WO2013056342A1 - Steam assisted gravity drainage processes with the addition of oxygen addition - Google Patents
Steam assisted gravity drainage processes with the addition of oxygen addition Download PDFInfo
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- WO2013056342A1 WO2013056342A1 PCT/CA2012/000899 CA2012000899W WO2013056342A1 WO 2013056342 A1 WO2013056342 A1 WO 2013056342A1 CA 2012000899 W CA2012000899 W CA 2012000899W WO 2013056342 A1 WO2013056342 A1 WO 2013056342A1
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- steam
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- bitumen
- sagdox
- combustion
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Classifications
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/04—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal by extraction
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/02—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal by distillation
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/2406—Steam assisted gravity drainage [SAGD]
- E21B43/2408—SAGD in combination with other methods
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/243—Combustion in situ
Definitions
- a cogeneration operation is locally provided to supply oxygen and steam requirements.
- ASU Air Separation Unit (to produce oxygen gas)
- SAGDOX (SAGD with oxygen) is another alternative process, for bitumen EOR that can be considered as a hybrid process combining the attributes of SAGD (steam) and ISC (oxygen).
- SAGDOX uses a modified SAGD geometry with extra wells or segregated injector systems to allow for separate continuous injection of oxygen and steam and removal on non-condensable gases produced by combustion.
- bitumen causes some difficulties. At reservoir conditions, bitumen viscosity is large (> 100,000 cp.), bitumen will not flow and gas/steam injectivity is very poor or near zero. Vertical well geometry will not easily work for bitumen EOR. We need a new geometry with short paths for bitumen recovery and a method to start-up the process so we can inject steam to heat bitumen. In the 1970-1980's using new technology to directionally drill wells and position the wells accurately, it became possible to drill horizontal wells for short-path geometry. Also, in the early 1970's, Dr. Roger Butler invented the SAGD process, using horizontal wells to recover bitumen (Butler (1991)).
- Figure 1 shows the basic SAGD geometry using twin parallel horizontal wells with a separation of about 5m, with the lower horizontal well near the reservoir bottom (about 2 to 8m. above the floor), and with a pattern length of about 500 to 1000m.
- the SAGD process is started by circulating steam until the horizontal well pair can communicate and form a steam (gas) chamber containing both wells.
- Figure 17 shows how the process works. Steam is injected through the upper horizontal well and rises into the steam chamber. The steam condenses at/near the cool chamber walls (the bitumen interface) and releases latent heat to the bitumen and the matrix rock. Hot bitumen and condensed steam drain by gravity to the lower horizontal production well and are pumped (or conveyed) to the surface.
- Figure 18 shows how SAGD matures -
- a young steam chamber has oil drainage from steep sides and from the chamber top.
- the ceiling top of the net pay zone
- drainage from the chamber top ceases and the sides become flatter, so bitumen drainage slows down.
- Steam injection i.e. energy injection
- the steam/water interface is controlled to be between the steam injector and the horizontal production well. But when fluids move along the production well there is a natural pressure drop that will tilt the water/steam interface ( Figure 13). If the interface floods the steam injector, we reduce the effective length. If the interface hits the producer, we short circuit the process and produce some live steam, reducing process efficiency. With typical tubulars/pipes, this can limit well lengths to about 1000m.
- SAGD has another interesting feature. Because it is a saturated-steam process and only latent heat contributes directly to bitumen heating, if pressure is raised (higher than native reservoir pressure) the temperature of saturated-steam is also increased, Bitumen can be heated to a higher temperature, viscosity reduced and productivity increased. But, at higher pressures, the latent heat content of steam is reduced, so energy efficiency is reduced (SOR increases). This is a trade off. But, productivity dominates the economics, so most producers try to run at the highest feasible pressures.
- ISC In situ combustion
- a vaporizing zone Downstream of the combustion front, in order, is a vaporizing zone with oil distillate and superheated steam, a condensing zone where oil and steam condense and an oil bank that is "pushed" by the injectant gas toward a vertical production well.
- the vaporizing zone fractionates oil and pyrolyzes the residue to produce a "coke” that is consumed as the combustion fuel.
- FIG. 31 shows how wet combustion worked, using the same simple vertical well geometry as dry combustion. A liquid water zone precedes the combustion- swept zone, otherwise the mechanisms are similar to dry ISC as shown in Figure 24.
- the operator of a wet combustion process has to be careful not to inject water too early in the process or not to inject too much water, or the water zone can overtake the combustion front and quench HTO combustion.
- ISC using oxygen or enriched air was attempted in a few field projects.
- ISC(0 2 ) ISC(0 2 ) projects active in North America - 4 in the USA and 6 in Canada.
- the advantages of using oxygen were purported as higher energy injectivity, production of near-pure C0 2 gas as a product of combustion, some C0 2 solubility in oil to reduce viscosity, sequestration of some C0 2 , improved combustion efficiency, better sweep efficiency and reduced GOR for produced oil.
- the purported disadvantages of using oxygen were safety, corrosion, higher capital costs and LTO risks (Sarathi (1999), Butler (1991 )).
