A method for improving oil recovery by changing the well pattern in developing oil reservoirs with multi-layer seven-point well pattern

Abstract

The present invention relates to a method for improving crude oil recovery, and in particular to a method for improving recovery by changing the well network of a multi-layer seven-point well network to develop an oil reservoir. The method comprises: conducting detailed geological research on the oil reservoir developed by the multi-layer seven-point well network, and establishing a detailed three-dimensional geological model; establishing a detailed numerical simulation model of the oil reservoir by historical matching, and analyzing the distribution law of residual oil in the late stage of the oil reservoir with extremely high water content developed by the multi-layer seven-point well network; analyzing the feasibility of improving the recovery of the oil reservoir developed by the multi-layer seven-point well network by adjusting the flow field by coordinating the vertical and horizontal streamlines; establishing a flow field mode for coordinating the vertical and horizontal streamlines to adjust the flow field in the development of the oil reservoir by the multi-layer seven-point well network; designing a plan for improving the recovery of the oil reservoir developed by the multi-layer seven-point well network by coordinating the vertical and horizontal streamlines to adjust the flow field, and optimizing and economically evaluating the plan, and selecting the best implementation plan. The method of the present invention can economically and effectively improve the recovery rate of such oil reservoirs, reduce water consumption, has good practicality, and is easy to promote.

Description

Technical Field

[0001] The invention relates to a method for improving crude oil recovery, in particular to a method for improving recovery by changing a well network in developing an oil reservoir using a multi-layer seven-point well network. Background Art

[0002] In the development of sandstone oilfields, the multi-layer seven-point well network that has undergone long-term water injection and scouring has developed oil reservoirs. The streamlines are fixed for a long time and the dynamic heterogeneity is strong. The distribution of remaining oil is controlled by the seven-point area well network. The differences between oil and water wells, between oil wells, and between water wells are increasing. The non-mainstream line area is much larger than the mainstream line area. At the same time, the seven-point well network has a high sweep coefficient compared to other area well networks, and the distribution of remaining oil is more complicated.

[0003] The mainstream line area of ​​the reservoir developed by the multi-layer seven-point well network has been flushed by water injection for a long time, forming a high water consumption area, the injected water is ineffective or inefficiently circulated, the water content of the oil wells is high, the implementation effect of conventional technology is poor, and it is very difficult to further improve the recovery rate under the current stratum well network conditions.

[0004] Therefore, it is urgent to establish an economical and effective method to enhance oil recovery and further improve the development effect and economic benefits of multi-layer seven-point well network development of oil reservoirs. Summary of the invention

[0005] The purpose of the present invention is to provide a method for improving the recovery rate of oil reservoirs developed by changing the well network of a multi-layer seven-point method. The method improves the recovery rate of oil reservoirs developed by the multi-layer seven-point method well network by changing the streamline to adjust the flow field, and has good practicality and implementation effect.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for improving oil recovery by transforming a well pattern in a multi-layer seven-point well pattern development oil reservoir, the method comprising:

[0008] Step 1: Develop a multi-layer seven-point well network to conduct detailed geological research on the reservoir and establish a detailed three-dimensional geological model;

[0009] Step 2: Establish a fine numerical simulation model of the reservoir through historical matching to analyze the distribution law of remaining oil in the late stage of reservoir with extremely high water cut in the multi-layer seven-point well network development;

[0010] Step 3, analyzing the feasibility of adjusting the flow field by changing the streamlines in the vertical and horizontal directions to improve the recovery rate of the reservoir by developing a multi-layer seven-point well pattern;

[0011] Step 4, establish a multi-layer seven-point method well network to develop the reservoir vertically and horizontally to coordinately change the streamlines and adjust the flow field pattern;

[0012] Step 5, design a multi-layer seven-point well pattern to develop a plan to improve oil recovery by changing the streamlines and adjusting the flow field in a coordinated manner in the vertical and horizontal directions, optimize and economically evaluate the plan, and select the best implementation plan.

[0013] To achieve the above object, the present invention can also adopt the following technical solutions:

[0014] In step 1, the multi-layer seven-point well pattern is used to develop a detailed geological study of the reservoir, including stratigraphic correlation and division, structure, vertical and horizontal reservoir heterogeneity, sedimentary microfacies, and oil-water pressure system.

