Method for improving recovery of low-permeability glutenite reservoirs by zonal gas and water injection

Abstract

The application provides a low-permeability sand-shale oil reservoir partitioned gas-water injection enhanced recovery method, which comprises the following steps: step 1, carrying out sand-shale different facies belt reservoir characteristic research; step 2, determining gas-water injection partitioned boundary; step 3, dividing partitioned range of different development modes; step 4, determining development technical policy in different partitioned ranges; step 5, preparing development scheme of full-area differential development mode and implementing; and step 6, tracking and adjusting partitioned range and implementing scheme. The low-permeability sand-shale oil reservoir partitioned gas-water injection enhanced recovery method is based on low-permeability sand-shale oil reservoir different facies belt reservoir connectivity characteristics, adopts differential partitioned gas-water injection mode to supplement formation energy, improves effectiveness of formation energy supplement, and greatly improves low-permeability sand-shale oil reservoir recovery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-permeability glutenite reservoir development, in particular to a method for improving recovery by zonal gas and water injection in low-permeability glutenite reservoirs. BACKGROUND

[0002] Low-permeability glutenite reservoirs are abundant in China and have great development potential, but due to complex reservoir connectivity, strong heterogeneity, and poor reservoir properties, the formation energy is weak, leading to rapid elastic development decline and low cumulative production; the conventional water injection development has low injection-production correspondence, and the water injection effect is difficult to achieve, so the formation energy is difficult to effectively supplement; currently, there is a lack of effective large-scale enhanced oil recovery technology for low-permeability glutenite reservoirs.

[0003] Glutenite reservoirs are mainly distributed near steep slope belts and are formed by near-source rapid deposition; due to the influence of sedimentation, the reservoir connectivity characteristics and reservoir properties of different facies belts differ greatly with different transport distances; the near-fan heel sand body has large thickness, poor lithology sorting, poor connectivity, and poor properties; the fan middle subfacies sand body has relatively thin thickness, gradually better sorting, better connectivity, and better properties; the near-fan edge subfacies is mainly composed of sand and mud interbeds, the sand body is distributed in layers, has thin thickness, good sorting, good layered connectivity, and generally good properties.

[0004] Low-permeability glutenite reservoirs have large differences in reservoir characteristics of different facies belts, and it is difficult to describe the reservoirs; the reservoir properties are poor, and the natural production capacity is low; in order to economically and effectively develop glutenite reservoirs, the current general development method is to use segmented large-scale fracturing and multi-layer simultaneous production; due to the fact that glutenite reservoirs are generally normal-pressure reservoirs and lack the energy supplement of edge and bottom water, the formation energy is weak, and the elastic development decline is rapid; in the later period, general water injection is used to supplement the formation energy, but due to the dual influence of the differences in interwell reservoir connectivity and large-scale fracturing, the injection-production correspondence differs greatly among different wells and layers, water injection breakthrough and non-effectiveness exist at the same time, leading to poor effect of conventional elastic development and water injection development and low recovery.

[0005] In the Chinese patent application No. CN201510420093.8, a method for improving recovery efficiency of a fault block reservoir in a super high water cut stage is disclosed. The method comprises: step 1, analyzing the structural and geological characteristics and well pattern evolution characteristics of the research area; step 2, conducting a reasonable zoning study through complex remaining oil characteristics and influencing factor research, and formulating a zoning scheme for complex fault block reservoirs in a super high water cut stage by analyzing the differences in water drive effect and influencing factors of typical fault block reservoirs; and step 3, using numerical simulation or reservoir engineering methods to determine the development contradictions of each zone and optimize the zoning control technology policy, and designing an optimized zoning injection-production control scheme. The method has a clear technical idea and is simple to apply, and provides a feasible method for effectively tapping the potential of remaining oil in complex fault blocks in a super high water cut stage in the late development stage.