- bitumen ISC EOR processes are very difficult. New well geometries using horizontal wells, with short paths for bitumen recovery and perhaps a gravity drainage recovery mechanism, can improve the prospects for bitumen ISC EOR.
- COFCAW water + air/oxygen injection for ISC
- ISC using COFCAW and air or oxygen could create steam + oxygen or steam +C0 2 mixtures when water was vaporized in the combustion-swept zone prior to (or after) the combustion front.
- COFCAW works for vertical well geometries (eg. Parrish (1969)) because of the long distance between injector and producer and the ability to segregate liquid water from the combustion zone until it is vaporized.
- FIG. 30 shows production forecasts using steam + oxygen mixtures varying from 0 to 80% (v/v) oxygen. But, the steam/gas chamber was contained with no provision to remove non-condensable gases. So, back pressure in the gas chamber inhibited gas injection and bitumen production, using steam + oxygen mixtures, was worse than steam-only (SAGD) performance ( Figure 30). Also, there was no consideration of the corrosion issue for steam + oxygen injection into a horizontal well, nor was there any consideration of minimum oxygen flux rates to initiate and sustain HTO combustion using a long horizontal well for 0 2 injection.
- Pfefferle (2008) suggested using oxygen + steam mixtures in a SAGD process, as a way to reduce steam demands and to partially upgrade heavy oil. Combustion was purported to occur at the bitumen interface (the chamber wall) and combustion temperature was controlled by adjusting oxygen concentrations. But, as shown by Yang, combustion will not occur at the chamber walls. It will occur inside the steam chamber, using coke produced from residual bitumen as a fuel not bitumen from/at the chamber wall. Also, combustion temperature is almost independent of oxygen concentration (Butler, 1991 ). It is dependant on fuel (coke) lay down rates by the combustion/pyrolysis process. Pfefferle also suggested oxygen injection over the full length of a horizontal well and did not address the issues of corrosion, nor of maintaining minimum oxygen flux rates if a long horizontal well is used for injection.
- Pfefferle, W.C. "Method for CAGD Recovery of Heavy Oil” US Pat. 2007/0187094 Al, Aug. 16, 2007 describes - a process similar to SAGD to recover heavy oil, using a steam chamber.
- the first version injects a steam + oxygen mixture using a SAGD steam injector well.
- the second version injects oxygen into a new horizontal well, parallel to the SAGD well pair, but completed in the upper part of the reservoir.
- steam is injected into the reservoir from the upper SAGD well to limit access of oxygen to the lower SAGD producer.
- Pfefferle(2007) proposes combustion occurs at the chamber walls (i.e. the steam - cold bitumen interface) and that temperature of combustion can be controlled by changing oxygen concentrations. It is proposed to increase combustion temperatures at the chamber walls sufficiently to crack and upgrade the oil.
- oxygen injection is spread out over a long horizontal well.
- oxygen is also diluted with steam.
- oxygen-reservoir contact There is no consideration to limiting oxygen-reservoir contact to ensure and control oxygen flux rates.
- combustion temperature can be adjusted by changing the oxygen concentration (claims 2,7,9). This is not possible.
- Combustion temperature is controlled by the coke concentration in the matrix where combustion occurs. This has been confirmed by lab combustion tube tests. Combustion temperatures are substantially independent of oxygen concentration at the combustion site.
- Pfefferle,W.C. Method for In Situ Combustion of In-Place Oils
- US Pat. 7,581 ,587 B2 Sept. 1, 2009 describes a geometry for dry in situ combustion using a vertical well and a horizontal production well.
- the vertical well has a dual completion and is located near the heel of the production well.
- the lower completion in the vertical well is near the horizontal producer and is used to inject air for ISC.
- the concentric upper completion is near the top of the reservoir and is used to remove non-condensable gases produced by combustion.
- SAGDOX None of the SAGDOX versions described herein are for heel-to-toe processes. SAGDOX always has steam injection. Pfefferle doesn't discuss steam as an additive or as an option.
- a process to recover hydrocarbons from a hydrocarbon reservoir namely bitumen (API ⁇ 10; in situ viscosity > 100,000 c.p.)
- said process comprising; establishing a horizontal production well in said reservoir; separately injecting an oxygen-containing gas and steam continuously into the hydrocarbon reservoir to cause heated hydrocarbons and water to drain, by gravity, to the horizontal production well, the ratio of oxygen/steam injectant gases being controlled in the range from 0.05 to 1.00 (v/v). removing non-condensable combustion gases from at least one separate vent-gas well, which is established in the reservoir to avoid undesirable pressures in the reservoir.
- steam is injected into a horizontal well of the same length as the production well, and parallel to said production well with a separation of 4 to 10 m, directly above the production well using for example a typical SAGD geometry.
- Preferably vertical oxygen injection and vent gas wells are established in the reservoir.
- said vertical wells for oxygen injection and vent gas removal are not separate wells but tubing strings are inserted within the existing horizontal steam injection well proximate the vertical section of the well, and packers are used to segregate oxygen injection and/or vent -gas venting.
