Critical construction pumping pressure decision-making method and system based on sleeve deformation risk analysis

Abstract

The invention provides a critical construction pumping pressure decision-making method and system based on casing deformation risk analysis, and the method comprises the steps: determining a ground stress parameter and a natural fracture attribute parameter of a horizontal section drilling encountering target layer of a target fractured well section for the target fractured well section; based on a multi-scale combined system mechanical calculation model and plane stress data matched with a well section, critical fluid pressure enabling natural fractures of the well section to generate shear slip is analyzed and calculated, and then corresponding fracturing construction pumping pressure data are inversed by utilizing a set operation model based on the critical fluid pressure and obtained construction operation parameters. And the pressure is used as critical construction pumping pressure of fracturing operation. By adopting the scheme, the defects of complicated operation and poor practicability in the prior art can be overcome, critical construction pumping pressure parameters are determined through casing deformation stress analysis, engineering technical guidance is provided for fracturing operation, the operation is simple and convenient, and the conclusion is reliable.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development engineering, and particularly to a critical construction pump pressure decision-making method and system based on casing deformation risk analysis. Background Art

[0002] Horizontal well fracturing technology plays an important role in the process of shale gas development. Among them, volume fracturing technology has strongly promoted the efficient development of shale gas resources. However, during the high-intensity volume fracturing process of shale gas wells, casing deformation and failure frequently occur, resulting in the inability to smoothly lower downhole tools in place, and even having to abandon the fracturing transformation of severely deformed well sections, which seriously affects the smooth implementation of the volume fracturing process. Thus, it can be seen that casing deformation has become one of the main difficult problems restricting the economic and efficient development of shale gas.

[0003] In order to avoid casing deformation during the fracturing construction process, most of the existing studies need to combine multiple parameters for complex data operations. For the decision-making problem at the fracturing construction site, such complex solutions often have limitations and lack convenience and practicality.

[0004] The information disclosed in the background art part of the present invention is only intended to deepen the understanding of the general background technology of the present invention, and should not be regarded as an admission or any form of implication that this information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0005] To solve the above problems, the present invention provides a critical construction pump pressure decision-making method based on casing deformation risk analysis. In one embodiment, the method includes:

[0006] Data preparation step: For the target fracturing well section, determine the in-situ stress parameters of the target layer drilled by its horizontal section, and obtain the fracture attribute parameters related to the development of natural fractures in each fracturing well section;

[0007] Stress analysis step: Establish a multi-scale combined system mechanics calculation model, and based on it, determine the plane stress data matching different well sections in combination with the in-situ stress parameters;

[0008] Critical fluid pressure analysis step: Calculate the critical fluid pressure that causes shear slip of natural fractures in the well section based on the plane stress data in combination with the fracture attribute parameters;

[0009] Critical pump pressure inversion step: Determine the construction operation parameters corresponding to the fracturing well section, and based on the construction operation parameters, inversely analyze the corresponding fracturing construction pump pressure data in combination with the critical fluid pressure of the natural fractures, and use it as the critical construction pump pressure to achieve construction configuration decision-making.

[0010] Optionally, in one embodiment, in the data preparation step, the determined formation stress parameters include the maximum horizontal principal stress and the minimum horizontal principal stress of the target layer drilled by the horizontal section of the target fracturing well; the obtained fracture property parameters include: the well depth and vertical depth of the fracturing well section with natural fractures, the angle between the natural fractures and the maximum horizontal principal stress, the basic friction angle of the natural fractures, the compressive strength of the natural fractures, and the roughness of the natural fractures.

[0011] Further, in one embodiment, the stress analysis step includes:

[0012] First, model the entire "formation-natural fracture-cement sheath-casing" combined system of the fracturing well section, establish a combined physical model, and then perform mechanical analysis based on it to establish a corresponding mechanical calculation model of the combined system as a multi-scale combined system mechanical calculation model.