[0006] In the Chinese patent application No. CN201910624106.1, a method and device for partitioning an oil reservoir seepage field are disclosed, which belong to the technical field of oil production engineering. The method comprises: obtaining water saturation, oil phase relative permeability, water phase relative permeability, oil reservoir absolute permeability, water phase viscosity, crude oil viscosity, and flow information of each region of the target oil reservoir seepage field; dividing the target oil reservoir seepage field into an ineffective water circulation zone and a non-ineffective water circulation zone; determining the flow field intensity of each region of the non-ineffective water circulation zone; determining the seepage velocity of each region of the non-ineffective water circulation zone; and dividing the non-ineffective water circulation zone into a high-speed high-potential zone, a low-speed low-potential zone, a high-speed low-potential zone, a low-speed high-potential zone, and an undeveloped reserve zone based on the flow field intensity and seepage velocity of each region of the non-ineffective water circulation zone. The application can effectively solve the technical problem of lacking a method for partitioning an oil reservoir seepage field in related technologies, and improve the recovery efficiency.

[0007] In the Chinese patent application No. CN201910370374.5, a multi-target injection-production control optimization method for complex fault block reservoirs is disclosed. The method comprises: step 1, collecting information of a target block and modeling the target block; step 2, dividing the target block into regions according to characteristics and contradictions; step 3, designing a corresponding objective function for the block according to the main contradictions of each block / region; step 4, performing multi-objective optimization on the objective function using a multi-objective optimization algorithm; and step 5, selecting part of the results as the final solution according to the objective function and economic benefits in the obtained multi-objective optimization result set. The method fully utilizes the existing well pattern, changes "local efficient tapping" to "zonal efficient control", optimizes the well pattern and injection-production control in different regions, realizes balanced water drive development, and thus solves the problem of being unable to improve the planar contradictions in the current technology.

[0008] The above prior art is quite different from the present application, and cannot solve the technical problems we want to solve, therefore we have invented a new method for improving recovery by zonal gas and water injection in low-permeability sandy conglomerate reservoirs. SUMMARY

[0009] The purpose of the present application is to provide a method for improving recovery by zonal gas and water injection in low-permeability sandy conglomerate reservoirs, based on the connectivity characteristics of different facies zones in the reservoir, using differentiated zonal gas and water injection to supplement formation energy and improve the effectiveness of formation energy supplementation, thereby substantially improving the recovery of low-permeability sandy conglomerate reservoirs.

[0010] The purpose of the present application can be achieved by the following technical measures: a method for improving recovery by zonal gas and water injection in low-permeability sandy conglomerate reservoirs, comprising:

[0011] Step 1: Research on the characteristics of different facies zones in the reservoir;

[0012] Step 2: Determine the zonal boundaries for gas and water injection;

[0013] Step 3: Divide the zonal range for different development methods;

[0014] Step 4: Determine the development technology policy in different zonal ranges;

[0015] Step 5: Develop a development plan for differentiated development methods in the entire area and implement it;

[0016] Step 6: Track and adjust the zonal range and implementation plan.

[0017] The purpose of the present application can also be achieved by the following technical measures:

[0018] In Step 1, for a specific research block, guided by the near-shore underwater fan deposition model of the steep slope sandy conglomerate reservoir, based on comprehensive geological research, according to the characteristics of different facies zones in the reservoir, the reservoir characteristics parameters such as reservoir thickness, reservoir connectivity rate, reservoir physical properties, and the dip angle of connected bodies in different well areas are described.

[0019] In Step 2, based on the reservoir adaptability of CO2 huff and puff, CO2 continuous gas drive, and water drive development methods, the reservoir connectivity rate zonal boundaries for CO2 huff and puff and CO2 continuous gas drive are determined based on the reservoir characteristics of the research area, and the connected body dip angle and reservoir physical property zonal boundaries for CO2 continuous gas drive and water drive are determined.

[0020] In step 3, according to the partition boundaries of different development modes, the research block is divided into different development mode partition ranges. The near-fan heel massive area with high reservoir thickness, low connectivity, and poor physical properties is divided into a well area mainly using CO2 huff and puff. The middle-fan superimposed area with relatively high connectivity, large connectivity body inclination, and poor physical properties is divided into a well area mainly using CO2 continuous gas drive. The fan end layered area with small reservoir thickness, highest connectivity, small connectivity body inclination, and best physical properties is divided into a well area mainly using water drive.

