US3451477A - Method and apparatus for effecting gas control in oil wells - Google Patents

Description

June 24, 1969 K. KELLEY 3,451,477

METHOD AND APPARATUS FOR EFFECTING GAS CONTROL IN OIL WELLS Filed June 30, 1967 Sheet INVENTOR. KOIZK KELLEY WIM ATTORNEYS K. KELLEY June 24, 1969 METHOD AND APPARATUS FOR EFFECTING GAS CONTROL IN OIL WELLS I INVENTOR.

Filed June 30, 1967 United States Patent 3,451,477 METHOD AND APPARATUS FOR EFFECTING GAS CONTROL IN OIL WELLS Kork Kelley, Liberal, Kans., assignor of one-half to Robert K. Kelley, Fort Worth, Tex. Continuation-impart of application Ser. No. 433,909, Feb. 19, 1965. This application June 30, 1967, Ser. No. 650,286

Int. Cl. E21b 43/12, 39/00; F04b 21/00 US. Cl. 166-265 11 Claims ABSTRACT OF THE DISCLOSURE This invention is a continuation-in-part of my copending application Ser. No. 433,909, filed Feb. 19, 1965, now abandoned and relates to improvements in A Method and Apparatus for Effecting Gas Control in Oil Wells. More particularly, this invention relates to systems for controlling the rate of production of oil wells without wasting gas.

. In many localities, the production of liquid oil and gas from wells is strictly regulated. Limited production is difficult to obtain without effective control over internal well pressure. Moreover, it has been demonstrated repeatedly that total production from the average well is very significantly increased where the gas pressure in the formation is retained and utilized instead of being wasted. Efficiency of operation alone is a powerful incentive to accomplish complete gas control, both as to well pressures and as to conservation of gas energy.

Many efforts have been made to accomplish accurate gas control inside the well but these attempts have been only partially successful. This is mainly due to a failure to appreciate all of the interacting conditions present in the producing zone of the well and resulting failure to solve all of the problems created by such conditions. It should be appreciated that the pressures encountered in modern wells, especially those drilled to comparatively great depths, coact with the gas and liquid phases of the hydrocarbons encountered to produce conditions which were either absent or much less important in earlier, shallower-wells.

The oil is forced into the well through the rock structure in the producing formation by gas pressure in the formation higher than that present in the well. This often produces turbulence and foaming within the well to such degree that the contents at the producing zone take on many of the characteristics of a fluid composed of a mixture of liquid and gas, the specific gravity of the fluid depending upon the relative proportions of each. The apparatus of the present invention is constructed to provide an environment conducive to the separation of the liquid and gas and is also constructed to provide removal of the liquid from the well either by gas pressure alone or gas pressure in combination with pumping. The configuration of the present apparatus also prevents frac sand and other highly abrasive debris from entering the pump string and causing damage to the pump, valves or other parts. The present apparatus is particularly Patented June 24, 1 969 suitable for use with pumping systems of the character disclosed in United States Patent No. 3,324,803, issued June 13, 1967, and entitled, Liquid Control for Gas Wells.

In many localities, oil and gas production is strictly limited by appropriate governmental agencies. Most of these agencies limit the production per well to as low as 15-25 barrels per day. Many of the wells are capable of producing up to 1,000 barrels per day and it has been the policy in most cases to operate the well long enough each day to produce the daily allowance and then shut the well down until the next day. In this procedure, although the flow of oil from the well has been stopped, the gas pressure in the well tends to equalize with the pressure in the surrounding formation. This equalizing of pressures halts the flow of oil through the formation into the well and the oil will not move into the bore hole until the gas is vented from the well. The venting of this gas in a relatively short time causes a surging action which drives sand, mud and cut oil into the bore and creates a foamy mixture which is difficult if not impossible to pump.

With the use of the gas control system of the present invention, the well is kept pumping 24 hours a day and positive control is exercised over the gas pressure in the well so that the daily allowable production is forced out of the formation into the well during each 24-hour period. This control of pressure in the well provides a stabilized condition which greatly reduces foaming and driving of unwanted debris into the well bore. Under these conditions, the present apparatus is highly effective to permit the pumping of liquid oil out of the well While retaining the gas therein.

