring device ~6 which is lnterposed in a branch condult 68 connected to the conduit ..
',, DP 50-6-1102A ~ 3~
46 to form a bypass around the valve 48. The device 66 lncludes an elongated condult 70, see Flgure 2 also, whlch forms an interlor chamber 72 whlch is generally cyllndrical ln configuratlon and devold of any poc:kets or portlons whlch may trap unwanted quantities of gas or llquid. The conduit ls connected at lts oppositle ends to remotely controllable shut off valves 76 and 78. The conduit 70 includes a branch portlon ~0 which lntersects the main portion of the condult 70 and ~ournal~ a reciprocable piston 82 disposed therein and adapted to pro;ect into the chamber 72. The normal retracted positlon of the piston 82 is such that little if any space is provided in the branch conduit portlon 80 for occupancy by fluid and therefore no gas may normally be trapped in the conduit 70 before and durlng pressure tests to determine the resldual gas content of the fluid flow6tream.
The piston 82 ls adapted for control to extend and retract with respect to the chamber 72 by an actuator 84 whlch is operable to be controlled by a suitable controller device 86. The controller devlce 86 is also suitably connected to a pressure transducer 88 to measure the change in pressure in the chamber 72 ln relation to the position of the piston 82. A devi~e which works in some ways slmllar to the resldual gas content measuring device 66 is disclosed ln U.S. Patent 4,329,869 to Toda. Furthermore, the device 66 may also lnclude suitabl~ temperature senslng means 90 for measuring the tempera~ure of the fluid flowlng through the chamber 72 and any change therein resulting from a change ~n pressure of the fluld as influenced by movement of the piston 82.
The system 10 is operable to measure total llquid flow continuously by the flowmeter 58, total gas flow contlnuously by the flowmeter 42 and the percentage of water in oll llquid or vice versa by continuous measuremen~ using the apparatus 50 to measure the transmissivity of mi~rowava radiation. Moreover, these flows may be corrected for the amount o~ residual gas ln the liquld flowstream flowlng DP 50-6-1102A ~ 5~
through the ~ondult 46 by periodlc batch sampllng of a quantlty of liquld wi~h residual gas therein by closing the valve 48 and openlng the valves 76 and 78 long enough to trap a representative sample of llqu:id ln the chamber 72, then simultaneously closlng the valve 76 and 78 and reopening the valve 48 to prevent bui:Ld-up of liquld ln the chamber 26. When a quantity of liguld with some residual gas entralned therein is trapped in the chamber 72 the piston 82 may be stroked to penetrate lnto the chamber 72 a predetermlned distance while measuring the corresponding change ln pressure inside the chamber 72 to detPrmine how much free gas is present in the li~uld stream. For example the followlng equation may be used to determine the gas fraction (fg) when lt is expected that the gas fraction is less than 10% of the total volume of the fluld in the chamber 72:
fg = (A~s)/[ll Pl/P2)(Vs)] (1) wherein~ A equals the cross sPctional area of the piston 82, s equals the plston penetration or stroke lnto the sample ln the chamber 72, Pl ls the sample pressure before the piStoQ activatlon, P2 is the pressure after the piston activatlon and V ls the batch sample volume lncluding th~ liquid and gas.
It may be determlned that the increase ln temperature of the sample for a gas fraction of about 10% or less is lnslgnificant and thus the process is essentially isothermal allowing the use of the ldeal gas laws. ~owever, certain corrections should b~ lncluded for elastlc stretch of the conduit 70 under the effect of the lncreaslng pressure in the chamber 72, the redlssol~ing of some of the gas into the llquid and the compr~ssibility of the liquid. When the piston 82 (of area A) is stroked (by dlstance s) into the sample in th~ chambsr 72, the sample volume i~ decreased by a.~ and the prassure lncreases. Each fluid component ,, ', :' ', . . .
' 5~
shrinks~ Conservation of volume lmplies the following about fluid volumes in the cylinder before and after the plston stroke: -dv = V2 - Vs (2) where v2 - fluld volume after the p~ston stroke, dv = fluid volume change = G.VS.dP - A.s, G = an ela~tic stretch factor of the volume of the space 72 dus to stretch or expansion of the condult 70 and dP = P2-Pl.