- oxygen-containing gas has an oxygen content of 95 to 99.9% (v/v).
- oxygen-containing gas is enriched air with an oxygen content of 20 to 95% (v/v).
- oxygen-containing gas has an oxygen content of 95 to 97% (v/v).
- the oxygen-containing gas is air.
- said process further comprises an oxygen contact zone portion of the well within the reservoir less than 50m long and said zone being implemented by aspects therein selected from perforations, slotted liners, and open holes.
- the horizontal wells are part of an existing SAGD recovery process and incremental SAGDOX wells, for oxygen injection and for non-condensable vent gas removal, are added subsequent to SAGD operation.
- said process further comprises a SAGDOX process that is started up by operating a horizontal well pair in the SAGD process and subsequently circulating steam in incremental SAGDOX wells until all the wells are communicating, prior to starting oxygen injection and vent gas removal.
- the SAGDOX process is started by circulating steam in all wells until all the wells are communicating, prior to starting oxygen injection and vent gas removal.
- a SAGDOX process is controlled and operated by steps selected from: i. Adjusting steam and oxygen flows to attain a predetermined; oxygen/steam ratio and energy injection rate targets,
- Steam trap control also called sub cool control for steam EOR or SAGDOX is used to control the production well rate so that only liquids (bitumen and water) are produced , not steam or other gases. The way this is done is as follows:
- the production well fluid production rate is controlled (pump or gas lift rates) so that the average T (or heel T) is less than the saturated steam T calculated, usually by 10 to 20 C of sub cool.
- oxygen/steam ratios start at about 0.05 (v/v) and ramp up to about 1.00 (v/v) as the process matures.
- oxygen/steam ratio is between 0.4 and 0.7 (v/v).
- the horizontal well length of the pattern is extended when compared to an original SAGD design.
- the horizontal well length extends beyond 1000 m.
- the process further comprises conversion of a mature SAGD project whereat adjacent patterns are in communication, to a SAGDOX project using 3 adjacent patterns where the steam injector of the central pattern is converted to an oxygen injector and the injector wells of the peripheral patterns are continued to be used as steam injectors.
- the oxygen/steam ratio is between 0.05 and 1.00 (v/v).
- the gases are produced, as separate streams, by an integrated ASU: Cogen Plant.
- the oxygen purity in the oxygen-containing gas is between 95 and 97% (v/v), iii.
- Steam and oxygen are produced in an integrated ASU: Cogen plant,
- the oxygen contact zone with the reservoir is less than 50 m.
- the oxygen injection well is no more than 50 m. of contact with the reservoir, to avoid oxygen flux rates dropping to less than that needed to start ignition or to sustain combustion.
- steam provides energy directly to the reservoir and oxygen provides energy by combusting residual bitumen (coke) in the steam chamber whereat the combustion zone is contained; residual bitumen being heated, fractionated and finally pyrolyzed by hot combustion gases, to make coke, the actual fuel for combustion.
- bitumen and water production well is controlled assuming saturated conditions using steam-trap control, without producing significant amounts of live steam, non-condensable combustion gases or unused oxygen.
- the steam-swept zone of the steam chamber in a SAGDOX process further comprises;
- bitumen drains, by gravity, from a hot bitumen bank and from a bitumen interface
- the fuel for combustion and the source of bitumen in the hot bitumen zone is residual bitumen in the steam-swept zone, combustion being contained inside of the steam chamber and preferably wherein hot combustion gases transfer heat to bitumen, in addition to steam mechanisms.
- carbon dioxide produced as a combustion product, can dissolve into bitumen and reduce viscosity.
- oxygen purity is reduced to substantially the 95-97% range whereat energy needed to produce oxygen from an ASU drops by about 25% and SAGDOX efficiencies improve significantly.
- the SAGDOX process uses water directly as steam is injected, but it also produces water directly from 2 sources, namely water produced as a combustion product and connate water vaporized in the combustion-swept zone.
- the maximum oxygen/steam ratio is 1.00 (v/v) with an oxygen concentration of 50.0%.
- the combustion front will move further away from the oxygen injector and requires increasing oxygen rates to sustain High Temperature Oxidation reactions.
- the SAGDOX gas mix is between 20 and 50% (v/v), oxygen in the steam/oxygen mixture.
- the SAGDOX gas mix is 35% oxygen (v/v), oxygen in the steam/oxygen mixture.
- the oxygen injection point needs to be preheated to about 200°C so oxygen will spontaneously react with residual fuel.
- Figure 1 is a SAGD Geometry.
- Figure 2 is a SAGD Production Simulation.
- Figure 3 is a SAGDOX Geometry 1.
- Figures 3A through 3E provide additional details of SAGDOX geometry regarding Figure 3.
- Figure 4 is a SAGDOX Bitumen Saturation Schematic.
- Figure 5 is a SAGDOX Geometry 2.
- Figure 6 is a SAGDOX Geometry 3.
- Figure 7 is a SAGDOX Geometry 4.
- Figure 8 is a SAGDOX Geometry 5.
- Figure 9 is a SAGDOX Geometry 6.
