Shale oil development method and system based on ternary storage and seepage

Abstract

The invention provides a shale oil development method and system based on ternary storage and seepage. The development method comprises the steps that 1, key evaluation factors of shale oil development are determined; 2, according to the key evaluation factors, evaluating the seepage space and path of the multi-scale fracture network after reconstruction to obtain an evaluation result; step 3, optimally designing target area development parameters according to the evaluation result; and 4, the working system of the shale oil horizontal well is optimized and regulated according to the development parameters of the target area. Geological features and engineering features of shale oil development are considered, sweet spot prediction, fracturing process optimization and pilot test scheme implementation can be effectively guided, and the method has important significance in guiding shale oil large-scale efficient development.

Description

Technical Field

[0001] The present invention relates to the technical field of unconventional oil and gas exploitation, and in particular to a shale oil development method and system based on ternary storage and permeability. Background Art

[0002] Shale oil is an emerging strategic oil and gas resource. The large-scale commercial development of shale oil and gas in the United States has not only reversed the United States' dependence on foreign oil and gas, but also shaped a new global oil and gas supply pattern. China's technically recoverable shale oil reserves are about 43.50×108t, mainly distributed in major basins such as Songliao, Ordos, Junggar, Qaidam, Lunpola, Qiangtang, Maoming, Dayangshu, and Fushun. Shale oil resources will surely become an important component of China's strategic resource replacement. Although my country's shale oil is widely distributed and rich in resources, compared with typical marine shale oil in North America, it has strong reservoir heterogeneity, poor reservoir quality, low single well production, and low recovery rate. It still faces great challenges to achieve effective utilization.

[0003] In recent years, China has formed a series of shale oil and gas exploration and development theories and understandings around the key issues that restrict shale oil and gas exploration and development. Through the shale gas exploration practice of the Longmaxi Formation in the Sichuan Basin and its surrounding areas, the "binary enrichment" law of marine shale gas was explored and proposed. Through the study of the shale oil in the second section of Kongdong Depression, the enrichment theory of continental shale oil "dominant structural phase-retained hydrocarbon surpassing effect" was proposed. Jiyang shale oil proposed that lithofacies are the basis for shale oil enrichment, microfractures are the place for free shale oil enrichment, and abnormally high pressure is the guarantee for shale oil enrichment and stable production. Shale gas development started earlier than shale oil, and "volume development" has been formed in the shale gas field. However, the theoretical aspects of shale oil are mainly based on shale oil geology, and methods for efficient development of shale oil have not yet been established. Summary of the invention

[0004] In view of the above problems, the present invention is proposed to provide a shale oil development method and system based on ternary storage and permeability that overcomes the above problems or at least partially solves the above problems.

[0005] According to one aspect of the present invention, a shale oil development method based on ternary storage and permeability is provided, the development method comprising:

[0006] Step 1: Determine the key evaluation factors for shale oil development;

[0007] Step 2: Based on the key evaluation factors, the seepage space and path after the multi-scale fracture network transformation are evaluated to obtain the evaluation results;

[0008] Step 3: Optimize and design the development parameters of the target area according to the evaluation results;

[0009] Step 4: Optimize and regulate the shale oil horizontal well working system according to the development parameters of the target area.

[0010] Optionally, the step 1: determining the key evaluation factors for shale oil development specifically includes three end members: storage element, fracture element, and pressure element.

[0011] Optionally, the reservoir elements include rock structure, reservoir space and hydrocarbon occurrence, which are the material basis for shale oil enrichment.

[0012] Optionally, the fracture element includes the seepage capacity of natural fractures and an artificial high seepage field, which is the seepage condition for high production of shale oil.

[0013] Optionally, the pressure element includes elastic energy and absorption energy, which are the dynamic conditions for high and stable production of shale oil.

[0014] Optionally, the step 2: evaluating the seepage space and path after the multi-scale fracture network transformation according to the key evaluation factors, and obtaining the evaluation results specifically includes:

[0015] The core pore structure at different pore pressures was scanned using online high-resolution nano-CT.