V2 is the sum of indlvidual component volumes V2 = vo~ + V~' + Vg' (3 where the primes denote shrunken volumes immedlately after the pressure increaseand the notations o, w and g denote oil, water and gas, respectively. Expresslons for each of these terms are llsted below:
Vg' = (fg-fgr).V.[Pl/P2)].~Z2/Zl] (4) Vo' ~ Vw' - (l-fg)~Vs.e b-dP (5) where fgr = gas fractlon re-dissolved due to dP, Zl,Z2 = gas compressibillty factors at Pl and P2, b = li~uid co~pr~ssiblllty coefflcient, and e = constant 2.71828 j The compressibillty factors Zl and Z2 may be obtalned from the Gas Processors Suppliers Assn., Englneering Data Book, Nlnth edition.
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DP 50-6-llO~.A
~3~P~
substltutlng ln equatlons 3 and 2, and re~rra~glng, yields the worklng eguations:
[A.s/V~] - dPo (b+a~ - fgr~
fg a ~ ] ( 6 ) in whlch fgr' ls an abbreviation of t~e product of terms ~.[Pl/P2~.tZ2/~13 (7) and in which e b-dP ls approxlmated by 1 - b.dP; slnce b.dP~1.
~ The value of the re-dissolvlng term, fgr, must be less than or equal to fg. ~oreover, fgr ls expected to be much less than fg (say, 1~ of fg) because tbe re-dissolvlng process will be limlted by the finlte gas-llquld lnterf~cial area, and because the pressure increase and measurement wlll be admlnistered qulckly; ln a few seconds. The product of terms, fgr', will therefore llkely be small enough to ignore. Regardless o~ lts sl~e, the effect of fgr' wlll be to sllghtly reduce the pressure lncrease and to ~ause a sllght overestimatlon of gaæ fraction, fg~
As the residual gas content or gas fractlon (fg) of the llquld sample ~pproache~ zero the pressur~ wlll lncrease rapldly lf the plsto~ 82 ls stro~ed when gas conten ls very small. For fg=0 and fgr~0, equatlon (6) ylelds:
: dP ~ (A.s/V~)/(b+G) (8) The piston 82 should not be stroked far lf ga~ con~ent of the fluld ls near zero; otherwlse overpre~suring ths components of the device 66 wlll re~ultO
As the resldual gas content (fg) lncreases, pressure will lncrease relatively slowIy as the plston ~2 i$ 9troked.
In the limlt fgal, fgr=0, lg~orlng ~ because of it~ small relativs value, and equatlo~ ylelds:
,, ~ . , .
: : ~
DP 50-6-1102A 3 3~55~
dP/Pl = (Z~l/Zl)/[l-~A.S/vs) ] - 1 ~9) A relatlvely large stroke is needed to produce a measurahle effect on pressure. As the effect becomes measurable, say 1%, the Z2/Zl factor will differ slightly from unlty and it can be expressed as a function of the lnltlal pr~ssure, temperature and the differentlal pressur~ increase.
On the basis of the above the operation of the devlce 66 should be controlled such that the pressure in conduit 70 should not be raised more than a few percent; so as to keep the "re-dlssolving error", (fgr'), as small as possible.
Since the gas fractlon (fg) may be anywhere i~ the 0 to 10%
range, and knowledge of even its approximate value should not be assumedl the piston 82 should be stroked in two stages. For example, initially s~roke the plston ~2 into chamber 72 a very short dlstance so as not to overpressure the valve seals in the event the gas fractlon is near zero.
Then, if the lnitial~pressure lncrease did not exceed 5%, advance the plston 82 untll 596 is achleved and compute the gas fraction ~fg) Yla eguation ~6~.
A resolution of 0.5% in estlmatlng fg vi2 ~quation (5) should be sufflclent for flowmeterlng purposes. For example, fg - 015 + .005. Tests lndicate accuracies of ~ .001. Thus approximate values ~from textbooks) of th~
compressiblllty coeficlent (b~ and the stretch factor (G~
of condui~ 70 can be used in equatlon (6).
.
Moreover, it should also be posslble to measurs the compressibllity of the liquld phase by stroking the piston : 82 until pressure rlse~ by 100 psi or more, and then stroke the piston 82 again until pressure rises by another 100 psi.
This provldes two sets of piston stroke(s) and pressure change (dP) data whlch can be substituted into equatlon (6) to solve simultaneously for ~fg) and compressiblllty ,: ,:
'' '` ' ~ , :
.
'': ' , , .
coefficlent (b~. The value o (b) should then be regarded as the compressibillty of the llquld phase, from which we may solve for oil fractlon (fo~ and water fractlon (fw) as follows:
fo + fw = 1 - fg ( 1 0 ) fo.bo + fw.bw = b (liquid phase compressibllity (ll) coefficient value) from which: b bo(l-fg) fw = - ~12) bw - bo where b,fg = values determined from equat~on (6) and bo,bw = compressibility coefflcients of the oil and water in the sample, respectively.