In wells that are capable of producing a lot of water along with the oil, the action of the present control system in reducing and controlling the rate of flow into the well from the surrounding formation often helps greatly in reducing the flow of Water into the Well, probably by reducing surging and allowing natural oilwater separation to take place. In addition, it should be clear that preventing excessive discharge of gas from the well tends to conserve the reservoir energy stored in the highly compressed gas, and this saved. energy is available to aid in lifting the oil from the well.

The present invention is adapted to produce oil at a desired rate of flow by controlling gas pressure in the well, so as to produce a desired quantity of oil during a 24-hour period. This is accomplished by bleeding or metering gas from the interior of the well at a selected rate of flow through a needle valve, or the like, in such manner that the gas pressure in the well controls production of oil from the formation at the desired rate of flow.

The liquid oil and the gas are separated at the bottom of the well, preferably by a positive-action, bucket-type separator, and the oil is removed from the Well through conventional production tubing. The separation of the oil and gas at the bottom of the well, in conjunction with the control of the gas pressure in the well, permits the adjusting of the production rate of flow of oil from the well to the desired amount, Without wasting gas on the one hand or allowing the liquid oil to fill up the bore and choke off the well on the other hand.

Broadly speaking, the liquid-gas separator is responsive to the level of liquid oil in the well, although it is recognized that foaming and frothing often occur within wells and it is really a desired differential in density of specific gravity which is utilized to control the action of the separator. The present invention minimizes surging and consequent forcing of sand and other unwanted materials into the well bore. The apparatus is formed in such manner that any sand or other debris which might enter the Well bore will be prevented from having deleterious effect on the working mechanism or contaminating the oil being produced.

Accordingly, it is a principal object of the present invention to provide a method and apparatus for controlling and conserving gas pressure in oil wells.

Another object of the invention is to provide a method and apparatus for effecting subsurface gas control in oil wells which will permit continuous production of daily allowances through an entire 24-hour period and which greatly reduces surging and consequent forcing of sand and other unwanted materials into the well bore.

A further object of the invention is to provide an apparatus of the character described which is formed for removing liquid oil from an oil well in a condition substantially free from contamination by sand, mud or other debris.

- Yet another object of the present invention is the provision, in apparatus of the character described, of a device responsive to changes in specific gravity of the fluid mixture of liquid oil and gas normally encountered at the producing zone of an oil well, the device being effective for separating the liquid oil from the gas, supplying the liquid oil to a pump string, and returning the gas to the interior of the well.

Another object of the invention is to provide apparatus of the character described which is adapted to function efficiently in wells of great depth and under a variety of pressure conditions.

Further objects and advantages of my invention will be apparent as the specification progresses, and the new and useful features of my Method and Apparatus for Effecting Gas Control in Oil Wells will be fully defined in the claims attached hereto.

The preferred forms of the invention are illustrated in the accompanying drawings, forming a part of this description, in which:

FIGURE 1 is a fragmentary schematic view of an oil well incorporating the apparatus of the present invention;

FIGURE 2 is an enlarged fragmentary view of the upper end of the oil well of FIGURE 1;

FIGURE 3 is an enlarged vertical cross-sectional view taken substantially on the plane of 33 of FIGURE 1;

FIGURE 4 is a further enlarged vertical cross-sectional view taken substantially on the plane of line 44 of FIGURE 3;

FIGURE 5 is a cross-sectional view taken substantially on the plane of line 5-5 of FIGURE 4;

FIGURE 6 is a cross-sectional view taken substantially on the plane of line 6-6 of FIGURE 4; and

FIGURE 7 is a cross-sectional view taken substantially on the plane line 7-7 of FIGURE 4.

While I have shown only the preferred form of my invention, it should be understood that various changes or modifications may be made within the scope of the claims attached hereto without departing from the spirit of the invention.

Referring to the drawings in detail, it will be seen that the gas control system of the present invention operates to control pressure and conserve gas in an oil well 11 by sealing the upper end 12 of the well against unwanted escape of gas, by venting gas through the sealed upper end of the well at a controlled rate to lower the gas pressure within the well sufficiently to cause the desired quantity of oil to be forced into the well from the surrounding formation 13, by separating the liquid oil from the gas within the well, and by thereafter removing the liquid oil from the well.

