Method, device, equipment and storage medium for determining timing of well shut-in and well opening

Abstract

The present application provides a method, device, equipment and storage medium for determining the timing of shut-in and well opening, the method comprising: obtaining historical data of historical fracturing wells, and obtaining the target maturity of the target fracturing well; the historical data comprises historical maturity and historical stable pressure; based on the historical maturity and historical stable pressure, determining the maturity engineering evaluation coefficient and the rock formation fracture evaluation coefficient; according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient and the target maturity, determining the target stable pressure of the target fracturing well; according to the target stable pressure and the pressure change trend of the target fracturing well, determining the target well opening timing. In this way, the accuracy of determining the timing of shut-in and well opening is improved, and simulation calculation is performed in combination with actual engineering data, which can also achieve effective guidance of the actual mining and production process of the mine.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas field development engineering, and in particular to a method, device, equipment and storage medium for determining the timing of well soaking and well opening. Background Art

[0002] The domestic continental shale formations are rich in oil resources and are an important strategic area for vigorously enhancing domestic oil exploration and development efforts and ensuring national oil security. Fracturing technology is usually used in oil exploration and production. Fracturing technology refers to the method of injecting fracturing materials to create cracks in oil and gas layers during oil production. Fracturing technology can improve the flow environment of oil underground and increase oil well production. After the shale oil well is completed with fracturing construction, the oil well is usually shut in and pressure is held, so that the injected fracturing materials can gradually diffuse to the far end of the formation. After the well is shut in for a period of time, the well can be opened and sprayed for subsequent mining and production operations.

[0003] The research on the soaking process in related technologies is often limited to geological perspectives and laboratory data, and only describes the geological characteristics from a mechanistic perspective. It is impossible to accurately determine the timing of soaking and opening the well, nor can it effectively guide the actual exploration, development and production process. Summary of the invention

[0004] The present application provides a method, device, equipment and storage medium for determining the timing of well soaking and well opening, which can accurately determine the timing of well soaking and well opening, and can also effectively guide the actual exploration, development and production of the mine.

[0005] In a first aspect, an embodiment of the present application provides a method for determining a well-sealing and well-opening timing, comprising:

[0006] Acquire historical data of historical fracturing wells, and acquire target maturity of target fracturing wells; the historical data includes historical maturity and historical stable pressure;

[0007] Determining a maturity engineering evaluation coefficient and a rock formation fracture evaluation coefficient based on the historical maturity and the historical stable pressure;

[0008] Determining a target stable pressure of the target fracturing well according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient and the target maturity;

[0009] The target well opening timing is determined according to the target stable pressure and the pressure variation trend of the target fracturing well.

[0010] In a possible implementation manner, the historical data further includes historical fracturing material related parameters, historical brittleness index, and historical fracture pressure; and determining the target stable pressure of the target fracturing well according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient, and the target maturity includes:

[0011] determining an external squeeze correction factor based on the historical fracturing material related parameters;

[0012] Determining a mechanical evaluation correction coefficient based on the historical brittleness index and the historical rupture pressure;

[0013] The target stable pressure of the target fracturing well is determined according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient, the external squeeze correction coefficient, the mechanical evaluation correction coefficient and the target maturity.

[0014] In a possible implementation, determining the external squeeze correction coefficient based on the historical fracturing material related parameters includes:

[0015] Calculating the historical fracturing fluid-solid ratio corresponding to the historical fracturing well according to the historical fracturing material related parameters;

[0016] According to the historical fracturing fluid-solid ratio, calculating the average historical fracturing fluid-solid ratio and the extreme difference of the historical fracturing fluid-solid ratio;

[0017] Obtaining parameters related to target fracturing materials of a target fracturing well, and calculating a target fracturing fluid-solid ratio corresponding to the target fracturing well;

[0018] The external squeeze correction coefficient is determined according to the target fracturing fluid-solid ratio, the average historical fracturing fluid-solid ratio and the historical fracturing fluid-solid ratio extreme difference.

[0019] In a possible implementation, determining the mechanical evaluation correction coefficient based on the historical brittleness index and the historical rupture pressure includes:

[0020] Calculating the ratio of the historical brittleness index to the historical fracture pressure to obtain a first ratio of each of the historical fracturing wells;

[0021] Based on the first ratios of the respective historical fracturing wells, determining an average value of the first ratio and a range of the first ratio;

[0022] Obtaining a target brittleness index and a target fracture pressure of the target fractured well, and using a ratio of the target brittleness index to the target fracture pressure as a second ratio of the target fractured well;

[0023] The mechanical evaluation correction coefficient is determined according to the second ratio, the average value of the first ratio and the range of the second ratio.

[0024] In a possible implementation manner, determining the target stable pressure of the target fracturing well according to the maturity engineering evaluation coefficient, the rock fracture evaluation coefficient, the external squeeze correction coefficient, the mechanical evaluation correction coefficient and the target maturity includes:

[0025] The product of the external extrusion correction coefficient and the maturity engineering evaluation coefficient is used as the first slope;

[0026] The product of the mechanical evaluation correction coefficient and the rock formation fracture evaluation coefficient is taken as the first intercept;

[0027] Based on the first slope and the first intercept, an objective function is constructed with stable pressure as the dependent variable and maturity as the independent variable;

[0028] The target maturity is substituted into the target function to obtain the target stable pressure.

[0029] In a possible implementation manner, determining the maturity engineering evaluation coefficient and the rock fracture evaluation coefficient based on the historical maturity and the historical stable pressure includes:

[0030] Constructing a rectangular coordinate system with maturity as the abscissa and stable pressure as the ordinate, and determining data points corresponding to the historical fracturing wells in the rectangular coordinate system;

[0031] Calculate the second slope and second intercept of the straight line connecting any two data points;

[0032] An average value of the second slope is determined as the maturity engineering evaluation coefficient, and an average value of the second intercept is determined as the formation fracture evaluation coefficient.

[0033] In a possible implementation, determining a target well opening timing according to the target stable pressure and the pressure change trend of the target fracturing well includes:

[0034] Determine a pressure drop function of the target fracturing well according to the pressure change trend of the target fracturing well; the independent variable of the pressure drop function is time, and the dependent variable is the pressure of the target fracturing well;

[0035] The target stable pressure is substituted into the pressure drop function to obtain the target well opening timing.

[0036] In a second aspect, an embodiment of the present application provides a device for determining a time to shut down a well and start a well, including an acquisition module, a first determination module, a second determination module, and a third determination module, wherein:

[0037] The acquisition module is used to acquire historical data of historical fracturing wells and to acquire target maturity of target fracturing wells; the historical data includes historical maturity and historical stable pressure;

[0038] The first determination module is used to determine a maturity engineering evaluation coefficient and a rock formation fracture evaluation coefficient based on the historical maturity and the historical stable pressure;

[0039] The second determination module is used to determine the target stable pressure of the target fracturing well according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient and the target maturity;

[0040] The third determination module is used to determine the target well opening timing according to the target stable pressure and the pressure change trend of the target fracturing well.

[0041] In a possible implementation manner, the historical data further includes historical fracturing material related parameters, historical brittleness index and historical fracture pressure; the second determination module includes:

[0042] A first determination submodule is used to determine an external squeeze correction coefficient based on the historical fracturing material related parameters;

[0043] A second determination submodule is used to determine a mechanical evaluation correction coefficient based on the historical brittleness index and the historical rupture pressure;

[0044] The third determination submodule is used to determine the target stable pressure of the target fracturing well according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient, the external squeeze correction coefficient, the mechanical evaluation correction coefficient and the target maturity.

[0045] In a possible implementation manner, the first determining submodule is specifically configured to:

[0046] Calculating the historical fracturing fluid-solid ratio corresponding to the historical fracturing well according to the historical fracturing material related parameters;

[0047] According to the historical fracturing fluid-solid ratio, calculating the average historical fracturing fluid-solid ratio and the extreme difference of the historical fracturing fluid-solid ratio;

[0048] Obtaining parameters related to target fracturing materials of a target fracturing well, and calculating a target fracturing fluid-solid ratio corresponding to the target fracturing well;

[0049] The external squeeze correction coefficient is determined according to the target fracturing fluid-solid ratio, the average historical fracturing fluid-solid ratio and the historical fracturing fluid-solid ratio extreme difference.

[0050] In a possible implementation manner, the second determining submodule is specifically configured to:

[0051] Calculating the ratio of the historical brittleness index to the historical fracture pressure to obtain a first ratio of each of the historical fracturing wells;

[0052] Based on the first ratios of the respective historical fracturing wells, determining an average value of the first ratio and a range of the first ratio;

[0053] Obtaining a target brittleness index and a target fracture pressure of the target fractured well, and using a ratio of the target brittleness index to the target fracture pressure as a second ratio of the target fractured well;

[0054] The mechanical evaluation correction coefficient is determined according to the second ratio, the average value of the first ratio and the range of the second ratio.

[0055] In a possible implementation manner, the third determining submodule is specifically configured to:

[0056] The product of the external extrusion correction coefficient and the maturity engineering evaluation coefficient is used as the first slope;

[0057] The product of the mechanical evaluation correction coefficient and the rock formation fracture evaluation coefficient is taken as the first intercept;

[0058] Based on the first slope and the first intercept, an objective function is constructed with stable pressure as the dependent variable and maturity as the independent variable;

[0059] The target maturity is substituted into the target function to obtain the target stable pressure.

[0060] In a possible implementation manner, the first determining module is specifically configured to:

[0061] Constructing a rectangular coordinate system with maturity as the abscissa and stable pressure as the ordinate, and determining data points corresponding to the historical fracturing wells in the rectangular coordinate system;

[0062] Calculate the second slope and second intercept of the straight line connecting any two data points;

[0063] An average value of the second slope is determined as the maturity engineering evaluation coefficient, and an average value of the second intercept is determined as the formation fracture evaluation coefficient.

[0064] In a possible implementation manner, the third determining module is specifically configured to:

[0065] Determine a pressure drop function of the target fracturing well according to the pressure change trend of the target fracturing well; the independent variable of the pressure drop function is time, and the dependent variable is the pressure of the target fracturing well;

[0066] The target stable pressure is substituted into the pressure drop function to obtain the target well opening timing.

[0067] In a third aspect, an embodiment of the present application provides a device, including: a processor and a memory;

[0068] The memory stores computer-executable instructions;

[0069] The processor executes the computer-executable instructions stored in the memory, so that the processor performs the method as described in any one of the first aspects.

[0070] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the method described in any one of the first aspects.

[0071] In a fifth aspect, an embodiment of the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the method described in any one of the first aspects.

