CA1246996A - Multiple zone oil recovery process - Google Patents
Multiple zone oil recovery processInfo
- Publication number
- CA1246996A CA1246996A CA000492366A CA492366A CA1246996A CA 1246996 A CA1246996 A CA 1246996A CA 000492366 A CA000492366 A CA 000492366A CA 492366 A CA492366 A CA 492366A CA 1246996 A CA1246996 A CA 1246996A
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Abstract
MULTIPLE ZONE OIL RECOVERY PROCESS
Abstract Viscous oil is recovered from a subterranean reservoir having two or more vertically separated oil bearing, permeable zones separated by impervious layers such as shale. A steam drive process is employed in each permeable layer, using ordered patterns of injection and production wells with the pattern in each layer staggered with respect to the pattern in the adjacent layer or layers. The injection and production wells are singly completed.
The use of staggered well patterns in this manner produces a greater recovery of oil at an earlier time than a regular, superimposed pattern of wells in each layer.
Abstract Viscous oil is recovered from a subterranean reservoir having two or more vertically separated oil bearing, permeable zones separated by impervious layers such as shale. A steam drive process is employed in each permeable layer, using ordered patterns of injection and production wells with the pattern in each layer staggered with respect to the pattern in the adjacent layer or layers. The injection and production wells are singly completed.
The use of staggered well patterns in this manner produces a greater recovery of oil at an earlier time than a regular, superimposed pattern of wells in each layer.
Description
MULTIPLE ZONE OIL RECOVERY PROCESS
. _ This invention relates to the recovery of oil from subterranean, oil-bearing formatîons and more particularly, to the recovery of oil from subterranean formations containing heavy oil in two or more zones which are separated by an impermeable barrier.
A number of different thermal recovery processes have been used or proposed for producing heavy or viscous oils from subterranean formations such as tar sands. Of these processes, those employing steam injection form one readily definable type;
steam injection processes in turn, are basically of two types, being either of the single well injection or "huff and puff" type or of the steam drive type. The steam drive processes operate by injecting steam through one or more injection wells into the formation and producing the formation fluids from one or more production wells which are situated at a horizontal distance or offset from the injection well or wells. As the steam enters the formation through the injection wells, the heat transferred to the Formation by the steam lowers the viscosity of the formation oil, improving its mobility. In addition, the continued injection of the steam provides a driving force for displacing the oil towards the production well. Other effects such as visbreaking may occur, depending upon the temperature of the steam.
One of the problems associated with steam drive recovery processes is the loss of heat by conduction into non-produc-tive zones including the strata above and below the producing interval and various measures have been proposed for minimizing thermal losses.
In certain oil bearing -Formations, there may be a number of vertically separated oil bearing strata separated by layers of impervious material such as shale. These shale layers may prevent or at least, substantially restrict, vertical fluid flow between the ~lf~ 't3~
layers and therefore in formations of this kind, it may be necessary to inject steam into each of the layers if complete recovery is to be ensured. It is possible to reduce the thermal losses by employing a countercurrent flow of the steam in adjacent zones, as described in U.S. Patent No. 3,180,413. In the recovery process described in this patent, two multiply completed wells are sunk into the two adjacent strata separated by the shale layer and steam is injected at one well into one of the layers with production being taken out at the other well in the same layer. In the adjacent layer, the direction of fluid flow is reversed so that the steam flow is countercurrent in the two layers, to permit the utilization of thermal energy which would otherwise be lost without contributing to the recovery process.
Although the recovery process described in U.S. 3,180,413 has a number of advantages, there are also disadvantages. First, the wells require to be multiply completed so that each well may be used for both injection and production purposes, albeit in different, vertically separated zones of the same reservoir and second, the use of a single, multiply completed well for injection and production purposes may have an undesirable effect upon the produced fluids as they are brought to the surface. For example, if particularly high temperature steam is being used as the injection fluid, the produced fluids may be vaporized or pyrolyzed in the production flow passages and this may give rise to handling problems at the surface. Other problems may arise from the pressure differentials between the injection and production streams in multiply completed wellso leaks around the packers and the cement may occur to the detriment of process efficiency. It would, therefore, be desirable to avoid the use of multiply completed wells without altogether losing the advantages of countercurrent steam flow recovery.
According to the present invention a method has been devised for the recovery of oil from subterranean reservoirs which have two or more vertically separated oil bearing, permeable zones separated by impervious layers such as shale layers, which method avoids the use oF multiple well completions but minimizes the thermal losses which occur with concurrent steam flow techniques.
