A development method using large pores in oil fields

Abstract

The present invention relates to a method for developing large pores in oil fields, the method comprising: S1, conducting large pore diagnosis to determine the presence of dominant large pores in the reservoir; S2, fitting the permeability distribution of the actual reservoir using numerical simulation software according to the diagnosis result in step S1, and finally determining the permeability of the large pores; S3, when the permeability of the large pores and the permeability of the actual reservoir meet a certain numerical range, shutting down or re-injecting the production wells on the large pores, so that the large pores are formed into secondary flexible micro-horizontal wells for development and utilization. The present invention proposes a new method for utilizing large pores that changes "blocking" of large pores to "unblocking", which is conducive to achieving economic and technical optimization and provides a basis for the improvement of water drive development technology for offshore oil fields in the next step.

Description

Technical Field

[0001] The invention relates to the technical field of oil development, and in particular to a development method utilizing large pores in an oil field. Background Art

[0002] Most of the reservoirs in my country's offshore oil fields are fluvial-deltaic sandstone deposits, with serious plane, interlayer and intralayer heterogeneity. After decades of long-term water injection development, large pores are common in loose sandstone reservoirs. The large pore permeability explained by the interwell tracer test results is much higher than the average reservoir permeability and core analysis permeability. The long-term water injection development of large pores leads to unidirectional advancement of injected water, and some production wells along the path with better physical properties see water quickly, and the permeability of large pores shows a trend of gradual increase with the extension of production time.

[0003] Most scholars have revealed the phenomenon of large pore development from the dynamic analysis of reservoir production. The existing understanding is mostly from the perspective of reservoir engineering, analyzing the impact of large pore development on well pattern adjustment and oil field recovery. Although these studies have guiding significance for the late stage of development, the late stage of dynamic adjustment of reservoirs with large pores, and the adoption of profile adjustment and water plugging measures, the current research, however, mostly adopts the method of plugging for the large pores formed, and there is no report on the utilization of large pores.

[0004] Therefore, it is necessary to propose a technical solution to the problem of large-pore utilization. Summary of the invention

[0005] In view of this, the present invention proposes a development method utilizing large pores in oil fields, so as to break through the traditional large pore management strategy with the purpose of "blocking", change "blocking" to "unblocking", give full play to the advantages of large pores, and thus improve the development effect.

[0006] The present invention provides a method for developing large pores in an oil field, the method comprising:

[0007] S1. Conduct macropore diagnosis to determine the presence of dominant macropores in the reservoir;

[0008] S2, according to the diagnosis result in step S1, using numerical simulation software to fit the permeability distribution of the actual reservoir, and finally determining the permeability of the macropores;

[0009] S3. When the permeability difference between the macropores and the actual reservoir permeability meets a certain numerical range, the production wells on the macropores are shut down or re-injected so that the macropores are formed into secondary flexible micro-horizontal wells for development and utilization.

[0010] According to one embodiment of the present invention, the method further comprises:

[0011] S4. According to different well network conditions and different water-containing times of actual oil reservoirs, by comparing the development effects of different measures, the final mode of regulating, plugging or developing and utilizing the large pores is determined.

[0012] According to an embodiment of the present invention, in step S4, the different well pattern conditions include a five-spot well pattern, a seven-spot well pattern, and a nine-spot well pattern.

[0013] According to an embodiment of the present invention, in step S1, the macropore diagnosis method includes a tracer detection method, a pressure pulse test method, a well testing method, and a production dynamic method.

[0014] According to one embodiment of the present invention, step S2 further includes:

[0015] S21. Using interpolation software, the initial permeability field and pressure field distribution of the oil field are obtained;

[0016] S22, performing numerical simulation using streamline numerical simulation software to obtain production data of each streamline;

[0017] S23, fitting the simulated production data with the actual production data, and adjusting the permeability distribution of each streamline so that the calculation result of step S22 and the actual production data are within a controllable error range;

[0018] S24, mapping the permeability distribution of each streamline fitted in step S23 to the numerical simulation grid, and obtaining the permeability of the large pores through the grid where the large pores are located.