[0013] Specifically, in a preferred embodiment, in the stress analysis step, the process of determining the plane stress data matching different well sections includes:

[0014] For different target layers drilled by the fracturing well section, respectively based on the cases where the angle between the natural fractures and the maximum horizontal principal stress is different, combined with the maximum horizontal principal stress and the minimum horizontal principal stress of the target layer drilled during the fracturing well construction, use the plane stress analysis calculation formula corresponding to the combined system mechanical calculation model to calculate and determine the plane stress data distribution corresponding to different angles between the natural fractures and the maximum horizontal principal stress;

[0015] Associate and store the plane stress data with the corresponding ground stress data and angle parameters to form a plane stress parameter list or chart for query and call when there is a need for plane stress analysis.

[0016] In practical applications, in an optional embodiment, the plane stress parameters calculated in the stress analysis step include the normal stress perpendicular to the natural fracture surface and the shear stress parallel to the natural fracture surface;

[0017] Use the following plane stress analysis calculation formula corresponding to the combined system mechanical calculation model to calculate the plane stress parameters:

[0018]

[0019]

[0020] In the formula: σ NF represents the normal stress perpendicular to the natural fracture surface, MPa; τ NF represents the shear stress parallel to the natural fracture surface, MPa; σ H represents the maximum horizontal principal stress, MPa; σ hdenotes the minimum horizontal principal stress, MPa; θ denotes the angle between the natural fracture and the maximum horizontal principal stress, °;

[0021] The shear stress τ parallel to the natural fracture surface NF is taken as the critical peak shear strength τ of the natural fracture f_min .

[0022] Furthermore, in one embodiment, in the critical fluid pressure analysis step, the critical fluid pressure of the natural fracture is calculated according to the following formula:

[0023]

[0024] In the formula: τ f_min denotes the critical peak shear strength of the natural fracture, MPa; σ NF denotes the normal stress perpendicular to the natural fracture surface, MPa; denotes the critical fluid pressure of the natural fracture, MPa; JRC denotes the roughness of the natural fracture, dimensionless; JCS denotes the compressive strength of the natural fracture, MPa; denotes the basic friction angle of the natural fracture, °.

[0025] In an alternative embodiment, in the critical pump pressure inversion step, the determined construction operation parameters include: the density of the fracturing fluid, the wellbore friction pressure drop and the perforation hole friction pressure drop during the fracturing construction in the well section.

[0026] Preferably, in one embodiment, in the critical pump pressure inversion step, the corresponding fracturing construction pump pressure data is inversely analyzed by using the wellbore flow system calculation model, and the wellbore flow system calculation model is as follows:

[0027]

[0028] In the formula: denotes the critical construction pump pressure, MPa; denotes the critical fluid pressure of the natural fracture, MPa; △p wb denotes the wellbore friction pressure drop, MPa; △p h denotes the perforation hole friction pressure drop, MPa, ρ denotes the density of the fracturing fluid, kg / m 3 ; h denotes the vertical depth of the well section with natural fractures, m; g denotes the acceleration of gravity, m / s 2 .

[0029] Based on other aspects of the method described in any one or more of the above embodiments, the present invention further provides a storage medium, on which program code for implementing the method described in any one or more of the above embodiments is stored.

[0030] In terms of the application aspect of the method described in any one or more of the above embodiments, the present invention further provides a critical construction pump pressure decision-making system based on casing deformation risk analysis, and this system executes the method described in any one or more of the above embodiments.

[0031] Compared with the closest prior art, the present invention also has the following beneficial effects:

[0032] A critical construction pump pressure decision-making method and system based on casing deformation risk analysis provided by the present invention calculates the critical fluid pressure that causes shear slip of natural fractures in a well section based on a multi-scale combined system mechanics calculation model and plane stress data matching the well section, and then inversely calculates the corresponding fracturing construction pump pressure data based on the critical fluid pressure and the obtained construction operation parameters by using a set operation model as the critical construction pump pressure for the fracturing operation; adopting this solution, the critical construction pump pressure parameters are determined through casing deformation stress analysis, and the critical construction pump pressure that can reduce the casing deformation risk is predicted conveniently and efficiently as the highest fracturing construction pump pressure to guide the fracturing operation; the principle of this method is simple, the conclusion is reliable, and the operation is simple, which has important guiding significance and practical significance for guiding the prevention and control of casing shear deformation and reducing the casing deformation risk during the hydraulic fracturing process of shale gas horizontal wells.