- Figure 10 is a SAGDOX Geometry 7.
- Figure 1 1 is a SAGDOX Geometry 8.
- Figure 12 is a SAGDOX Geometry 9.
- Figure 13 is a SAGD Hydraulic Limits.
- Figure 14 is a SAGD/SAGDOX Pattern Extension.
- Figure 15 is a SAGDOX - 3 well-pair pattern.
- Figure 16 is a Cogen Electricity Production (Cogen/ASU).
- Figure 16A is a schematic representation of an integral ASU & COGEN for a SAGDOX process.
- Figure 17 is a SAGD Steam Chamber.
- Figure 18 is SAGD stages.
- Figure 19 is a Residual Bitumen in Steam-Swept Zones.
- Figure 20 is a SAGD Production History.
- Figure 21 is SAGD Technology.
- Figure 22 is the THAI Process.
- Figure 23 is COSH, COGD Processes.
- Figure 24 is an In situ Combustion Schematic.
- Figure 25 is ISC Minimum Air Flux Rates.
- Figure 26 is CSS using Steam + C0 2 : Production.
- Figure 27 is CSS using Steam + C0 2 : Gas Retention (9% C0 2 in steam mix).
- FIG. 28 is Steam + Oxygen Combustion Tube Tests I.
- Figure 29 is Steam + Oxygen Combustion Tube Tests II.
- Figure 30 is SAGD using Steam + Oxygen mixes.
- FIG. 31 is a Wet ISC. DETAILED DESCRIPTION OF THE INVENTION
- Production well (bitumen + water) pressure gradients can limit SAGD productivity and energy (steam) injectivity.
- SAGD productivity For a typical horizontal well length of 1000 m., using a typical tubing/pipe sizes fluid productivity is limited to about 4000 bbl/d, otherwise the liquid/gas interface (steam/water) can flood the toe of the steam injector and/or steam can break through to the producer heel.
- the effective well length is limited to about 1000 m, so the pattern size is also limited. If the well separation is increased from say 5 to 10 meters, the effective well length (or injectivity) can be increased, but the start up period is prolonged significantly. If well/pipe sizes are increased to increase well length or injectivity, capital costs and heat losses are increased.
- Carbon dioxide emissions from SAGD steam boilers are significant (about 0.08 tonnes C0 2 /bbl bitumen).
- the emitted C0 2 is not easily captured for sequestration. It is diluted in boiler flue gas, or in cogen flue gas.
- SAGD is a steam-only, saturated-steam process. Temperature is determined by operating pressure
- SAGD cannot mobilize connate water by vaporization.
- SAGD cannot reflux steam/water in the reservoir. It is a once-through water process.
- Oxygen needs to be injected, at first, into (or near to) a steam- swept zone, so combustion of residual fuel components occurs and injectivity is not a serious limit.
- the zone also needs to be preheated (at start-up) so spontaneous HTO ignition occurs (not LTO).
- the well configuration should ensure that oxygen (and steam) is mostly contained within the well pattern volume.
- SAGD is a process that uses 2 parallel horizontal wells separated by about 5 m., each up to about 1000 m. long, with the lower horizontal well (the bitumen + water producer) about 2 to 8 m. above the bottom of the reservoir (see Figure 1). After a startup period where steam is circulated in each well to attain communication between the wells, steam is injected into the upper horizontal well and bitumen + water are produced from the lower horizontal well.
- SAGDOX is a bitumen EOR process using horizontal wells, similar to SAGD, for steam injection and for bitumen + water production, with extra vertical wells to inject oxygen gas and to remove non-condensable combustion gases (Figure 3). Steam and oxygen are injected separately and continuously into a bitumen reservoir as sources of energy.
- Table 1 summarizes properties of steam/oxygen mixes, assuming 1000 BTU/lb steam and 480 BTU/SCF oxygen (Butler, 1991) used for in-situ combustion. The heat assumptions include heat released directly to the reservoir and heat recovered from produced fluids, assuming that produced fluid heat recovery is useful.
- the reservoir is preheated by steam either by conducting a SAGD process in the horizontal wells or by steam circulation in the SAGDOX extra wells, until communication is established between the wells. Then oxygen and steam are introduced in separate or segregated injectors, otherwise corrosion can be a problem.
- the oxygen injection well (or segregated section) should be no more than 50 m. of contact with the reservoir, otherwise oxygen flux rates can drop to less than that needed to start ignition or to sustain combustion (Figure 25).
- Steam provides energy directly to the reservoir.
- Oxygen provides energy by combusting residual bitumen (coke) in the steam chamber.
- the combustion zone is contained within the steam chamber.
- Residual bitumen is heated, fractionated and finally pyrolyzed by hot combustion gases, to make coke that is the actual fuel for combustion.
- a gas chamber is formed containing injected steam, combustion gases, refluxed steam and vaporized connate (formation) water.
- Heated bitumen drains from the gas chamber (residual bitumen) and from the chamber walls.
- Condensed steam drains from the saturated steam area and from the chamber walls. Condensed water and bitumen are collected by the lower horizontal well and conveyed (or pumped) to the surface. Please see Figures 3A through D in this regard.