[0015] In step 1, based on the detailed geological research of the reservoir developed by the multi-layer seven-point well pattern, a detailed three-dimensional geological model is established to accurately characterize the vertical and horizontal heterogeneity of the reservoir and describe the reservoir physical properties.

[0016] In step 2, based on the fine three-dimensional geological model, after adding the fluid model, rock model and production dynamic model, a reservoir numerical simulation model is established to perform fine historical fitting.

[0017] In step 2, after completing the detailed historical fitting of the reservoir numerical simulation model, the production dynamic data of oil and water wells, dynamic monitoring, inspection wells, and numerical simulation data are statistically analyzed, and combined with reservoir engineering methods, the vertical and horizontal distribution patterns of residual oil in multi-layer reservoirs in the late stage of ultra-high water cut after long-term seven-point fixed well network water injection development are studied.

[0018] In step 3, the geological reserves, reservoir thickness, distribution characteristics of remaining oil in the reservoir developed by the multi-layer seven-point well pattern, and the development of interlayers are comprehensively considered to analyze whether the study area has the conditions for coordinated conversion flow field of vertical stratum subdivision and stratified water injection and plane well pattern adjustment.

[0019] In step 4, based on the feasibility analysis of changing streamlines to adjust flow fields in the multi-layer seven-point well pattern for developing oil reservoirs, a vertical and horizontal coordinated conversion flow field model is established, and the vertical contradiction is alleviated by using wellbore technology stratified water injection or oil-water well subdivision. Considering the long-term fixed characteristics of the multi-layer seven-point well pattern for developing oil reservoirs, the seven-point well pattern is converted into a determinant well pattern, traversing four displacement directions, and optimizing the well spacing by increasing the well spacing, maintaining the well spacing, and reducing the well spacing to alleviate the horizontal contradiction.

[0020] Preferably, the principles of adjusting the flow field by changing the streamlines in a coordinated manner in the longitudinal and planar directions include:

[0021] (1) Consider economic benefits, reduce investment, increase output, and make full use of old wells;

[0022] (2) Adjust the water well joint injection to subdivided stratum water injection: use the wellbore to subdivide water injection and use the well network to dilute and inject;

[0023] (3) Based on the original seven-point well pattern, the determinant well pattern is considered, different displacement directions and well spacings are designed, and the variable streamline method is optimized;

[0024] Preferably, the four displacement methods are left oblique, right oblique, vertical and horizontal directions;

[0025] In step 5, when designing the seven-point well network adjustment conversion flow field plan, the differences in the displacement degree of the seven-point well network are comprehensively considered to alleviate the vertical and horizontal contradictions.

[0026] In step 5, when designing the seven-point method well network adjustment conversion flow field plan, under the conditions of ensuring the scale of geological reserves, controlling geological reserves by a single well, and making full use of the optimal old wells, the weak drive flow field displacement is strengthened, the strong drive flow field is suppressed, and the strong drive and weak drive flow field are adjusted by changing the streamlines to avoid being affected by the current high water consumption areas and reducing invalid water circulation. The newly designed well network can better utilize the remaining oil, increase the degree of sweep, and reduce the risk of poor conversion flow field effect.

[0027] In step 5, after completing the conversion flow field plan, use reservoir numerical simulation technology to predict the final recovery rate of the flow field plan for changing the streamline to adjust the flow field plan for developing the reservoir with a multi-layer seven-point well network. Calculate the investment based on the workload, compare the advantages and disadvantages of the plans based on actual operability and input-output ratio, and select the optimal plan for implementation.

[0028] Beneficial effects achieved by the present invention:

[0029] The method for improving oil recovery by transforming the well pattern in the multi-layer seven-point well pattern development of oil reservoirs in the present invention is to conduct a detailed study on the geological characteristics of the multi-layer seven-point well pattern reservoirs, establish a detailed three-dimensional geological model, integrate fluid, rock and production dynamic data to establish a reservoir numerical simulation model, perform detailed historical fitting in stages, and comprehensively analyze the differences in the distribution of remaining oil in the multi-layer seven-point well pattern development oil reservoirs.