According to the present invention, ~urthermore, the method for recovering the viscous oil from a subterranean reservoir having upper and lower oil bearing permeable zones separated by an impervious layer comprises (l) injecting steam through a first injection well into the upper zone and producing fluids including oil from a first production well in the upper zone which is situated at a horizontal distance from the first injection well; and (2) injecting steam into the lower zone through a second injection well which is situated at a horizontal distance from the First injection well and producing fluids, including oil from a second production well in the lower zone which is situated at a horizontal distance from the second injection well.
The method of the present invention is, of course, applicable to reservoirs which have more than two vertically separated production intervals and in such cases, each adjacent pair of zones is produced by the same technique.
In practice, of course, more than one injection well and more than one production well will invariably be used in order to cover the entire producing field and to maximize recovery. The wells may be arranged in any convenient pattern such as in straight lines, for a line drive flooding process, or in conventional patterns such as five spot, inverted five spot, seven spot or inverted seven spot. Regardless of the nature of the pattern, the injection and production wells in any one layer are arranged in a pattern which is staggered with respect to that oF the next adjacent layer. This has the result that the steam flow in each two adjacent layers proceeds partly by concurrent flow and partly by countercurrent flow.
~ ~f$,~
The present invention, therefore, in one aspect, resides in a method for the recovery of oil from a subterranean reservoir having upper and lower oil bearing, permeable zones separated by an impervious layer, comprising injecting steam into thP upper and lower zones through patterns of injection wells which extend respectively into the upper and lower zones and producing fluids including oil from patterns of production wells which extend respectively into the upper and lower zones, the injection and production wells in each pattern in the upper and lower zones being horizontally separated from one another, with the patterns of injection wells being staggered with respect to one another in the two zones and the patterns of production wells being staggered with respect to one another in ths two zones, and causir,g the steam flow in said zones to proceed partly in concurrent fashion and partly in countercurrent ashion.
In another aspect, the present invention resides in a method for recovering ~iscous oil from a subterranean reser~oir having an upper permeable zone and a lower permeable zone, each of said permeable zones being oil bearing and separated by ~n impermeable layer, which comprises (1) in~ecting steam through a first pattern of injection wells axtending from the surface of the earth into the upper zone and producing fluids including oil from a first pattern of production wells extending from the surface o the earth into the llpper zone, each of which is at a horizontal distance from the injection wells in the first pattern; (2) in~ecting steam into the lower zone through a second pattern of injection wells each of which is situated at a horizontal distance from the wells of the first pattern of injection wells; (3) controlling the steam flow in said zones 80 that said steam flow proceeds partly in concurrent fashion and partly in countercurrent fashion; and (4) producing fluids including oil from a second pattern of production wells in the lower zone, each of which is at a ~J~ 6 - 4a -horizontal distance from the injection wells in said second pattern of injection wells.
The invention is better understood by refe~ence ~o the accompanying dr~wings, wherein:
Fiyure 1 is a vertical section in a simplified schematic form of a subterranean oil reservoir with uppex and lower oil bearing formations with staggered steam drive well patterns;
Figure 2 is a simplified vertical section of a three layer subterranean reservoir using staggered well patterns; and Figure 3 is a graph showiny the respective oil recoveries obtained with a staggered pattern of wells as in Figure 1 and a regular pattern of wells.
Figure 1 shows a simplified vertical section of a subterranean oil reservoir having an upper, oil bearing, permeable zone 10 and a lower, oil bearing, permeable zone 20 separated by a substantially impermeable shale layer S, underlying overburden 0. A
number of injection wells I-ll and I-12 extend into upper layer 10 from the surface of the earth and a number of separate injection wells I-21 and I-22 extend into lower zone 20 from the surface of the earth. Production wells P-ll, P-21 and P-22 extend into the upper and lower zones at horizontal distances or offsets from the injection wells in their respective zones. In addition, the injection wells of the two zones are situated at horizontal distances or offsets from each other so that the steam flow in the two layers proceeds partly in concurrent fashion and partly in countercurrent fashion. For example, the steam flow in the upper zone proceeds countercurrent to the steam flow in the lower zone between wells I-ll and I-21 and concurrent between I-21 and P-ll.
Similarly, in the lower zone, the steam flow is concurrent between wells I-21 and P-ll and countercurrent between wells P-ll and P-22.