Values of the compressibillty factors bo and bw can be measured by the piston/cyllnder unit ltself, by periodlcally sampling from layers of oll and water from a small settllng tank.
.
A computer controlled linear actuator 84 should have no difficulty in stepping through as many stroking ~tages as might be necessary to measure ga~ fraction and llquid compressibility with reasonable accuracy, Referring now to Flgure 3~ there is illustrated a modlfication of the system illustrated ~n Flgure 1 and whlch is designated by the numeral 100. The ~ystem 100 is simllar to the ~ystem 10 ln essentlally all respects except for the inclusion of a return condult 102 whlch is connected to the conduit 46 and lncludes lnterposed therein a raci.rcula~lng .
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DP 50-6-1102A ~L3~
pump 104 and a throttling valve 106. The condult 102 is connected to the separator vessel 14 for recirculating som~
of the liquld flow back to the separator vessel for us ln certain applications of a system in accoidance with the presen~ invention whereln seYere disruptions ln the llquld flow occur or an extremely hlgh percentage of gas ls present. The system 100 may, in fact, be used as a so called well test system for determinlng the exact specifications of a system which would measure the flow rate on a continuous or production basis.
Referrlng to Figure 4, th~re ls illustrated a second alternate embodiment of a system for measuring multl-phase fluld flow rates in accordance wlth the present :Lnvention.
The system illustrated ln Figure 4 ls deslgnated by the numeral 110 and includes a separator vessel 14, a gas flow rate measuring meter 42 lnterposed in a gas outlet cond~it 34 and an outlet conduit 40 for conductlng substantlally gas free liquid from the sep~rator vessel. The conduit 40 is connected to the lnlet of an apparatus 150 ldentical to the apparatus 50 for measuring the fraction of oll in water or vlce versa, the outlet of which ls ln communicatlon by way of a conduit 112 with a flowmeter 58. A second apparatus 250 also identlcal to the apparatus 50 ls provided ln the system 110 in communicatlnn wlth the condult 112 by way of a branch condult 113 and a pressure boostlng pump 114 and is connected to the separator vessel 14 by way of an outlet conduit 116 having a suitable throttiing valve 118 interposed therein.
The arrangement of the system 113 is such that the residual gas content of the llquid flowing through the conduit 40 may be determined by reading the transmlssivity of microwave radiation through th~ apparatus lS0 interposed in ~he conduit 40 and comparing the reading of the apparatus 150 with the readlng taken from the apparatus 250 at a higher pressure as provided by the pump 114. By circulatlng llquid through the condult 40 and the branch conduit 113, ~16 by way o~ th~ pump 114 a comparison of the measurements ' .
~3~
taken by the two appara~uses 150 and 250 can indlcate the resldual gas content ln the llquld flowstream. For example by provi.ding a pump 11~ havlng a sma:Ll capacity of about 5.0 to 10.0 gallons per minute pressure may be boosted for the fluld enterlng the apparatus 250 downstream of the pump to shrink the gas bubbles that may be present in the llquld flow stream and thus the two apparatus~s 150 and 250 will register slightly dlfferen~ xeadlngs of the dlelPctric constants of the fluid flowing therethrough.
The fl~w rates for the respeetive fractlons of oil, water and gas may ~e determ~ned from the following.
Slnce the pressure boost ls small, the ideal gas laws may be used.
fg2 = fgl [ P/ ( P+dP)] (Al) where (fgl,fg2) are volumetric yas fractions ln the apparatus 150 and 250 respectively, P is the pressure in apparatus 150, and dP is the pressure boost achieved in apparatus 250. Equatlon (Al) ls modlfied to account for some of the fre~ gas (fgr) re-dlssolving ln the liquid.
fg2 = fgl [ P/ ( P/ ( P+dP ~ ~ - f~r ( A2 As discussed previously, fgr ls expected to be less than 1%
when dP/P ls on the order of . 05 or less .
The volumetric l~guld fractlons (fP) and gas fractlons (fg) are related as follows (the numerals 1 and 2 re~er to the conditions in the apparatus 150 and 250, respectively?:
ffl ~ fgl = 1 (A3 ~15-. .
ff2 ~ fg2 = 1 ~A4 ) ~f2/~fl - ~ g2)/(1-fgl~
.
~ fgr~Pr.fgl)~ fgl) (A5 J
where Pr = P/ ~ P~dP ) = Pl/P2 .