[0021] In step 4, for the CO2 huff and puff development mode of the high-position near-fan heel massive area, the reasonable well spacing, injection-production cycle, and cycle injection volume are mainly optimized. When the production is lower than the economic limit production in the late CO2 huff and puff stage, the well area with relatively good connectivity is converted to CO2 continuous gas drive to further improve the recovery efficiency.

[0022] In step 4, for the CO2 continuous gas drive development mode of the middle-high position middle-fan superimposed area, the reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio, and reasonable pressure maintenance level of CO2 gas drive are mainly optimized.

[0023] In step 4, for the water drive development mode of the low-position fan end layered area, the reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio, and reasonable pressure maintenance level of water drive are mainly optimized.

[0024] In step 5, for the development technology policy of different partitions, the development scheme of differentiated development mode is prepared, and the injection-production wells in different partitions are cooperatively deployed and systematically optimized. The high-position near-fan heel mainly uses CO2 huff and puff, the low-position with relatively good connectivity in the late stage is converted to CO2 continuous gas drive, the middle-high position middle-fan superimposed area is transitioned to CO2 continuous gas drive, and the low-position fan end layered area mainly uses water drive. Finally, an integrated development scheme of high-position gas injection and low-position water injection three-dimensional injection-production is formed.

[0025] In step 5, according to the scheme design, the CO2 huff and puff in the fan heel massive area and the water drive in the fan end layered area are preferentially implemented, and the CO2 gas drive in the middle-fan superimposed area is gradually promoted.

[0026] In step 6, the implementation effects of the injection-production wells in different partitions are tracked and evaluated, and the partition ranges and the overall implementation scheme are dynamically adjusted and optimized. Finally, the effective supplement of the formation energy in the whole area is realized, and the development effect in the whole area is improved to increase the ultimate recovery efficiency.

[0027] The low-permeability sandy conglomerate reservoir partitioned gas-water injection enhanced recovery method in the application is based on the connectivity characteristics of different facies reservoirs in the low-permeability sandy conglomerate reservoir, and differential partitioned gas-water injection is adopted to supplement the formation energy, so as to improve the effectiveness of the formation energy supplement and greatly improve the recovery of the low-permeability sandy conglomerate reservoir. The low-permeability sandy conglomerate reservoir partitioned gas-water injection enhanced recovery method in the application can guide the design and adjustment of the development plan of the new and old areas of the low-permeability sandy conglomerate reservoir, so as to effectively supplement the formation energy, improve the sweep efficiency and oil displacement efficiency, improve the single-well productivity and slow down the decline, improve the development effect of the low-permeability sandy conglomerate reservoir, and improve the ultimate recovery. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flow chart of a specific embodiment of the low-permeability sandy conglomerate reservoir partitioned gas-water injection enhanced recovery method in the application;

[0029] Figure 2 is a development effect comparison chart of CO2 huff and puff and CO2 flooding under different connectivity rates in a specific embodiment of the application;

[0030] Figure 3 is a development effect comparison chart of CO2 flooding and water flooding under different formation dip angles in a specific embodiment of the application;

[0031] Figure 4 is a development effect comparison chart of CO2 flooding and water flooding under different permeability rates in a specific embodiment of the application. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0033] It should be noted that the terms used herein are only intended to describe specific embodiments, and are not intended to limit the exemplary embodiments according to the application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, there is a presence of the features, steps, operations and / or combinations thereof.

[0034] The low-permeability sandy conglomerate reservoir partitioned gas-water injection enhanced recovery method in the application includes the following steps:

[0035] Step 1, research on the characteristics of different facies reservoirs in sandy conglomerate;

[0036] Based on the research of the specific study area, the reservoir characteristics parameters such as reservoir thickness, reservoir connectivity, reservoir physical property and the dip angle of the connected body are described in different well areas according to the different facies reservoir characteristics of the sandstone conglomerate reservoir in the steep slope belt nearshore underwater fan deposition mode.