[0019] According to one implementation of the present invention, the interpolation software is SUFER.

[0020] According to one embodiment of the present invention, the streamline numerical simulation software is ECLIPSE.

[0021] According to an embodiment of the present invention, in step S22, the production data of each flow line includes tracer concentration, flow rate, and pressure data.

[0022] According to an embodiment of the present invention, when the difference between the permeability of the macropores and the actual reservoir permeability is greater than or equal to 50, the production wells on the macropores are shut in or switched for injection.

[0023] According to one embodiment of the present invention, in step S3, when the macropore is formed into a secondary flexible micro-horizontal well, a flow field perpendicular to the macropore is continuously formed to achieve the extension of the macropore in the oil layer, so that the fluid flows along the direction of the macropore similar to a horizontal well.

[0024] The present invention adopts the above technical scheme, thereby overcoming the problems of high cost and short validity period caused by conventional water plugging methods alone; and solving the problem that the large pores in some old oil fields are too large and cannot be plugged by conventional profile control and water plugging processes.

[0025] In summary, the present invention proposes a new method for utilizing large pores to change "blocking" into "unblocking", which is conducive to achieving economic and technical optimization and provides a basis for the improvement of the next step of offshore oilfield water drive development technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A simplified schematic diagram of a five-point well pattern model according to an embodiment of the present invention;

[0027] Figure 2 Comparison of recovery rates of different treatment methods for large pores in a five-point well pattern model according to an embodiment of the present invention;

[0028] Figure 3 A simplified schematic diagram of an inverse nine-spot well pattern model according to an embodiment of the present invention;

[0029] Figure 4 The comparison of recovery factors of different treatment methods for large pores in the reverse nine-spot well pattern model according to one embodiment of the present invention is shown;

[0030] Figure 5a The streamline distribution of a five-point well pattern model with large pores developed in one embodiment of the present invention when it is put into production;

[0031] Figure 5b The streamline distribution of a five-point well pattern model with large pores developed in one embodiment of the present invention after two years of production;

[0032] Figure 5c This is the streamline distribution of a five-point well pattern model with large pores developed in one embodiment of the present invention after being put into production for 4 years. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings so that the purpose, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solution of the present invention.

[0034] To achieve the above-mentioned purpose, the method for developing large pores in oil wells according to the embodiment of the present invention comprises the following contents:

[0035] 1) Conduct macropore diagnosis to determine the presence of dominant macropores in the reservoir; dominant macropores refer to high-permeability strips with large porosity formed by the reservoir due to long-term scouring of injected water, differences in permeability and gravity differentiation of oil and water. As a result, during oilfield development, injected water preferentially advances along this strip to the oil well, gradually forming highly permeable strong water-washing channels that are interconnected between oil and water wells. The pore radius is generally between 30μm and 5mm;

[0036] 2) According to the tracer results in step 1), numerical simulation software is used to fit the permeability distribution of the actual reservoir, and finally the permeability of the macropores is determined;

[0037] 3) When the permeability difference between the macropore and the actual reservoir permeability is greater than or equal to 50, the production wells on the macropore are shut down or re-injected to continuously form a flow field perpendicular to the macropore, so that the macropore can extend in the oil layer. At this time, the fluid flows along the macropore in the direction of the macropore, similar to a horizontal well. This macropore is called a "secondary flexible micro-horizontal well". Unlike conventional horizontal wells, this horizontal well is narrow and small, and may have an irregular shape.

[0038] 4) According to the different well network conditions and different water content periods of the actual oil reservoir, the final large-pore plugging or utilization mode is determined by comparing the development effects of different measures.

[0039] In the step 1), the large pore diagnosis method includes tracer detection method, pressure pulse test method, well testing method, production dynamic method and the like. The tracer detection method used in this embodiment mainly uses isotope tracers for downhole measurement, and finds the dominant channel direction and layer through the detection results.