[0072] The method, device, equipment and storage medium for determining the timing of shut-in and well opening provided in the embodiments of the present application obtain the historical data of historical fracturing wells and the target maturity of the target fracturing well; the historical data include the historical maturity and the historical stable pressure; based on the historical maturity and the historical stable pressure, the maturity engineering evaluation coefficient and the rock formation fracture evaluation coefficient are determined; according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient and the target maturity, the target stable pressure of the target fracturing well is determined; according to the target stable pressure and the pressure change trend of the target fracturing well, the target well opening timing is determined. In this way, based on the actual engineering data of the historical fracturing wells, the target stable pressure of the target fracturing well is simulated, and the target well opening timing is further determined based on the actual pressure change trend of the target fracturing well, which improves the accuracy of determining the timing of shut-in and well opening, and can also achieve effective guidance of the actual mining and production process of the mine by combining simulation calculations with actual engineering data. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 A schematic diagram of an application scenario provided for an embodiment of the present application;

[0074] Figure 2 A flow chart of a method for determining the timing of well soaking and well opening provided in an embodiment of the present application;

[0075] Figure 3 A schematic flow chart of another method for determining the timing of well soaking and well opening provided in an embodiment of the present application;

[0076] Figure 4 A scatter plot of maturity and stable pressure provided in an embodiment of the present application;

[0077] Figure 5 A schematic diagram of the calculation logic of a maturity engineering evaluation coefficient α and a rock formation fracture evaluation coefficient β provided in an embodiment of the present application;

[0078] Figure 6 A schematic diagram of a model construction of a method for determining a well soaking and well opening provided in an embodiment of the present application;

[0079] Figure 7 A schematic diagram of a shale oil well casing pressure change curve provided in an embodiment of the present application;

[0080] Figure 8 A schematic diagram of diffusion of a four-degree superimposed fracturing medium provided in an embodiment of the present application;

[0081] Fig. 9 A schematic diagram of a spatial coordination model of a fracturing extension equilibrium body provided in an embodiment of the present application;

[0082] Fig.10 A bar chart of the amount of sand added for fracturing in 10 shale oil vertical wells in the study area provided in the examples of this application;

[0083] Fig.11 A bar chart of the amount of fluid added for fracturing of 10 shale oil vertical wells in the study area provided in the examples of this application;

[0084] Fig.12 A bar chart of carbon dioxide injection volume during fracturing of 10 shale oil vertical wells in the study area provided in the examples of this application;

[0085] Fig.13 A schematic diagram of the calculation results of the external squeeze correction coefficients of 10 shale oil vertical wells in the study area provided in the embodiment of the present application;

[0086] Fig.14 A bar graph of the brittleness index BI of 10 shale oil vertical wells in the study area provided in the embodiment of the present application;

[0087] Fig.15 A histogram of the fracture pressure PF of 10 shale oil vertical wells in the study area provided in the embodiment of the present application;

[0088] Fig.16 A schematic diagram of the calculation results of the mechanical evaluation correction coefficients of 10 shale oil vertical wells in the study area provided in the embodiment of the present application;

[0089] Fig.17 A schematic diagram of Ro, PF, and BI data of the JHB-H1112 well provided in the embodiment of the present application;

[0090] Fig.18 A schematic diagram of Ro, PF, and BI data of the JHB-H22 well provided in the embodiment of the present application;

[0091] Fig.19 A schematic diagram of Ro, PF, and BI data of the JHB-H32 well provided in the embodiment of the present application;

[0092] Fig. 20 The histogram of fracturing materials for wells JHB-H1112, JHB-H22, and JBH-H32 provided in the examples of the present application;

[0093] Fig.21 A schematic diagram of the target well opening timing for the JHB-H1112 well provided in the embodiment of the present application;

[0094] Fig. 22 A schematic diagram of the target well opening timing for the JHB-H22 well soaking provided in the embodiment of the present application;

[0095] Fig.23 A schematic diagram of the target well opening timing for the JHB-H32 well soaking provided in the embodiment of the present application;

[0096] Fig.24 A bar graph comparing the actual stable pressure and the target stable pressure provided in the embodiment of the present application;

[0097] Fig.25 A schematic diagram of the structure of a device for determining the timing of well soaking and well opening provided in an embodiment of the present application;

[0098] Fig.26 A schematic diagram of the structure of a device for determining the timing of well soaking and well opening provided in an embodiment of the present application. DETAILED DESCRIPTION

[0099] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0100] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0101] Figure 1 This is a schematic diagram of an application scenario provided by the embodiment of this application. Figure 1 , which shows the specific process of oil fracturing and extraction, mainly including three main processes: fracturing, well soaking and well opening.

[0102] In the field of unconventional oil and gas exploration and development, fracturing is usually required when exploring and developing large freshwater lake basin terrestrial shale oil fields. The fracturing process may refer to the process of injecting fracturing fluids, fracturing sands and other fracturing materials into the formation through fracturing equipment such as fracturing trucks to cause the formation to break or expand the formation cracks. The well-sucking process may refer to the process of closing the well and holding the pressure after the fracturing construction technology, so that the injected fracturing materials gradually diffuse to the far end. During the well-sucking process, the pressure of the fracturing well gradually decreases, and finally the casing pressure of the fracturing well remains basically unchanged, reaching a stable pressure. After the well-sucking is completed, the pressure well is opened and sprayed to carry out oil production operations.

[0103] In related technologies, when studying the fracturing and well-simmering process, many geological characteristics of the well-simmering process are often described from a mechanism perspective. For example, in the following literature: (1) Sun Longde et al. "Analysis of Major Scientific Issues and Research Paths of Daqing Gulong Shale Oil" (Petroleum Exploration and Development, Issue 3, 2021); (2) Guo Jianchun et al. "Experimental Study on the Forced Imbibition Law of Water Phase in Shale Reservoirs" (Computational Physics, April 2021); (3) Zeng Fanhui et al. "Shale Hydration and Water Lock Release Mechanism" (Petroleum Exploration and Development, June 2021); (4) Hou Lianhua et al. "Geological Main Control Factors of Shale Oil and Gas Final Recovery - Taking the United States as an Example" (5) Lang Dongjiang et al., “Nuclear magnetic resonance experiment on factors affecting oil recovery by CO2 injection into shale oil” (Petroleum Exploration and Development, June 2021); (6) You Lijun et al., “Water self-imbibition experiment in shale fracture network” (Journal of China University of Petroleum, February 2018); (7) Kang Yili et al., “Quantitative characterization and engineering application of microscopic forces of shale hydration” (Petroleum Exploration and Development, April 2017).

[0104] The above-mentioned document (1) preliminarily clarified the mechanism of CO2 pre-injection to improve oil recovery, namely, through the extraction of organic matter by CO2 and the dissolution of minerals such as potassium feldspar, sodium feldspar, and calcite, new organic pores and dissolved inorganic pores are generated, which effectively improve the physical properties of the reservoir.

[0105] In the above-mentioned document (2), the forced imbibition process of well soaking is divided into three stages: imbibition diffusion, imbibition transition, and imbibition balance. In the early stage of well soaking, the shale imbibition capacity is greatly improved due to the fluid pressure, providing imbibition liquid for the subsequent spontaneous imbibition of shale. The document (2) believes that the reservoir confining pressure will inhibit the imbibition capacity of shale, and the stronger the imbibition capacity, the earlier the hydration-induced microcracks will be generated, and the shortest well soaking experiment time is 5 days.

[0106] The above-mentioned document (3) analyzes the hydration characteristics of different types of clay minerals. Illite is not easy to hydrate and swell. It mainly expands through microcracks, has a high proportion of small-diameter pores, has a large capillary force, strong self-absorption, poor diffusion, and is easy to form water locks. Montmorillonite is easy to hydrate and swell, which can improve the pore structure. It has weak self-absorption and strong diffusion in the initial stage, and has a certain ability to self-release after water locks. This document (3) proposes that there is an optimal hydration time for shale, and the optimal soaking time can be determined by the hydration effect results.

[0107] The above-mentioned document (4) points out that shales with different Ro values ​​are controlled by the thermal maturity of shale, and different estimated ultimate recovery values ​​(EUR values) have different relationships with the original formation pressure and formation pressure gradient. EUR has a good quadratic polynomial relationship with the formation pressure gradient and a good cubic polynomial relationship with the original formation pressure. As the formation pressure gradient and the original formation pressure increase, the EUR value shows a trend of first increasing and then decreasing.

[0108] In the above-mentioned document (5), the nuclear magnetic resonance imaging experiment of CO2 injection into the matrix-fracture core showed that in the initial stage, the oil in the fractures and the surrounding areas was produced first, and the recovery rate increased significantly. As the CO2 injection time increased, CO2 diffused from the fracture space and the core surface to the inside of the core, mobilizing the oil inside the core, and the recovery rate gradually slowed down. The fractures expanded the contact area between the injected CO2 and the crude oil. The more fractures there were and the greater the evaluation index of the fractures, the greater the recovery rate of shale oil.

[0109] The above-mentioned document (6) points out that during the post-fracturing well shut-in period, slick water and proppant fill the primary fractures, and only slick water seeps into the secondary fractures. Under high flowback pressure, the flowback rate of fracturing fluid in primary fractures with strong conductivity is high; secondary fractures have poor conductivity and are subjected to relatively low flowback pressure, so the flowback difficulty leads to a large amount of fracturing fluid retention. The self-imbibition of water phase in the shale fracture network expands the distribution range of fracturing fluid in the shale reservoir and widens the contact area between fracturing fluid and shale, which is conducive to enhancing the water-rock interaction to generate new fractures and further optimize the reservoir transformation.

[0110] The above-mentioned document (7) points out that the hydration repulsion pressure of illite crystal layer in the initial stage of hydration is greater than 50 MPa, but it decays rapidly with the expansion of the crystal layer, making it difficult to produce long-range expansion. Therefore, at the microscopic level, the expansion degree of the crystal layer during illite hydration is very low, and the required water molecules are also relatively small; at the macroscopic level, the hydration stress of shale with illite as the main clay mineral is large and the strain is small, and the critical water content that induces hydration damage is low. In the process of post-pressure soaking, the shale reservoir can be further transformed by making full use of shale hydration to induce the initiation and expansion of microcracks.

[0111] The above-mentioned documents (1) to (7) firstly describe the distribution characteristics of fracturing sand support and fracturing fluid during the soaking process; secondly, they discuss the formation reaction mechanism during soaking from the aspects of imbibition and hydration, and also describe the effects of clay mineral expansion and water lock; finally, they summarize the transformation mechanism of soaking on shale reservoirs and put forward the concept of "optimal soaking time" in a targeted manner. However, the theories in the above-mentioned documents only analyze the soaking process from a geological perspective, and do not provide an evaluation model or application method to guide development and production, nor can they accurately determine the specific timing of soaking and opening. Therefore, the relevant technologies mainly have the following defects:

[0112] First, there are limitations in the analysis perspective. Specifically, most of the existing research results on the soaking process are only analyzed from a geological perspective. The research scope is mostly limited to the laboratory, and is rarely combined with the actual development process. The soaking process research should adopt the method of combining geological theory with development laws, and should be a combination of laboratory analysis and mine dynamic analysis.

[0113] Second, there is a lack of guidance in the evaluation and application. Specifically, the existing research results on the soaking process lack a set of evaluation standards that can be easily applied and widely promoted in the mine. At present, there is no clear method for simulating the stable pressure of soaking and predicting the best time to open a well. The geological theories obtained in the laboratory need to be strengthened in terms of the degree of transformation of results and on-site guidance.

[0114] In summary, although the relevant technologies have explained many geological characteristics of the soaking process from the perspective of mechanism, and put forward the concept that shale oil wells need to optimize the soaking time. However, the relevant technologies do not provide an evaluation model that can correspond to the geological meaning, and it is difficult to solve the problem of optimizing the soaking timing of shale oil wells and effectively guiding exploration, development and production. In other words, the relevant technologies cannot accurately determine the timing of soaking and opening wells, nor can they effectively guide the actual exploration, development and production processes of the mine.