[0030] On this basis, a feasibility study on the vertical and horizontal coordinated conversion flow field of multi-layer seven-point well network to improve oil recovery was conducted, and a vertical and horizontal coordinated conversion flow field model was established. Under the optimal conditions of ensuring the geological reserve scale of the stratum, the corresponding situation of injection and production, the geological reserve controlled by a single well, and making full use of old wells, the best strong drive and weak drive to change the streamline adjustment flow field were achieved.

[0031] On the basis of making it conducive to mitigating the displacement differences of the seven-point well network, according to the model of establishing longitudinal and planar coordinated conversion flow fields, a scheme design for longitudinal and planar coordinated streamline adjustment flow field of the seven-point well network is carried out, the specific forms of longitudinal and planar coordinated streamline adjustment flow field of the seven-point well network are studied and deployed, the indicators of the deployment scheme are predicted and the economic evaluation is carried out, and the best scheme for improving the recovery rate of oil reservoirs developed by the multi-layer seven-point well network in the late development stage of ultra-high water cut is selected.

[0032] The method of the present invention can slow down the decline of production in the late stage of a multi-layer seven-point well network oil reservoir with extremely high water content and reduce water consumption; it has a significant effect on improving the recovery rate of oil reservoirs developed by the multi-layer seven-point well network, and at the same time can reduce the adjustment risk of old areas and obtain better economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0034] Figure 1 A flowchart of a specific embodiment of the method for improving oil recovery by transforming a reservoir well pattern to develop a multi-layer seven-point well pattern according to the present invention;

[0035] Figure 2 In one embodiment of the present invention, 22 Sedimentary microfacies diagram of the layer;

[0036] Figure 3 In one embodiment of the present invention, 52 Sedimentary microfacies diagram of the layer;

[0037] Figure 4 In one embodiment of the present invention, 42 Sedimentary microfacies diagram of the layer;

[0038] Figure 5 A porosity model of a fine three-dimensional geological model in a specific example of the present invention;

[0039] Figure 6 A permeability model of a fine three-dimensional geological model in a specific example of the present invention;

[0040] Figure 7 A net-to-gross ratio model of a fine three-dimensional geological model in a specific example of the present invention;

[0041] Figure 8 A historical fitting curve of comprehensive water content and monthly oil production of a reservoir numerical simulation model in a specific embodiment of the present invention;

[0042] Fig. 9 This is a plane residual oil saturation distribution diagram of Ng3-4 layer in a specific embodiment of the present invention;

[0043] Fig.10 In a specific embodiment of the present invention, Ng3 52 Distribution diagram of remaining oil saturation in the layer plane;

[0044] Fig.11 In a specific embodiment of the present invention, Ng4 42 Distribution diagram of remaining oil saturation in the layer plane;

[0045] Fig.12 In a specific embodiment of the present invention, a multi-layer seven-point well pattern is used to develop a reservoir by vertically and horizontally coordinating and changing streamlines to adjust the flow field mode;

[0046] Fig.13 A conceptual model diagram of a seven-point well network in a specific embodiment of the present invention;

[0047] Fig.14 In a specific embodiment of the present invention, 52 and 4 42 Conceptual model diagram of well pattern deployment for each layer;

[0048] Fig.15 3 in scheme 2 of a specific embodiment of the present invention 52 and 4 42 Conceptual model diagram of well pattern deployment for each layer;

[0049] Fig.16 3 in scheme 3 of a specific embodiment of the present invention 52 and 4 42 Conceptual model diagram of well pattern deployment for each layer;

[0050] Fig.17 3 in scheme 4 of a specific embodiment of the present invention 52 and 4 42 Conceptual model diagram of well pattern deployment for each layer;

[0051] Fig.18 3 in scheme 5 of a specific embodiment of the present invention 52 and 4 42 Diagram of the conceptual model of well pattern deployment in different layers. DETAILED DESCRIPTION

[0052] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0053] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0054] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0055] like Figure 1 As shown, Figure 1 The flowchart of a specific embodiment of the method for improving oil recovery by changing the well pattern of the multi-layer seven-point method well pattern development oil reservoir of the present invention is given. The method takes into account the late stage of development of multi-layer oil reservoirs with extremely high water content, and also considers the long-term development form of a seven-point method regular well pattern.