In apparatus 250, the gas fraction will be lower, and therefore the liquid fraction will be compensatingly higher, than ln apparatus 150 by the factor ff2/ffl. However, the water-to-oll ratio wlll be identical in both apparatus 150 and 250~ Therefore the oil fraction ~ fo) ancl the water fraction (fw) ln apparatus 250 will both be higher by the same factor ff2/ffl (fw) fo2 = fol~ff2/ffl~ (A6) fw2 - fwl~ff2/ffl) (A7) The mixture dielectrlc constants or microwave transmissivity factors (El,E2) regist~red by the two apparatus~s 150 and 250 can ~e expressed ln terms of the oil, water and ga~
dielectric constants (eo,ew,eg) and volumetric fractions (fo~fw~fg) as ollows:
fol~eo + fwl.ew + fgl.eg = ~1 (A8j fo2.eo ~ fw2.ew ~ fg2.eg = ~2 ~A9) These dielectric constants may b~ considered ln terms of the frequency at which the osclllator circults of the apparatu~e~ 150 and 250 operate for a particular mi~ture composition at the respective operating pressures.
Substitutl~g equations ~Al), (A5), ~A6~ and ~A7~ into ~A9 , ~L3 ylelds (ff2/ffl).[fol.eo + fwl.ew] ~ Pr.fgl.eg - fgr.eg = E2 (A10) Comblning equation (A10) with equatlon (~8) yields the solutlon for the gas fractlon (fgl) E2 - El~l+fgr) ~ eg(fgr) fgl = ~ (All) E2 - El(Pl/P2) + ~g(l-Pl/P2) Substitutlng (All ) ln (A~) and utllizing the continulty equation: ;
fol + fwl ~ fgl = 1 ~ Al 2 ) ylelds the following solutlon for oil fractlon (ew - El) + (ew - eg)~fgl fol ~ (A~3) ~ew - eo) The oil volumetrlc flow rate Qo ls obtalned from QO = Q~fol (A143 where Q is the total volumetric flow rate ~rom the flowmeter ~8 ~ eferrlng to Figure ~ there is illustra~ed yet another embodiment of tha present lnve~tion whereln an apparatus 350 is adapted te be lnterposed ln the liquid dlscharge conduit ~0 from the separator vessel 14 ln place of the device 66 ~3~
and the apparatus 50 ln the ~ystem 10, for example. The apparatus 350 ls essentially the same as the apparatus 50 but is also utllized to measure the resldual gas content in the llquld by allowing a quantlty of the llquld to enter the apparatus and reside therein untll the resldual gas fraction separates from ths liquld fraction. In the modificatlon of the inventlon illustrated ln Figure 5 the apparatus 3sO
includes an outer housing or conductor 120 formlng a chamber 122 for receipt of a quantlty of liquid which has undergone primary gas separation. The conduit 120 ls adapted to receive a liquid sample ln the chamber 122 through an inlet valve 124 and discharge a sample through a valve 126 connected to the condult 46 and flowmeter 58 ~see Figure 1).
The center conductor 5,~ extends through the chamber 122 in the same manner as described earlier herein. The condult 120 is arranged generally vertically so that residual gas entrapped ln the liquid sample may separate and collect at the top of the chamber 122 wherein a suitable liquld level sensing device 128 is disposed for determining the liquid level in the chamber 122. Accordingly, a liquid sample may be trapped in the chamber 122 and allowed to reslde a sufficient length o~ time to permit separatlon of the resldual gas. Then readings of the dlelectric strPngth of the liqul~ sample ln the chamber 122 may be made to determine the fraction o~ water and oll and correcting for the now known amount of gas in the chamber 122. By knowing the residual gas content of the liquld ~ample the flowme$er 58 may be corrected for any error~ in reading the flow rate therethrough.
Accordingly, the steps of measuring the flow rates and gas fraction uslng the modifled system of Figure 5 would be to conduct flow through the apparatus 350 to flush a previous sample, isolate a sample ln the chamber 122 by closing the valv~ 124 and 12~ and allowing the residual gas to segregate in the upper part of the chamber 122 and then measure the height of the gas column to determine the -la-"
:~3~
percent by volume of the gas in the sample. The fractlon of water and oll may then be obtalned by taking readings ~f the mlcrowave radiation transmlsslvity or dielectrlc strength of the fluid in the chamber 122. These steps would provide sufficlent lnformatlon regardlng all t.hree components of the multl-phase fluld flowstream.
Flgure 6 illustrates a further modificatlon of the system of Figure 5 whereln an apparatus 50 ls interposed in supply and return branch conduits 130 and 132 which are connected to a column type ~essel 134 ln which the llquid sample is allowed to reslde sufficlently long to allow gas to collect at the top of a chamber 136 as lllustrated.