[0115] In the embodiment of the present application, the historical data of the historical fracturing wells are obtained, and the target maturity of the target fracturing well is obtained; based on the historical maturity and the historical stable pressure, the maturity engineering evaluation coefficient and the rock fracture evaluation coefficient are determined; according to the maturity engineering evaluation coefficient, the rock fracture evaluation coefficient and the target maturity, the target stable pressure of the target fracturing well is determined; according to the target stable pressure and the pressure change trend of the target fracturing well, the target well opening time is determined. In this way, based on the actual engineering data of the historical fracturing wells, the target stable pressure of the target fracturing well is simulated, and the target well opening time is further determined based on the actual pressure change trend of the target fracturing well, which improves the accuracy of determining the timing of well shut-in and well opening. Combined with the actual engineering data for simulation calculation, it can also achieve effective guidance of the actual mining and production process of the mine, solve the problems of shale oil well shut-in stable pressure evaluation, well shut-in timing optimization, and effectively guide shale oil well opening production and development system.

[0116] The scheme shown in the present application is described in detail below through specific embodiments. It should be noted that the following embodiments can exist independently or in combination with each other, and the same or similar contents will not be described repeatedly in different embodiments.

[0117] Next, combine Figure 2 The embodiment shown illustrates the process of determining the timing of well soaking and well opening.

[0118] Figure 2 A flow chart of a method for determining the timing of well shut-in and well opening provided in an embodiment of the present application. Figure 2 , the method may include:

[0119] S201. Acquire historical data of historical fracturing wells, and acquire target maturity of target fracturing wells; the historical data includes historical maturity and historical stable pressure.

[0120] In the embodiments of the present application, the historical fracturing well may refer to an existing shale oil well in a mine development block or an existing shale oil well in an adjacent development block. Historical data may refer to the basic data information corresponding to the historical fracturing well, including historical maturity and historical stable pressure. Historical maturity may refer to the average maturity Ro in the perforation section of the historical fracturing well. The maturity may refer to the vitrinite reflectance of the rock formation in the shale oil well, which is an indicator of organic matter maturity and is represented by the symbol Ro. The historical stable pressure may refer to the stable casing pressure reached by the historical fracturing well during the well shut-in process. The target fracturing well may refer to the target well for which the timing of well shut-in and well opening needs to be determined. The target maturity may refer to the average maturity of the target fracturing well.

[0121] In this step, the data of historical fracturing wells can be obtained based on the collection of historical records and other related information, and the embodiment of the present application obtains data in the development block or in the vicinity of the development block, and the geological characteristics and geological environment are relatively small, which can avoid the problem of large errors in the final results caused by excessive differences in the geological environment. Of course, if it is impossible to obtain historical data in the development block or in the vicinity of the development block, historical data can also be obtained through laboratory analysis, simulation, etc., and the embodiment of the present application is not limited to this.

[0122] In this step, when obtaining the target maturity of the target fracturing well, multiple rock samples can be obtained from the target fracturing well, the maturity of each rock sample can be measured respectively, and finally the target maturity corresponding to the target fracturing well can be obtained by taking the average value.

[0123] S202. Determine a maturity engineering evaluation coefficient and a rock formation fracture evaluation coefficient based on the historical maturity and the historical stable pressure.

[0124] In the embodiment of the present application, there is a high linear fitting relationship between maturity Ro and stable pressure, and maturity Ro will play a controlling role in the wellbore stable pressure. The maturity engineering evaluation coefficient (α) can refer to the slope in the linear fitting relationship, that is, the degree of inclination of the fitted straight line. The rock formation fracture evaluation coefficient (β) can refer to the intercept in the linear fitting relationship, that is, the difference between the coordinates of the intersection of the fitted straight line and the coordinate axis.

[0125] S203. Determine the target stable pressure of the target fracturing well according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient and the target maturity.

[0126] In the embodiment of the present application, the target stable pressure may refer to the stable casing pressure finally reached by the target fracturing well during the soaking process. After determining the maturity engineering evaluation coefficient α and the rock fracture evaluation coefficient β, the linear relationship between the stable pressure P and the maturity Ro can be approximately obtained:

[0127] P = α*Ro + β (Formula 1)

[0128] Based on the pressure stabilization fitting model formed by the above linear relationship, the target maturity of the target fracturing well is substituted into Formula 1 to obtain the target stable pressure corresponding to the target fracturing well.

[0129] S204: Determine a target well opening timing according to the target stable pressure and the pressure change trend of the target fracturing well.

[0130] In the embodiment of the present application, the pressure change trend may refer to the downward trend of the casing pressure of the target fracturing well in the early stage of well shut-in. The target well opening time may refer to the duration from the start of well shut-in to the opening of the well for blowout. The change law of the casing pressure during well shut-in is a composite monotonic function. In the embodiment of the present application, according to the pressure change trend of the target fracturing well in the early stage of well shut-in, a variety of functions can be used for regression fitting to obtain the functional relationship between pressure and well shut-in time, so as to realize the prediction of the later casing pressure change. The various functions may include power functions, exponential functions or polynomial functions, etc., which are not limited in the embodiment of the present application. After obtaining the functional relationship between pressure and well shut-in time, the target stable pressure is substituted into the functional relationship to obtain the time required for the target fracturing well to drop to the target stable pressure, and then the target well opening time required in the end can be obtained.

[0131] The method for determining the timing of shut-in and well opening provided in the embodiment of the present application obtains historical data of historical fracturing wells and obtains the target maturity of the target fracturing well; the historical data includes historical maturity and historical stable pressure; based on the historical maturity and historical stable pressure, the maturity engineering evaluation coefficient and the rock fracture evaluation coefficient are determined; according to the maturity engineering evaluation coefficient, the rock fracture evaluation coefficient and the target maturity, the target stable pressure of the target fracturing well is determined; according to the target stable pressure and the pressure change trend of the target fracturing well, the target well opening timing is determined. In this way, based on the actual engineering data of the historical fracturing wells, the target stable pressure of the target fracturing well is simulated, and the target well opening timing is further determined based on the actual pressure change trend of the target fracturing well, which improves the accuracy of determining the timing of shut-in and well opening, and can also achieve effective guidance of the actual mining and production process of the mine by combining simulation calculations with actual engineering data.

[0132] Next, combine Figure 3 The embodiment shown describes in detail the process of determining the timing of well soaking and well opening.

[0133] Figure 3 A flow chart of another method for determining the timing of well soaking and well opening provided in an embodiment of the present application.

[0134] See also Figure 3 , the method may include:

[0135] S301, obtaining historical data of historical fracturing wells, and obtaining target maturity of target fracturing wells; the historical data includes historical maturity, historical stable pressure, historical fracturing material related parameters, historical brittleness index, and historical fracture pressure.

[0136] In the embodiment of the present application, the historical fracturing material related parameters may include the volume of solid (fracturing sand and other proppants), liquid (fracturing fluid, etc.) and gas (CO2, etc.) injected into the formation during the fracturing operation, respectively represented by V s 、V l and V g Indicated. The historical brittleness index may refer to the average brittleness index of the fracturing perforation section in the historical fracturing well, represented by the symbol BI. The historical fracture pressure may refer to the pressure that can break the rock, represented by the symbol PF. Among them, the larger the brittleness index BI, the easier the rock is to break; the larger the fracture pressure PF, the less likely the rock formation is to break. These two parameters can be directly obtained through measurement in engineering, and the embodiments of the present application do not limit the specific measurement process.

[0137] S302, constructing a plane rectangular coordinate system with maturity as the horizontal coordinate and stable pressure as the vertical coordinate, and determining data points corresponding to historical fracturing wells in the plane rectangular coordinate system.

[0138] In the embodiment of the present application, after obtaining the historical maturity and historical stable pressure, a plane rectangular coordinate system can be constructed, wherein the stable pressure is the ordinate and the maturity is the abscissa. Then, the historical maturity and historical stable pressure of each historical fracturing well are combined into coordinates and annotated as a data point in the plane rectangular coordinate system, so that a scatter plot including multiple data points can be obtained.

[0139] S303, calculating the second slope and the second intercept of the straight line obtained by connecting any two data points.

[0140] In the embodiment of the present application, any two data points corresponding to the historical fracturing wells are connected to obtain a straight line, and the second slope and the second intercept of the straight line are calculated. Taking the i-th data point and the j-th data point as an example, the coordinates of the i-th data point are (Ro i , P i ), the coordinates of the jth data point are (Ro j , P j )The second slope can be expressed as: (P i -P j ) / (Ro i -Ro j ); The second intercept can be expressed as: -[Ro i *(P j -P i)+P i *(Ro j -Ro i )] It should be noted that i and j are random and do not need to be arranged in a certain order.

[0141] S304: Determine the average value of the second slope as the maturity engineering evaluation coefficient, and determine the average value of the second intercept as the rock formation fracture evaluation coefficient.

[0142] In the embodiment of the present application, after the data points corresponding to all historical fracturing wells are combined and connected in pairs, and the second slope and the second intercept of all straight lines are calculated, the average value of the second slope can be taken as the maturity engineering evaluation coefficient α, and the average value of the second intercept can be taken as the rock fracture evaluation coefficient β. The specific formula is as follows:

[0143]

[0144]

[0145] Among them, the denominator n in the above formula 2 and formula 3 is the total number of operations, that is, the number of data points corresponding to the historical fracturing wells. It should be noted that the maturity engineering evaluation coefficient α and the rock fracture evaluation coefficient β are both iterative quantities. The more historical fracturing wells there are and the more data points there are, the more accurate the corresponding two simulation coefficients will be. Therefore, in the embodiments of the present application, the data of historical fracturing wells in similar geological environments can be obtained as much as possible to further improve the accuracy of determining the timing of target well opening.

[0146] For example, Figure 4 A scatter plot of maturity and stable pressure in an embodiment of the present application is shown in FIG. Figure 4 As shown, the horizontal coordinate of the plane rectangular coordinate system is maturity Ro, and the vertical coordinate is stable pressure, in megapascals (MPa). According to the historical maturity and historical stable pressure of each historical fracturing well, the specific coordinate position of the data point corresponding to each historical fracturing well can be determined in the plane rectangular coordinate system, and a scatter plot consisting of the data points of all historical fracturing wells can be obtained by marking them in the plane rectangular coordinate system.

[0147] For example, Figure 5 FIG. 1 is a schematic diagram showing the calculation logic of a maturity engineering evaluation coefficient α and a rock formation fracture evaluation coefficient β in an embodiment of the present application. Figure 5As shown, there are three data points A (Ro1, P1), B (Ro2, P2), and C (Ro3, P3) corresponding to historical fracturing wells in the plane rectangular coordinate system. Among them, the two data points AB are connected by a straight line. According to the coordinates of points A and B, the second slope of the straight line obtained by connecting the two points AB can be calculated to be α1, and the second intercept is β1; the two data points BC are connected by a straight line. According to the coordinates of points B and C, the second slope of the straight line obtained by connecting the two points BC can be calculated to be α2, and the second intercept is β2. By analogy, when there are more data points, they can be combined in pairs to calculate all the second slopes and all the second intercepts, and finally the average value can be taken to obtain the maturity engineering evaluation coefficient α and the rock fracture evaluation coefficient β.

[0148] In the embodiment of the present application, by constructing a "maturity-stable pressure" plane rectangular coordinate system, and determining the data points corresponding to the historical fracturing wells in the plane rectangular coordinate system according to the historical data of the historical fracturing wells; then all the data points are combined in pairs, and the second slope and the second intercept of the straight line obtained by connecting any two data points are calculated; finally, the average value of all the second slopes is determined as the maturity engineering evaluation coefficient α, and the average value of all the second intercepts is determined as the rock formation fracture evaluation coefficient β. In this way, the fitting coefficient between maturity and stable pressure can be accurately determined, providing a feasible data basis for determining the timing of well soaking and well opening.

[0149] S305. Calculate the historical fracturing fluid-solid ratio corresponding to the historical fracturing well according to the relevant parameters of the historical fracturing materials.

