Shale oil and gas multi-stage fracturing well cementation quality boundary condition evaluation method and system

Abstract

The invention provides a shale oil and gas multi-stage fracturing well cementation quality boundary condition evaluation method and system, and belongs to the technical field of well cementation quality evaluation.The method comprises the steps that the minimum micro-annulus gap size is determined when fracturing fluid of shale oil and gas multi-stage fracturing flows along cement sheath micro-gaps; based on the constructed stratum-cement sheath-sleeve assembly model, simulating cement sheath micro-annular-space fracturing sizes under different initial cement sheath micro-annular-space sizes, and taking the initial cement sheath micro-annular-space size as a critical micro-annular-space size when the cement sheath micro-annular-space fracturing size is the same as the minimum micro-annular-space size; and constructing a corresponding relation between the micro-annulus size and the relative amplitude of the casing wave, determining the relative amplitude of the critical casing wave based on the corresponding relation and the critical micro-annulus size, and taking the relative amplitude of the critical casing wave as a well cementation quality boundary value. Quantitative evaluation of the multi-stage fracturing well cementation quality is achieved, the cement sheath packing integrity during multi-stage fracturing is ensured, and then safe operation of multi-stage fracturing is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of cementing quality assessment, and in particular to a method and system for assessing boundary conditions of shale oil and gas multi-stage fracturing cementing quality. Background Art

[0002] As an important unconventional energy source, the development of shale oil and gas is of great significance to the global energy supply. However, shale reservoirs usually have characteristics such as low permeability and high porosity, which makes direct exploitation difficult. Therefore, multi-stage fracturing technology has become one of the key technologies in shale oil and gas development. Through multi-stage fracturing, a complex fracture network can be formed in the shale reservoir, thereby significantly increasing oil and gas production. In the process of multi-stage fracturing of shale oil and gas, the cementing quality is directly related to the fracturing effect and the long-term stability of oil and gas wells. Poor cementing quality may lead to problems such as fracturing fluid crossflow, oil and gas leakage, and wellhead annular pressure, which seriously affects the production efficiency and safety of oil and gas wells. In the actual cementing and fracturing operations, there are many cases of annular pressure due to poor quality of primary cementing, weak isolation, or multi-stage fracturing that destroys the integrity of the primary cementing isolation seal. Therefore, accurate evaluation of the cementing quality of shale oil and gas multi-stage fracturing wells has become an important research topic in the field of shale oil and gas development.

[0003] At present, the indicators of cementing quality requirements for fracturing are very general, and there is no clear quantitative relationship between cementing quality and fracturing feasibility. In the prior art, acoustic amplitude logging curves or acoustic amplitude-variable density logging curves are usually used to evaluate the quality of cementing on site. The cementing quality is qualitatively classified according to the logging values, and the cementing isolation capacity is comprehensively qualitatively evaluated in combination with the cement sheath strength and effective isolation length. This method has strong field applicability and can effectively apply field data to cementing quality analysis. However, this method still qualitatively evaluates cementing quality and cannot quantitatively evaluate the boundary conditions of shale oil and gas cementing quality.

[0004] Therefore, there is an urgent need to provide a shale oil and gas multi-stage fracturing cementing quality boundary condition assessment method and system to quantitatively evaluate the cementing quality boundary conditions under shale oil and gas multi-stage fracturing and ensure the cementing isolation integrity under multi-stage fracturing conditions. Summary of the invention

[0005] In view of this, it is necessary to provide a shale oil and gas multi-stage fracturing cementing quality boundary condition evaluation method and system to solve the technical problem that the existing technology cannot quantitatively evaluate the cementing quality boundary conditions under shale oil and gas multi-stage fracturing, resulting in insufficient cement ring sealing capacity.

[0006] On the one hand, in order to solve the above technical problems, the present invention provides a method for evaluating boundary conditions of shale oil and gas multi-stage fracturing cementing quality, comprising: Determine the minimum micro-annulus size when the fracturing fluid flows along the micro-gap of the cement annulus during multi-stage fracturing of shale oil and gas; Simulating cement ring micro-annulus fracturing sizes under different initial cement ring micro-annulus sizes based on the constructed formation-cement ring-casing combination model, and taking the initial cement ring micro-annulus size when the cement ring micro-annulus fracturing size is the same as the minimum micro-annulus size as the critical micro-annulus size; A corresponding relationship between the micro-annulus size and the relative amplitude of the casing wave is constructed, a critical relative amplitude of the casing wave is determined based on the corresponding relationship and the critical micro-annulus size, and the critical relative amplitude of the casing wave is used as a cementing quality boundary value.