Sample shut off valves 124 and 126 are interposed in the system to trap the sample of liquld with residual gas interposed therein and liquid may be clrculated through the apparatus 50 by a pump 138 and a suitable mlxing device 140 to assure a homogenous mlxture of liquid to be measured by the apparatus 50. A llquid level sensor 128 is also provided for the sample vessel 134 to determine the percent by volume of the fluld samplP which is liquld and gas, knowing the volume of the chamber 136. The system of ~igure 6 provldes for thoroughly homogenlzing the liquid free of any residual gas to more accurately determlne the oil and water fractlon~
Although preferred embodlments of a system and method for measurlng the volumetric flow rate of a multi-phase fluid flowstream have been disclosed hereln those skilled ln the art will recognlze that various substitutions and modificatlons may be made to the system without departing from the scope and splrit of the lnvention as recited in the appended claims.
What is claimed is:
. , .
Claims (20)
1. A system for measuring multi-phase fluid flow including a water-oil-gas mixture comprising:
conduit means for conducting a multi-phase fluid flow stream;
separator means connected to said conduit means for separating the liquid phase of said fluid flowstream from the gas phase, said separator means including a gas outlet conduit and a liquid outlet conduit;
gas flow rate measuring means interposed in said gas outlet conduit;
means for measuring the residual gas content of a liquid flowstream leaving said separator vessel through said liquid outlet conduit; and means for measuring the fraction of one liquid in another in said liquid flowstream leaving said separator vessel through said liquid outlet conduit.
conduit means for conducting a multi-phase fluid flow stream;
separator means connected to said conduit means for separating the liquid phase of said fluid flowstream from the gas phase, said separator means including a gas outlet conduit and a liquid outlet conduit;
gas flow rate measuring means interposed in said gas outlet conduit;
means for measuring the residual gas content of a liquid flowstream leaving said separator vessel through said liquid outlet conduit; and means for measuring the fraction of one liquid in another in said liquid flowstream leaving said separator vessel through said liquid outlet conduit.
2. The system set forth in Claim 1 wherein:
said separator means comprises a separator vessel including means for inducing a cyclonic flow of said fluid flowstream.
said separator means comprises a separator vessel including means for inducing a cyclonic flow of said fluid flowstream.
3. The system set forth in Claim 2 wherein:
said separator vessel includes spiral baffle means for receiving said fluid flowstream from said conduit for inducing said cyclonic flow of said fluid flowstream, said baffle comprising a single spiral plate and a generally cylindrical member depending from one end of said vessel, said spiral plate disposed around said cylindrical member and projecting radially outwardly to within a small distance of the wall of said vessel.
said separator vessel includes spiral baffle means for receiving said fluid flowstream from said conduit for inducing said cyclonic flow of said fluid flowstream, said baffle comprising a single spiral plate and a generally cylindrical member depending from one end of said vessel, said spiral plate disposed around said cylindrical member and projecting radially outwardly to within a small distance of the wall of said vessel.
4. The system set forth in Claim 1 wherein:
said means for measuring the residual gas content of said liquid flowstream includes a sampling apparatus including a generally cylindrical conduit section, valve means at opposite ends of said conduit section operable to be closed to define a closed chamber in said conduit section, a piston adapted for reciprocal movement into said chamber a predetermined amount, and means for measuring a pressure increase in said chamber in relation to the movement of said piston to determine the change in volume as compared with the increase in pressure to measure the volumetric fraction of residual gas remaining in the liquid of a sample of fluid trapped in said conduit section.
said means for measuring the residual gas content of said liquid flowstream includes a sampling apparatus including a generally cylindrical conduit section, valve means at opposite ends of said conduit section operable to be closed to define a closed chamber in said conduit section, a piston adapted for reciprocal movement into said chamber a predetermined amount, and means for measuring a pressure increase in said chamber in relation to the movement of said piston to determine the change in volume as compared with the increase in pressure to measure the volumetric fraction of residual gas remaining in the liquid of a sample of fluid trapped in said conduit section.
5. The system set forth in Claim 1 wherein:
said means for measuring the fraction of one liquid in another comprises a conduit section including microwave frequency range conductor means including a portion of said conduit section and means for conducting microwave radiation through said conduit section and said conductor means for determining the fraction of one liquid in another by the change in microwave transmissivity through said conduit section in the presence of said liquid mixture.
said means for measuring the fraction of one liquid in another comprises a conduit section including microwave frequency range conductor means including a portion of said conduit section and means for conducting microwave radiation through said conduit section and said conductor means for determining the fraction of one liquid in another by the change in microwave transmissivity through said conduit section in the presence of said liquid mixture.