[0033] Other features and advantages of the present invention will be described in the subsequent specification, and part of them will become obvious from the specification, or be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained through the structures specifically pointed out in the specification, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0035] Figure 1 is a schematic flow chart of a critical construction pump pressure decision-making method based on casing deformation risk analysis provided by an embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of plane stress analysis of a critical construction pump pressure decision-making method based on casing deformation risk analysis provided by an embodiment of the present invention;

[0037] Figure 3 is a schematic diagram of the distribution of plane stress results of a critical construction pump pressure decision-making method based on casing deformation risk analysis provided by an embodiment of the present invention;

[0038] Figure 4It is a schematic diagram of the distribution of the recognition results of the normal stress perpendicular to the natural fracture surface and the shear stress parallel to the natural fracture surface of the critical construction pump pressure decision method provided by the embodiments of the present invention;

[0039] Figure 5 It is a schematic structural diagram of the critical construction pump pressure decision system based on casing deformation risk analysis provided by the embodiments of the present invention. Detailed implementation manners

[0040] The following will combine the drawings and embodiments to detail the implementation manners of the present invention, so that the implementers of the present invention can fully understand how to apply technical means to solve technical problems and achieve the implementation process of technical effects, and specifically implement the present invention according to the above implementation process. It should be noted that as long as there is no conflict, each embodiment in the present invention and each feature of each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.

[0041] Although the flowchart describes the operations as sequential processes, many of the operations can be implemented in parallel, concurrently, or simultaneously. The order of the operations can be rearranged. The process can be terminated when its operations are completed, but there can also be additional steps not included in the drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0042] Computer devices include user devices and network devices. Among them, user devices or clients include, but are not limited to, computers, smart phones, PDAs (Personal Digital Assistants), etc.; network devices include, but are not limited to, a single network server, a server group composed of multiple network servers, or a cloud composed of a large number of computers or network servers based on cloud computing. The computer device can run alone to implement the present invention, or can be connected to the network and implement the present invention through interactive operations with other computer devices in the network. The network where the computer device is located includes, but is not limited to, the Internet, wide area network, metropolitan area network, local area network, VPN network, etc.

[0043] Here, terms such as "first" and "second" may be used to describe each unit, but these units should not be limited by these terms. These terms are only used to distinguish one unit from another. The term "and / or" used here includes any and all combinations of one or more of the listed related items. When a unit is referred to as being "connected" or "coupled" to another unit, it can be directly connected or coupled to the other unit, or there can be an intermediate unit.

[0044] The terms used herein are merely for describing specific embodiments and are not intended to limit the exemplary embodiments. Unless the context clearly dictates otherwise, the singular forms "a" and "an" used herein are also intended to include the plural. It should also be understood that the terms "comprises" and / or "comprising" specify the presence of the stated features, integers, steps, operations, units and / or components, without precluding the presence or addition of one or more other features, integers, steps, operations, units, components and / or combinations thereof.

[0045] Benefiting from the great progress of exploration and development theories and technologies, new discoveries and breakthroughs have been continuously made in shale gas in the Sichuan Basin, and it is entering a golden era of rapid development. The horizontal well fracturing technology plays an important role in the process of shale gas development. In existing research, the volume fracturing technology based on the principle of "multiple clusters within a stage + high-intensity sand addition + large displacement" has strongly promoted the efficient development of shale gas resources. However, during the high-intensity volume fracturing process of shale gas wells, casing deformation and failure frequently occur, resulting in the inability to smoothly lower downhole tools in place, and even having to abandon the fracturing transformation of severely deformed well sections, which seriously affects the smooth implementation of the volume fracturing process. Thus, it can be seen that casing deformation has become one of the main difficult problems restricting the economic and efficient development of shale gas.

[0046] In order to avoid casing deformation during the fracturing construction process, most existing research requires complex data calculations by combining multiple parameters. For the decision-making problem at the fracturing construction site, such complex solutions often have limitations and lack convenience and practicality.