A similar staggered well pattern for a three layer reservoir is shown in Figure 2. The permeable, oil bearing zones 10, 20 and 30 are separated by impermeable shale layers S-l and S-2, all underlying overburden 0. Injection wells I-ll and I-12 are completed into the uppermost layer 10, injection wells I-21 and I-22 in-to the middle layer 20 and injection wells I-31 and I-32 into the lowest layer 30. Production well P-ll is completed into uppermost layer 10, production well P-21 into middle layer 20 and production well P-31 into the lowest layer 30. Injection and production is carried out in the same manner as described above so that the steam flow has between any two adjacent layers proceeds partly in concurrent and partly in countercurrent fashion. For example, the steam flow in uppermost layer 10 proceeds countercurrent to the steam flow in middle layer 20 between wells I-ll and I-21 and then proceeds concurrently between wells I-21 and P-ll.
The injection and production wells may be of conventional type since no multiple completions are required. Steam injection temperatures may suitably vary from about 120 to 350 C and the , quality of the injec-ted steam is suitably within the range of 50-100%, more usually 50-90%. The steam injection rate will generally vary depending upon the thickness of the individual oil bearing zones but is preferably within the range of 65 to 325 litres/days/1000 m3 (about 0.5 to about 2.5 barrels of steam per day per acre foot of oil bearing strata).
It has been found that -the use of staggered production patterns as described above not only avoids the problem associated with multiple well completions but also offers a definite advantage in oil recovery as more oil is obtained at an earlier time, as compared to a process using completely concurrent steam flow. A
computer simulation was made for a two layer reservoir with an impermeable shale layer separating the two permeable, oil bearing zones. The major reservoir characteristics are shown in Table 1 below.
1?J~ 96 Table 1 Major Reservoir Characteristics Rock Properties Temperature, F 80F
Depth, ft 1300 Porosity, % 35 Average Permeability, md 5000 kv/kh . 1 Compressibility, psi .0001 Heat Capacity, Btu/lb rock-F .248 Heat Conductivity, Btu/F-ft-hr 1.25 Net Pay, ft 80 Sw 0.35 SO 0.64 Oil Characteristics API Gravity, 11.4 Density, lb/ft 61.8 Compressibility, psi~l 3.2 x 10-6 Heat Capacity, Btu/lb-F 0.46 F-~261 -8-The reservoir was then subjected to a simulated steam flood oil recovery using a staggered pattern of wells as shown in Figure 1 and second, a regular pattern of wells in which the steam flow in the two layers is wholly concurrent (see Figure 3). The results are shown in Figure 3 which shows that a greater amount of oil is recovered at an earlier time, making for a more economically favorable process. The improvement in recovery may be attributed to a more favorable heat transfer between the reservoirs.
Generally, it will be preferred that in any two layer system, the staggering between the well patterns in the two layers will be uniform although conditions may dictate a departure from uniform staggering in particular instances. Thus, it is normally preferred that an injection well for the lower layer should lie midway between a pair of injection and production wells for the upper layer and a production well for the lower layer should be midway between a pair of injection and production wells for the upper layer, as shown in Figure 1. Similarly, an injection well for the upper layer should lie midway between a pair of injection and production wells for the lower layer and a production well for the upper layer should lie midway be-tween a pair of injection and production wells for the lower layer. However, in arrangements where the wells are disposed other than in a straight line drive arrangement, the spacings may be somewhat different and more complicated.
Generally, the thickness of the oil bearing, permeable layers will not exceed about 15m (about 49 feet) and, in order to maximize thermal conduction between adjacent permeable layers, the thickness of the shale layer should not be more than about 3m (about 10 feet). However, greater or less thicknesses may be encountered with corresponding changes in the efficiency oF the process. It should be remembered, of course, that when the shale layer becomes much thicker than about 5m, the heat flow beween adjacent oil bearing layers will be greatly reduced and the advantages of the present staggered well patterns will be reduced correspondingly.
. _ This invention relates to the recovery of oil from subterranean, oil-bearing formatîons and more particularly, to the recovery of oil from subterranean formations containing heavy oil in two or more zones which are separated by an impermeable barrier.
A number of different thermal recovery processes have been used or proposed for producing heavy or viscous oils from subterranean formations such as tar sands. Of these processes, those employing steam injection form one readily definable type;
steam injection processes in turn, are basically of two types, being either of the single well injection or "huff and puff" type or of the steam drive type. The steam drive processes operate by injecting steam through one or more injection wells into the formation and producing the formation fluids from one or more production wells which are situated at a horizontal distance or offset from the injection well or wells. As the steam enters the formation through the injection wells, the heat transferred to the Formation by the steam lowers the viscosity of the formation oil, improving its mobility. In addition, the continued injection of the steam provides a driving force for displacing the oil towards the production well. Other effects such as visbreaking may occur, depending upon the temperature of the steam.