- Figure 3 shows one geometry suitable for SAGDOX.
- a SAGD horizontal well pair (wells 1 and 2) has been augmented by 3 new vertical SAGDOX wells - 2 wells to remove non-condensable combustion gases (wells 3 and 4) and a separate oxygen injection well (well 5).
- the vertical gas- remover wells are on the pattern boundary and are shared by neighbor patterns (i.e. only 1 net well).
- An oxygen injection well (well 5) is near the SAGD toe, and completed low enough in the pay zone to ensure that oxygen injection is into a steam-swept zone.
- the produced gas removal wells are operated separately to control conformance and reservoir pressure, while minimizing production of steam and/or unused oxygen.
- Oxygen and steam injection are controlled to attain oxygen/steam ratio targets (oxygen "concentration") and energy injection rates.
- the bitumen + water production well is controlled assuming saturated conditions using steam-trap control, without producing significant amounts of live steam, non-condensable combustion gases or unused oxygen.
- the SAGDOX process may be considered as a SAGD process using wells 1 and 2 and a simultaneous in situ combustion (ISC) process using wells 3, 4 and 5.
- ISC simultaneous in situ combustion
- SAGDOX creates some energy in a reservoir by combustion.
- the "coke” that is prepared by hot combustion gases fractionating and pyrolyzing residual bitumen, can be represented by a reduced formula of CH. 5 . This ignores trace components (S, N, 0...etc.) and it doesn't imply a molecular structure, only that the "coke” has a H/C atomic ratio of 0.5.
- CO in the product gases is about 10% of the carbon combusted
- combustion temperature is controlled by "coke” content.
- HTO combustion T is between about 400 and 800°C (Yang (2009(2))).
- SAGDOX injects both steam and oxygen gas. Each can deliver heat to a bitumen reservoir.
- Table 1 shows the properties of various steam + oxygen "mixtures”. The term “mixture” doesn't imply that we inject a mixture or that we have expectations of good mixing in the reservoir. It is only a convenient way to label the net properties of separately injected steam and oxygen gases.
- SAGDOX (z), where z is the percentage concentration (v/v) of oxygen gas in the steam + oxygen "mixture”. The mechanisms of SAGDOX are important factors to assess expected productivity of the process.
- Figure 4 shows a plot of bitumen saturation, perpendicular to the horizontal well plane, about half-way in the net pay zone, for a mature SAGDOX process, based on a simulation (Yang, (2009(1)). The plot shows the extra process mechanisms of SAGDOX compared to SAGD.
- SAGDOX has a combustion-swept zone with zero residual bitumen and no connate water, a combustion front, a bank of bitumen heated by combustion gases, a superheated steam zone, a saturated-steam zone, and a gas/steam bitumen interface (chamber wall) where steam condenses and releases latent heat.
- Bitumen drains, by gravity, from the hot bitumen bank and from the bitumen interface. Water drains, by gravity, from the saturated steam zone and from the bitumen interface. Energy (heat) in the hot bitumen and in the superheated-steam zone is partially used to reflux some steam.
- the hot bitumen bank appears as a spike; in two dimensions, for a homogeneous reservoir, it appears as a circle (halo), and; in three dimensions, it appears as a sphere.
- the fuel for combustion and the source of bitumen in the hot bitumen zone is residual bitumen in the steam-swept zone. The combustion is contained inside of the steam chamber.
- Water/steam is an important factor for heat transfer. Compared to hot non-condensable gases, steam has two important advantages to transfer heat - it contains much more energy because of latent heat and when it condenses it creates a transient-low pressure area to help draw in more steam.
- Non-condensable gases can block steam access to the cold bitumen interface
- Extra steam in addition to injected steam, is produced by vaporizing connate water and as a product of combustion.
- Hot combustion gases can transfer heat to bitumen, in addition to steam mechanisms.
- a hot bitumen bank is created near the combustion front ( Figure 4), sourcing residual bitumen left behind by the steam-swept zone. This bitumen can drain to the production well, add to productivity and it can contribute to steam reflux.
- Carbon dioxide produced as a combustion product, can dissolve into bitumen and reduce viscosity.
- Top-down gas drive and solution gas drive mechanisms can add to productivity.
- Non condensable gas accumulates at/near the ceiling zone of the gas chamber. This can insulate the ceiling and reduce heat losses.
- Table 2 presents a scenario whereby for the same bitumen productivity, the energy to oil ratio (ETOR) for SAGDOX increases as the oxygen content increases (or as the steam content decreases) - from 1.18 MMBTU/bbl for SAGD to 1.623 MMBTU/bbl for SAGDOX(75). This scenario is used for various comparisons (Tables) herein.
- ETOR energy to oil ratio
- FIG 3 shows a simple well configuration that is suitable for SAGDOX.
- the SAGD well pair (well 1 and 2) is conventional, with parallel horizontal wells with lengths of 400-1000 m. and separation of 4-6 m.
- the lower horizontal well is 2-8 m. above the bottom of the bitumen reservoir.