[0056] In step 101, a detailed geological study of the multi-layer reservoir is conducted, mainly focusing on the stratigraphic comparison and division, structure, vertical and horizontal heterogeneity of the reservoir, sedimentary microfacies, and oil-water pressure system.

[0057] In step 101, a fine three-dimensional geological model is established to finely characterize reservoir heterogeneity and describe reservoir physical properties in combination with fine geological research of multi-layer oil reservoirs. The process proceeds to step 102.

[0058] In step 102, based on the fine three-dimensional geological model, after adding the fluid model, rock model, and production dynamic model, a reservoir numerical simulation model is established, and a detailed historical fitting is performed in stages, laying a foundation for studying the analysis and prediction of the remaining oil saturation of the reservoir developed by the multi-layer seven-point well network.

[0059] In step 102, the production dynamic data, dynamic monitoring, numerical simulation and other information are statistically analyzed, and combined with reservoir engineering methods, the vertical and horizontal residual oil distribution patterns of multi-layer reservoirs in the late stage of ultra-high water cut after long-term seven-point fixed well pattern water injection development are studied. The process enters step 103.

[0060] In step 103, considering geological reserves, reservoir thickness, distribution characteristics of remaining oil in reservoirs developed by multi-layer seven-point well pattern, interlayer development, etc., it is analyzed whether the study area has the conditions for coordinated conversion flow field of vertical layer subdivision or layered water injection and plane well pattern adjustment. The process enters step 104.

[0061] In step 104, based on the feasibility analysis of changing streamlines and adjusting flow fields in developing oil reservoirs with a multi-layer seven-point well network, a vertical and horizontal coordinated conversion flow field model is established, and the vertical contradiction is alleviated by using wellbore technology to inject water in layers or subdivide the layers of oil and water wells; considering the long-term fixed characteristics of oil reservoirs developed with a multi-layer seven-point well network, the seven-point well network is converted into a determinant well network, traversing four displacement directions (left oblique, right oblique, vertical and horizontal), and the well spacing is optimized by increasing the well spacing, maintaining the well spacing or reducing the well spacing to alleviate the plane contradiction.

[0062] In step 105, under the optimal conditions of ensuring geological reserve scale, single well control of geological reserves, and full use of old wells, the best strong drive and weak drive change streamline adjustment flow field is achieved, high water consumption area is suppressed, and the displacement is balanced to the greatest extent. In one embodiment, when designing the seven-point method well network vertical and plane coordinated conversion flow field scheme, the weak drive flow field displacement is strengthened, the strong drive flow field is suppressed, the influence of the current high water consumption area is avoided, the invalid water circulation is reduced, and the newly designed well network can better use the remaining oil, improve the sweep degree, and reduce the risk of poor conversion flow field effect.

[0063] In step 105, the reservoir numerical simulation technology is used to predict the final recovery rate of the streamline adjustment scheme for developing the reservoir with the multi-layer seven-point well pattern, calculate the investment according to the workload, compare the advantages and disadvantages of the schemes according to the actual operability and input-output ratio, and select the optimal scheme for implementation. The process ends.

[0064] In order to make the above contents of the present invention more clearly understandable, the following is a detailed description of the 3-4 research area of ​​Zhongzhongguan in the Gudao Oilfield of Shengli Oilfield as an example:

[0065] The geological reserves of the 3-4 study area of ​​Zhongzhong Pavilion in Gudao Oilfield are 374×10 4 t, multi-layer oil reservoir. It was put into development in 1972. In 1975, a 225-meter four-point well network was used for water injection development. In 1982, the subdivision of the strata was adjusted and divided into two sets of strata, Ng3-4 and Ng5. In 1988, the Ng3-4 strata was adjusted to a 225-meter seven-point injection and production well network (combined injection and separate production). In 1998, polymer was injected and switched to subsequent water flooding in 2005. As of February 2014, the daily liquid production level of a single well in the study area was 98.0t / d, the daily oil production level of a single well was 2.5t / d, the comprehensive water content was 97.7%, and the recovery degree was 56.8%. At present, it has entered the late stage of ultra-high water content, and the oil layers are seriously flooded. The seven-point well network has a high degree of recovery, high oil displacement efficiency, large displacement differences, developed high water consumption areas, serious ineffective water circulation, and poor effects of conventional technical measures. It is difficult to further improve the recovery rate under the current stratum well network conditions. It is urgent to establish a seven-point well network strong drive and weak drive to change the streamline and adjust the flow field technology, change the liquid flow direction, suppress the high water consumption area, and increase the sweep degree to achieve the purpose of improving the recovery rate and economic benefits.