[0016] Construct three-dimensional digital core models of cores under different pore pressures;

[0017] Calculate the pore parameters at different pore pressures.

[0018] Optionally, the core specifications are 2.5 cm in diameter and 2-5 cm in length.

[0019] Optionally, the pore parameters specifically include: porosity, connected pore ratio, permeability, seepage space and seepage path.

[0020] Optionally, the step 3: optimizing and designing the development parameters of the target area according to the evaluation results specifically includes:

[0021] To improve the pore connectivity in the matrix, a three-dimensional geological model and geomechanical model of the target area were established;

[0022] The integrated geology-fracturing-reservoir simulation technology is used to optimize the design of fracturing sections and fracturing clusters to maximize the complexity of the fracture network.

[0023] Optionally, the horizontal well working system includes well blocking after fracturing, high-speed fluid drainage and fine pressure control stages.

[0024] Optionally, step 4: based on the optimization and regulation of the working system of shale oil horizontal wells according to the development parameters of the target area, numerical simulation optimization is used to determine the number of days of well blocking and the return fluid rate, the number of days of well blocking is 10-20 days, the high-speed fluid discharge rate is greater than 200 tons / day, and the fracturing drop amplitude in the fine pressure control stage is less than 0.02MPa / day.

[0025] The present invention also provides a shale oil development system based on ternary storage and permeability, which is applied to the above-mentioned shale oil development method based on ternary storage and permeability, and the shale oil development system includes:

[0026] Evaluation factor determination module, used to determine the key evaluation factors for shale oil development;

[0027] An evaluation result acquisition module is used to evaluate the seepage space and path after the multi-scale fracture network transformation according to the key evaluation factors to obtain the evaluation results;

[0028] A development parameter optimization module, used for optimizing the development parameters of the design target area according to the evaluation results;

[0029] The working system control module is used to optimize and control the working system of shale oil horizontal wells according to the development parameters of the target area.

[0030] The present invention provides a shale oil development method and system based on ternary storage and permeability, the development method comprising: step 1: determining key evaluation factors for shale oil development; step 2: evaluating the seepage space and path after multi-scale fracture network transformation according to the key evaluation factors, and obtaining evaluation results; step 3: optimizing and designing the development parameters of the target area according to the evaluation results; step 4: optimizing and regulating the shale oil horizontal well working system according to the development parameters of the target area. Taking into account the geological characteristics and engineering characteristics of shale oil development, it can effectively guide the prediction of sweet spots, the optimization of fracturing processes and the implementation of pilot test plans, and has important significance for guiding the large-scale and efficient development of shale oil.

[0031] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0033] Figure 1 A flow chart of a shale oil development method based on ternary storage and permeability provided in an embodiment of the present invention;

[0034] Figure 2 It is a reservoir space shown in a thin slice under a microscope in a specific embodiment of the present invention;

[0035] Figure 3 It is a three-dimensional digital core under different pore pressures of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0036] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0037] The terms "comprises" and "having" and any variations thereof in the description embodiments, claims and drawings of the present invention are intended to cover non-exclusive inclusions, for example, including a series of steps or units.

[0038] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0039] Example 1

[0040] The object of the present invention can be achieved by the following technical measures: a shale oil development method based on ternary storage and permeability, the shale oil development method based on ternary storage and permeability comprises:

[0041] Step 1: determine the key evaluation factors for shale oil development; Step 2: based on step 1, evaluate the seepage space and path after multi-scale fracture network transformation; Step 3: based on step 2, optimize the design of target area development parameters; Step 4: based on step 3, optimize and control the working system of shale oil horizontal wells.

[0042] The purpose of the present invention can also be achieved by the following technical measures:

[0043] In step 1, the shale oil evaluation factors include three end elements: "reservoir element, fracture element, and pressure element". The "reservoir element" includes rock structure, reservoir space, and hydrocarbon occurrence, which is the material basis for shale oil enrichment. The "fracture element" includes the seepage capacity of natural fractures and artificial high seepage flow field, which is the seepage condition for high yield of shale oil. The "pressure element" includes elastic energy and permeation energy, which is the dynamic condition for high and stable yield of shale oil. See Table 1;

[0044] Table 1

[0045]

[0046] In step 2, based on step 1, online high-resolution nano-CT is used to scan the core pore structure (core specifications are 2.5 cm in diameter and 2-5 cm in length) at different pore pressures, and a three-dimensional digital core model of the core at different pore pressures is constructed to calculate the porosity, connected pore ratio, and permeability at different pore pressures.