- the upper well is a steam injector and the lower horizontal well is a bitumen + water producer. Bitumen and condensed steam drain to the lower well, by gravity, from a steam chamber formed above the steam injector (1).
- the oxygen injector (5) is a vertical well that is not at the end of the pattern, but it is about 5 to 20 m, in from the end.
- the perforated zone is less than 50m long.
- Two produced gas removal wells (3 and 4) are on the pattern lateral boundaries toward the heel area of the horizontal well pair.
- the wells are completed near the top of the reservoir (1 to 10 m. below the ceiling).
- This configuration enables separate control of oxygen and steam injection, separation of oxygen/steam and mixing in the reservoir, oxygen containment in the pattern.
- Figure 9 shows an oxygen injector (6) near the end (toe) of the pattern and a central well (5) that initially can operate as a produced gas removal well and after the process is established it can be converted to a second oxygen injector for better oxygen conformance control.
- Figure 1 1 shows a packer in the steam injector (well 1) to segregate the well toe for oxygen injection in a separate oxygen string.
- the toe of the horizontal injector well can be sacrificed to corrosion, if the packer is not a good seal, with little consequence.
- Figure 12 shows another packer segregating part of the vertical rise section of the steam injector (well 1) for produced gas removal.
- This version of the SAGDOX has no new SAGDOX wells. Oxygen injection and produced gas removal are small volume applications and need not occupy a lot of the steam injector capacity, especially for lower oxygen concentrations in the steam + oxygen mix.
- ETOR(steam) The steam component (ETOR(steam)) will be similar to SAGD. If we assume our ASU plant uses 390 kWh/tonne 0 2 (99.5% purity) and that electricity is produced from a gas-fired combined-cycle power plant at 55% efficiency, then for every MMBTU of gas consumed in the power plant, the oxygen produced (at 480 BTU/SCF) releases 5.191 MMBTU of combustion energy to the reservoir.
- Table 3 shows the efficiencies for various SAGDOX processes using the energy consumptions of Table 2. The following points are noteworthy:
- the SAGD energy loss is 26%.
- the equivalent loss for SAGDOX is from 6 to 16%, depending on oxygen content. This is an improvement of 10 to 20% or a factor of 1.6 to 4.3.
- Incineration - Produced gas may (probably) contain some sour gas components (eg.
- Table 4 shows expected C0 2 emissions for SAGD and various versions of SAGDOX.
- Table 5 show expected C0 2 emissions if the pure C0 2 streams are captured or sequestered on-site. The following comments are noteworthy:
- SAGDOX is the lowest C0 2 emitter, from 19 to 58% of SAGD emissions.
- CH 0 5 is the reduced formula for coke and hydrogen produced was from shift reactions downstream of the combustion zone (favored by excess steam).
- the combustion water make is 0.140 SCF/SCF 0 2 or .0351 bbl/MMBTU (0 2 ).
- connate water occupies 20% of the pore space.
- the steam swept zone with 15 to 20% residual bitumen per barrel of bitumen produced our connate water is 0.308 to 0.333 bbl/bbl bit.
- Table 6 shows SAGDOX water make, assuming 20% residual bitumen in the steam swept zone and all injected steam is produced as water.
- SAGDOX produces 20 to 260% excess water (excess to steam injected). No make-up water should be needed for SAGDOX steam generators.
- SAGD steam (energy) injection is usually controlled by a target pressure for a reservoir (i.e. we can increase steam injection rates until we hit a target pressure). This may work well if the reservoir has no "leaks” and we can increase pressures beyond the original native reservoir pressures. But, if we have a "leaky” reservoir or even if we have a contained chamber, our injection rates may be limited by hydraulic effects in our production well. The bitumen and water flow in the horizontal production well cannot create pressure drops that cause the steam/water interface to tilt and flood the toe of the steam injector or to allow gas/steam to enter near the heel of the production well (Figure 13). This can create a fundamental limit on energy injectivity (steam) for SAGD. Depending on actual well geometry and reservoir characteristics, this limit may supersede our pressure target limit.
- SAGDOX can have the same behavior. The process still produces a bitumen and water mix in the lower horizontal well. But, the limits on energy injection are changed because a significant part of the energy injected is due to oxygen, which produces little water compared to steam. Also, if we have separate wells to remove produced gases (e.g. Figure 3), we can control pressure by produced gas removal rates. So, if our energy injectivity is limited by fluid flows in the production well, Table 10 shows potential bitumen productivity increases, assuming fluid flow rate in the production well is constant. Extra bitumen productivity potential varies from 21 to 148% for our preferred oxygen concentration range (5 to 50%(v/v)). Our preferred case (SAGDOX (35)) can more than double bitumen production.
- steam (energy) injectivity for SAGD can be limited by one of two factors - the pressure in the reservoir or the hydraulic limits of the production well. If the pressure drop in the production well is the limiting factor, and if we convert SAGD to SAGDOX we can increase energy injectivity because per unit energy injected SAGDOX produces less water and less fluid in the production well than does SAGD.