[0007] In a possible implementation, determining the minimum micro-annulus size when the fracturing fluid of shale oil and gas multi-stage fracturing flows along the micro-annulus of the cement annulus includes: Determining the cross-flow pressure difference between the fractured section and the unfractured section in the multi-stage fracturing of shale oil and gas; Determine the maximum allowable crossflow rate based on the fracturing fluid displacement requirement; The minimum micro-annular gap size is determined based on the crossflow pressure difference and the maximum allowable crossflow amount.

[0008] In a possible implementation, the determining of the crossflow pressure difference between the fractured section and the unfractured section in the shale oil and gas multi-stage fracturing includes: Obtaining a first minimum geostress, a first maximum geostress, a first minimum formation pore pressure and a formation rock tensile strength of the unfractured section; Determining a first fracturing pressure of the unfractured section based on the first minimum geostress, the first maximum geostress, the first minimum formation pore pressure, and the formation rock tensile strength; Obtaining a second minimum geostress, a second maximum geostress, and a second minimum formation pore pressure of the fractured section; determining a second fracturing pressure of the fractured section based on the second minimum geostress, the second maximum geostress, and the second minimum formation pore pressure; The pressure difference between the first fracture initiation pressure and the second fracture initiation pressure is used as the crossover pressure difference.

[0009] In a possible implementation, the first crack initiation pressure is:

[0010] The second cracking pressure is:

[0011] In the formula, is the first cracking pressure; is the first minimum geostress; is the first maximum in-situ stress; is the first minimum formation pore pressure; is the tensile strength of the formation rock; is the second cracking pressure; is the second minimum in-situ stress; is the second maximum in-situ stress; is the second minimum formation pore pressure.

[0012] In a possible implementation, the minimum micro-annular gap size is:

[0013] In the formula, is the minimum micro-annular gap size; is the fracturing fluid viscosity; is the fracturing stage spacing; is the maximum allowable cross-flow rate; is the crossflow pressure difference; is the outer diameter of the casing; is the ratio of pi.

[0014] In a possible implementation, the formation-cement ring-casing combination model includes a casing, a cement ring and a formation that are concentrically arranged from the inside to the outside, a micro-annulus is formed between the casing and the cement ring, and the formation covers the cement ring.

[0015] In a possible implementation, the step of constructing the corresponding relationship between the micro-annular gap size and the relative amplitude of the casing wave includes: Obtain the free casing wave amplitude of the free casing and the casing wave amplitude when there are micro-annuli of different sizes between the casing and the cement sheath; The casing wave relative amplitude under different micro-annular gap sizes is determined based on the free casing wave amplitude and the casing wave amplitude, and a corresponding relationship between the casing wave relative amplitude and the micro-annular gap size is established.

[0016] On the other hand, the present invention also provides a shale oil and gas multi-stage fracturing cementing quality boundary condition evaluation system, comprising: The minimum micro-annulus size determination unit is used to determine the minimum micro-annulus size when the fracturing fluid of shale oil and gas multi-stage fracturing flows along the micro-gap of the cement annulus; A critical micro-annulus size determination unit is used to simulate the cement ring micro-annulus fracturing size under different initial cement ring micro-annulus sizes based on the constructed formation-cement ring-casing combination model, and take the initial cement ring micro-annulus size when the cement ring micro-annulus fracturing size is the same as the minimum micro-annulus size as the critical micro-annulus size; The cementing quality boundary value determination unit is used to establish a corresponding relationship between the micro-annulus size and the relative amplitude of the casing wave, determine the critical relative amplitude of the casing wave based on the corresponding relationship and the critical micro-annulus size, and use the critical relative amplitude of the casing wave as the cementing quality boundary value.

[0017] On the other hand, the present invention also provides a shale oil and gas multi-stage fracturing cementing quality boundary condition assessment device, comprising a memory and a processor, wherein: The memory is used to store programs; The processor is coupled to the memory and is used to execute the program stored in the memory to implement the steps in the shale oil and gas multi-stage fracturing cementing quality boundary condition assessment method described in any one of the possible implementations above.