6. The system set forth in Claim 1 where:
said means for determining the residual gas content of said liquid flowstream includes a first apparatus including a first liquid conduit through which liquid is conducted and microwave frequency range conductor means including a portion of said first liquid conduit for determining the fraction of one liquid in another at one pressure condition of said liquid flowstream, and a second apparatus including a second liquid conduit through which liquid is conducted and microwave frequency range conductor means including a portion of said conduit section for determining the fraction of one liquid in another at a pressure different from the pressure of the liquid being conducted through said first apparatus whereby by comparing the attenuation of microwave radiation transmissions through said first and second apparatus the gas content of said liquid phase may be determined.
said means for determining the residual gas content of said liquid flowstream includes a first apparatus including a first liquid conduit through which liquid is conducted and microwave frequency range conductor means including a portion of said first liquid conduit for determining the fraction of one liquid in another at one pressure condition of said liquid flowstream, and a second apparatus including a second liquid conduit through which liquid is conducted and microwave frequency range conductor means including a portion of said conduit section for determining the fraction of one liquid in another at a pressure different from the pressure of the liquid being conducted through said first apparatus whereby by comparing the attenuation of microwave radiation transmissions through said first and second apparatus the gas content of said liquid phase may be determined.
7. The system set forth in Claim 1 including:
volumetric flow measuring means interposed in said liquid outlet conduit for measuring the volumetric flow rate of liquid.
volumetric flow measuring means interposed in said liquid outlet conduit for measuring the volumetric flow rate of liquid.
8. The system set forth in Claim 5 wherein:
said conduit section includes means for holding a quantity of liquid to allow residual gas to separate from said liquid and means for measuring the level of liquid in said conduit section after separation of said gas.
said conduit section includes means for holding a quantity of liquid to allow residual gas to separate from said liquid and means for measuring the level of liquid in said conduit section after separation of said gas.
9. The system set forth in Claim 1 including:
branch conduit means interconnecting said liquid outlet conduit and said separator means, pump means interposed in said branch conduit means for returning at least a portion of the liquid flowstream to said separator means during periods of relatively high gas to liquid flow ratios of said flowstream entering said separator means
branch conduit means interconnecting said liquid outlet conduit and said separator means, pump means interposed in said branch conduit means for returning at least a portion of the liquid flowstream to said separator means during periods of relatively high gas to liquid flow ratios of said flowstream entering said separator means
10. A method for measuring the volumetric flow rate of a multi-phase fluid flowstream including a gas phase and a liquid phase and wherein said liquid phase includes a mixture of at least two liquid compositions, said method comprising the steps of:
separating said gas phase from said liquid phase in primary separation means;
measuring the flow rate of gas leaving said primary separation means;
conducting the liquid phase from said primary separation means to means for measuring the residual gas content of said liquid phase;
measuring the change in pressure of a known initial volume of a quantity of said liquid phase with residual gas therein in relation to a volumetric displacement of a piston in said means for measuring the residual gas content to determine the residual gas content in said liquid phase;
measuring the fraction of at least one liquid composition in said mixture; and measuring the volumetric flow rate of said liquid phase.
separating said gas phase from said liquid phase in primary separation means;
measuring the flow rate of gas leaving said primary separation means;
conducting the liquid phase from said primary separation means to means for measuring the residual gas content of said liquid phase;
measuring the change in pressure of a known initial volume of a quantity of said liquid phase with residual gas therein in relation to a volumetric displacement of a piston in said means for measuring the residual gas content to determine the residual gas content in said liquid phase;
measuring the fraction of at least one liquid composition in said mixture; and measuring the volumetric flow rate of said liquid phase.
11. The method set forth in Claim 10 including:
determining the elastic stretch of said means for measuring the residual gas content in response to said change in pressure and comparing the volume change of said means f or measuring the residual gas content due to said elastic stretch with the volume change of said known initial volume of said quantity of liquid phase due to the volumetric displacment of said piston.
determining the elastic stretch of said means for measuring the residual gas content in response to said change in pressure and comparing the volume change of said means f or measuring the residual gas content due to said elastic stretch with the volume change of said known initial volume of said quantity of liquid phase due to the volumetric displacment of said piston.