[0150] In fracturing technology, the coordination relationship between fluid and space, and between space and solid determines the casing pressure. The concept of "fluid-solid ratio" is proposed in the embodiments of this application, and the "fracturing fluid-solid ratio" and "development fluid-solid ratio" are defined from the two perspectives of engineering and geology. From an engineering perspective, the fracturing fluid-solid ratio may refer to the ratio of fluid (liquid and gas) to solid in the injected medium during the fracturing construction process inside the fracturing balance body, that is, the ratio of the sum of the volumes of fracturing fluid and carbon dioxide injected into the fracturing to the volume of fracturing sand. From a geological perspective, the development fluid-solid ratio refers to the ratio of internal fluid to solid during the development of the fracturing balance body. On the basis of the fracturing fluid-solid ratio, it is necessary to additionally consider the impact of fluid hydrocarbons discharged from the rock formation.

[0151] During the fracturing process, the fluid field has the following characteristics: the position of the fracturing sand no longer changes after it starts to support, and it has the characteristics of a rock skeleton. The multiphase fluids migrate and interact inside the fracturing expansion balance body to form a fluid field. The fluid field is mainly composed of two parts: one part is the hydrocarbon fluid released after the shale rock layer is broken, and the other part is the gas-liquid two-phase fluid injected by fracturing. During the soaking period, inside the fracturing balance body, the former is synchronous and unified, and the latter is gradual and diffuse. In a stable state, the fluid-solid ratio inside the fracturing expansion balance body is the same, the volume of fluid contained in the space supported by each fracturing sand is the same, and the casing pressure is stable.

[0152] In this step, after obtaining the historical fracturing material related parameters V s 、V l and V g The fracturing fluid-solid ratio of the historical fracturing well can be expressed as (V l +V g ) / V s In this way, the fracturing fluid-solid ratio corresponding to each historical fracturing well can be determined.

[0153] S306. Calculate the average historical fracturing fluid-solid ratio and the extreme value of the historical fracturing fluid-solid ratio according to the historical fracturing fluid-solid ratio.

[0154] In the embodiments of the present application, the average historical fracturing fluid-solid ratio may refer to the average value of the historical fracturing fluid-solid ratios of all historical fracturing wells. The extreme value of the historical fracturing fluid-solid ratio may refer to the difference between the maximum value and the minimum value of the historical fracturing fluid-solid ratios of all historical fracturing wells.

[0155] S307, obtaining parameters related to the target fracturing material of the target fracturing well, and calculating the target fracturing fluid-solid ratio corresponding to the target fracturing well.

[0156] In the embodiment of the present application, the target fracturing material correlation coefficient may refer to the volume of solid, liquid and gas injected into the formation of the target fracturing well. The target fracturing fluid-solid ratio may refer to the fracturing fluid-solid ratio of the target fracturing well, and the calculation method may refer to step 305, which will not be described in detail in the embodiment of the present application.

[0157] S308, determining an external squeeze correction coefficient according to the target fracturing fluid-solid ratio, the average historical fracturing fluid-solid ratio, and the extreme difference of the historical fracturing fluid-solid ratio.

[0158] In the embodiment of the present application, the external extrusion correction coefficient may refer to a correction coefficient for the maturity engineering evaluation coefficient α. Figure 4It can be seen that the scattered points in the rectangular coordinate system of the oil well maturity Ro-stable pressure plane in the development area do not fall completely on the fitting line. The scattered points are evenly and symmetrically distributed above and below the linear model, and there is a certain degree of deviation. The fitting line is determined by the geological characteristics and engineering geological characteristics of the shale formations in the development area, and the deviation is controlled by a single well. Changes in construction parameters during fracturing construction and the special properties of single well engineering are likely to affect the deviation. On the basis of the stable pressure fitting model established based on geology and engineering geology, the deviation needs to be further corrected and improved. The correction of the deviation in the stable pressure fitting model is to correct the deviation between the actual fracturing conditions and the ideal fracturing conditions in engineering. Based on the structural characteristics of the stable pressure fitting model, the two parameters of the maturity engineering evaluation coefficient, i.e. the slope α, and the shale layer rupture evaluation coefficient, i.e. the intercept β, are corrected based on the correction function. The specific correction function can be:

[0159]

[0160] Based on the correction function, the maturity engineering evaluation coefficient α is corrected by the external squeeze correction coefficient in the embodiment of the present application. Specifically, the fracturing fluid-solid ratio can be used for calculation. Substituting the fracturing fluid-solid ratio as the independent variable x into formula 4 can obtain the following calculation formula for the external squeeze correction coefficient, which is as follows:

[0161]

[0162] In this step, after calculating the average historical fracturing fluid-solid ratio (ave) and the extreme value of the historical fracturing fluid-solid ratio (max is the maximum value, min is the minimum value) of the historical fracturing wells, the target fracturing fluid-solid ratio of the target fracturing well (i.e., the i-th well) is substituted into Formula 4 to obtain Formula 5, and the external squeeze correction coefficient can be obtained based on Formula 5. In this way, by comparing the fracturing material related parameters of the target fracturing well with the fracturing material related parameters of all historical fracturing wells in the block, it is possible to correct the particularity of the single well of the target fracturing well on the basis of the integrity of the development area, thereby improving the applicability of the pressure stabilization fitting model to the current target fracturing well and improving the accuracy of determining the target well opening timing.

[0163] S309, calculating the ratio of the historical brittleness index to the historical fracture pressure, and obtaining a first ratio of each historical fracturing well.

[0164] In the embodiment of the present application, the first ratio can be used to characterize the original formation fracture characteristics of the historical fracturing well. The first ratio is obtained by dividing the historical brittleness index and the historical fracture pressure. This can more comprehensively represent the bottom fracture characteristics of the historical fracturing well and improve the engineering applicability of the subsequent pressure stabilization fitting model. The first ratio can be expressed as (BI / PF).

[0165] S310: Based on the first ratios of the historical fracturing wells, determine an average value of the first ratio and a range of the first ratio.

[0166] In the embodiment of the present application, after obtaining the first ratio of each historical fracturing well, the average value of the first ratio can be calculated. At the same time, the range of the first ratio can be calculated based on the maximum and minimum values ​​of the first ratio of each historical fracturing well.

[0167] S311, obtaining a target brittleness index and a target fracture pressure of a target fracturing well, and using a ratio of the target brittleness index to the target fracture pressure as a second ratio of the target fracturing well.

[0168] In the embodiment of the present application, the second ratio may refer to the ratio of the target brittleness index and the target fracture pressure of the target fracturing well.

[0169] S312. Determine a mechanical evaluation correction coefficient according to the second ratio, the average value of the first ratio, and the range of the second ratio.

[0170] In the embodiment of the present application, when correcting the rock formation fracture evaluation coefficient, i.e., the intercept β, it is corrected by the mechanical evaluation correction coefficient. The mechanical evaluation correction coefficient is calculated by the ratio of the brittleness index to the fracture pressure. Substituting (BI / PF) into Formula 4, the calculation method of the mechanical evaluation correction coefficient can be obtained.

[0171] The details are as follows:

[0172]

[0173] In this step, after calculating the average value (ave) of the first ratio of the historical fracturing wells and the range of the first ratio (max is the maximum value, min is the minimum value), the second ratio of the target fracturing well (i.e., the i-th well) is substituted into Formula 6 to obtain the mechanical evaluation correction coefficient. In this way, by comparing the parameters related to the original formation fracture characteristics of the target fracturing well with the parameters related to the original formation fracture characteristics of all historical fracturing wells in the block, it is possible to correct the particularity of the single well of the target fracturing well on the basis of the integrity of the development area, thereby improving the applicability of the pressure stabilization fitting model to the current target fracturing well.

[0174] S313. The product of the external extrusion correction coefficient and the maturity engineering evaluation coefficient is taken as the first slope; and the product of the mechanical evaluation correction coefficient and the rock formation fracture evaluation coefficient is taken as the first intercept.

[0175] In the embodiment of the present application, after the external extrusion correction coefficient is calculated, the external extrusion correction coefficient can be multiplied by the maturity engineering evaluation coefficient α to obtain the first slope of the objective function in the final pressure stabilization fitting model.

[0176] After calculating the mechanical evaluation correction coefficient, the mechanical evaluation correction coefficient can be multiplied by the rock fracture evaluation coefficient β to obtain the first intercept of the objective function in the final pressure stabilization fitting model. It should be noted that due to the large value of the mechanical evaluation correction coefficient, the denominator can be multiplied by 10 when calculating the first intercept. m Correspondingly, the result of the first intercept can be accurate to m decimal places to ensure the accuracy of the data while reducing the amount of calculation.

[0177] S314. Based on the first slope and the first intercept, an objective function is constructed with stable pressure as the dependent variable and maturity as the independent variable; the target maturity is substituted into the objective function to obtain the target stable pressure.

[0178] In the embodiment of the present application, after determining the first slope and the first intercept, the objective function between maturity and stable pressure can be determined to form the final stable pressure fitting model. Based on formula 1, the functional relationship between stable pressure P and maturity Ro can be obtained by introducing the correction function f(x):

[0179]

[0180] Based on formula 7, the objective function of the pressure stabilization fitting model in the embodiment of the present application can be obtained by substituting the calculation formula 2 of the maturity engineering evaluation coefficient α, the calculation formula 3 of the rock fracture evaluation coefficient β, the calculation formula 5 of the external extrusion correction coefficient, and the calculation formula 6 of the mechanical evaluation correction coefficient into the calculation formula 7:

[0181]

[0182] The objective function of the pressure stabilization fitting model can be iteratively updated as the data increases. The more data there is, the more accurate the objective function is. After obtaining the objective function in the pressure stabilization fitting model, the target maturity of the target fracturing well can be substituted to obtain the target stable pressure of the target fracturing well during the soaking process.

[0183] In the embodiment of the present application, the product of the external extrusion correction coefficient and the maturity engineering evaluation coefficient is used as the first slope, and the product of the mechanical evaluation correction coefficient and the rock fracture evaluation coefficient is used as the first intercept; based on the first slope and the first intercept, the stable pressure is used as the dependent variable and the maturity is used as the independent variable to construct the objective function, and the target maturity can be subsequently substituted into the objective function to calculate the target stable pressure. In this way, the corresponding relationship between maturity and wellbore stable pressure can be accurately reflected, which is a high degree of integration and comprehensive application of geological engineering integration, and the target stable pressure can be accurately calculated, which can effectively guide the actual exploration and development process.

[0184] S315. Determine the pressure drop function of the target fracturing well according to the pressure change trend of the target fracturing well; the independent variable of the pressure drop function is time, and the dependent variable is the pressure of the target fracturing well; substitute the target stable pressure into the pressure drop function to obtain the target well opening timing.

[0185] In the embodiment of the present application, the pressure change trend of the target fracturing well can be fitted by a power function, and the specific pressure drop function is expressed as follows:

[0186] P=a*t b (Formula 9)

[0187] Among them, a and b are fitting parameters, t is the soaking time, and P is the pressure.

[0188] In this step, after obtaining the pressure drop function, the target stable pressure can be substituted into the pressure drop function to obtain the time required for the casing pressure of the target fracturing well to drop to the target stable pressure during the well soaking process, and the final target well opening timing can be obtained, thereby improving the convenience and accuracy of the calculation.

[0189] Figure 6 A schematic diagram of a model construction for a method for determining a well shut-in and well opening provided in an embodiment of the present application. Figure 6 From the perspective of model building, the process of determining the timing of well soaking and well opening in the embodiment of the present application is specifically introduced.