[0018] On the other hand, the present invention also provides a computer-readable storage medium for storing computer-readable programs or instructions, which, when executed by a processor, can implement the steps in the shale oil and gas multi-stage fracturing cementing quality boundary condition assessment method described in any of the above possible implementation methods.

[0019] The beneficial effects of the present invention are as follows: the shale oil and gas multi-stage fracturing cementing quality boundary condition assessment method provided by the present invention, by taking the initial cement ring micro-annulus size when the cement ring micro-annulus fracturing size is the same as the minimum micro-annulus size as the critical micro-annulus size, achieves the purpose of determining the cementing quality boundary value to meet the cement ring isolation capacity, and ensures the cement ring isolation integrity during the multi-stage fracturing process. In addition, by constructing the corresponding relationship between the micro-annulus size and the relative amplitude of the casing wave to determine the critical casing wave relative amplitude, a quantitative assessment of the multi-stage cementing quality boundary is achieved, which makes up for the shortcomings of the existing qualitative assessment of cementing quality and ensures the normal progress of on-site fracturing construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A schematic flow chart of an embodiment of a method for evaluating boundary conditions of shale oil and gas multi-stage fracturing cementing quality provided by the present invention; Figure 2 A schematic structural diagram of an embodiment of a formation-cement sheath-casing assembly model provided by the present invention; Figure 3 For the present invention Figure 1A schematic flow chart of an embodiment of step S101; Figure 4 For the present invention Figure 3 A schematic flow chart of an embodiment of step S301; Figure 5 For the present invention Figure 1 A schematic flow chart of an embodiment of step S103; Figure 6 A schematic diagram of the structure of an embodiment of the shale oil and gas multi-stage fracturing and cementing quality boundary condition evaluation system provided by the present invention; Figure 7 A schematic structural diagram of an embodiment of a shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device provided by the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0023] It should be understood that the schematic drawings are not drawn to scale. The flowchart used in the present invention shows the operations implemented according to some embodiments of the present invention. It should be understood that the operations of the flowchart can be implemented out of order, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art, under the guidance of the content of the present invention, can add one or more other operations to the flowchart, and can also remove one or more operations from the flowchart. Some of the block diagrams shown in the accompanying drawings are functional entities, which do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor systems and / or microcontroller systems.

[0024] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0025] The present invention provides a method and system for evaluating boundary conditions of shale oil and gas multi-stage fracturing cementing quality, which are described below.

[0026] Figure 1 A schematic flow chart of an embodiment of a method for evaluating boundary conditions of shale oil and gas multi-stage fracturing cementing quality provided by the present invention is shown in FIG. Figure 1 As shown in the figure, the boundary condition evaluation method for shale oil and gas multi-stage fracturing cementing quality includes: S101, determining the minimum micro-annulus size when the fracturing fluid of shale oil and gas multi-stage fracturing flows along the micro-annulus of the cement annulus; S102, simulating cement ring micro-annulus fracturing sizes under different initial cement ring micro-annulus sizes based on the constructed formation-cement ring-casing combination model, and taking the initial cement ring micro-annulus size when the cement ring micro-annulus fracturing size is the same as the minimum micro-annulus size as the critical micro-annulus size; S103, constructing a corresponding relationship between the micro-annulus size and the relative amplitude of the casing wave, determining a critical relative amplitude of the casing wave based on the corresponding relationship and the critical micro-annulus size, and taking the critical relative amplitude of the casing wave as a cementing quality boundary value.

[0027] The formation-cement ring-casing assembly model in step S102 is as follows: Figure 2 As shown, it includes a casing, a cement ring and a formation that are concentrically arranged from the inside to the outside, a micro-annulus is formed between the casing and the cement ring, and the formation covers the cement ring.

[0028] The specific implementation process of determining the critical maintenance size in step S102 is as follows: establish the following in the finite element software ABAQUS: Figure 2 The formation-cement ring-casing combination model shown, specifically, the size of the formation-cement ring-casing combination model is 3mx3m, friction contact is set between the casing and the cement ring, alternating fluid pressure is applied on the inner wall of the casing, normal displacement constraint is set on the outer boundary of the formation, and the ground stress load is applied by the predefined field method. By setting different micro-annulus sizes for trial calculation, the initial cement ring micro-annulus size when the cement ring micro-annulus fracturing size is the same as the minimum micro-annulus size is taken as the critical micro-annulus size.