[0037] Step 2, determine the gas-water injection partition boundary;

[0038] According to the reservoir adaptability of CO2 huff and puff, CO2 continuous gas drive and water drive development methods, the reservoir connectivity partition boundary of CO2 huff and puff and CO2 continuous gas drive is determined based on the reservoir characteristics of the study area, and the connected body dip angle and reservoir physical property partition boundary of CO2 continuous gas drive and water drive.

[0039] Step 3, divide the partition range of different development methods;

[0040] According to the partition boundary of different development methods, the study area is divided into different development method partition range. The near-fan heel massive area with high reservoir thickness, low connectivity and poor physical property in the high position is divided into the well area dominated by CO2 huff and puff, the fan middle superimposed area with relatively high connectivity, large connected body dip angle and poor physical property in the middle-high position is divided into the well area dominated by CO2 continuous gas drive, and the fan end layered area with small reservoir thickness, highest connectivity, small connected body dip angle and best physical property in the low position is divided into the well area dominated by water drive.

[0041] Step 4, determine the development technology policy in different partition range;

[0042] For the development method of CO2 huff and puff in the near-fan heel massive area in the high position, the reasonable well spacing, injection-production cycle and cycle injection volume are mainly optimized. When the production of CO2 huff and puff in the later stage is lower than the economic limit production, the well area with relatively good connectivity is converted to CO2 continuous gas drive to further improve the recovery efficiency. For the development method of CO2 continuous gas drive in the fan middle superimposed area in the middle-high position, the reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio and reasonable pressure maintenance level of CO2 gas drive are mainly optimized. For the development method of water drive in the fan end layered area in the low position, the reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio and reasonable pressure maintenance level of water drive are mainly optimized.

[0043] Step 5, develop the development plan of the whole area differentiated development method and implement it;

[0044] According to the development technical policy of different partitions, a development plan of differential development mode is prepared, and injection-production wells in different partitions are cooperatively deployed and systematically optimized. CO2 huff and puff is mainly used in the high part near the fan, CO2 continuous gas drive is used in the low part with relatively good connectivity in the later period, CO2 continuous gas drive is used in the middle and high part of the fan superimposed area, and water drive is mainly used in the low part of the fan end layered area. Finally, an integrated development plan of three-dimensional injection and production of high part gas injection and low part water injection is formed. According to the plan, the injection of CO2 huff and puff in the fan block area and the water drive in the fan end layered area are preferentially implemented, and the CO2 gas drive in the fan superimposed area is gradually promoted.

[0045] Step 6, tracking adjustment of partition range and implementation scheme.

[0046] The implementation effect of injection-production wells in different partitions is tracked and evaluated, and the partition range and the overall implementation scheme are dynamically adjusted and optimized. Finally, the effective supplement of the formation energy in the whole area is realized, and the development effect in the whole area is improved to increase the ultimate recovery.

[0047] The following are several specific embodiments of the application

[0048] Embodiment 1

[0049] In a specific embodiment 1 of the application, as shown in Figure 1 , the flow chart of the low-permeability glutenite reservoir partition gas-water injection enhanced oil recovery method of the application is shown in Figure 1 , which includes the following steps:

[0050] Step 101, for a specific research block, based on the near-shore underwater fan sedimentary mode of the steep slope sand glutenite reservoir, on the basis of comprehensive geological research, according to the reservoir characteristics of different facies belts of sand glutenite, the reservoir characteristics parameters such as reservoir thickness, reservoir connectivity, reservoir physical property and dip angle of connected body in different well areas are described.