[0040] The step 2) mainly includes:

[0041] ① Using interpolation software to obtain the initial permeability field and pressure field distribution, the interpolation software is generally SUFER;

[0042] ② Use streamline numerical simulation software to perform numerical simulation to obtain production data of each streamline, including tracer concentration, flow rate, pressure and other data. The streamline numerical simulation software is generally ECLIPSE;

[0043] ③ Fitting the production data obtained in step ② with the actual production data, and adjusting the permeability distribution of each streamline so that the calculation result of step ② and the actual production data are within a controllable error range.

[0044] ④ Map the permeability distribution of each streamline obtained by fitting in step ③ to the numerical simulation grid to obtain the final permeability distribution of each grid.

[0045] In the step 3), the secondary flexible micro-horizontal wells may be caused during the water injection development of loose sandstone reservoirs, or they may be artificial or natural fractures, which are widely present near a single well or between two wells. The main factors affecting the formation of secondary flexible micro-horizontal wells are the permeability difference between the large pores and the permeability of the oil layer, and are also affected by the viscosity of the crude oil and the location and length of the large pores.

[0046] The large-pore permeability can be calculated through fitting with numerical simulation software, and the permeability difference can be calculated using the following formula. Through numerical simulation of different difference sensitivity analysis, it is found that when the difference is greater than 50, the use of large-pore development will have a significant effect.

[0047]

[0048] In the formula, K 级差 is the permeability difference, K d is the macropore permeability, mD, and K is the reservoir permeability, mD.

[0049] In step 4), different well pattern conditions can be conventional reservoir well layout methods such as five-point well pattern, seven-point well pattern, nine-point well pattern, etc. The different measures mainly consider shutting down production wells or transferring injection to form secondary flexible micro-horizontal wells, and adjusting profile and plugging water.

[0050] The present invention adopts the above technical scheme, thereby overcoming the problems of high cost and short validity period caused by conventional water plugging methods alone; and solving the problem that the large pores in some old oil fields are too large and cannot be plugged by conventional profile control and water plugging processes.

[0051] In summary, the present invention proposes a new method for utilizing large pores to change "blocking" into "unblocking", which is conducive to achieving economic and technical optimization and provides a basis for the improvement of the next step of offshore oilfield water drive development technology.

[0052] Embodiment 1

[0053] This embodiment provides a method for developing secondary flexible micro-horizontal wells in a five-point well pattern. The simplified five-point well pattern model is as follows: Figure 1 As shown, the development method includes the following steps:

[0054] 1) Using the reservoir numerical simulation software ECLIPSE, a five-point well pattern mechanism model with large pores was established. Figure 1 As shown;

[0055] 2) The model is vertically homogeneous, the reservoir permeability is 2000mD, the macropore is located on the line connecting production well P2, injection well I1, and production well P4, and the permeability of the macropore is set to 200D in the model;

[0056] 3) Using the ECLIPSE streamline simulation module, three modes were set up: injection transfer and well shut-in for the production well P2, and profile adjustment for the injection well I1. The permeability of the macropores after profile adjustment was the reservoir permeability (2000mD). Other parameters of the model were based on the actual situation of Block D of Bohai A Oilfield.

[0057] 4) According to the above three different large pore treatment methods, the development effects of production well P2 under different water cut conditions (98%, 95%, 85%) are simulated respectively. The simulation results are shown in Figure 2 and Table 1.

[0058] Table 1 Comparison of recovery factors of different treatment methods for large pores in five-point well pattern model

[0059]

[0060] After comparative analysis, it can be found that compared with the basic plan, profile adjustment, well shut-in and injection can all increase the recovery rate, and the treatment method of forming a quasi-horizontal well through injection has the highest increase in recovery rate. By optimizing the implementation timing, it was finally determined to use the mode of injection to form a quasi-horizontal well when the water cut is 85%.