One of the problems associated with steam drive recovery processes is the loss of heat by conduction into non-produc-tive zones including the strata above and below the producing interval and various measures have been proposed for minimizing thermal losses.
In certain oil bearing -Formations, there may be a number of vertically separated oil bearing strata separated by layers of impervious material such as shale. These shale layers may prevent or at least, substantially restrict, vertical fluid flow between the ~lf~ 't3~
layers and therefore in formations of this kind, it may be necessary to inject steam into each of the layers if complete recovery is to be ensured. It is possible to reduce the thermal losses by employing a countercurrent flow of the steam in adjacent zones, as described in U.S. Patent No. 3,180,413. In the recovery process described in this patent, two multiply completed wells are sunk into the two adjacent strata separated by the shale layer and steam is injected at one well into one of the layers with production being taken out at the other well in the same layer. In the adjacent layer, the direction of fluid flow is reversed so that the steam flow is countercurrent in the two layers, to permit the utilization of thermal energy which would otherwise be lost without contributing to the recovery process.
Although the recovery process described in U.S. 3,180,413 has a number of advantages, there are also disadvantages. First, the wells require to be multiply completed so that each well may be used for both injection and production purposes, albeit in different, vertically separated zones of the same reservoir and second, the use of a single, multiply completed well for injection and production purposes may have an undesirable effect upon the produced fluids as they are brought to the surface. For example, if particularly high temperature steam is being used as the injection fluid, the produced fluids may be vaporized or pyrolyzed in the production flow passages and this may give rise to handling problems at the surface. Other problems may arise from the pressure differentials between the injection and production streams in multiply completed wellso leaks around the packers and the cement may occur to the detriment of process efficiency. It would, therefore, be desirable to avoid the use of multiply completed wells without altogether losing the advantages of countercurrent steam flow recovery.
According to the present invention a method has been devised for the recovery of oil from subterranean reservoirs which have two or more vertically separated oil bearing, permeable zones separated by impervious layers such as shale layers, which method avoids the use oF multiple well completions but minimizes the thermal losses which occur with concurrent steam flow techniques.
According to the present invention, ~urthermore, the method for recovering the viscous oil from a subterranean reservoir having upper and lower oil bearing permeable zones separated by an impervious layer comprises (l) injecting steam through a first injection well into the upper zone and producing fluids including oil from a first production well in the upper zone which is situated at a horizontal distance from the first injection well; and (2) injecting steam into the lower zone through a second injection well which is situated at a horizontal distance from the First injection well and producing fluids, including oil from a second production well in the lower zone which is situated at a horizontal distance from the second injection well.
The method of the present invention is, of course, applicable to reservoirs which have more than two vertically separated production intervals and in such cases, each adjacent pair of zones is produced by the same technique.
In practice, of course, more than one injection well and more than one production well will invariably be used in order to cover the entire producing field and to maximize recovery. The wells may be arranged in any convenient pattern such as in straight lines, for a line drive flooding process, or in conventional patterns such as five spot, inverted five spot, seven spot or inverted seven spot. Regardless of the nature of the pattern, the injection and production wells in any one layer are arranged in a pattern which is staggered with respect to that oF the next adjacent layer. This has the result that the steam flow in each two adjacent layers proceeds partly by concurrent flow and partly by countercurrent flow.
~ ~f$,~
The present invention, therefore, in one aspect, resides in a method for the recovery of oil from a subterranean reservoir having upper and lower oil bearing, permeable zones separated by an impervious layer, comprising injecting steam into thP upper and lower zones through patterns of injection wells which extend respectively into the upper and lower zones and producing fluids including oil from patterns of production wells which extend respectively into the upper and lower zones, the injection and production wells in each pattern in the upper and lower zones being horizontally separated from one another, with the patterns of injection wells being staggered with respect to one another in the two zones and the patterns of production wells being staggered with respect to one another in ths two zones, and causir,g the steam flow in said zones to proceed partly in concurrent fashion and partly in countercurrent ashion.