[0029] Compared with the prior art, the method for evaluating the quality boundary conditions of shale oil and gas multi-stage fracturing cementing provided by the embodiment of the present invention uses the initial cement ring micro-annulus size when the cement ring micro-annulus fracturing size is the same as the minimum micro-annulus size as the critical micro-annulus size, so as to achieve the purpose of determining the cementing quality boundary value to meet the cement ring isolation capacity and ensure the integrity of the cement ring isolation during the multi-stage fracturing process. In addition, by constructing the corresponding relationship between the micro-annulus size and the relative amplitude of the casing wave to determine the critical casing wave relative amplitude, the quantitative evaluation of the multi-stage cementing quality boundary is achieved, which makes up for the shortcomings of the existing qualitative evaluation of cementing quality and ensures the normal progress of on-site fracturing construction.

[0030] In some embodiments of the present invention, Figure 3 As shown, step S101 includes: S301, determining the crossflow pressure difference between the fractured section and the unfractured section in the multi-stage fracturing of shale oil and gas; S302, determining a maximum allowable crossflow flow rate based on the fracturing fluid displacement requirement; S303, determining the minimum micro-annular gap size based on the crossflow pressure difference and the maximum allowable crossflow flow rate.

[0031] The fracturing fluid displacement in step S302 has a great influence on the complexity of the fracture network and the expansion of the hydraulic fracture height, so the maximum allowable crossflow rate of the fracturing fluid can be determined according to the requirements of the on-site hydraulic fracturing for the fracturing fluid displacement.

[0032] The embodiment of the present invention establishes a relationship between the maximum allowable crossflow rate and the minimum micro-annulus size, ensures the correlation between the minimum micro-annulus size and the on-site fracturing operation, and further ensures the compatibility of the determined cementing quality boundary with the on-site fracturing operation.

[0033] In some embodiments of the present invention, Figure 4 As shown, step S301 includes: S401, obtaining a first minimum geostress, a first maximum geostress, a first minimum formation pore pressure, and a formation rock tensile strength of an unfractured section; S402, determining a first fracturing pressure of the unfractured section based on a first minimum geostress, a first maximum geostress, a first minimum formation pore pressure, and a formation rock tensile strength; S403, obtaining the second minimum geostress, the second maximum geostress, and the second minimum formation pore pressure of the fractured section; S404, determining a second fracturing pressure of the fracturing section based on the second minimum geostress, the second maximum geostress, and the second minimum formation pore pressure; S405: taking the pressure difference between the first fracture initiation pressure and the second fracture initiation pressure as the crossflow pressure difference.

[0034] Specifically, the first fracture initiation pressure is:

[0035] The second cracking pressure is:

[0036] In the formula, is the first cracking pressure; is the first minimum geostress; is the first maximum in-situ stress; is the first minimum formation pore pressure; is the tensile strength of the formation rock; is the second cracking pressure; is the second minimum in-situ stress; is the second maximum in-situ stress; is the second minimum formation pore pressure; The crossflow pressure difference is:

[0037] In the formula, is the crossflow pressure difference.

[0038] In a specific embodiment of the present invention, the minimum micro-annular gap size is:

[0039] In the formula, is the minimum micro-annular gap size; is the fracturing fluid viscosity; is the fracturing stage spacing; is the maximum allowable cross-flow rate; is the crossflow pressure difference; is the outer diameter of the casing; is the ratio of pi.

[0040] It should be noted that the relative amplitude of the casing wave in step S103 refers to the difference between the free casing amplitude and the casing wave amplitude with a micro-annular gap between the casing cement ring. Therefore, in some embodiments of the present invention, Figure 5 As shown, step S103 includes: S501, obtaining the free casing wave amplitude of the free casing and the casing wave amplitude when there are micro-annular gaps of different sizes between the casing and the cement sheath; S502, determining the relative amplitude of the casing wave under different micro-annulus sizes based on the free casing wave amplitude and the casing wave amplitude, and establishing a corresponding relationship between the relative amplitude of the casing wave and the micro-annulus size.

[0041] Among them, the free casing wave amplitude and the casing wave amplitude are both determined based on the elastic wave propagation theory.