[0047] The researchers of the present invention considered that casing shear deformation is the main casing failure mode during the hydraulic fracturing process, and the vast majority of casing deformations are related to the natural fractures developed nearby. During the high-intensity volume fracturing process of shale gas wells, since the fracturing fluid enters the natural fractures intersecting the wellbore, the fluid pressure in the natural fractures continuously increases, and the natural fractures are partially or completely opened. The frictional resistance between the fracture surfaces continuously decreases, making the natural fractures no longer maintain mechanical stability, thus activating and shearing the casing and inducing casing deformation and failure.

[0048] The induction of casing deformation by natural fracture shear slip is a mechanical problem affected by complex multiple factors through the common coupling of the formation, natural fractures, cement sheath, and casing under the action of the stress field and displacement field. Therefore, the researchers of the present invention proposed that from the perspective of the essence of mechanics and displacement, the maximum fracturing construction pump pressure that can effectively reduce the risk of casing deformation can be calculated. By determining the angle between the developed natural fractures and the shale gas well, the critical fluid pressure in the natural fractures can be obtained, and further combined with wellbore flow calculation to obtain the critical construction pump pressure value, providing important engineering and technical guidance for the prevention and control of casing deformation in fracturing construction operations.

[0049] Next, the detailed process of the method according to the embodiments of the present invention will be described in detail with reference to the accompanying drawings. The steps shown in the flowcharts of the accompanying drawings can be executed in a computer system including, for example, a set of computer-executable instructions. Although the logical order of the steps is shown in the flowcharts, in some cases, the steps shown or described may be executed in a different order than here.

[0050] Embodiment 1

[0051] Figure 1 The schematic flow diagram of the critical construction pump pressure decision-making method based on casing deformation risk analysis provided by Embodiment 1 of the present invention is shown. Referring to Figure 1 it can be seen that the method includes the following steps.

[0052] Data preparation step: For the target fracturing interval, determine the in-situ stress parameters of the target layer drilled by the horizontal section, and obtain the fracture attribute parameters related to the development of natural fractures in each fracturing interval;

[0053] Stress analysis step: Establish a multi-scale combined system mechanics calculation model, and based on it, determine the plane stress data matching different intervals in combination with the in-situ stress parameters;

[0054] Critical fluid pressure analysis step: Further, calculate the critical fluid pressure that causes the shear slip of the natural fractures in the interval based on the plane stress data in combination with the fracture attribute parameters;

[0055] Critical pump pressure inversion step: Determine the construction operation parameters corresponding to the fracturing interval, and based on the construction operation parameters, inversely analyze the corresponding fracturing construction pump pressure data by using the critical fluid pressure of the natural fractures; Use the obtained fracturing construction pump pressure data as the critical construction pump pressure for the fracturing operation to realize the construction configuration decision.

[0056] Adopting the solution of the above embodiment of the present invention can realize the reliable prediction of the critical construction pump pressure for the fracturing operation. This method considers the multi-factor combined system mechanics calculation model of the fracturing interval, analyzes the peak shear strength of the natural fractures and the shear stress parallel to the natural fracture surface, and based on this, discriminates the critical state of the shear slip of the natural fractures inducing casing deformation. At the same time, combined with the relevant hydraulics calculation of the wellbore flow system in the hydraulic fracturing construction process, predict the corresponding maximum fracturing construction pump pressure to control the probability and risk of casing deformation.

[0057] In a preferred embodiment, the data preparation step includes:

[0058] According to the in-situ stress distribution of the work area where the target fracturing well is located, obtain the in-situ stress parameters of the target layer drilled by the horizontal section of the target fracturing well, including the maximum horizontal principal stress and the minimum horizontal principal stress;

[0059] According to the natural fracture development situation of the target layer drilled by the horizontal section of the fracturing well, relevant fracture attribute parameters related to the natural fracture development situation are obtained; including the well depth and vertical depth of the fracturing well section with natural fractures (i.e., the well section to which the natural fractures belong), the angle between the natural fractures and the maximum horizontal principal stress, the basic friction angle of the natural fractures, the compressive strength of the natural fractures, and the roughness of the natural fractures, etc.