In another aspect, the present invention resides in a method for recovering ~iscous oil from a subterranean reser~oir having an upper permeable zone and a lower permeable zone, each of said permeable zones being oil bearing and separated by ~n impermeable layer, which comprises (1) in~ecting steam through a first pattern of injection wells axtending from the surface of the earth into the upper zone and producing fluids including oil from a first pattern of production wells extending from the surface o the earth into the llpper zone, each of which is at a horizontal distance from the injection wells in the first pattern; (2) in~ecting steam into the lower zone through a second pattern of injection wells each of which is situated at a horizontal distance from the wells of the first pattern of injection wells; (3) controlling the steam flow in said zones 80 that said steam flow proceeds partly in concurrent fashion and partly in countercurrent fashion; and (4) producing fluids including oil from a second pattern of production wells in the lower zone, each of which is at a ~J~ 6 - 4a -horizontal distance from the injection wells in said second pattern of injection wells.
The invention is better understood by refe~ence ~o the accompanying dr~wings, wherein:
Fiyure 1 is a vertical section in a simplified schematic form of a subterranean oil reservoir with uppex and lower oil bearing formations with staggered steam drive well patterns;
Figure 2 is a simplified vertical section of a three layer subterranean reservoir using staggered well patterns; and Figure 3 is a graph showiny the respective oil recoveries obtained with a staggered pattern of wells as in Figure 1 and a regular pattern of wells.
Figure 1 shows a simplified vertical section of a subterranean oil reservoir having an upper, oil bearing, permeable zone 10 and a lower, oil bearing, permeable zone 20 separated by a substantially impermeable shale layer S, underlying overburden 0. A
number of injection wells I-ll and I-12 extend into upper layer 10 from the surface of the earth and a number of separate injection wells I-21 and I-22 extend into lower zone 20 from the surface of the earth. Production wells P-ll, P-21 and P-22 extend into the upper and lower zones at horizontal distances or offsets from the injection wells in their respective zones. In addition, the injection wells of the two zones are situated at horizontal distances or offsets from each other so that the steam flow in the two layers proceeds partly in concurrent fashion and partly in countercurrent fashion. For example, the steam flow in the upper zone proceeds countercurrent to the steam flow in the lower zone between wells I-ll and I-21 and concurrent between I-21 and P-ll.
Similarly, in the lower zone, the steam flow is concurrent between wells I-21 and P-ll and countercurrent between wells P-ll and P-22.
A similar staggered well pattern for a three layer reservoir is shown in Figure 2. The permeable, oil bearing zones 10, 20 and 30 are separated by impermeable shale layers S-l and S-2, all underlying overburden 0. Injection wells I-ll and I-12 are completed into the uppermost layer 10, injection wells I-21 and I-22 in-to the middle layer 20 and injection wells I-31 and I-32 into the lowest layer 30. Production well P-ll is completed into uppermost layer 10, production well P-21 into middle layer 20 and production well P-31 into the lowest layer 30. Injection and production is carried out in the same manner as described above so that the steam flow has between any two adjacent layers proceeds partly in concurrent and partly in countercurrent fashion. For example, the steam flow in uppermost layer 10 proceeds countercurrent to the steam flow in middle layer 20 between wells I-ll and I-21 and then proceeds concurrently between wells I-21 and P-ll.
The injection and production wells may be of conventional type since no multiple completions are required. Steam injection temperatures may suitably vary from about 120 to 350 C and the , quality of the injec-ted steam is suitably within the range of 50-100%, more usually 50-90%. The steam injection rate will generally vary depending upon the thickness of the individual oil bearing zones but is preferably within the range of 65 to 325 litres/days/1000 m3 (about 0.5 to about 2.5 barrels of steam per day per acre foot of oil bearing strata).
It has been found that -the use of staggered production patterns as described above not only avoids the problem associated with multiple well completions but also offers a definite advantage in oil recovery as more oil is obtained at an earlier time, as compared to a process using completely concurrent steam flow. A
computer simulation was made for a two layer reservoir with an impermeable shale layer separating the two permeable, oil bearing zones. The major reservoir characteristics are shown in Table 1 below.
1?J~ 96 Table 1 Major Reservoir Characteristics Rock Properties Temperature, F 80F
Depth, ft 1300 Porosity, % 35 Average Permeability, md 5000 kv/kh . 1 Compressibility, psi .0001 Heat Capacity, Btu/lb rock-F .248 Heat Conductivity, Btu/F-ft-hr 1.25 Net Pay, ft 80 Sw 0.35 SO 0.64 Oil Characteristics API Gravity, 11.4 Density, lb/ft 61.8 Compressibility, psi~l 3.2 x 10-6 Heat Capacity, Btu/lb-F 0.46 F-~261 -8-The reservoir was then subjected to a simulated steam flood oil recovery using a staggered pattern of wells as shown in Figure 1 and second, a regular pattern of wells in which the steam flow in the two layers is wholly concurrent (see Figure 3). The results are shown in Figure 3 which shows that a greater amount of oil is recovered at an earlier time, making for a more economically favorable process. The improvement in recovery may be attributed to a more favorable heat transfer between the reservoirs.