- reservoir pressure is the limiting factor we cannot increase energy injectivity per unit length of our horizontal producer, but we can certainly increase the length of the producer without hitting the hydraulic limits and we can also thus increase bitumen production and increase reserves (by increasing the pattern size).
- Table 10 shows the expected production volumes (water + bitumen), per unit bitumen production, for each of our SAGDOX cases compared to SAGD.
- the production volume decreases as the oxygen content in steam increases, even including connate water production and water produced directly by combustion.
- water + bitumen volumes decrease by 18 to 60% as we progress from SAGDOX (5) to SAGDOX (50) mixtures. By itself, this can reduce pressure drops in the production well considerably and enable extended well lengths, if desired.
- Pressure drop is a strong function of volume throughput (much stronger than a linear relationship).
- bitumen is essentially immobile in a reservoir. Most bitumen reservoirs have no initial gas injectivity, so it is difficult (impossible) to initiate an EOR process with a combustion component without pre-steaming to heat and remove bitumen to create some gas injectivity.
- SAGD can accomplish this objective.
- SAGDOX can work on a heavy oil reservoir (where there is some initial gas injectivity) the preference is a bitumen reservoir, where SAGDOX is initiated using SAGD methods.
- bitumen For the purposes of this document we will define "bitumen” as ⁇ 10 API gravity and ⁇ 1 million c.p. in situ viscosity. Heavy oil is then defined as between 10 and 20 API and 1 million c.p.
- Oxygen is different in its effectiveness compared to steam. Steam has a positive effect (adding heat) no matter how low the flux rate is or no matter how low the concentration.
- Oxygen and steam mixtures are very corrosive particularly to carbon steel.
- the metallurgy of a conventional SAGD steam injector well could not withstand a switch to steam and oxygen mixtures without significant corrosion that could (quickly) compromise the well integrity. Corrosion has been cited as one of the issues for ISC projects that used enriched air or oxygen (Sarathi (1999)).
- the SAGDOX preferred embodiment solution to these issues is to inject oxygen and steam in separate wells to minimize corrosion.
- the injector well (either a separate vertical well or the segregated portion of a horizontal well) should have a maximum perforated zone (or zone with slotted liners) of about 50 m so that oxygen flux rates can be maximized.
- a maximum perforated zone or zone with slotted liners
- Oxygen concentration in steam/oxygen injectant mix is a convenient way to quantify oxygen levels and to label SAGDOX processes (e.g. SAGDOX (35) is a process that has 35% oxygen in the mix). But, in reality we expect to inject oxygen and steam as separate gas streams without any real expectations of mixing in the reservoir or in average or actual in situ gas concentration. Rather than controlling "concentrations", in practice we would control to flow ratios of oxygen/steam (or the inverse). So SAGDOX (35) would be a SAGDOX process where the flow ratio of oxygen/steam was 0.5385(v/v).
- HTO combustion starts to become unstable. It becomes more difficult to attain minimum oxygen flux rates to sustain HTO, particularly for a mature SAGDOX process where the combustion front is far away from the injector.
- the preferred range for oxygen/steam ratios is 0.05 to 1.00 (v/v) corresponding to a concentration range of 5 to 50% (v/v) of oxygen in the mix.
- a separate economic study shows the preferred range of oxygen/steam ratios to be about 0.4 to 0.7 (v/v) or an average concentration of about 35% (v/v) oxygen in the mix.
- SAGDOX (35) is our preferred case.
- Oxygen is more cost-effective than steam as a way to inject energy (heat) into a bitumen reservoir.
- all-in oxygen costs are about one third the equivalent steam costs. So, at least ultimately, there is an economic incentive to maximize the oxygen concentration in our SAGDOX gas mixture.
- the combustion front will move further away from the oxygen injector. In 3-D, the front will appear as an expanding sphere. To sustain oxygen flux rates at the sphere surface we may require increasing oxygen rates to sustain HTO reactions.
- oxygen injection can produce back pressure (injectivity) constraints with a build-up of non-condensable combustion gases.
- a cryogenic air separation unit can produce oxygen gas with a purity variation from about 95 to 99.9(v/v)% oxygen concentration.
- the higher end (99.0-99.9%) purity produces chemical grade oxygen.
- the lower end of the range (95-97%) purity consumes about 25% less energy (electricity) per unit oxygen produced (Praxair, (2010)).
- the "contaminant" gas is primarily argon. Argon and oxygen have boiling points that are close, so cryogenic separation becomes difficult and costly, if argon and nitrogen in air remain unseparated, the resulting mixture is 95.7% "pure” oxygen (see Table 8).
- argon is an inert gas that should have no impact on the process.
- the range of oxygen purity is 95 to 99.5% (v/v) purity.
- the preferred oxygen concentration is 95-97% purity (i.e. the least energy consumed in ASU operations).
- Oxygen and steam for SAGDOX can be produced in separate steam generator (boiler) and ASU facilities.
- Steam generators (boilers) require fuel - usually natural gas - and ASU requires electricity to operate.
- a cogen plant can produce steam and electricity, with steam used for SAGDOX steam and electricity used for ASU oxygen production. The net effect is to use natural gas to produce steam and oxygen in volumes needed for SAGDOX.