The apparatus for accomplishing this is adapted for use in the conventional Well casing 14 positioned in the bore hole 15 and the usual pump string 16 mounted in the casing with its lower end in communication with the producing zone of the well and its upper end 17 passing through a gas tight sealing device 18 secured to the upper end of the well casing 14. It should be understood that the casing 14 may be positioned in the well in any of a number of conventional ways, the main essential being that the well bore is normally sealed against the escape of gas and consequent drop in gas pressure.

Means 19 is provided for venting gas from the well at a controlled rate of flow so as to lower the gas pressure within the well comparatively slowly and only by an amount sufficient to accomplish the purpose of the present invention. The slowness of the drop in pressure prevents surging which ordinarily causes excessive foaming and carrying of sand, mud and other debris into the interior of the well casing. The controlled venting of the gas permits the operator to attain a drop in pressure which is just enough to accomplish continuous and relatively non-surging flow of oil from the surrounding formation into the well casing in amounts equal to the permitted production rate of the well over a 24-hour period.

The means 19 may be located in any suitable place to accomplish the described controlled venting of gas from the well, but preferably is mounted above ground at the casing head, Christmas tree, or other structure used to seal the well. As here shown, the means 19 consists of a conventional needle valve mounted on the seal 18 in communication with the interior of the well casing. While a needle valve is preferred, it should be apparent that any other suitable means for accomplishing controlled venting of gas from the well at a desired rate of flow could be used.

In accordance with the present invention, and referring specifically to FIGURES 3-7 of the drawings, it will be seen that the liquid oil is separated from the gas and supplied to the pump string 16 by apparatus positioned within the well casing at the producing zone. As here shown, this apparatus includes valve means 21 positioned at the lower end of the pump string 16 and formed for selectively communicating the interior of the pump string with the interior of the well casing, together with control means 22 responsive to changes in the specific gravity of the fluid mixture, usually liquid oil and gas, encountered at the producing zone of the well, the control means 22 having an operative connection to valve means 21 formed for opening and closing the latter in accordance with the rise and fall of the said specific gravity, so as to supply liquid oil only to the pump suction line.

As here shown, the control means 22 includes an open top cylindrical bucket 23 formed for vertical reciprocation within the well and having a weight suflicient to pull the valve means 21 to open condition against the gas pressure in the Well when the bucket is only partly filled. Thus, as liquid oils cascade into the bucket through its open top, the combined weight of oil and the bucket will open the valve means 21 and provide access for the liquid oil to the pump string.

The bucket 23 is formed and proportioned to provide an effective displacement sufficient to float the bucket in the surrounding fluid mixture when the bucket is substantially empty of liquid oil, the floating action being sufiicient for urging the valve means 21 to closed condition. Thus, so long as liquid oil is available in the bucket, the valve means 21 will remain open, but as the amount of liquid oil in the bucket is depleted, the bouyancy of the bucket will cause the valve means 21 to close before any gas can enter the pump string. This prevents gas lock and ensures that gas will not be discharged from the well through the pump string even if mistakes are made by the operators above ground level.

As may best be seen in FIGURE 4 of the drawings, the valve means 21 is of the valve-on-valve type in order to reduce the bucket weight necessary to open the valve means, thus also reducing the length of bucket necessary to provide the described flotation displacement. Accordingly, valve means 21 includes a main valve member 20 moveable vertically toward and away from a valve seat 24 provided by the lower end of a nipple 26 threadably secured to and communicating with the lower end of the pump string 16. The main valve member 20 is formed with a central opening 27 extending axially therethrough, opening 27 being of considerably smaller cross-sectional area than the opening in nipple 26 surrounded by seat 24.

The valve means 21 also includes a secondary valve member 28 mounted for vertical movement toward and away from a valve seat 29 formed around the lower end of opening 27 in main valve member 20. Secondary valve member 28 is operatively connected to bucket 23 by a rod 31 so it will move up and down with the rise and fall of the bucket. This up-and-down movement is guided by a vertically elongated cage 32 which is threadably secured to main valve member 20. As the secondary valve member 28 moves downwardly away from its seat 29 under the influence of the weight of the bucket 23, it encounters a ring member 33 secured to the lower end of cage 32 in closely surrounding relation to rod 31 so that the weight of the partially-filled bucket 23 will be transferred to the main valve member 20 as the bucket continues to descend.