[0051] Step 102, according to the reservoir adaptability of CO2 huff and puff, CO2 continuous gas drive and water drive, based on the reservoir characteristics of the research area, the reservoir connectivity partition boundaries of CO2 huff and puff and CO2 continuous gas drive are determined, and the connected body dip angle and reservoir physical property partition boundaries of CO2 continuous gas drive and water drive are determined. With the change of connectivity, the development effect of CO2 huff and puff and CO2 drive changes greatly, CO2 huff and puff is relatively small, CO2 drive is greatly affected by reservoir connectivity, as shown in Figure 2When the well area connectivity is less than 38%, the development mode of CO2 huff and puff is adopted, and when the well area connectivity is greater than 38%, the development mode of CO2 continuous gas drive is adopted. When the reservoir connectivity is high, the development effect of CO2 drive and water drive varies greatly with the change of the formation dip angle. With the increase of the formation dip angle, the superposition of high injection and low production increases, and the development effect of CO2 drive is greatly affected. With the change of the formation dip angle, the oil-water differentiation is relatively small, and the development effect of water drive is less affected, for example Figure 3 When the well area dip angle is less than 12°, the development mode of water drive is adopted; when the well area dip angle is greater than 12°, the development mode of CO2 gas drive is adopted. When the reservoir connectivity is high, the development effect of CO2 drive and water drive varies greatly with the change of the reservoir permeability. Under the condition of immiscible drive, with the increase of the permeability, the gas absorption capacity increases, the breakthrough pressure becomes small, the gas channeling in the updip direction accelerates, and the development effect of CO2 gas drive becomes poor. With the decrease of the permeability, the water absorption capacity decreases greatly, and the development effect of water drive becomes poor, for example Figure 4 When the well area permeability is less than 3 mD, the development mode of CO2 gas drive is adopted; when the well area permeability is greater than 3 mD, the development mode of water drive is adopted, which takes advantage of the mature water injection technology and low cost.

[0052] Step 103, according to the partition limits of different development modes, the study block is divided into different development mode partition ranges. The near-fan heel massive area with high reservoir thickness, low connectivity, and poor physical properties is divided into a well area mainly developed by CO2 huff and puff. The middle-fan superimposed area with relatively high connectivity, large connectivity dip angle, and poor physical properties is divided into a well area mainly developed by CO2 continuous gas drive. The fan-end layered area with small reservoir thickness, highest connectivity, small connectivity dip angle, and best physical properties is divided into a well area mainly developed by water drive.

[0053] Step 104, for the development mode of CO2 huff and puff in the high-position near-fan heel massive area, the reasonable well spacing, injection-production cycle, and cycle injection volume are mainly optimized. When the production is lower than the economic limit after CO2 huff and puff, the well area with relatively good connectivity is converted to CO2 continuous gas drive to further improve the recovery. For the development mode of CO2 continuous gas drive in the middle-high-position middle-fan superimposed area, the reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio, and reasonable pressure maintenance level of CO2 gas drive are mainly optimized. For the development mode of water drive in the low-position fan-end layered area, the reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio, and reasonable pressure maintenance level of water drive are mainly optimized.

[0054] Step 105: Develop differentiated development plans based on the development technology policies for different zones, and coordinate the deployment and system optimization of injection and production wells in different zones. High-performing areas near the fan base will primarily utilize CO2 injection and huff-and-puff, while lower-performing areas with relatively good connectivity will transition to continuous CO2 gas drive. The transition to continuous CO2 gas drive will continue in the mid-to-high-performing fan-internal overlapping areas, while water drive will be the primary method in the low-performing fan-end layered areas. Ultimately, an integrated development plan combining gas injection in high-performing areas and water injection in low-performing areas will be formed. The plan will be implemented systematically, prioritizing CO2 injection and huff-and-puff in the fan-base blocky areas and water drive in the fan-end layered areas, gradually advancing CO2 gas drive in the fan-internal overlapping areas.

[0055] Step 106: Track and evaluate the implementation effect of injection and production wells in different zones, dynamically adjust the zone scope and optimize the overall implementation plan, and ultimately achieve effective replenishment of formation energy in the whole area, improve the development effect of the whole area and increase the final recovery rate.