[0190] like Figure 6 As shown, the embodiment of the present application is based on the geological model of the fracturing-expanding equilibrium body, and optimizes the timing of well opening by simulating the operation of the well-holding stable pressure, and finally provides a geological-engineering integrated evaluation method based on big data, which can accurately determine the timing of well-holding and well opening. The embodiment of the present application mainly includes four geological models and four simulation parameters, namely, the four geological models of the fracturing-expanding equilibrium body development dynamic model, the fracturing-expanding equilibrium body material diffusion model, the fracturing-expanding equilibrium body spatial coordination model and the fracturing-expanding equilibrium body stable pressure fitting model, and the four simulation parameters of the maturity engineering evaluation coefficient α, the rock rupture evaluation coefficient β, the external extrusion correction coefficient and the mechanical evaluation correction coefficient. The following is a detailed description of each geological model and simulation parameter:

[0191] 1. Dynamic model of fracturing expansion balance body development

[0192] Fracturing equilibrium body can refer to the stable system formed when the shale oil well is shut down after fracturing is completed and the well is shut down, the fracturing injection medium gradually diffuses to the distal end, and the stress field is balanced again. Here, the concept of shutting down is relative rather than absolute. In a narrow sense, shutting down is an engineering concept. The well is in a shut-in state from the time the well is shut down for fracturing until it is reopened for blowout. In a broad sense, shutting down is a development concept. If the casing pressure is restored after shutting down the well, the oil well is still in a shut-in state, and the effects of imbibition and hydration between the fracturing injection fluid and the shale formation continue to exist.

[0193] (1) Structural characteristics of the fracturing expansion balance body

[0194] The spatial range of the fracturing expansion balance body is the artificial transformation area of ​​the shale formation, which is a response to the control range of the fracturing cluster point and provides the entire source of production capacity during the development process. The fracturing expansion balance body includes the following parts: ① stress crushing area, ② fracturing sand support area, ③ fracturing fluid passing, spreading, and retention area, ④ the area where the original formation is infiltrated due to imbibition, and ⑤ the micro-crushed area of ​​the shale layer due to hydration.

[0195] After the shale oil well is fracturing-treated, the fracturing injectants gradually diffuse to the far end of the formation. This stage mainly corresponds to the well-sleeping period in the whole life cycle of shale oil well development. The well-sleeping concept has relative attributes. According to the time period occupied in the whole life cycle, it can be divided into two categories: the narrow well-sleeping concept in engineering and the broad well-sleeping concept in development. Figure 7 A schematic diagram of a shale oil well casing pressure change curve in an embodiment of the present application is shown. Figure 7 The narrow concept of well blocking in engineering and the broad concept of well blocking in development are described.

[0196] (2) Narrow concept of well blocking (engineering well blocking)

[0197] The narrow concept of well shut-in is engineering well shut-in, which refers to the well shut-in and pressure holding state after the fracturing trial is completed. Figure 7 The casing pressure change curve over time shows the characteristics of a power function. The pressure drop rate is the fastest in the early stage of well soaking, and the pressure drop rate gradually decreases until the casing pressure of the oil well remains almost unchanged. This is the final stable casing pressure (i.e., well soaking stable pressure). Since the medium migration speed will become slower and slower at the end of diffusion, the daily drop in casing pressure is usually less than 0.1MPa as the standard for opening a well in production, rather than waiting for the ideal stable casing pressure state. Therefore, well opening and blowout are often carried out before reaching the final stable casing pressure. At this time, there is a "diffusion pressure reserve" inside the fracturing expansion balance body.

[0198] (3) Broad concept of well-simmering (development well-simmering)

[0199] The broad concept of well soaking is development well soaking, which refers to the stage when the casing pressure of the oil well can be restored to the stable casing pressure (casing pressure before opening the well) after the fracturing construction is completed, corresponding to the time period 0 to E in the casing pressure change curve. In the two time periods A to B and C to D, the well is opened and blown, the oil well continues to flow back, and the casing pressure gradually decreases. However, after the pressure is held in the two time periods B to C and D to E before the well is shut down, the casing pressure can rise to the stable casing pressure baseline. This is because when the oil well is opened and blown, the internal part of the fracturing expansion balance body has not reached the final ideal equilibrium state. Therefore, in the early stage of blowing, although the system continues to flow back, the diffusion effect in the deep formation continues under the action of the "diffusion pressure reserve". However, when the continuous blowout in the E to F section consumes the "diffusion pressure reserve", the casing pressure cannot be restored to the stable casing pressure baseline at the next well shut-in and pressure holding (F to G section), so the diffusion effect is completely over and the soaking process ends.

[0200] 2. Material Diffusion Model of Fracturing Extension Equilibrium

[0201] After the fracturing construction is completed, the fracturing injection medium (fracturing material or fracturing medium) will diffuse outward based on the stress fracture network until the stress field is balanced and stable. Inside the fracturing expansion equilibrium body, the diffusion process of the material does not only include a single diffusion effect, but a combination of a series of complex effects. The diffusion process can be divided into four parts: the supporting effect of fracturing sand on artificial fractures; the mutual carrying and migration effect between fracturing sand, fracturing fluid and injected carbon dioxide; the spontaneous infiltration and replacement effect of the rock after the fluid is fully in contact with the shale formation; and the hydration effect mainly based on clay minerals. These four processes promote each other and constitute a "support, migration, infiltration, hydration-four-degree superposition" material diffusion model.

[0202] (1) Fracturing medium diffusion mechanism

[0203] Figure 8 FIG. 1 shows a schematic diagram of diffusion of a four-dimensional superimposed fracturing medium according to an embodiment of the present application. Figure 8 As shown in the figure, during the diffusion process of the fracturing medium inside the fracturing expansion equilibrium body, four main effects occur, which are: support effect, migration effect, imbibition effect and hydration effect in order of occurrence. These four effects are superimposed and alternate, promoting each other, and together constitute the diffusion process of the entire fracturing medium.

[0204] ①Supporting function

[0205] The supporting effect mainly refers to the maintenance of the open form of fracturing sand in artificial fractures. The support of fracturing sand is a "passive" effect, which can be divided into four stages: occupation, closure, extrusion, and support. Due to the heterogeneity of the shale layer and the directionality of the combined force, fracturing sand cannot achieve "full contact surface occupation" for all open fractures, but can only achieve "half contact surface occupation". After the external force decays and the fractures begin to close, the cracks in the area occupied by unsupported sand will disappear first. As the degree of closure deepens, the supporting sand is squeezed in both directions, and the original arrangement of the sand particles is disrupted. In this process, the initial multi-layer support of the fracturing sand may weaken and transform into a single-layer support. The fracturing sand is eventually transformed into a fixed "rock skeleton" under strong extrusion.

[0206] ② Migration

[0207] Migration mainly refers to the process of fracturing medium moving from the fracturing cluster point to the deep formation, which mainly includes three elements: medium type, channel characteristics, and mode state. Migration medium is mainly divided into two types: solid-fluid multiphase mixed suspension and separate fluid phase; among them, the near-well end has sufficient transportation capacity and sand-carrying migration, and the far-well end has narrow spatial channels and single-phase liquid seepage. The movement channel can be divided into two stages: in the early stage of diffusion, the fracturing sand has not yet completed its position, and the medium diffusion channel is an unobstructed fracture space; when the fracturing sand completes its position in the main fracture, the medium migration channel is the residual gap between the occupied areas. The migration mode can be divided into two stages: before the fracture is closed, the medium migration channel inside the fracturing expansion equilibrium body is smooth, and the migration mode is similar to the sand body migration characteristics during the deposition process, which is a macroscopic flow; after the fracture is closed in the later stage, the migration channel is transformed into a porous medium, which is more in line with the microscopic seepage characteristics.

[0208] ③Imbibition

[0209] The imbibition effect mainly refers to the process in which the fluid spontaneously absorbs the matrix rock and displaces the internal crude oil when the fracturing fluid is in full contact with the shale formation. There are two elements in the imbibition of the shale fracturing expansion balance body, namely, the penetration depth and the penetration position. In terms of the penetration depth, the greater the penetration depth, the greater the amount of material exchange, and the greater the degree of matrix utilization. On the basis of making full use of the fracture-controlled reserves, the matrix reserves are effectively developed. In terms of the infiltration area, the first is the "internal infiltration" between the fractures, which can enhance the utilization of the internal space of the fracturing expansion balance body; the second is the "external edge infiltration" that diffuses to the outside based on the fracture surface. This process can expand the spatial volume of the fracturing expansion balance body and increase the actual control range of the fracturing cluster point.

[0210] ④ Hydration

[0211] Hydration mainly refers to the effect of fluid entering the shale matrix, penetrating into the mineral crystal framework, or attaching to the ions of soluble rocks, causing the structure of the rock to change. Hydration can open microcracks, increase the density of small-scale pores, enhance the connectivity between cracks, organic pores, and inorganic pores, improve pressure permeability, and further promote the diffusion of fracturing media. The main targets of hydration are clay minerals in the matrix, mainly illite and montmorillonite. The interlayer force of illite is mainly controlled by the double electrical layer repulsion, and only surface hydration occurs, with high hydration stress, small strain, and short hydration equilibrium time; the hydration process of montmorillonite is mainly controlled by the osmotic pressure difference between the fracturing fluid and the pore fluid. After surface hydration, it continues to absorb water for osmotic hydration, which can produce long-range expansion of dozens of times the interlayer spacing, with small hydration stress, large strain, and long hydration equilibrium time. The results of hydration are not linear, and hydration for too long will damage the formation, so there is an optimal hydration time. Since the optimal hydration time cannot be controlled in the actual production process, the hydration degree can only be indirectly controlled by adjusting the ratio of fracturing fluid to fracturing sand in the fracturing medium.

[0212] (2) Fracture composition of the equilibrium body of fracturing extension

[0213] The internal cracks of the fracturing expansion balance body can be divided into three levels: the first level is the sand-supported main cracks, where the fracturing sand moves to the far end, or the fine sand spreads to the far end in the gap space of the coarse sand. The system is mainly composed of fracturing sand, which is in a state of "supporting and moving";

[0214] The second level is force-destroyed microcracks, which are tiny cracks formed in shale formations under the action of external stress from fracturing. There is no fracturing sand inside to support them, but fluids can enter them, increasing the contact area. The system is mainly composed of fracturing fluid, which is in a state of "migration and absorption".

[0215] The third level is liquid contact hydration fracture. After the fracturing injected fluid fully contacts the shale formation, spontaneous imbibition, replacement and hydration occur. Mineral expansion causes new tiny cracks in the rock and increases the density of cracks. The interior of the system is dominated by fluid, presenting a state of "imbibition and hydration at the same time".

[0216] 3. Spatial coordination model of fracturing extension equilibrium

[0217] Fig. 9A schematic diagram of a spatial coordination model of a fracturing expansion equilibrium body provided in an embodiment of the present application. When fracturing is completed and converted to a stable state, there are three-phase media of solid (fracture sand), liquid (fracture fluid, liquid hydrocarbons), and gas (carbon dioxide, gaseous hydrocarbons) inside the fracturing expansion equilibrium body. The fracturing sand and the original formation form a new rock skeleton, and the fracturing fluid, carbon dioxide, and hydrocarbons discharged from the shale formation constitute a new pore fluid. The volume of the fracturing expansion space is controlled by the volume of the fracturing sand, and the pressure field characteristics are related to the volume of the fluid contained in the unit space. Based on this, the concept of "fluid-solid ratio" is proposed, and the fluid-solid ratio plays a controlling role in the casing pressure of the well.