12. The method set forth in Claim 11 including the step of:
determining the gas fraction of the residual gas content of said quantity of said liquid redisolved in said liquid due to said change in pressure for determining the volume of said gas in said quantity of said liquid.
determining the gas fraction of the residual gas content of said quantity of said liquid redisolved in said liquid due to said change in pressure for determining the volume of said gas in said quantity of said liquid.
13. The method set forth in Claim 12 including the step of:
determining the gas compressibility factors at an initial pressure of said quantity of said liquid and at the pressure due to said change in pressure of said quantity of liquid and determining the volumetric fraction of said quantity of liquid which is gas (fg) from the equation:
wherein A is the cross sectional area of said piston, s is the stroke length of said piston, Vs is the initial volume of said quantity of liquid, dP is the change in pressure due to the volumetric displacement of said piston into said means for measuring the residual gas content, b is the liquid compressibility coefficient, G is the elastic stretch factor of said means for measuring the residual gas content, fgr' is the gas fraction redissolved in the liquid due to the change in pressure, P1 is the initial pressure, P2 is the pressure after displacement of said piston, Z1 is the gas compressibility factor at the initial pressure and Z2 is the gas compressibility factor at the pressure after volumetric displacement of said piston.
determining the gas compressibility factors at an initial pressure of said quantity of said liquid and at the pressure due to said change in pressure of said quantity of liquid and determining the volumetric fraction of said quantity of liquid which is gas (fg) from the equation:
wherein A is the cross sectional area of said piston, s is the stroke length of said piston, Vs is the initial volume of said quantity of liquid, dP is the change in pressure due to the volumetric displacement of said piston into said means for measuring the residual gas content, b is the liquid compressibility coefficient, G is the elastic stretch factor of said means for measuring the residual gas content, fgr' is the gas fraction redissolved in the liquid due to the change in pressure, P1 is the initial pressure, P2 is the pressure after displacement of said piston, Z1 is the gas compressibility factor at the initial pressure and Z2 is the gas compressibility factor at the pressure after volumetric displacement of said piston.
14. The method set forth in Claim 13 including the step of:
increasing the pressure during an initial volumetric displacment of said piston by not more than about 5% of the initial pressure of said quantity of liquid prior to determining the gas fraction (fg) from the equation of Claim 13.
increasing the pressure during an initial volumetric displacment of said piston by not more than about 5% of the initial pressure of said quantity of liquid prior to determining the gas fraction (fg) from the equation of Claim 13.
15. The method set forth in Claim 13 including the step of:
determining the compressibility of said quantity of said liquid by displacing said piston in said means for measuring until the pressure increases at least approximately 100 psi while measuring said volumetric displacement of said piston followed by displacing said piston an additional volumetric displacement to obtain a further increase of pressure of said quantity of liquid in said means for measuring and determining the fraction of one liquid (fw) of said liquid wherein:
wherein bw is the compressibility coefficient of said one liquid in said mixture and bo is the compressibility coefficient of the other liquid in said mixture.
determining the compressibility of said quantity of said liquid by displacing said piston in said means for measuring until the pressure increases at least approximately 100 psi while measuring said volumetric displacement of said piston followed by displacing said piston an additional volumetric displacement to obtain a further increase of pressure of said quantity of liquid in said means for measuring and determining the fraction of one liquid (fw) of said liquid wherein:
wherein bw is the compressibility coefficient of said one liquid in said mixture and bo is the compressibility coefficient of the other liquid in said mixture.
16. The method set forth in Claim 15 including the step of:
measuring the compressibility coefficient of said liquid compositions in said mixture.
measuring the compressibility coefficient of said liquid compositions in said mixture.
17. The method set forth in Claim 10 including:
providing means for collecting a sample of the liquid phase to permit separation of residual gas in the liquid phase and measuring the volume occupied by the liquid phase and the separated residual gas in said sample.
providing means for collecting a sample of the liquid phase to permit separation of residual gas in the liquid phase and measuring the volume occupied by the liquid phase and the separated residual gas in said sample.
18. A method for measuring the volumetric flow rate of a multiphase fluid flowstream including a gas phase and a liquid phase and wherein said liquid phase includes a mixture of at least two liquid compositions, said method comprising the steps of:
separating said gas phase from said liquid phase in a primary separation means:
conducting said liquid phase from said primary separation means to means for measuring the residual gas content of said liquid phase comprising a first apparatus including a first conduit section through which said liquid phase is transmitted and including means for measuring the transmission of microwave radiation through said first conduit section at a first pressure of said liquid phase flowing through said first conduit section, and conducting said liquid phase to a second apparatus including a second conduit section and means for measuring the transmissivity of microwave radiation through said second conduit section at a second pressure of said liquid phase greater than said first pressure; and comparing the change in microwave transmissivity in said first conduit section and said second conduit section to determine the volumetric fraction of gas in said liquid phase.