The pressure drop across valve means 21 can be very considerable when working with very deep wells or wells having high gas pressures. In order to bodily pull the main valve open under these conditions, the bucket would have to be unnecessarily heavy and, accordingly, unnecessarily long. With the structure described, much less weight is required to pull the secondary valve member from its seat and this permits liquid to flow from the well into the pump string, greatly reducing the amount of pressure drop across the main valve. Thus, when the lost motion connection provided by the secondary valve member 23 engaging ring 33 transfers the Weight of the partially-filled bucket to the main valve, such weight will be suflicient to pull the main valve member 20 from its seat 24. When the supply of liquid oil in the bucket is substantially depleted, the bucket will float upwardly and urge secondary valve member 28 against its seat. This, in turn, will urge main valve member 20 to closed condition against its seat 24, thus closing oif the pump string 16 from the well and preventing the entry of gas from the well into the pump string.

The structure of the valve means 21 and control means 22 thus far described is basically similar to the structure of the oil-gas separator disclosed in my Patent No. 2,291,902, issued Aug. 4, 1942 and entitled Gas Anchor. While the device shown in that patent might work effectively in some wells, if substituted for the apparatus illustrated in FIGURES 3-7 of the present drawings, the present apparatus contains several features of novelty which provide fool-proof operation in a great variety of wells under a great variety of conditions. Accordingly, it is preferred that the gas-oil bottom hole separating device shown and described herein be used in my gas control system.

In accordance with the present invention, and as a valuable feature thereof, the valve means 21 and control means 22 of the present invention are formed and mounted in such a way as to ensure that substantially uncontaminated liquid oil is the only material allowed to pass through the valve means 21 and enter the pump string 16. The value of this accomplishment should be apparent when it is realized that contaminants and debris such as sand, mud, rock chips and the like normally found in oil wells are all highly abrasive and could cause excessive wear to the valve structures as well as to the pumpsusually employed for lifting the oil out of the well.

In the present invention, most of the debris are prevented from entering the bucket 23, and those that do enter are trapped in the bucket and do not pass through the valve means 21 into the pump string 16. Preventing almost all of the debris from entering bucket 23 is accomplished by routing the flow of fluid upwardly through an annular space between the bucket 23 and the bellshaped skirt 34 mounted in surrounding relation thereto. As here shown, skirt 34 is provided as a downward extension of a tubular member 36 carried on the lower end of pump string 16 in surrounding relation to an elongated cylindrical housing 37, also carried by the lower end of pump string 16. With this construction, the fluid mixture of gas and oil passes downwardly between the skirt 34 and well casing 14, then makes a degree bend to enter the open bottom of skirt 34 and pass upwardly through the annular space 38 between skirt 34 and bucket 23. Since the bucket 23 and skirt 34 may be as much as 30 or 40 feet long, depending upon weight and flotation characteristics required of the bucket, and because of the abrupt 180 degree bend required, most of the unwanted debris 39 drop down to the bottom of the well and are not carried up through annular space 38. The latter space also serves to reduce the foaming effect and promote separation of the gas from the liquid oil. Once the liquid oil level reaches the open top 41 of the bucket 23, it cascades down into the bucket. As the bucket fills, its buoyancy is reduced and eventually the combined weight of bucket and oil causes the bucket to sink down and pull the valve means 21 to open condition.

Trapping of any minor amounts of debris which might have been carried into the bucket is effected by mounting the valve means 21 in spaced relation above the bucket and extending a tubular probe member 42 downwardly from the housing 37 in concentrically spaced relation around the rod 31 and with its lower end 43 terminating at short distance above the bottom 44 of the bucket when the latter is in its uppermost position, From FIGURE 3 of the drawing, it may be seen that the probe 42 not only provides a conduit for the liquid oil. to pass from the bucket 23 upwardly through the valve means 21 and into pump string 16, but also serves as a guide for the rod 31.