[0056] Example 2:

[0057] In a specific embodiment 2 of the present invention, such as Figure 1 The diagram shows a flowchart of a method for enhancing oil recovery through CO2 huff and puff and gas injection in low-permeability sandstone and conglomerate reservoirs with poor overall physical properties and permeability below 3 mD, provided by this invention. The specific implementation steps of this method are as follows:

[0058] Step 101: For specific research blocks, guided by the nearshore underwater fan sedimentary model of sandstone and conglomerate reservoirs in steep slope zones, based on comprehensive geological research, and according to the reservoir characteristics of different facies zones of sandstone and conglomerate, focus on describing reservoir characteristic parameters such as reservoir thickness, reservoir connectivity, reservoir properties, and dip angle of interconnected bodies in different well areas.

[0059] Step 102: Based on the reservoir adaptability of CO2 injection huff and puff and continuous CO2 gas drive, determine the reservoir connectivity zoning boundaries for CO2 injection huff and puff and continuous CO2 gas drive based on the reservoir characteristics of the study area. The development effects of CO2 injection huff and puff and CO2 gas drive vary greatly with changes in connectivity. CO2 injection huff and puff is relatively less affected by reservoir connectivity, while CO2 gas drive is significantly affected. Figure 2 As shown, when the well connectivity is less than 38%, a CO2 throughput development method is adopted; when the well connectivity is greater than 38%, a CO2 continuous gas drive development method is adopted.

[0060] Step 103: Based on the zoning boundaries of different development methods, the study block is divided into zoning ranges for different development methods. The near-fan and blocky areas with large reservoir thickness and low connectivity in the high part are classified as well areas mainly for CO2 injection and huffing and puffing, while the overlapping areas in the fan with relatively high connectivity in the low part are classified as well areas mainly for CO2 continuous gas drive.

[0061] Step 104, for the development method of CO2 injection and huff-and-puff in high-position near-fan and blocky areas, mainly optimizes the reasonable well spacing, injection-production cycle, and cycle injection volume. When the CO2 huff-and-puff production is lower than the economic limit production in the later stage, well areas with relatively good connectivity are switched to continuous CO2 gas drive to further improve the recovery rate. For the development method of continuous CO2 gas drive in overlapping areas of mid-to-low-position fans, the main optimizations are the reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio, and reasonable pressure maintenance level.

[0062] Step 105: Develop differentiated development plans based on the development technology policies for different zones, and coordinate the deployment and system optimization of injection and production wells in different zones. High-level near-fan areas will primarily utilize CO2 injection and huff-and-puff, while lower-level areas with relatively good connectivity will transition to continuous CO2 gas drive. The transition to continuous CO2 gas drive will then extend to the overlapping areas within the mid-to-low-level fan areas, ultimately forming a three-dimensional integrated injection and production development plan with injection and huff-and-puff in high-level areas and gas drive in lower-level areas. The plan will be implemented systematically according to the design, prioritizing CO2 injection and huff-and-puff in the fan-based blocky areas and gradually advancing CO2 gas drive in the overlapping areas within the fan areas.

[0063] Step 106: Track and evaluate the implementation effect of injection and production wells in different zones, dynamically adjust the zone scope and optimize the overall implementation plan, and ultimately achieve effective replenishment of formation energy in the whole area, improve the development effect of the whole area and increase the final recovery rate.

[0064] Example 3:

[0065] In a specific embodiment 3 of the present invention, such as Figure 1 The diagram shows a flowchart of a method for enhancing oil recovery through gas-water injection in low-permeability sandstone and conglomerate reservoirs with good overall physical properties and permeability exceeding 3 mD, as provided by this invention. The specific implementation steps of this method are as follows:

[0066] Step 101: For specific research blocks, guided by the nearshore underwater fan sedimentary model of sandstone and conglomerate reservoirs in steep slope zones, based on comprehensive geological research, and according to the reservoir characteristics of different facies zones of sandstone and conglomerate, focus on describing reservoir characteristic parameters such as reservoir thickness, reservoir connectivity, reservoir properties, and dip angle of interconnected bodies in different well areas.