[0066] 1. Detailed geological research on reservoir development using multi-layer seven-point well network and establishment of a detailed three-dimensional geological model of the reservoir

[0067] In the late stage of extremely high water cut, the distribution of remaining oil is extremely complex, and detailed geological research is the basis for changing streamlines and adjusting flow fields in the multi-layer seven-point well network development of oil reservoirs. Figures 2 to 4 For example, the geological characteristics of the formation, structure, vertical and horizontal heterogeneity of the reservoir, sedimentary microfacies, oil-water pressure system, etc. are studied. Figures 5 to 7As shown, a detailed three-dimensional geological model is established to accurately characterize the reservoir heterogeneity and describe the reservoir physical properties.

[0068] 2. Establishment of a multi-layer seven-point well network reservoir numerical simulation model and study of the distribution law of residual oil saturation

[0069] like Figure 8 As shown in the figure, based on the fine three-dimensional geological model, a reservoir numerical simulation model is established to perform detailed historical fitting in stages. After completing the historical fitting of the model, the production dynamic data, dynamic monitoring, numerical simulation and other data are comprehensively used for statistical analysis to study the vertical and horizontal residual oil distribution of multi-layer reservoirs in the late stage of ultra-high water cut after long-term seven-point fixed well network water injection development. Figures 9 to 11 As shown, due to the influence of multi-layer joint injection of water wells, long-term fixation of the seven-point well pattern, and imperfect local well pattern, large areas of water flooding are serious on the plane, the mainstream line forms a high water consumption area, and the remaining oil saturation of the mainstream line is much greater than that of the non-mainstream line.

[0070] 3. Establish a seven-point well network to coordinate vertical and horizontal changes in streamlines and adjust flow field patterns

[0071] like Fig.12 As shown in the figure, a vertical and horizontal coordinated conversion flow field mode is established: the vertical contradiction is alleviated by using wellbore technology to inject water in layers or subdivide the layers of oil and water wells; considering the long-term fixed characteristics of the reservoir developed by the multi-layer seven-point well network, the seven-point well network is converted into a matrix well network, traversing four displacement directions (left oblique, right oblique, vertical and horizontal), and the well spacing is optimized by increasing the well spacing, maintaining the well spacing, and reducing the well spacing to alleviate the horizontal contradiction.

[0072] 4. Create a multi-layer seven-point well pattern to develop reservoir well pattern transformation to improve oil recovery

[0073] When developing oil reservoirs with a multi-layer seven-point well network, after long-term water injection and flushing with fixed flow lines, dynamic heterogeneity intensifies, forming high water consumption areas, the distribution differences of remaining oil saturation in different parts increase, and invalid water circulation intensifies. It is urgent to reform the flow field, improve the development effect, and increase the recovery rate.

[0074] Strata subdivision and stratified water injection can alleviate vertical contradictions. Due to the difference in vertical permeability between Pavilion 3 and Pavilion 4 in the middle of the second layer, the production conditions are quite different (the permeability of Pavilion 3 is higher than that of Pavilion 4, and the production degree of Pavilion 3 is higher than that of Pavilion 4). The sedimentary microfacies of Pavilion 3 is different from that of Pavilion 4. The distribution of the interlayers between Pavilion 3 and Pavilion 4 is stable. The geological reserves, reservoir thickness and interlayer development of Pavilion 3 and Pavilion 4 all meet the basic principles of stratigraphic subdivision or stratified water injection. Therefore, Pavilion 3 can be divided into a set of stratigraphic systems, Pavilion 4 can be divided into a set of stratigraphic systems, or the wellbore string can be used to realize stratified water injection in Pavilion 3 and Pavilion 4.