[0047] In step 3, with the goal of improving the pore connectivity in the matrix, a three-dimensional geological model and geomechanical model of the target area are established. Through the integrated geology-fracturing-reservoir simulation technology, the fracturing section and fracturing cluster design are optimized to maximize the complexity of the fracture network.

[0048] In step 4, the horizontal well operation system includes post-fracturing well shut-in, high-speed fluid discharge and fine pressure control stages. Based on step 3, numerical simulation optimization determines the well shut-in days and return fluid rate. The well shut-in days are 10-20 days, the high-speed fluid discharge rate is greater than 200 tons / day, and the fracturing drop in the fine pressure control stage is less than 0.02MPa / day.

[0049] Example 2

[0050] like Figure 1 As shown, Figure 1 The present invention is a flow chart of a specific embodiment of the shale oil development method based on ternary storage and permeability of the present invention.

[0051] In step 101, key evaluation factors for shale oil development are determined. The reservoir characteristics of the A depression are evaluated. Through the comprehensive logging interpretation map of the A-1 well in the A depression, the gray-mud laminae structure is mainly developed at 3310-3320m, with a laminae density of 16,000 laminae / m. The thin sections under the microscope show that the reservoir space is mainly composed of nano-scale inorganic pores such as calcite intercrystalline pores, such as Figure 2 As shown, nanoscale inorganic pores account for 87%, the layer TOC is 4.2%, Ro is 0.9%, and S is 3.4 mg / g.

[0052] In step 102, based on step 101 and step 1, an online high-resolution nano-CT scan is used to scan the core pore structure (core specification is 2.5 cm in diameter and 2-5 cm in length) at different pore pressures to construct a three-dimensional digital core model of the core at different pore pressures, such as Figure 3 As shown, the porosity, connected pore ratio and permeability under different pore pressures are calculated.

[0053] Nano-CT scans the three-dimensional pore structure of core 1# (core diameter 2.5 cm, length 2 cm) at pore pressures of 0 MPa, 11 MPa and 27 MPa, and constructs a three-dimensional digital core model of core 1# at 0 MPa, 11 MPa and 27 MPa. The porosity, connected pore ratio and permeability at different pore pressures are shown in Table 2 below:

[0054] Table 2

[0055]

[0056] In step 103, based on step 102, a three-dimensional geological model and a geomechanical model of the target area are established with the goal of improving the pore connectivity in the matrix. The fracturing stage and fracturing cluster design are optimized through the integrated geology-fracturing-reservoir simulation technology to maximize the complexity of the fracture network.

[0057] Horizontal well A-1HF was deployed through the geological model of depression A, with a horizontal section length of 2000m. Design scheme 1: 30 fracturing sections, 6 clusters / section, and scheme 2: 35 fracturing sections, 4 clusters / section. The integrated simulation of geology, fracturing and reservoir shows that the fracturing transformation space of scheme 1 is 16 million cubic meters, and the fracturing transformation volume of scheme 2 is 1700 cubic meters. The fracturing volume space of scheme 2 is large, so scheme 2 is preferred.

[0058] In step 104, based on step 103, the A-1HF horizontal well operation system includes post-fracturing well blocking, high-speed fluid drainage and fine pressure control stages. Numerical simulation optimization determines that the A-1HF well blocking days are 10 days, the high-speed fluid drainage rate is 230 tons / day, and the fracturing drop amplitude in the fine pressure control stage is 0.02MPa / day.

[0059] This method was used to design 31 shale oil horizontal wells in multiple depressions in Shengli Oilfield, of which more than half of the wells have accumulated more than 10,000 tons, achieving good development results.