Generally, it will be preferred that in any two layer system, the staggering between the well patterns in the two layers will be uniform although conditions may dictate a departure from uniform staggering in particular instances. Thus, it is normally preferred that an injection well for the lower layer should lie midway between a pair of injection and production wells for the upper layer and a production well for the lower layer should be midway between a pair of injection and production wells for the upper layer, as shown in Figure 1. Similarly, an injection well for the upper layer should lie midway between a pair of injection and production wells for the lower layer and a production well for the upper layer should lie midway be-tween a pair of injection and production wells for the lower layer. However, in arrangements where the wells are disposed other than in a straight line drive arrangement, the spacings may be somewhat different and more complicated.
Generally, the thickness of the oil bearing, permeable layers will not exceed about 15m (about 49 feet) and, in order to maximize thermal conduction between adjacent permeable layers, the thickness of the shale layer should not be more than about 3m (about 10 feet). However, greater or less thicknesses may be encountered with corresponding changes in the efficiency oF the process. It should be remembered, of course, that when the shale layer becomes much thicker than about 5m, the heat flow beween adjacent oil bearing layers will be greatly reduced and the advantages of the present staggered well patterns will be reduced correspondingly.
Claims (7)
1. Method for recovering viscous oil from a subterranean reservoir having an upper permeable zone and a lower permeable zone, each of said permeable zones being oil bearing and separated by an impermeable layer, which comprises (1) injecting steam through a first pattern of injection wells extending from the surface of the earth into the upper zone and producing fluids including oil from a first pattern of production wells extending from the surface of the earth into the upper zone, each of which is at a horizontal distance from the injection wells in the first pattern; (2) injecting steam into the lower zone through a second pattern of injection wells each of which is situated at a horizontal distance from the wells of the first pattern of injection wells; (3) controlling the steam flow in said zones so that said steam flow proceeds partly in concurrent fashion and partly in countercurrent fashion; and (4) producing fluids including oil from a second pattern of production wells in the lower zone, each of which is at a horizontal distance from the injection wells in said second pattern of injection walls.
2. Method according to claim 1 in which each injection well in the second pattern of injection wells in the lower zone is situated midway between an injection and a production well in the upper zone and each production well in the second pattern of production wells in the lower zone is situated midway between an injection well and a production well in the upper zone.
3. Method according to claim 1 in which each injection well in the first pattern of injection wells in the upper zone is situated midway between an injection well and a production well in the lower one and each production well in the first pattern of production wells in the upper zone is situated midway between an injection well and a production well in the lower zone.
4. Method according to claim 1 in which the steam is of 50 to 90% quality and is injected at a rate from 65 to 325 litres/day/1000 m3.
5. Method for the recovery of oil from a subterranean reservoir having upper and lower oil bearing, permeable zones separated by an impervious layer, comprising injecting steam into the upper and lower zones through patterns of injection wells which extend respectively into the upper and lower zones and producing fluids including oil from patterns of production wells which extend respectively into the upper and lower zones, the injection and production wells in each pattern in the upper and lower zones being horizontally separated from one another, with the patterns of injection wells being staggered with respect to one another in the two zones and the patterns of production wells being staggered with respect to one another in the two zones, and causing the steam flow in said zones to proceed partly in concurrent fashion and partly in countercurrent fashion.
6. Method according to claim 5 in which each well is singly completed.
7. Method according to claim 5 in which the steam is of 50 to 90% quality and is injected at a rate from 65 to 325 litres/day/1000 m3.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US68787684A | 1984-12-31 | 1984-12-31 | |
| US687,876 | 1984-12-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1246996A true CA1246996A (en) | 1988-12-20 |
Family
ID=24762234
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000492366A Expired CA1246996A (en) | 1984-12-31 | 1985-10-07 | Multiple zone oil recovery process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1246996A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5201815A (en) * | 1991-12-20 | 1993-04-13 | Chevron Research And Technology Company | Enhanced oil recovery method using an inverted nine-spot pattern |
-
1985
- 1985-10-07 CA CA000492366A patent/CA1246996A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5201815A (en) * | 1991-12-20 | 1993-04-13 | Chevron Research And Technology Company | Enhanced oil recovery method using an inverted nine-spot pattern |
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