[0061] Embodiment 2

[0062] This embodiment provides a method for developing secondary flexible micro-horizontal wells in an inverted nine-spot well pattern, a simplified inverted nine-spot well pattern model, and the development method includes the following steps:

[0063] 1) Using the reservoir numerical simulation software ECLIPSE, a mechanism model of the anti-nine-spot well pattern with large pores was established. Figure 3 As shown;

[0064] 2) The model has three vertical layers, and the permeabilities of each layer are 1000mD, 3000mD, and 5000mD respectively. The macropore is located on the line connecting the production well P2, the injection well I1, and the production well P8. The permeability of the macropore is set to 500D in the model;

[0065] 3) Using the ECLIPSE streamline simulation module, three modes of injection, shut-in and water plugging were set for the production well P1. The permeability of the macropores after water plugging was the average permeability of the reservoir (3000mD). Other parameters of the model were based on the actual situation of Block F of Bohai A Oilfield.

[0066] 4) According to the above three different large pore treatment methods, the development effects of production well P2 under different water cut conditions (98%, 90%, 80%) are simulated respectively. The simulation results are shown in Figure 4 and Table 2.

[0067] Table 2 Comparison of recovery factors of different treatment methods for large pores in the reverse nine-spot well pattern model

[0068]

[0069]

[0070] After comparative analysis, it can be found that compared with the basic plan, profile adjustment, well shut-in and injection can all increase the recovery rate, and the treatment method of forming a quasi-horizontal well through injection has the highest increase in recovery rate. By optimizing the implementation timing, it was finally determined to use the mode of injection to form a quasi-horizontal well when the water cut is 80%.

[0071] Figure 5a , 5b Figures 5 and 5c correspond to the streamline distribution of the five-point well pattern with large pores at the initial stage of production, 2 years after production, and 4 years after production. The changes in streamline distribution show that the previously unused areas have been used after the shut-in / re-injection measures, which increases the swept volume and thus improves the recovery factor.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit its protection scope. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the present application, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the protection scope of the claims to be approved.

Claims

1. A method for developing large pores in an oil field, characterized in that: The method comprises: S1. Conduct macropore diagnosis to determine the presence of dominant macropores in the reservoir; S2, according to the diagnosis result in step S1, using numerical simulation software to fit the permeability distribution of the actual reservoir, and finally determining the permeability of the macropores; S3. When the permeability difference between the macropores and the actual reservoir permeability meets a certain numerical range, shut down or transfer the production wells on the macropores so that the macropores are formed into secondary flexible micro-horizontal wells for development and utilization; In step S1, the macropore diagnosis method includes a tracer detection method, a pressure pulse test method, a well testing method, and a production dynamic method; The step S2 further comprises: S21. Using interpolation software, the initial permeability field and pressure field distribution of the oil field are obtained; S22, performing numerical simulation using streamline numerical simulation software to obtain production data of each streamline; S23, fitting the simulated production data with the actual production data, and adjusting the permeability distribution of each streamline so that the calculation result of step S22 and the actual production data are within a controllable error range; S24, mapping the permeability distribution of each streamline fitted in step S23 to the numerical simulation grid, and obtaining the permeability of the large pores through the grid where the large pores are located; In step S3, when the macropore is formed into a secondary flexible micro-horizontal well, a flow field perpendicular to the macropore is continuously formed to achieve the extension of the macropore in the oil layer, so that the fluid flows along the macropore direction similar to a horizontal well.

2. The method for developing large pores in oil fields according to claim 1, characterized in that: The method further comprises: S4. According to different well network conditions and different water-containing times of actual oil reservoirs, by comparing the development effects of different measures, the final mode of regulating or developing the large pores is determined.

3. The method for developing large pores in oil fields according to claim 2, characterized in that: In step S4, different well pattern conditions include a five-spot well pattern, a seven-spot well pattern, and a nine-spot well pattern.

4. The method for developing large pores in oil fields according to claim 1, characterized in that: The interpolation software is SUFER.

5. The method for developing large pores in oil fields according to claim 1, characterized in that: The streamline numerical simulation software is ECLIPSE.

6. The method for developing large pores in oil fields according to claim 1, characterized in that: In step S22, the production data of each flow line includes tracer concentration, flow rate, and pressure data.

7. The method for developing large pores in oil fields according to claim 1, characterized in that: When the difference between the permeability of the macropores and the actual reservoir permeability is greater than or equal to 50, the production wells on the macropores are shut in or switched for injection.

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