[0042] The embodiment of the present invention establishes a corresponding relationship between the relative amplitude of the casing wave and the size of the micro-annulus, and uses the free casing wave amplitude as a reference, thereby ensuring the accuracy and reliability of the determined corresponding relationship, thereby further improving the accuracy of the determined cementing quality boundary value.

[0043] It should be noted that when the evaluation index of cementing quality is other indexes besides casing wave relative amplitude, a conversion relationship between casing wave relative amplitude and other indexes can also be established, and cementing quality boundary values ​​under other evaluation indexes can be determined based on the conversion relationship.

[0044] Among them, the conversion relationship between the relative amplitude of the casing wave and other indicators is the existing technology and will not be described in detail here.

[0045] In summary, the method for evaluating the quality boundary conditions of shale oil and gas multi-stage fracturing cementing proposed in the embodiment of the present invention, 1. With the goal of quantitatively evaluating the sealing capacity of the cement sheath, the influence of the initial cementing interface micro-annulus and the subsequent fracturing conditions on the change of the cementing interface micro-annulus is considered, and the relationship between the cementing interface micro-annulus and the fracturing fluid flow rate is established, and the cementing interface micro-annulus is associated with the relative amplitude of the casing wave, and then the relationship between the cementing quality logging value and the fracturing fluid flow rate is formed, so as to evaluate the quality boundary of multi-stage fracturing cementing. 2. The influence of multi-stage fracturing conditions and initial cementing quality on the sealing capacity of the cement sheath is considered, and the cement sheath cementing quality boundary conditions that meet the inter-stage sealing requirements are clarified, which makes up for the deficiency of the existing method of qualitatively evaluating the sealing capacity of the cement sheath based on the initial cementing quality logging value, and helps the normal progress of on-site fracturing construction.

[0046] In order to better implement the shale oil and gas multi-stage fracturing cementing quality boundary condition evaluation method in the embodiment of the present invention, based on the shale oil and gas multi-stage fracturing cementing quality boundary condition evaluation method, the embodiment of the present invention also provides a shale oil and gas multi-stage fracturing cementing quality boundary condition evaluation system, such as Figure 6 As shown, the shale oil and gas multi-stage fracturing cementing quality boundary condition evaluation system 600 includes: The minimum micro-annulus size determination unit 601 is used to determine the minimum micro-annulus size when the fracturing fluid of shale oil and gas multi-stage fracturing flows along the cement annulus micro-gap; The critical micro-annulus size determining unit 602 is used to simulate the cement annulus micro-annulus fracturing size under different initial cement annulus micro-annulus sizes based on the constructed formation-cement annulus-casing combination model, and take the initial cement annulus micro-annulus size when the cement annulus micro-annulus fracturing size is the same as the minimum micro-annulus size as the critical micro-annulus size; The cementing quality boundary value determination unit 603 is used to construct a corresponding relationship between the micro-annulus size and the relative amplitude of the casing wave, determine the critical relative amplitude of the casing wave based on the corresponding relationship and the critical micro-annulus size, and use the critical relative amplitude of the casing wave as the cementing quality boundary value.

[0047] The shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment system 600 provided in the above embodiment can implement the technical solution described in the above embodiment of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment method. The specific implementation principles of the above modules or units can refer to the corresponding contents in the above embodiment of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment method, which will not be repeated here.

[0048] like Figure 7 As shown, the present invention also provides a shale oil and gas multi-stage fracturing cementing quality boundary condition assessment device 700. The shale oil and gas multi-stage fracturing cementing quality boundary condition assessment device 700 includes a processor 701, a memory 702 and a display 703. Figure 7Only some components of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700 are shown, but it should be understood that it is not required to implement all of the shown components, and more or fewer components may be implemented instead.

[0049] In some embodiments, the processor 701 may be a central processing unit (CPU), a microprocessor or other data processing chip, and is used to run program codes or process data stored in the memory 702, such as the shale oil and gas multi-stage fracturing cementing quality boundary condition assessment method of the present invention.

[0050] In some embodiments of the present invention, the processor 701 may be a single server or a server group. The server group may be centralized or distributed. In some embodiments, the processor 701 may be local or remote. In some embodiments, the processor 701 may be implemented in a cloud platform. In one embodiment, the cloud platform may include a private cloud, a public cloud, a hybrid cloud, a community cloud, a distributed cloud, an internal cloud, a multi-cloud, etc., or any combination thereof.