[0218] (1) Space

[0219] Under ideal conditions, the effective transformation space in the fracturing expansion balance body has the following two characteristics:

[0220] ① Ineffectiveness of external form

[0221] The external morphology of the fracturing expansion balance body is affected by many factors, such as engineering (fracturing construction parameters), geology (rock brittleness, fracture pressure, and geostress characteristics). However, its external three-dimensional spatial morphology (fracture length, fracture height, and fracture width), stimulated reservoir volume (SRV) and other geometric parameters, and internal fracture morphology (straight fractures, volume fractures), density (single fracture, multiple fractures, and mesh fractures) and other engineering geological parameters do not directly affect the effective transformation space of shale formations. The effective transformation space in the fracturing expansion balance body has nothing to do with its spatial morphology, and has the ineffectiveness of external morphology.

[0222] ② Single particle validity

[0223] Under ideal conditions such as the fracturing sand not breaking, not deforming, and not squeezing into the rock, the size of the support space of a single fracturing sand (particle) is controlled by factors such as the degree of ground stress compression, rock mineral composition, and strength. Inside the fracturing expansion equilibrium body, these parameters can be equivalent to mean values, so the effective transformation space that a unit volume of fracturing sand can support is the same. The effective transformation space in the fracturing expansion equilibrium body is positively correlated with the effective supporting volume of the fracturing sand, and is composed of many single particles, with single particle effectiveness.

[0224] (2) Substance

[0225] ① Fluid-to-solid ratio concept

[0226] The coordination relationship between fluid and space, and between space and solid determines the casing pressure. In this regard, the concept of "fluid-solid ratio" is proposed for the first time in the embodiments of the present application for the fracturing expansion balance body, and the "fracturing fluid-solid ratio" and "development fluid-solid ratio" are defined from the two perspectives of engineering and geology, respectively.

[0227] From an engineering perspective, the fluid-to-solid ratio of fracturing refers to the ratio of fluid to solid in the injected medium during the fracturing construction process inside the fracturing balance body, that is, the ratio of the total volume of fracturing fluid and carbon dioxide injected into the fracturing to the volume of fracturing sand.

[0228] From a geological perspective, the development fluid-solid ratio refers to the ratio of internal fluid to solid during the development of the fracturing equilibrium body. On the basis of the fracturing fluid-solid ratio, it is necessary to additionally consider the impact of fluid hydrocarbons discharged from the rock formation.

[0229] ② Fluid field characteristics

[0230] After the fracturing sand starts to support, its position no longer changes, and it has the characteristics of a rock skeleton. The multiphase fluids inside the fracturing expansion balance body migrate and interact to form a fluid field. The fluid field is mainly composed of two parts: one is the hydrocarbon fluid released after the shale rock layer is broken, and the other is the gas-liquid two-phase fluid injected by fracturing. During the soaking period, inside the fracturing balance body, the former is synchronous and unified, and the latter is gradual and diffuse. In a stable state, the fluid-solid ratio inside the fracturing expansion balance body is the same, the volume of fluid contained in the space supported by each fracturing sand is the same, and the casing pressure is stable.

[0231] 4. Fracturing extension equilibrium body pressure stabilization fitting model

[0232] Based on the three geological models of fracturing expansion equilibrium body development dynamics, material diffusion, and spatial coordination, and on the basis of laboratory analysis, well logging interpretation results, and fracturing engineering parameters, a pressure stabilization fitting model (Formula 8) was established to achieve the simulation calculation of the target stable pressure of the fracturing expansion equilibrium body.

[0233] (1) Model composition characteristics

[0234] The fracturing expansion equilibrium body stable pressure fitting model is a mathematical model based on a linear function relationship with maturity Ro as the main control variable, in which the maturity engineering evaluation coefficient α is the slope and the rock fracture evaluation coefficient β is the intercept. There are two-level nested functions in the simulation formula, and the model also contains two correction functions composed of fracturing fluid-solid ratio, fracture pressure and brittleness index, which are respectively calculated to obtain the two correction parameters of external extrusion and mechanical evaluation (Formula 5, 6).

[0235] According to the structural characteristics of the operation formula, the pressure stabilization fitting model can be divided into three modules: variable control, regional parameters, and correction function. These three modules are based on laboratory data, dynamic data, and construction data, and respectively describe the influence of geology, engineering geology, and engineering on the pressure field during the fracturing and soaking of shale formations. The pressure stabilization fitting model provided in the embodiment of the present application is a research result formed under the guidance of the integration of geology and engineering, and is a direct application and efficient transformation of geological theory.

[0236] (2) Variable control module

[0237] In the pressure stabilization fitting model, the variable control module describes the influence of maturity Ro on the pressure field during the soaking process from a geological perspective.

[0238] ① Establish a mathematical model

[0239] The function of the variable control module is to describe the influence of geological characteristics in shale formations on the pressure field during fracturing and well soaking. During the study, 10 shale oil vertical wells were selected in the Qingshankou Formation in the Gulong area. Based on laboratory analysis and logging interpretation results, the average maturity Ro and many other reservoir geological parameters in the perforation section were statistically analyzed. At the same time, in engineering, the well was opened and blown out with the daily casing pressure drop below 0.01MPa as the limit, and the casing pressure at this time was used to represent the stable casing pressure of the well soaking. Different geological parameters were intersected with the stable casing pressure of the well soaking. After selecting and numerically analyzing many geological parameters, it was finally found that there was a high linear fitting relationship between maturity Ro and the stable pressure of the well soaking. Based on this statistical law, the main formula structure of the well soaking stable pressure fitting model was established.

[0240] ② Improve geological connotation

[0241] After completing the big data analysis and establishing a preliminary statistical model, it is necessary to give the mathematical model geological connotations, thereby deepening the integrity of the model, sublimating the theoretical nature of the model, and strengthening the practicality of the model.

[0242] Maturity Ro will control the stable pressure of the well, and the pressure field is determined by the fluid-solid ratio. Under the same fracturing process conditions and similar construction environment, there will be no essential difference in the fracturing fluid-solid ratio between different shale oil wells in a certain block. However, due to the rapid phase change of shale formations and strong reservoir heterogeneity, the geological characteristics of different wells vary greatly, which leads to a large difference in the development fluid-solid ratio. Therefore, the selected geological parameter Ro corresponds to the development fluid-solid ratio in the model.

[0243] When the fracturing construction completes the dense cutting of the formation rock, under the constraint of the starting pressure, a part of the hydrocarbons in the matrix will be discharged from the matrix and enter the fracture system of the fracturing expansion balance body, affecting the casing pressure of the oil well. Here we need to introduce three parameters: area s, depth h, and hydrocarbon discharge volume v.

[0244] The area s may refer to the surface area of ​​the matrix space, specifically the surface area of ​​the matrix in contact with the fracturing fluid after the shale formation is fractured, or the surface area of ​​the fracture space.

[0245] Depth h can refer to the hydrocarbon-expellable depth of the matrix, specifically, the maximum hydrocarbon-expellable depth of the shale matrix from the mudstone fracture surface to the inside, that is, the movable thickness of the mudstone matrix contacted by the fracturing fluid after the fracture is formed. When the shale rock is densely cut, if the radius of a single matrix rock block is smaller than the hydrocarbon-expellable depth, all the oil and gas in the shale formation can be completely discharged.

[0246] The hydrocarbon expulsion volume v can refer to the unit hydrocarbon expulsion volume of the matrix, specifically the sum of the hydrocarbon expulsion volume per unit volume or per unit depth within the available depth of the matrix. However, as the hydrocarbon expulsion depth extends into the rock, the hydrocarbon expulsion volume does not necessarily change linearly. This parameter mainly reflects the amount of oil and gas in the shale matrix.

[0247] When s is fixed, the larger h and v are, the more hydrocarbons are discharged, and the larger the development fluid-solid ratio is. The two parameters h and v will increase with the increase of maturity Ro.

[0248] (3) Regional parameter module

[0249] In the pressure stabilization fitting model, the regional parameter module describes the influence of regional rock formation characteristics on the pressure field during the soaking process from the perspective of engineering geology.

[0250] ①Mathematical model characteristics

[0251] The regional parameter module describes two properties of the pressure stabilization fitting model, regionality and iterativeness.

[0252] Regionality specifically means that the pressure stabilization fitting model is based on a linear relationship. Since the fitting straight line does not pass through the origin of the coordinate axis, the fitting formula needs to be characterized by two parameters: slope α and intercept β. The two parameters, slope α and intercept β, are subject to regional constraints and control, and are a response to the characteristics of the shale fracturing expansion equilibrium body in a specific study area.

[0253] Iteration specifically means that for different oilfield development blocks, it is necessary to obtain the two parameters α and β based on the relationship between the maturity of the perforation section and the stable casing pressure of the wells that have completed fracturing and well production. With the increase in the number of production wells, the amount of "maturity-pressure" related data will gradually increase. Therefore, it is necessary to continuously iterate the calculation of the two parameters α and β according to the characteristics of "maturity-pressure" of the newly opened oil wells to improve the matching degree between the stable pressure fitting model and the development block.

[0254] ②Engineering geological description

[0255] After building a bridge between mathematical models and geological theories, it is necessary to carry out engineering geological description, and then improve the geological functionality, engineering practice, and integrated applicability of the model. The two parameters of slope α and intercept β correspond to different connotations in the field of engineering geology.

[0256] α: In engineering geology, the slope α is defined as the maturity engineering evaluation coefficient. The wellbore stable pressure increases with the increase of maturity. In the same block, the increase is similar, and there may be large differences in different oil fields. The parameters associated with α are mainly the development fluid-solid ratio and the fracturing fluid-solid ratio.

[0257] β: In engineering geology, the intercept β is defined as the rock formation fracture evaluation coefficient. This coefficient directly reflects the stable casing pressure of the fractured well of the rock formation with maturity 0. If the fitting straight line intersects with the positive interval of the x-axis, the maturity corresponding to the intersection is the minimum maturity required for development; if it intersects with the positive interval of the y-axis, it reflects the pressure characteristics after the initial fracture of the formation. Associated with β are parameters related to the fracture characteristics of the original formation, such as brittleness index, fracture pressure, etc.

[0258] (4) Correction function module

[0259] The correction function module describes the influence of engineering construction parameters on the pressure field during the soaking process from an engineering perspective in the fitting model.

[0260] ①Mathematical model characteristics

[0261] The scatter points of oil well maturity Ro-well stable casing pressure in the region do not fall completely on the fitting line. The scatter points are evenly and symmetrically distributed above and below the linear model, with a certain degree of deviation. The fitting line is determined by the geological characteristics and engineering geological characteristics of the shale formation in the region, while the deviation is controlled by a single well. Changes in construction parameters during fracturing construction and the special properties of single well engineering are likely to affect the deviation. On the basis of the fitting model established based on geology and engineering geology, the deviation needs to be further corrected and improved.

[0262] ②Engineering application correction

[0263] After completing the initial establishment of the geological engineering integration model, engineering application correction should be carried out to enhance the model's theoretical application depth, production guidance breadth, and model promotion matching degree.

[0264] The correction of the deviation in the pressure-stabilizing fitting model is to correct the deviation between the actual fracturing conditions and the ideal fracturing conditions in engineering. Based on the structural characteristics of the pressure-stabilizing fitting model, the two parameters of slope α and intercept β are corrected respectively. The slope α is corrected by the "external extrusion correction coefficient" and the fracturing fluid-solid ratio is used for calculation; the intercept β is corrected by the "mechanical evaluation correction function" and the brittleness index and the fracture pressure are used for calculation, so that the final first slope and first intercept can be obtained, and then the complete objective function (Formula 8) can be constructed.