In operation, needle valve 19 is opened sufiiciently to bleed oif enough gas from the interior of the well to cause a slight pressure drop suflicient for the reservoir gas pressure to urge the desired quantity of oil through the formation and through the usual holes 46 into the well casing 14. As the specific gravity of the fluid mixture in the bucket increases, due to an increasing percentage of liquid oil, the buoyancy of the bucket will be reduced and it will eventually sink down far enough to pull valve means 21 to open condition. So long as liquid oil is being supplied to the bucket as fast or faster than it is being removed through the pump string 16, the apparatus will remain in the described condition. As soon as the specific gravity of the mixture drops, due to the depletion of the amount of liquid oil in the bucket 23, buoyancy will be reestablished and the bucket will rise so as to close the valve means 21 before the probe 42 starves for oil and unwanted gas enters the pump string.

Preferably, the needle valve is adjusted so that the well will flow only a small quantity of the oil that would otherwise flow with full venting. Generally, this small quantity will be equal to that allowed by appropriate governmental agencies and will be less than, say, two or three percent of the production which would be possible on full venting. In this way, the pressure within the gas casing is retained at such a high degree that volatile components do not come out of the solution in the producing zone at an undue rate. In this way, more produceable liquids flow into the well and considerably greater overall productivity is achieved from the well.

In conclusion, it should be noted that the method and apparatus of the present invention is effective for use in wells in which gas pressure alone is relied upon to force the liquid from the well. However, in. the great majority of wells, some type of pumping means is normally employed. Any suitable pumping means may be used which can accommodate closing of the valve means 21 during the periods when no liquid oil is available for pumping. Many such pumping devices are well known in the oil well industry.

From the foregoing, it will be seen that I have provided a novel and efficient gas control system for controlling gas pressures within the well, regulating oil production, and

7 furnishing relatively uncontaminated oil to the pump string.

I claim:

1. The method of producing an oil well having a well casing and producing line and removing a desired quantity of liquid oil therefrom per day comprising sealing the well casing against unwanted escape of gas therefrom, controlling the gas pressure in the well casing by venting gas from the well casing at a controlled substantially uniform rate to keep the gas pressure within the well at a level just suflicient to cause oil to be forced into the well from the surrounding formation at a desired rate of production, effecting separation of the liquid oil from the gas at the bottom of the well in response to the level of the oil in the well, and removing the separated liquid oil from the well through the producing line.

2. The method as described in claim 1 and wherein said controlling of gas pressure within the well is accomplished by metering gas from the well through a needle valve at the upper end of the well.

3. Apparatus for producing an oil well while controlling pressure and conserving gas therein, comprising a well casing positioned in the bore of an oil well and having a gas tight seal at the upper end thereof, venting means in the gas tight seal for venting selected amounts of gas from said casing at a substantially uniform rate so as to prevent excessive increase of pressure in the casing, and maintain the casing pressure at a desired level, a pump string mounted in said casing-and having a lower end in communication with the producing zone of the well and an upper end passing through said gas tight seal in the upper end of said casing, pump means connected to said pump string and formed for producing a lowered pressure therein for drawing liquid oil out of said well, valve means at said lower end of said pump string formed for selectively communicating the interior of said pump string with the interior of said casing, and control means inside said casing at the producing zone of the well and responsive to changes in specific gravity of the fluid mixture encountered thereat, said control means having an operative connection to said valve means formed for opening and closing the latter in accordance with the rise and fall of the said specific gravity so as to supply liquid oil only to the pump suction line.

4. Apparatus for producing an oil well having a pump and pump suction line while effecting gas control therein, comprising a well casing positioned in the bore of an oil well, a gas tight seal at the upper end of said casing, a control valve in the gas tight seal for venting controlled amounts of gas from said casing at a substantially uniform rate so as to maintain the pressure in the casing at a desired level, and separating means for separating oil and gas in the producing zone of the well; said separating means comprising valve means adapted for connection to the intake end of the pump suction line, and control means adapted for positioning at the producing zone of the oil well and responsive to changes in specific gravity of the fluid mixture encountered thereat, said control means having an operative connection to said valve means formed for opening and closing the latter in accordance with the rise and fall of the said specific gravity so as to supply liquid oil only to the pump suction line.