[0060] Beneficial effects: The ternary storage and permeability-based shale oil development method system of the present invention takes into account the geological characteristics and engineering characteristics of shale oil development, can effectively guide the prediction of sweet spots, the optimization of fracturing processes and the implementation of pilot test programs, and is of great significance in guiding the large-scale and efficient development of shale oil.

[0061] The above specific implementation methods further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A shale oil development method based on ternary storage and permeability, characterized in that: The development method comprises: Step 1: Determine the key evaluation factors for shale oil development; Step 2: Based on the key evaluation factors, the seepage space and path after the multi-scale fracture network transformation are evaluated to obtain the evaluation results; Step 3: Optimize and design the development parameters of the target area according to the evaluation results; Step 4: Optimize and regulate the shale oil horizontal well working system according to the development parameters of the target area.

2. A shale oil development method based on ternary storage and permeability according to claim 1, characterized in that: The step 1: determining the key evaluation factors for shale oil development specifically includes three end elements: storage element, fracture element, and pressure element.

3. A shale oil development method based on ternary storage and permeability according to claim 2, characterized in that: The reservoir elements include rock structure, reservoir space and hydrocarbon occurrence, and are the material basis for shale oil enrichment.

4. A shale oil development method based on ternary storage and permeability according to claim 2, characterized in that: The fracture element includes the seepage capacity of natural fractures and artificial high seepage flow field, which is the seepage condition for high yield of shale oil.

5. The shale oil development method based on ternary storage and permeability according to claim 2, characterized in that: The pressure element includes elastic energy and permeation energy, which is the dynamic condition for high and stable production of shale oil.

6. The shale oil development method based on ternary storage and permeability according to claim 1, characterized in that: The step 2: evaluating the seepage space and path after the multi-scale fracture network transformation according to the key evaluation factors, and obtaining the evaluation results specifically includes: The core pore structure at different pore pressures was scanned using online high-resolution nano-CT. Construct three-dimensional digital core models of cores under different pore pressures; Calculate the pore parameters at different pore pressures.

7. A shale oil development method based on ternary storage and permeability according to claim 6, characterized in that: The core specifications are 2.5 cm in diameter and 2-5 cm in length.

8. A shale oil development method based on ternary storage and permeability according to claim 6, characterized in that: The pore parameters specifically include: porosity, connected pore ratio, permeability, seepage space and seepage path.

9. The shale oil development method based on ternary storage and permeability according to claim 1, characterized in that: The step 3: optimizing and designing the development parameters of the target area according to the evaluation results specifically includes: To improve the pore connectivity in the matrix, a three-dimensional geological model and geomechanical model of the target area were established; The integrated geology-fracturing-reservoir simulation technology is used to optimize the design of fracturing sections and fracturing clusters to maximize the complexity of the fracture network.

10. The shale oil development method based on ternary storage and permeability according to claim 1, characterized in that: The horizontal well working system includes well blocking after fracturing, high-speed fluid discharge and fine pressure control stages.

11. The shale oil development method based on ternary storage and permeability according to claim 1, characterized in that: The step 4: based on the optimization and regulation of the shale oil horizontal well working system according to the development parameters of the target area, numerical simulation optimization is used to determine the number of well blocking days and the return fluid rate, the well blocking days are 10-20 days, the high-speed fluid discharge rate is greater than 200 tons / day, and the fracturing drop amplitude in the fine pressure control stage is less than 0.02MPa / day.

12. A shale oil development system based on ternary storage and permeability, applied to a shale oil development method based on ternary storage and permeability as described in any one of claims 1 to 11, characterized in that: The shale oil development system comprises: Evaluation factor determination module, used to determine the key evaluation factors for shale oil development; An evaluation result acquisition module is used to evaluate the seepage space and path after the multi-scale fracture network transformation according to the key evaluation factors to obtain the evaluation results; A development parameter optimization module, used for optimizing the development parameters of the design target area according to the evaluation results; The working system control module is used to optimize and control the working system of shale oil horizontal wells according to the development parameters of the target area.

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