- the advantages of the integrated cogen ASU plant are reduced cost, improved energy efficiency, improved reliability (compared to grid power purchase) and reduced surface footprints.
- Figure 16A is a schematic representation of an integral ASU & COGEN for a SAGDOX process.
- the cogen plant has 20% waste energy, 80% of the inlet natural gas is converted to either steam or electricity.
- Oxygen heat release in the reservoir is 480 BTU/SCF (Butler, (1991)).
- our preferred SAGDOX gas mix is between 20 and 50% (v/v), oxygen in the steam/oxygen mixture.
- Communication is established between all wells, or at least between one oxygen injector, one produced gas removal well and the horizontal well pair. Steam circulation or steam injection is used for SAGDOX vertical wells. (6) The oxygen flux rate is high enough to initiate and sustain HTO combustion in situ.
- the preferred steady-state operation strategy includes the following:
- Oxygen helps steam by the following:
- Extra steam is created by oxygen heat via oxidation of hydrocarbons, vaporization of connate water and reflux of water/steam.
- Non-condensable combustion gases migrate to the top of the pay zone and insulate the ceiling to reduce heat losses.
- Non-condensable gases can increase lateral growth rates of the gas (steam) chamber).
- Steam can also help oxygen/combustion by the following: i. Steam pre-heats the reservoir so oxygen will auto-ignite to start combustion.
- LTO Low temperature oxidation
- HTO can produce acids that cause emulsions and treating problems.
- LTO also releases less heat per unit 0 2 consumed than HTO.
- Oxygen gas is more effective than air. In air, oxygen is diluted by nitrogen that is not beneficial in the reservoir. Although compressed air may be less costly than oxygen gas, if the produced gas must be treated (e.g. incinerated) before venting, air costs, all- in, can easily exceed oxygen costs
- SAGDOX can have higher energy injectivity than SAGD.
- Total ETOR is prorated based on 0 2 content in SAGDOX, between SAGD and 1.375x SAGD for SAGDOX (75).
- Incinerator C0 2 213 SCF/MMBTU (0 2 ) in reservoir.
- Reflux % % of total steam.
Abstract
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BR112014009436A BR112014009436A2 (en) | 2011-10-21 | 2012-09-27 | oxygen-assisted gravity assisted steam drainage processes |
CN201280063455.7A CN104011331B (en) | 2011-10-21 | 2012-09-27 | With the SAGD method of oxygenation |
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US61/549,770 | 2011-10-21 | ||
US13/543,012 US9828841B2 (en) | 2011-07-13 | 2012-07-06 | Sagdox geometry |
US13/543,012 | 2012-07-06 |
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US4860827A (en) * | 1987-01-13 | 1989-08-29 | Canadian Liquid Air, Ltd. | Process and device for oil recovery using steam and oxygen-containing gas |
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US20080264635A1 (en) * | 2005-01-13 | 2008-10-30 | Chhina Harbir S | Hydrocarbon Recovery Facilitated by in Situ Combustion Utilizing Horizontal Well Pairs |
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US20100212894A1 (en) * | 2009-02-20 | 2010-08-26 | Conocophillips Company | Steam generation for steam assisted oil recovery |
RU2425969C1 (en) * | 2010-08-18 | 2011-08-10 | Открытое акционерное общество "Татнефть" им. В.Д. Шашина | Development method of high-viscous oil deposit |
-
2012
- 2012-09-27 CA CA2791323A patent/CA2791323A1/en not_active Abandoned
- 2012-09-27 WO PCT/CA2012/000899 patent/WO2013056342A1/en active Application Filing
Patent Citations (8)
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US4573530A (en) * | 1983-11-07 | 1986-03-04 | Mobil Oil Corporation | In-situ gasification of tar sands utilizing a combustible gas |
US4682652A (en) * | 1986-06-30 | 1987-07-28 | Texaco Inc. | Producing hydrocarbons through successively perforated intervals of a horizontal well between two vertical wells |
US4860827A (en) * | 1987-01-13 | 1989-08-29 | Canadian Liquid Air, Ltd. | Process and device for oil recovery using steam and oxygen-containing gas |
US5456315A (en) * | 1993-05-07 | 1995-10-10 | Alberta Oil Sands Technology And Research | Horizontal well gravity drainage combustion process for oil recovery |
US20080264635A1 (en) * | 2005-01-13 | 2008-10-30 | Chhina Harbir S | Hydrocarbon Recovery Facilitated by in Situ Combustion Utilizing Horizontal Well Pairs |
US20090188667A1 (en) * | 2008-01-30 | 2009-07-30 | Alberta Research Council Inc. | System and method for the recovery of hydrocarbons by in-situ combustion |
US20100212894A1 (en) * | 2009-02-20 | 2010-08-26 | Conocophillips Company | Steam generation for steam assisted oil recovery |
RU2425969C1 (en) * | 2010-08-18 | 2011-08-10 | Открытое акционерное общество "Татнефть" им. В.Д. Шашина | Development method of high-viscous oil deposit |
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