[0075] like Fig.13The figure shows a schematic diagram of a 225m seven-point injection-production well pattern that has been used for about 20 years. The principles of adjusting the flow field by changing the streamlines in the vertical and horizontal directions include: (1) considering economic benefits, less investment, more output, and making full use of old wells; (2) adjusting the combined injection of water wells to subdivided layer injection: using the wellbore for subdivided injection and using the well pattern for dilution injection; (3) on the basis of the original seven-point pattern, considering the determinant pattern, designing different displacement directions and well spacings, and optimizing the streamline change method. Here are five representative methods of changing the streamlines to adjust the flow field using the seven-point pattern.

[0076] Plan 1: Subdividing the wells into layers, Ng3 is thinned out, Ng4 is thinned out, Ng3 and Ng4 are thinned out every other time, left oblique staggered well pattern, flow line rotation 30°, row spacing 195m, such as Fig.14 As shown. This plan designs 14 oil wells and 15 water wells. The favorable conditions are that the old wells are fully utilized, and the development of two sets of layers alleviates the contradiction between layers, changes the displacement direction, changes the flow line by 30°, and has a relatively small investment.

[0077] Plan 2: Subdivide the strata, thin out Ng3, thin out Ng4, thin out every other well to Ng3 and Ng4, right oblique staggered well pattern, turn the flow line 30°, and the row spacing is 195m. Fig.15 As shown. This scheme designs 14 oil wells and 14 water wells. The favorable conditions are that the streamline is changed by 30°, the old wells are fully utilized, the displacement direction is changed, and the workload is small.

[0078] Scheme 3: Subdividing the layers, thinning out Ng3, thinning out Ng4, thinning out Ng3 and Ng4 one by one, vertically staggered well pattern, flow line rotation 30°, row spacing 195m, such as Fig.16 As shown. This plan designs 15 oil wells and 14 water wells. The favorable conditions are that the displacement direction is changed, the streamline turns 30°, and the interlayer contradiction is alleviated; the workload is relatively small and the investment is low. The unfavorable conditions are that more oil wells are converted into water wells, and the initial production is affected.

[0079] Plan 4: Make full use of old wells, subdivide the strata, thin out Ng3, thin out Ng4, thin out Ng3 and Ng4 one by one, stagger the well pattern in the horizontal direction, and turn the streamline 30°, such as Fig.17 As shown in the figure, this scheme designs 13 oil wells and 14 water wells. The favorable conditions are that the displacement direction is changed, the streamline is changed by 30°, and the investment is relatively low.

[0080] Plan 5: Water well subdivision and water injection, Ng3 and Ng4 thinning, right oblique staggered determinant, flow line rotation 30°, row spacing 195m, such as Fig.18 As shown. This scheme designs 14 oil wells and 6 water wells. The favorable conditions are changing the displacement direction, the streamline turns 30°, making full use of the old wells for subdivision water injection, low investment and low production cost.

[0081] 5. Change the flow field and adjust the flow field scheme to optimize

[0082] Using reservoir numerical simulation technology, the final recovery rate of the streamline adjustment flow field scheme is predicted. The highest recovery rate is scheme 2, which predicts a 1.0% recovery rate increase by the end of 2015 and an input-output ratio of 20.1. However, scheme 5 has an input-output ratio of 21.7 and predicts a 0.9% recovery rate increase by the end of 2015. It has better economic benefits, and the operation measures are highly operational, the flow field adjustment intensity of streamline adjustment is high, the vertical contradiction is alleviated after stratified water injection, and the old wells are fully utilized. Therefore, scheme 5 with subdivided water injection and streamline adjustment is selected as the optimal scheme.