[0265] 5. Evaluation of the final well opening time

[0266] The final evaluation of the timing of well opening is to determine the target well opening timing. This not only involves the stable pressure model of the fracturing expansion equilibrium body well shut-in provided in the embodiment of the present application, but also requires regression and fitting of the change in the well shut-in casing pressure of the target fracturing well. According to the pressure drop trend of the target fracturing well, the change trend of the well shut-in pressure over time is more in line with the power function characteristics, and the pressure drop function (Formula 9) can be fitted to obtain the pressure drop function, and the pressure P in Formula 8 is replaced by the pressure drop function, that is, the prediction function of the target well opening timing t is obtained (Formula

[0267] Formula 10):

[0268]

[0269] The two concepts of wellbore stable casing pressure and well opening timing are both geological models and engineering concepts. The shale fracturing expansion balance wellbore stable pressure simulation method provided in the embodiment of the present application is a highly integrated and comprehensive application of geological engineering integration.

[0270] The embodiment of the present application mainly utilizes the parameters such as shale oil well maturity Ro, splitting pressure PF, brittleness index BI, fluid-solid ratio, etc. to simulate and calculate the stable pressure value during the fracturing and well holding process of the oil well, and predicts the best time to open the well in combination with the single well pressure drop law, and finally determines the target well opening time. In terms of geological models, the embodiment of the present application creates a shale fracturing expansion equilibrium body theory that includes four geological models: development dynamic model, material diffusion model, spatial coordination model, and pressure stabilization fitting model, optimizes the well holding definition, and proposes the concept of fluid-solid ratio, which greatly enriches the geological theoretical basis for shale oil exploration and development. In terms of engineering application, the connotation of well holding pressure drop is explained through the maturity engineering evaluation coefficient, rock formation rupture evaluation coefficient, external extrusion correction coefficient, and mechanical evaluation correction coefficient, four geological engineering integrated simulation coefficients, which greatly promotes the engineering applicability of geological theory in the process of shale oil development and production. In terms of integrated research, the embodiments of this application are the results of the integrated research of big data, geology, and engineering. During the research process, the research idea of ​​"integration of data, geography, and engineering" was proposed: ① Establish statistical models through big data analysis; ② Transform geological models by assigning geological connotations; ③ Enrich engineering theories to form an integrated model of geology and engineering; ④ Correct and improve the final application model through engineering applications. Therefore, based on geological and engineering data, the embodiments of this application established a pressure stabilization fitting model, realized the prediction of the stable pressure of the well, and could accurately determine the timing of well opening, providing strong support for the exploration and development of shale and effective guidance for the actual production of the mine.

[0271] From the perspective of specific examples, the following uses the simulation of the target stable pressure of a shale oil well in the continental shale reservoir of the JHB test area in the northern large freshwater lake basin of the Songliao Basin in the Daqing exploration area as an example to illustrate the implementation process of the method for determining the timing of well shut-in and well opening in the embodiment of the present application.

[0272] The JHB block in the study area is located in the central depression area in the northern part of the Songliao Basin. The exploration target strata are Q1 to Q9 of the Qingshankou Formation. The lithology is mainly mud-grade felsic shale with a high clay mineral content. The shale is a mud-grade layered and laminated shale with a particle size of less than 3.9 microns (μm), accounting for more than 95% of the thickness. The average total porosity is less than 10% and the average movable oil porosity is 6%. Although the macroscopic lamination fractures can develop up to 3,000 per meter, the average horizontal permeability is only 0.21mD under an overburden pressure of 42MPa. In order to achieve effective development and utilization, it is necessary to accurately determine the timing of well shut-in and well opening after fracturing. Therefore, it is of great significance to establish a convenient and effective method for simulating the stable pressure of well shut-in.

[0273] 1. Improve basic data

[0274] In this example application, the monitoring results of 10 shale oil vertical wells that have completed well shut-in and well opening production are selected to improve and establish the basic data required for simulation. These 10 wells are: JHB-V12, JHB-V15, JHB-V20, JHB-V23, JHB-V24, JHB-V25, JHB-V29, JHB-V34, JHB-V41, and JHB-V43. The maturity Ro and the well shut-in stable pressure scatter points of these 10 wells are shown in Figure 1. Figure 4 After improving the fitting model operation parameters based on these data, the wellbore stable pressure of three horizontal wells JHB-H1112, JHB-H22, and JBH-H32 in the development area was predicted and compared with the actual stable casing pressure value to verify the accuracy of the embodiment of the present application.

[0275] 2. Evaluation calculation of maturity engineering evaluation coefficient α

[0276] based on Figure 5 The calculation idea shown is that after multiple calculations are performed according to Formula 2 (10 groups of data, a maximum of 45 calculations, that is, n is 45), the maturity engineering evaluation coefficient α of the study area is obtained, and the value is 30.47 after retaining two decimal places.

[0277] 3. Evaluation calculation of rock rupture evaluation coefficient β

[0278] based on Figure 5 The calculation idea shown is that after multiple calculations are performed according to Formula 3 (10 sets of data, a maximum of 45 calculations, that is, n is 45), the rock stratum fracture evaluation coefficient β in the study area is obtained, and the value is -21.79 after retaining two decimal places.

[0279] 4. Evaluation of external extrusion correction coefficient

[0280] Based on the fracturing design and field monitoring data, a statistical analysis was conducted based on the volume parameters of the three-phase materials of gas, liquid and sand injected into the fracturing of 10 vertical wells. According to the final monitoring results, the final volume of fracturing sand injected into each well was calculated ( Fig.10 ), volume of injected fracturing fluid ( Fig.11 ), and the injected carbon dioxide volume ( Fig.12 ). According to the above data, the fluid-solid ratio of the study area is 9-14, the average value is 11.5, and the range is 5. According to formula 5, the calculation results of the external squeeze correction coefficient of these 10 vertical wells are obtained ( Fig.13 ).

[0281] 5. Mechanical evaluation correction coefficient calculation

[0282] Based on the comprehensive interpretation results of the laboratory and well logging, a statistical analysis was conducted based on the two parameters of brittleness index and fracture pressure of the development section of 10 vertical wells. The minimum value of the brittleness index BI in the study area is 30, the maximum value is 60, the median value is 45, and the range is 30 ( Fig.14 ); the minimum value of the burst pressure PF is 50MPa, the maximum value is 75MPa, the median value is 62.5MPa, and the range is 25MPa ( Fig.15 ). Therefore, the BI / PF value is 0.4-1.2, the average value is 0.8, and the range is 0.8. According to Formula 6, the mechanical evaluation correction coefficient calculation results of these 10 vertical wells are obtained ( Fig.16 ). Finally, the fitting model formula of the fracturing expansion equilibrium body well-simmering pressure stabilization suitable for the study area is obtained (Formula 11):

[0283]

[0284] 6. Basic data characteristics of horizontal wells

[0285] After completing the basic data collection of the JHB test area and establishing the simulation formula applicable to the region, the simulation calculation of the stable casing pressure of the fracturing expansion balance body of the three horizontal wells JHB-H1112, JHB-H22, and JBH-H32 was carried out. Based on the three parameters of maturity Ro, fracture pressure PF, and brittleness index BI interpreted by the logging interpretation of the horizontal section of these three horizontal wells ( Fig.17 , Fig.18 , Fig.19 ), and the volume of the three-phase materials of injection fluid, gas and sand in the whole well monitored during the fracturing operation ( Fig. 20 ) and determine the various parameters involved in the model operation (Table 1).

[0286] hashtag Ro PF BI Fracturing fluid-solid ratio JHB-H1112 1.68 53.79 42.55 10.15 JHB-H22 1.67 45.86 40.73 10.62 JBH-H32 1.66 50.08 39.23 10.63

[0287] Table 1 Horizontal well simulation parameter selection table

[0288] 7. Comprehensive results of well soaking timing in JHB test area

[0289] Substituting the data in Table 1 into Formula 11, the stable casing pressure of the fracturing extension balance body of the three horizontal wells is simulated: the target stable pressure of the well JHB-H1112 is 29.27MPa; the target stable pressure of the well JHB-H22 is 28.98MPa; the target stable pressure of the well JHB-H32 is 28.61MPa.

[0290] According to the initial pressure drop characteristics of the three horizontal wells, the casing pressure change law of the entire well soaking process was regressed and predicted to obtain the target well soaking time: the target well soaking time of JHB-H1112 is from the 28th to the 29th day of soaking ( Fig.21 ); The target time for opening the well JHB-H22 is from the 21st to the 22nd day of well soaking ( Fig. 22 ); The target time for opening the well JHB-H32 is from the 28th to the 29th day of soaking ( Fig.23 ).

[0291] 8. Simulation accuracy evaluation

[0292] The simulation results of the target stable pressure of the 13 wells selected in the JHB test area were compared with the actual results to verify the accuracy of the stable pressure fitting model provided in the embodiment of the present application ( Fig.24 ). For the 10 vertical wells used to construct the fitting model, the actual-simulation deviation values ​​are as follows: the maximum deviation value is 1.56MPa, the minimum deviation value is 0.16MPa, and the average deviation value is 0.67MPa; the actual-simulation deviation ratio is as follows: the maximum deviation ratio is 7.18%, the minimum deviation ratio is 0.83%, and the average deviation ratio is 3.42%. The deviation values ​​of the three purely simulated horizontal wells are 0.29MPa, 0.11MPa, and 0.23MPa, respectively, all lower than 0.3MPa; the deviation ratios are 0.99%, 0.37%, and 0.81%, respectively, all less than one percentage point. The good fitting accuracy of the JHB test area shows that the shale fracturing expansion balance body well-simmering and well-opening timing method provided in the embodiment of the present application has a high accuracy in the well-simmering stable pressure and the well-simmering and well-opening timing, has great application value, and can effectively guide actual exploration, development and production.

[0293] Based on the above specific examples, the embodiment of the present application takes the JHB test area of ​​the large freshwater lake basin terrestrial shale oil field in the Songliao Basin as an example to carry out the evaluation study on the timing of well shut-in and well opening, and verifies the method for determining the timing of well shut-in and well opening in the embodiment of the present application. First, through the logging interpretation, engineering monitoring and other data of 10 shale oil wells in production in the JHB block, the basic data of the study area is improved, and the various evaluation coefficients in the simulation formula are calculated to complete the establishment of the simulation formula for the stable casing pressure of the shale fracturing expansion equilibrium body well shut-in in the JHB block. Secondly, the simulation formula is used to simulate the target stable pressure of the shut-in of the other three horizontal wells in the JHB block, and the corresponding casing pressure change law is combined to predict the optimal time for well shut-in and well opening. Finally, the target stable pressure value obtained by calculation is compared with the actual stable pressure value to verify the accuracy of the pressure stabilization fitting model. Among them, the average deviation ratio of the vertical well simulation value constructed by the model is 3.42%, and the average deviation ratio of the horizontal well simulation value is 0.21%. Taking the shale oil wells in the JHB test area as an example, the fit and applicability of the method for determining the well shut-in and well opening provided in the embodiment of the present application have been fully verified. It can accurately simulate the target stable pressure of the well shut-in and the target opening timing of the well shut-in and well opening, effectively guide the exploration, development and production of shale oil, and enrich the connotation of unconventional oil and gas geology and the basic theory of shale oil exploration and development.