[0067] Step 102: Based on the reservoir adaptability of development methods such as CO2 injection huff and puff, continuous CO2 gas drive, and water drive, determine the reservoir connectivity zoning boundaries for CO2 injection huff and puff and continuous CO2 gas drive, and the connectivity dip angle zoning boundaries for continuous CO2 gas drive and water drive, based on the reservoir characteristics of the study area. The development effects of CO2 injection huff and puff vary greatly with changes in connectivity. CO2 injection huff and puff is relatively less affected by reservoir connectivity, while CO2 drive is significantly affected. Figure 2As shown. When the well connectivity is less than 38%, CO2 huff and puff development is used; when the well connectivity is greater than 38%, continuous CO2 gas drive development is used. When the reservoir connectivity is high, the development effects of CO2 drive and water drive vary greatly with changes in formation dip. As the formation dip increases, the over-covering effect of high injection and low production intensifies, and the development effect of CO2 drive is greatly affected. The difference in oil and water content is relatively small with changes in formation dip, and the development effect of water drive is less affected. Figure 3 As shown, water drive development is adopted when the formation dip angle in the well area is less than 12°; CO2 gas drive development is adopted when the formation dip angle in the well area is greater than 12°.

[0068] Step 103: Based on the zoning boundaries of different development methods, the study block is divided into zoning ranges for different development methods. The near-fan and blocky areas with large reservoir thickness and low connectivity in the high part are classified as well areas mainly for CO2 injection and huffing and puffing. The superimposed areas in the mid-high part of the fan with relatively high connectivity and large dip angle of the connected body are classified as well areas mainly for CO2 continuous gas drive. The layered areas at the end of the fan with small reservoir thickness, highest connectivity and small dip angle of the connected body in the low part are classified as well areas mainly for water drive.

[0069] Step 104, for the CO2 injection huff and puff development method in the high-position near-fan and blocky areas, mainly optimizes the reasonable well spacing, injection-production cycle, and cycle injection volume. When the CO2 huff and puff production in the later stage is lower than the economic limit production, well areas with relatively good connectivity are switched to continuous CO2 gas drive to further improve the recovery rate. For the CO2 injection continuous gas drive development method in the overlapping areas of the mid-to-high-position fan, mainly optimizes the reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio, and reasonable pressure maintenance level of CO2 gas drive. For the water drive development method in the low-position fan-end layered areas, mainly optimizes the reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio, and reasonable pressure maintenance level of water drive.

[0070] Step 105: Develop differentiated development plans based on the development technology policies for different zones, and coordinate the deployment and system optimization of injection and production wells in different zones. High-performing areas near the fan base will primarily utilize CO2 injection and huff-and-puff, while lower-performing areas with relatively good connectivity will transition to continuous CO2 gas drive. The transition to continuous CO2 gas drive will continue in the mid-to-high-performing fan-internal overlapping areas, while water drive will be the primary method in the low-performing fan-end layered areas. Ultimately, an integrated development plan combining gas injection in high-performing areas and water injection in low-performing areas will be formed. The plan will be implemented systematically, prioritizing CO2 injection and huff-and-puff in the fan-base blocky areas and water drive in the fan-end layered areas, gradually advancing CO2 gas drive in the fan-internal overlapping areas.

[0071] Step 106: Track and evaluate the implementation effect of injection and production wells in different zones, dynamically adjust the zone scope and optimize the overall implementation plan, and ultimately achieve effective replenishment of formation energy in the whole area, improve the development effect of the whole area and increase the final recovery rate.

[0072] Based on the above methods, the method of zonal gas-water injection to enhance oil recovery in low-permeability sandstone and conglomerate reservoirs can guide the design and development adjustment of new and old zones in low-permeability sandstone and conglomerate reservoirs. This can effectively replenish formation energy, improve sweep efficiency and oil displacement efficiency, increase single-well productivity and slow down decline, improve the development effect of low-permeability sandstone and conglomerate reservoirs, and increase the final recovery rate.

[0073] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0074] Except for the technical features described in the specification, all other technologies are known to those skilled in the art.