[0051] In some embodiments, the memory 702 may be an internal storage unit of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700, such as a hard disk or memory of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700. In other embodiments, the memory 702 may also be an external storage device of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700.

[0052] Furthermore, the memory 702 may include both an internal storage unit and an external storage device of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700. The memory 702 is used to store application software and various data for installing the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700.

[0053] In some embodiments, the display 703 may be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, an OLED (Organic Light-Emitting Diode) touch device, etc. The display 703 is used to display information of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700 and to display a visual user interface. The components 701-703 of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700 communicate with each other through a system bus.

[0054] In some embodiments of the present invention, when the processor 701 executes the shale oil and gas multi-stage fracturing cementing quality boundary condition evaluation program in the memory 702, the following steps may be implemented: Determine the minimum micro-annulus size when the fracturing fluid flows along the micro-gap of the cement annulus during multi-stage fracturing of shale oil and gas; Based on the constructed formation-cement sheath-casing combination model, the cement sheath micro-annulus fracturing size under different initial cement sheath micro-annulus sizes is simulated, and the initial cement sheath micro-annulus size when the cement sheath micro-annulus fracturing size is the same as the minimum micro-annulus size is taken as the critical micro-annulus size. The corresponding relationship between micro-annulus size and casing wave relative amplitude is established. The critical casing wave relative amplitude is determined based on the corresponding relationship and critical micro-annulus size. The critical casing wave relative amplitude is used as the boundary value of cementing quality.

[0055] It should be understood that: when the processor 701 executes the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment program in the memory 702, in addition to the above functions, other functions can also be implemented. For details, please refer to the description of the corresponding method embodiment above.

[0056] Furthermore, the embodiment of the present invention does not specifically limit the type of the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700 mentioned. The shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700 may be a portable shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device such as a mobile phone, a tablet computer, a personal digital assistant (PDA), a wearable device, a laptop computer, etc. Exemplary embodiments of portable shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment devices include but are not limited to portable shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment devices equipped with IOS, Android, Microsoft or other operating systems. The above-mentioned portable shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device may also be other portable shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment devices. It should also be understood that in some other embodiments of the present invention, the shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device 700 may not be a portable shale oil and gas multi-stage fracturing and cementing quality boundary condition assessment device, but a desktop computer with a touch-sensitive surface (such as a touch panel).

[0057] Accordingly, an embodiment of the present invention also provides a computer-readable storage medium, which is used to store computer-readable programs or instructions. When the program or instructions are executed by a processor, it can implement the steps or functions in the shale oil and gas multi-stage fracturing cementing quality boundary condition evaluation method provided by the above-mentioned method embodiments.

[0058] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware (such as a processor, a controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0059] The above is a detailed introduction to a shale oil and gas multi-stage fracturing cementing quality boundary condition assessment method and system provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for evaluating boundary conditions of shale oil and gas multi-stage fracturing cementing quality, characterized in that: include: Determine the minimum micro-annulus size when the fracturing fluid flows along the micro-gap of the cement annulus during multi-stage fracturing of shale oil and gas; Simulating cement ring micro-annulus fracturing sizes under different initial cement ring micro-annulus sizes based on the constructed formation-cement ring-casing combination model, and taking the initial cement ring micro-annulus size when the cement ring micro-annulus fracturing size is the same as the minimum micro-annulus size as the critical micro-annulus size; A corresponding relationship between the micro-annulus size and the relative amplitude of the casing wave is constructed, a critical relative amplitude of the casing wave is determined based on the corresponding relationship and the critical micro-annulus size, and the critical relative amplitude of the casing wave is used as a cementing quality boundary value.

2. The method for evaluating the quality boundary conditions of shale oil and gas multi-stage fracturing and cementing according to claim 1, characterized in that: The method of determining the minimum micro-annulus size when the fracturing fluid of shale oil and gas multi-stage fracturing flows along the micro-annulus of the cement annulus comprises: Determining the cross-flow pressure difference between the fractured section and the unfractured section in the multi-stage fracturing of shale oil and gas; Determine the maximum allowable crossflow rate based on the fracturing fluid displacement requirement; The minimum micro-annular gap size is determined based on the crossflow pressure difference and the maximum allowable crossflow amount.