[0294] Fig.25 This is a schematic diagram of a device for determining the timing of well soaking and well opening provided in an embodiment of the present application. Fig.25 The device 10 for determining the timing of well shut-in and well opening may include: an acquisition module 11, a first determination module 12, a second determination module 13 and a third determination module 14, wherein:

[0295] An acquisition module 11 is used to acquire historical data of historical fracturing wells and to acquire target maturity of target fracturing wells; the historical data includes historical maturity and historical stable pressure;

[0296] A first determination module 12 is used to determine a maturity engineering evaluation coefficient and a rock formation fracture evaluation coefficient based on the historical maturity and the historical stable pressure;

[0297] The second determination module 13 is used to determine the target stable pressure of the target fracturing well according to the maturity engineering evaluation coefficient, the rock fracture evaluation coefficient and the target maturity;

[0298] The third determination module 14 is used to determine the target well opening time according to the target stable pressure and the pressure change trend of the target fracturing well.

[0299] The device for determining the timing of well shut-in and well opening provided in the embodiment of the present application can execute the technical solution shown in the above method embodiment, and its implementation principle and beneficial effects are similar, which will not be repeated here.

[0300] In a possible implementation, the historical data also includes historical fracturing material related parameters, historical brittleness index and historical fracture pressure; the second determination module 12 includes:

[0301] A first determination submodule is used to determine an external squeeze correction coefficient based on historical fracturing material related parameters;

[0302] The second determination submodule is used to determine the mechanical evaluation correction coefficient based on the historical brittleness index and the historical rupture pressure;

[0303] The third determination submodule is used to determine the target stable pressure of the target fracturing well according to the maturity engineering evaluation coefficient, the rock fracture evaluation coefficient, the external squeeze correction coefficient, the mechanical evaluation correction coefficient and the target maturity.

[0304] In a possible implementation manner, the first determining submodule is specifically configured to:

[0305] According to the relevant parameters of historical fracturing materials, the historical fracturing fluid-solid ratio corresponding to the historical fracturing wells is calculated;

[0306] According to the historical fracturing fluid-solid ratio, the average historical fracturing fluid-solid ratio and the historical fracturing fluid-solid ratio extreme value are calculated;

[0307] Obtaining parameters related to target fracturing materials of the target fracturing well, and calculating the target fracturing fluid-solid ratio corresponding to the target fracturing well;

[0308] The external squeeze correction coefficient is determined based on the target fracturing fluid-solid ratio, the average historical fracturing fluid-solid ratio and the extreme value of the historical fracturing fluid-solid ratio.

[0309] In a possible implementation manner, the second determining submodule is specifically configured to:

[0310] Calculating the ratio of the historical brittleness index to the historical fracture pressure to obtain a first ratio of each historical fracturing well;

[0311] Based on the first ratios of the various historical fractured wells, determining an average value of the first ratio and a range of the first ratio;

[0312] Obtaining a target brittleness index and a target fracture pressure of a target fractured well, and using a ratio of the target brittleness index to the target fracture pressure as a second ratio of the target fractured well;

[0313] A mechanical evaluation correction coefficient is determined based on the second ratio, the average value of the first ratio, and the range of the second ratio.

[0314] In a possible implementation manner, the third determining submodule is specifically configured to:

[0315] The product of the external extrusion correction coefficient and the maturity engineering evaluation coefficient is taken as the first slope;

[0316] The product of the mechanical evaluation correction coefficient and the rock formation fracture evaluation coefficient is taken as the first intercept;

[0317] Based on the first slope and the first intercept, the objective function is constructed with stable pressure as the dependent variable and maturity as the independent variable;

[0318] Substitute the target maturity into the objective function to obtain the target stable pressure.

[0319] In a possible implementation manner, the first determining module 12 is specifically configured to:

[0320] A plane rectangular coordinate system is constructed with maturity as the horizontal coordinate and stable pressure as the vertical coordinate, and data points corresponding to historical fracturing wells are determined in the plane rectangular coordinate system;

[0321] Calculate the second slope and second intercept of the straight line connecting any two data points;

[0322] The average value of the second slope is determined as the maturity engineering evaluation coefficient, and the average value of the second intercept is determined as the formation fracture evaluation coefficient.

[0323] In a possible implementation manner, the third determining module 14 is specifically configured to:

[0324] According to the pressure change trend of the target fracturing well, a pressure drop function of the target fracturing well is determined; the independent variable of the pressure drop function is time, and the dependent variable is the pressure of the target fracturing well;

[0325] Substitute the target stable pressure into the pressure drop function to obtain the target well opening timing.

[0326] The device for determining the timing of well shut-in and well opening provided in the embodiment of the present application can execute the technical solution shown in the above method embodiment, and its implementation principle and beneficial effects are similar, which will not be repeated here.

[0327] Fig.26 This is a schematic diagram of a device for determining the timing of well soaking and well opening provided in an embodiment of the present application. Fig.26 The well soaking and well opening timing determination device 20 may include: a memory 21 and a processor 22. Exemplarily, the memory 21 and the processor 22 are interconnected via a bus 23.

[0328] The memory 21 is used to store program instructions;

[0329] The processor 22 is used to execute the program instructions stored in the memory, so as to enable the processor to execute the method for determining the timing of well shut-in and well opening shown in the above embodiment.

[0330] Fig.26The device for determining the timing of well shut-in and well opening shown in the embodiment can execute the technical solution shown in the above method embodiment, and its implementation principle and beneficial effects are similar, which will not be repeated here.

[0331] An embodiment of the present application provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the above-mentioned method for determining the timing of well shut-in and well opening.

[0332] The embodiment of the present application may also provide a computer program product, including a computer program, which, when executed by a processor, can implement the above-mentioned method for determining the timing of well shut-in and well opening.

[0333] All or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a readable memory. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned memory (storage medium) includes: read-only memory (English: read-only memory, abbreviated: ROM), RAM, flash memory, hard disk, solid state drive, magnetic tape (English: magnetic tape), floppy disk (English: floppy disk), optical disc (English: optical disc) and any combination thereof.

[0334] The embodiments of the present application are described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processing unit of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processing unit of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0335] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0336] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0337] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

[0338] In the present application, the term "include" and its variations may refer to non-restrictive inclusion; the term "or" and its variations may refer to "and / or". The terms "first", "second", etc. in this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. In the present application, "plurality" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previously associated objects are in an "or" relationship.

Claims

1. A method for determining the timing of well soaking and well opening, characterized in that: include: Obtaining historical data of historical fracturing wells and obtaining target maturity of target fracturing wells; The historical data include historical maturity and historical stability pressure; Performing linear fitting based on the historical maturity and the historical stable pressure to determine a maturity engineering evaluation coefficient and a rock formation fracture evaluation coefficient, wherein the maturity engineering evaluation coefficient is a fitting slope, and the rock formation fracture evaluation coefficient is a fitting intercept; Determining a target stable pressure of the target fracturing well according to a fitting model composed of the maturity engineering evaluation coefficient, the rock fracture evaluation coefficient, and the target maturity; The target well opening timing is determined according to the target stable pressure and the pressure variation trend of the target fracturing well.

2. The method according to claim 1, characterized in that The historical data also includes historical fracturing material related parameters, historical brittleness index and historical fracture pressure; the fitting model formed by the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient and the target maturity is used to determine the target stable pressure of the target fracturing well, including: determining an external squeeze correction factor based on the historical fracturing material related parameters; Determining a mechanical evaluation correction coefficient based on the historical brittleness index and the historical rupture pressure; The target stable pressure of the target fracturing well is determined according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient, the external squeeze correction coefficient, the mechanical evaluation correction coefficient and the target maturity.

3. The method according to claim 2, characterized in that The step of determining the external squeeze correction coefficient based on the historical fracturing material related parameters includes: Calculating the historical fracturing fluid-solid ratio corresponding to the historical fracturing well according to the historical fracturing material related parameters; According to the historical fracturing fluid-solid ratio, calculating the average historical fracturing fluid-solid ratio and the extreme difference of the historical fracturing fluid-solid ratio; Obtaining parameters related to target fracturing materials of a target fracturing well, and calculating a target fracturing fluid-solid ratio corresponding to the target fracturing well; The external squeeze correction coefficient is determined according to the target fracturing fluid-solid ratio, the average historical fracturing fluid-solid ratio and the historical fracturing fluid-solid ratio extreme difference.

4. The method according to claim 2, characterized in that: The determining of the mechanical evaluation correction coefficient based on the historical brittleness index and the historical rupture pressure comprises: Calculating the ratio of the historical brittleness index to the historical fracture pressure to obtain a first ratio of each of the historical fracturing wells; Based on the first ratios of the respective historical fracturing wells, determining an average value of the first ratio and a range of the first ratio; Obtaining a target brittleness index and a target fracture pressure of the target fractured well, and using a ratio of the target brittleness index to the target fracture pressure as a second ratio of the target fractured well; The mechanical evaluation correction coefficient is determined according to the second ratio, the average value of the first ratio and the range of the second ratio.

5. The method according to claim 2, characterized in that: The step of determining the target stable pressure of the target fracturing well according to the maturity engineering evaluation coefficient, the rock formation fracture evaluation coefficient, the external squeeze correction coefficient, the mechanical evaluation correction coefficient and the target maturity comprises: The product of the external extrusion correction coefficient and the maturity engineering evaluation coefficient is used as the first slope; The product of the mechanical evaluation correction coefficient and the rock formation fracture evaluation coefficient is taken as the first intercept; Based on the first slope and the first intercept, an objective function is constructed with stable pressure as the dependent variable and maturity as the independent variable; The target maturity is substituted into the target function to obtain the target stable pressure.

6. The method according to claim 1, characterized in that The determining of the maturity engineering evaluation coefficient and the rock formation fracture evaluation coefficient based on the historical maturity and the historical stable pressure includes: Constructing a rectangular coordinate system with maturity as the abscissa and stable pressure as the ordinate, and determining data points corresponding to the historical fracturing wells in the rectangular coordinate system; Calculate the second slope and second intercept of the straight line connecting any two data points; An average value of the second slope is determined as the maturity engineering evaluation coefficient, and an average value of the second intercept is determined as the formation fracture evaluation coefficient.

7. The method according to any one of claims 1 to 6, characterized in that: Determining the target well opening timing according to the target stable pressure and the pressure change trend of the target fracturing well includes: Determine a pressure drop function of the target fracturing well according to the pressure change trend of the target fracturing well; the independent variable of the pressure drop function is time, and the dependent variable is the pressure of the target fracturing well; The target stable pressure is substituted into the pressure drop function to obtain the target well opening timing.

8. A device for determining the timing of well soaking and well opening, characterized in that: include: an acquisition module, a first determination module, a second determination module and a third determination module, wherein: The acquisition module is used to acquire historical data of historical fracturing wells and to acquire target maturity of target fracturing wells; the historical data includes historical maturity and historical stable pressure; The first determination module is used to perform linear fitting based on the historical maturity and the historical stable pressure to determine a maturity engineering evaluation coefficient and a rock formation fracture evaluation coefficient, wherein the maturity engineering evaluation coefficient is a fitting slope, and the rock formation fracture evaluation coefficient is a fitting intercept; The second determination module is used to determine the target stable pressure of the target fracturing well according to the fitting model composed of the maturity engineering evaluation coefficient, the rock fracture evaluation coefficient and the target maturity; The third determination module is used to determine the target well opening timing according to the target stable pressure and the pressure change trend of the target fracturing well.

9. A device for determining the timing of well soaking and well opening, characterized in that: include: Processor, memory; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory, so that the processor performs the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 7 when executed by a processor.

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