Claims

1. A method for zonal gas and water injection EOR in low permeability glutenite reservoirs, characterized in that, The low-permeability glutenite reservoir partitioned gas-water injection enhanced recovery method comprises: Step 1, research on reservoir characteristics of different facies belts of glutenite, including: for a specific research block, guided by the near-shore subaqueous fan sedimentary model of glutenite reservoirs in steep slope belts, on the basis of comprehensive geological research, according to the reservoir characteristics of different facies belts of glutenite, the reservoir characteristics parameters of different well areas are described, including reservoir thickness, reservoir connectivity, reservoir physical property and dip angle of connected bodies; Step 2, determination of gas-water injection partitioning boundaries, including: according to the reservoir adaptability of CO2 huff and puff, CO2 continuous gas drive and water drive development modes, based on the reservoir characteristics of the research area, the reservoir connectivity partitioning boundaries of CO2 huff and puff and CO2 continuous gas drive are determined, and the connected body dip angle and reservoir physical property partitioning boundaries of CO2 continuous gas drive and water drive are determined; Step 3, division of partitioning ranges of different development modes, including: according to the partitioning boundaries of different development modes, the research block is divided into partitioning ranges of different development modes, the near-fan heel massive area with high reservoir thickness, low connectivity, poor physical property in the high position is divided into a well area mainly developed by CO2 huff and puff, the fan middle superimposed area with relatively high connectivity, large connected body dip angle and poor physical property in the middle-high position is divided into a well area mainly developed by CO2 continuous gas drive, and the fan end layered area with small reservoir thickness, highest connectivity, small connected body dip angle and best physical property in the low position is divided into a well area mainly developed by water drive; Step 4, determination of development technical policies in different partitioning ranges; Step 5, preparation of development schemes of different development modes in the whole area and implementation; Step 6, tracking and adjustment of partitioning ranges and implementation schemes.

2. The zonal gas water injection EOR method for low permeability glutenite reservoirs as claimed in claim 1 wherein, In step 4, for the development mode of CO2 huff and puff in the near-fan heel massive area in the high position, reasonable well spacing, injection-production cycle and cycle injection volume are optimized, when the production of CO2 huff and puff in the later stage is lower than the economic limit production, the well area with relatively good connectivity is converted into CO2 continuous gas drive to further improve the recovery.

3. The zonal gas water injection EOR method for low permeability glutenite reservoirs as claimed in claim 2 wherein, In step 4, for the development mode of CO2 continuous gas drive in the fan middle superimposed area in the middle-high position, reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio and reasonable pressure maintenance level of CO2 gas drive are optimized.

4. The zonal gas water injection EOR method for low permeability glutenite reservoirs as claimed in claim 2 wherein, In step 4, for the development mode of water drive in the fan end layered area in the low position, reasonable injection-production well pattern, reasonable injection-production well spacing, reasonable injection-production ratio and reasonable pressure maintenance level of water drive are optimized.

5. The low permeability glutenite reservoir zonal gas water injection EOR method, as claimed in claim 1, wherein, In step 5, according to the development technical policies of different partitions, the development schemes of different development modes are prepared, and the injection-production wells in different partitions are cooperatively deployed and systematically optimized, the near-fan heel in the high position is mainly developed by CO2 huff and puff, the low position with relatively good connectivity in the later stage is converted into CO2 continuous gas drive, the transition to the fan middle superimposed area in the middle-high position is CO2 continuous gas drive, and the fan end layered area in the low position is mainly developed by water drive, finally forming an integrated development scheme of three-dimensional injection-production of gas injection in the high position and water injection in the low position.

6. The zonal gas water injection EOR method for low permeability glutenite reservoirs as claimed in claim 5 wherein, In step 5, according to the scheme design, the implementation is carried out in an orderly manner, the injection of CO2 huff and puff in the fan heel massive area and the water drive in the fan end layered area are given priority to, and the CO2 gas drive in the fan middle superimposed area is gradually promoted.

7. The low permeability glutenite reservoir zonal gas water injection EOR method, as claimed in claim 1, wherein, In step 6, the implementation effect of injection-production wells in different partitions is tracked and evaluated, and the partition range and the overall implementation scheme are dynamically adjusted and optimized, so as to finally realize effective supplement of formation energy in the whole region, improve the development effect in the whole region, and increase the ultimate recovery.

Images