[0083] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for improving oil recovery by transforming the well pattern of a multi-layer seven-point well pattern in developing an oil reservoir, characterized in that: The method comprises: Step 1: Develop a multi-layer seven-point well network to conduct detailed geological research on the reservoir and establish a detailed three-dimensional geological model; Step 2: Establish a fine numerical simulation model of the reservoir through historical matching to analyze the distribution law of remaining oil in the late stage of reservoir with extremely high water cut in the multi-layer seven-point well network development; Step 3, analyzing the feasibility of adjusting the flow field by changing the streamlines in the vertical and horizontal directions to improve the recovery rate of the reservoir by developing a multi-layer seven-point well pattern; Step 4, establish a multi-layer seven-point method well network to develop the reservoir vertically and horizontally to coordinately change the streamlines and adjust the flow field pattern; Step 5, design a multi-layer seven-point well pattern to develop a plan for improving oil recovery by changing the streamlines and adjusting the flow field in the vertical and horizontal directions, optimize and economically evaluate the plan, and select the best implementation plan; In step 4, based on the feasibility analysis of changing streamlines to adjust flow fields in the multi-layer seven-point well pattern for developing oil reservoirs, a vertical and horizontal coordinated conversion flow field model is established, and the vertical contradiction is alleviated by using wellbore technology stratified water injection or oil-water well subdivision. Considering the long-term fixed characteristics of the multi-layer seven-point well pattern for developing oil reservoirs, the seven-point well pattern is converted into a determinant well pattern, traversing four displacement directions, and optimizing the well spacing by increasing the well spacing, maintaining the well spacing, and reducing the well spacing to alleviate the horizontal contradiction. The principles of adjusting the flow field by changing the streamlines in the longitudinal and lateral directions include: (1) Consider economic benefits, reduce investment, increase output, and make full use of old wells; (2) Adjust the water well joint injection to subdivided stratum water injection: use the wellbore to subdivide water injection and use the well network to dilute and inject; (3) Based on the original seven-point well pattern, the determinant well pattern is considered, different displacement directions and well spacings are designed, and the variable streamline method is selected; The four displacement methods are left oblique, right oblique, vertical, and horizontal directions; In step 5, when designing the seven-point well pattern adjustment conversion flow field scheme, the differences in displacement degree of the seven-point well pattern are comprehensively considered to alleviate the vertical contradiction and the plane contradiction; In step 5, when designing the seven-point method well network adjustment conversion flow field plan, under the conditions of ensuring the scale of geological reserves, controlling geological reserves by a single well, and making full use of the optimal old wells, the weak drive flow field displacement is strengthened, the strong drive flow field is suppressed, and the strong drive and weak drive flow field are adjusted by changing the streamlines to avoid being affected by the current high water consumption areas and reducing invalid water circulation. The newly designed well network can better utilize the remaining oil, increase the degree of sweep, and reduce the risk of poor conversion flow field effect.

2. The method according to claim 1, characterized in that: In step 1, the multi-layer seven-point well pattern is used to develop a detailed geological study of the reservoir, including stratigraphic correlation and division, structure, vertical and horizontal reservoir heterogeneity, sedimentary microfacies, and oil-water pressure system.

3. The method according to claim 1, characterized in that: In step 1, based on the detailed geological research of the reservoir developed by the multi-layer seven-point well pattern, a detailed three-dimensional geological model is established to accurately characterize the vertical and horizontal heterogeneity of the reservoir and describe the reservoir physical properties.

4. The method according to claim 1, characterized in that: In step 2, based on the fine three-dimensional geological model, after adding the fluid model, rock model and production dynamic model, a reservoir numerical simulation model is established to perform fine historical fitting.

5. The method according to claim 1, characterized in that: In step 2, after completing the detailed historical fitting of the reservoir numerical simulation model, the production dynamic data of oil and water wells, dynamic monitoring, inspection wells, and numerical simulation data are statistically analyzed, and combined with reservoir engineering methods, the vertical and horizontal distribution patterns of residual oil in multi-layer reservoirs in the late stage of ultra-high water cut after long-term seven-point fixed well network water injection development are studied.

6. The method according to claim 1, characterized in that: In step 3, the geological reserves, reservoir thickness, distribution characteristics of remaining oil in the reservoir developed by the multi-layer seven-point well pattern, and the development of interlayers are comprehensively considered to analyze whether the study area has the conditions for coordinated conversion flow field of vertical stratum subdivision and stratified water injection and plane well pattern adjustment.

7. The method according to claim 1, characterized in that: In step 5, after completing the conversion flow field plan, use reservoir numerical simulation technology to predict the final recovery rate of the flow field plan for changing the streamline to adjust the flow field plan for developing the reservoir with a multi-layer seven-point well network. Calculate the investment based on the workload, compare the advantages and disadvantages of the plans based on actual operability and input-output ratio, and select the optimal plan for implementation.

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