separating said gas phase from said liquid phase in a primary separation means:
conducting said liquid phase from said primary separation means to means for measuring the residual gas content of said liquid phase comprising a first apparatus including a first conduit section through which said liquid phase is transmitted and including means for measuring the transmission of microwave radiation through said first conduit section at a first pressure of said liquid phase flowing through said first conduit section, and conducting said liquid phase to a second apparatus including a second conduit section and means for measuring the transmissivity of microwave radiation through said second conduit section at a second pressure of said liquid phase greater than said first pressure; and comparing the change in microwave transmissivity in said first conduit section and said second conduit section to determine the volumetric fraction of gas in said liquid phase.
19, The method set forth in Claim 18 including the step of:
providing pump means interposed in a conduit connecting said first apparatus and said second apparatus for increasing the pressure of said liquid flowstream passing through said second conduit section with respect to the pressure of said liquid flowstream passing through said first conduit section.
providing pump means interposed in a conduit connecting said first apparatus and said second apparatus for increasing the pressure of said liquid flowstream passing through said second conduit section with respect to the pressure of said liquid flowstream passing through said first conduit section.
20. The method set forth in Claim 18 wherein:
the volumetric fraction of gas (fgl) is determined from the equation:
wherein E1 and E2 are constants related to the microwave transmissivity through said liquid flowstream in said first apparatus and said second apparatus, respectively, fgr is the quantity of gas redissolved into said liquid phase at the pressure in said second apparatus, eg is the dielectric constant of the gas, and P1 and P2 are the pressures in said first apparatus and said second apparatus, respectively, at which measurements of microwave transmissivity are measured.
the volumetric fraction of gas (fgl) is determined from the equation:
wherein E1 and E2 are constants related to the microwave transmissivity through said liquid flowstream in said first apparatus and said second apparatus, respectively, fgr is the quantity of gas redissolved into said liquid phase at the pressure in said second apparatus, eg is the dielectric constant of the gas, and P1 and P2 are the pressures in said first apparatus and said second apparatus, respectively, at which measurements of microwave transmissivity are measured.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/281,421 | 1988-12-08 | ||
| US07/281,421 US4852395A (en) | 1988-12-08 | 1988-12-08 | Three phase fluid flow measuring system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1305518C true CA1305518C (en) | 1992-07-21 |
Family
ID=23077228
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000609751A Expired - Lifetime CA1305518C (en) | 1988-12-08 | 1989-08-29 | Three phase fluid flow measuring system |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4852395A (en) |
| CA (1) | CA1305518C (en) |
| FR (1) | FR2640375B1 (en) |
| GB (1) | GB2225863B (en) |
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-
1988
- 1988-12-08 US US07/281,421 patent/US4852395A/en not_active Expired - Lifetime
-
1989
- 1989-08-29 CA CA000609751A patent/CA1305518C/en not_active Expired - Lifetime
- 1989-09-15 GB GB8920952A patent/GB2225863B/en not_active Expired - Fee Related
- 1989-12-07 FR FR898916179A patent/FR2640375B1/en not_active Expired - Fee Related
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107882547A (en) * | 2016-09-29 | 2018-04-06 | 中国石油化工股份有限公司 | Duct type high-water-cut oil-producing well produces liquid three-phase metering mechanism and method |
| CN107882547B (en) * | 2016-09-29 | 2023-08-04 | 中国石油化工股份有限公司 | Pipeline type high-water-content oil well liquid production three-phase metering device and method |
| CN112781946A (en) * | 2019-11-08 | 2021-05-11 | 国家能源投资集团有限责任公司 | Split-phase collecting device and method for multiphase mixed materials and application of split-phase collecting device and method |
| CN112781946B (en) * | 2019-11-08 | 2023-09-12 | 国家能源投资集团有限责任公司 | Phase-splitting collecting device and method for multiphase mixed materials and application of phase-splitting collecting device and method |
| CN110905481A (en) * | 2019-12-23 | 2020-03-24 | 西安长庆科技工程有限责任公司 | Mobile single-well multiphase metering integrated device and metering method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8920952D0 (en) | 1989-11-01 |
| FR2640375A1 (en) | 1990-06-15 |
| US4852395A (en) | 1989-08-01 |
| GB2225863B (en) | 1993-03-24 |
| FR2640375B1 (en) | 1993-04-30 |
| GB2225863A (en) | 1990-06-13 |
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