5. Apparatus as described in claim 4, in which the control valve in the gas tight seal is a needle valve.

6. In a system for eifecting gas control in an oil well, an apparatus for separating oil and gas in the producing zone of the well, comprising a main valve providing a main valve member moveable vertically toward and away from a valve seat adapted for connection to the intake end of a pump suction line, said main valve member being formed with an opening therethrough of smaller crosssectional area than said seat of said main valve, a secondary valve providing a secondary valve member moveable vertically toward and away from a valve seat formed around said opening through said main valve member,

an open top bucket formed for vertical reciprocation within the well, with its open top a spaced distance below said main valve, means communicating said main and secondary valves with the interior of said bucket, a rod secured to the bottom of said bucket and said secondary valve member, and a lost motion connection between said main valve member and said secondary valve member, said bucket having a weight sufiicient to pull said secondary valve member from its seat against the gas pressure in the well when said bucket is partially filled with liquid so as to reduce the pressure drop across said main valve, said lost motion connection being formed for pulling said main valve from its seat after said secondary valve is opened, said bucket having an effective displacement suflicient to float said bucket in the surrounding fluid mixture when said bucket is substantially empty of separated liquid so as to urge said main and secondary valve members against their respective seats.

7. An apparatus as described in claim 6 and wherein an elongated cylindrical housing is mounted in enveloping relation around said main and secondary valves, and a tubular probe member extends downwardly from said housing in concentrically spaced relation around said rod and terminates adjacent to the bottom of the said bucket when the latter is in its uppermost position for guiding said rod and providing said means and communicating said valves in the interior of said housing with the interior of said bucket near the b ottom thereof.

'8. An apparatus as described in claim 7 and wherein a tubular member having an elongated bell-shaped skirt open at the bottom is mounted in concentrically spaced relation around said bucket and cooperates therewith to define an annular passage whereby the fluid mixture from the well enters the open bottom of said bell-shaped skirt and passes upwardly through said annular space and into the open top of the bucket whereby sand and other unwanted debris will drop into the bottom of the well and will not be carried into the bucket with said fluid mixture.

9. Apparatus for producing an oil well having a pump and pump suction line while effecting gas control therein, comprising a well casing positioned in the bore of an oil well, a gas tight seal at the upper end of said casing, a control valve in the gas tight seal for venting selected amounts of gas from said casing so as to reduce the pressure in the casing by a desired amount, and separating means for separating oil and gas in the producing zone of the well; said separating means comprising valve means adapted for connection to the intake end of the pump suction line, and control means adapted for positioning at the producing zone of the oil well and responsive to changes in specific gravity of the fluid mixture encountered thereat, said control means having an operative connection to said valve means formed for opening and closing the latter in accordance with the rise and fall of the said specific gravity so as to supply liquid oil only to the pump suction line, said control means also having an open-top bucket formed for vertical reciprocation within the well, said bucket having a weight sufficient to pull said valve means open against the gas pressure in the well when said bucket is partially filled and having an effective displacement suflicient to float said bucket in the surrounding fluid mixture when said bucket is substantially empty for urging said valve means closed.

10. An apparatus as described in claim 9 and wherein a tubular member having an elongated bell-shaped skirt open at the bottom is mounted in concentrically-spaced relation around said bucket in such manner that the fluid mixture from the well enters the open bottom of the skirt and passes upwardly through the annular space between said bucket and bell-shaped skirt and into the open top of the bucket whereby sand and other unwanted debris will drop into the bottom of the well and will not be carried into the bucket with said fluid mixture.

11. An apparatus as described in claim 10 and wherein said tubular member extends vertically above the open 9 10 top of said bucket and is formed with an opening there- 2,905,246 9/ 1959 Rodgers 166-54 through for venting gas trapped in the upper part of said 3,045,751 7/ 1962 Rodgers 16654 tubular member back into the well. OTHER REFERENCES e e c Cited Uren, Lester C., Petroleum Production Engineering: UNITED STATES P T Oil Field Exploitation, New York, McGraw-Hill, 3rd Ed.,

M- Pendleton I L E 1,431,777 10/1922 Conrader 166- -6 CH ES E L 2123475 3/1938 Rodgers 5 10 I. A. CALVERT, Assistant Exammer. 2,142,376 1/1939 Rodgers 166541 2,291,902 8/1942 Kelley 1- 10340 2,370,296 2/1945 Ehretsman et al 137-191 103-203; 13719l; 166-54, 68, 314

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