3. The method for evaluating the quality boundary conditions of shale oil and gas multi-stage fracturing and cementing according to claim 2, characterized in that: The determining of the crossflow pressure difference between the fractured section and the unfractured section in the shale oil and gas multi-stage fracturing comprises: Obtaining a first minimum geostress, a first maximum geostress, a first minimum formation pore pressure and a formation rock tensile strength of the unfractured section; Determining a first fracturing pressure of the unfractured section based on the first minimum geostress, the first maximum geostress, the first minimum formation pore pressure, and the formation rock tensile strength; Obtaining a second minimum geostress, a second maximum geostress, and a second minimum formation pore pressure of the fractured section; determining a second fracturing pressure of the fractured section based on the second minimum geostress, the second maximum geostress, and the second minimum formation pore pressure; The pressure difference between the first fracture initiation pressure and the second fracture initiation pressure is used as the crossover pressure difference.

4. The method for evaluating the quality boundary conditions of shale oil and gas multi-stage fracturing and cementing according to claim 3 is characterized in that: The first cracking pressure is: The second cracking pressure is: In the formula, is the first cracking pressure; is the first minimum geostress; is the first maximum in-situ stress; is the first minimum formation pore pressure; is the tensile strength of the formation rock; is the second cracking pressure; is the second minimum in-situ stress; is the second maximum in-situ stress; is the second minimum formation pore pressure.

5. The method for evaluating the quality boundary conditions of shale oil and gas multi-stage fracturing and cementing according to claim 2, characterized in that: The minimum micro-annular gap size is: In the formula, is the minimum micro-annular gap size; is the fracturing fluid viscosity; is the fracturing stage spacing; is the maximum allowable cross-flow rate; is the crossflow pressure difference; is the outer diameter of the casing; is the ratio of pi.

6. The method for evaluating the quality boundary conditions of shale oil and gas multi-stage fracturing and cementing according to claim 1, characterized in that: The formation-cement ring-casing combination model comprises a casing, a cement ring and a formation which are concentrically arranged from the inside to the outside, a micro-annulus is formed between the casing and the cement ring, and the formation covers the cement ring.

7. The method for evaluating the quality boundary conditions of shale oil and gas multi-stage fracturing and cementing according to claim 1, characterized in that: The constructing of the corresponding relationship between the micro-annular gap size and the relative amplitude of the casing wave includes: Obtain the free casing wave amplitude of the free casing and the casing wave amplitude when there are micro-annuli of different sizes between the casing and the cement sheath; The casing wave relative amplitude under different micro-annular gap sizes is determined based on the free casing wave amplitude and the casing wave amplitude, and a corresponding relationship between the casing wave relative amplitude and the micro-annular gap size is established.

8. A shale oil and gas multi-stage fracturing cementing quality boundary condition assessment system, characterized in that: include: The minimum micro-annulus size determination unit is used to determine the minimum micro-annulus size when the fracturing fluid of shale oil and gas multi-stage fracturing flows along the micro-gap of the cement annulus; A critical micro-annulus size determination unit is used to simulate the cement ring micro-annulus fracturing size under different initial cement ring micro-annulus sizes based on the constructed formation-cement ring-casing combination model, and take the initial cement ring micro-annulus size when the cement ring micro-annulus fracturing size is the same as the minimum micro-annulus size as the critical micro-annulus size; The cementing quality boundary value determination unit is used to establish a corresponding relationship between the micro-annulus size and the relative amplitude of the casing wave, determine the critical relative amplitude of the casing wave based on the corresponding relationship and the critical micro-annulus size, and use the critical relative amplitude of the casing wave as the cementing quality boundary value.

9. A shale oil and gas multi-stage fracturing cementing quality boundary condition assessment device, characterized in that: comprising a memory and a processor, wherein: The memory is used to store programs; The processor is coupled to the memory and is used to execute the program stored in the memory to implement the steps in the shale oil and gas multi-stage fracturing cementing quality boundary condition assessment method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: Used to store computer-readable programs or instructions, which, when executed by a processor, can implement the steps in the shale oil and gas multi-stage fracturing cementing quality boundary condition assessment method described in any one of claims 1 to 7.

Images