[0060] After determining the in-situ stress parameters and the fracture attribute parameters related to the natural fracture development, further carry out the stress analysis step, establish a multi-scale combined system mechanics calculation model, and based on it, determine the plane stress data matching different well sections in combination with the in-situ stress parameters.

[0061] Among them, the established multi-scale combined system mechanics calculation model is the "formation-natural fracture-cement sheath-casing" combined system mechanics analysis model, and the following logic operations are carried out:

[0062] First, the entire "formation-natural fracture-cement sheath-casing" system is modeled to establish a corresponding combined physical model. When actually applied, the following factors can be considered: the horizontal wellbore in the same horizontal plane consists of a layer of casing and the cement sheath outside it. The cement sheath and the casing jointly bear the shear stress of the wellbore, and the shear stress acting on the wellbore is transmitted through the cement sheath to act on the casing; the natural fractures perpendicular to the wellbore completely penetrate the reservoir longitudinally and are also completely penetrated by the horizontal wellbore.

[0063] After establishing the entire combined physical model, based on the combined physical model, mechanical analysis is carried out to establish the corresponding "formation-natural fracture-cement sheath-casing" combined system mechanics calculation model.

[0064] In an optional embodiment, the plane stress data can be calculated based on the maximum horizontal principal stress and the minimum horizontal principal stress, including the normal stress perpendicular to the natural fracture surface and the shear stress parallel to the natural fracture surface, as Figure 2 shown.

[0065] Considering that the pressure of the fluid inside the fracture generates a force opposite to the formation stress, acting on the matrix around the fracture and affecting the peak shear strength that the fracture can withstand. The peak shear strength refers to the maximum shear strength that the fracture itself can withstand; the peak shear strength of the actual natural fracture decreases with the increase of the fluid pressure inside the fracture; in order to control the fluid pressure not to exceed the peak shear strength of the fracture and prevent the fracture from shear slip, in the embodiment of the present invention, the calculated shear stress parallel to the natural fracture surface is set to the critical minimum peak shear strength of the natural fracture to achieve the optimized control of the fluid pressure inside the fracture.

[0066] Based on the requirements of this plane stress analysis, considering multiple operation requirement scenarios with different included angles that may exist in the formations drilled in the fracturing well section. For example, during the fracturing construction process, there are multiple well sections in a target layer that need to be calculated and analyzed separately, and there may be multiple natural fracture objects to be analyzed in a single well section. To improve the efficiency of operation and processing, in a preferred embodiment, the critical shear strength of natural fractures is determined through the following logic:

[0067] Based on the cases where the natural fractures have different included angles with the maximum horizontal principal stress respectively, combined with the maximum horizontal principal stress and the minimum horizontal principal stress of the target layer drilled during the fracturing well construction, use the plane stress analysis calculation formula corresponding to the combined system mechanics calculation model to calculate and determine the plane stress data corresponding to different included angles between the natural fractures and the maximum horizontal principal stress, including the normal stress perpendicular to the natural fracture surface and the shear stress parallel to the natural fracture surface.

[0068] In practical applications, within the range of 0° to 180° of the included angle between the natural fracture and the maximum horizontal principal stress, divide the operation included angle according to the set requirements, and then calculate and obtain the changes in the normal stress perpendicular to the natural fracture surface and the shear stress parallel to the natural fracture surface corresponding to the operation included angle respectively, as Figure 3 shown.

[0069] Preferably, in an embodiment, for different drilled target layers, the calculated plane stress data can be associated and stored with the corresponding ground stress data and included angle parameters respectively to form a plane stress parameter list or chart for direct query and call in subsequent scenarios with plane stress analysis. Among them, the shear stress parallel to the natural fracture surface calculated is set as the minimum critical value of the peak shear strength of the natural fracture, that is, the critical peak shear strength.

[0070] Specifically, in an optional embodiment, the plane stress analysis calculation formula corresponding to the combined system mechanics calculation model is as follows:

[0071]

[0072]

[0073] In the formula: σ NF represents the normal stress perpendicular to the natural fracture surface, MPa;

[0074] τ NF represents the shear stress parallel to the natural fracture surface, MPa;

[0075] σ H represents the maximum horizontal principal stress, MPa;

[0076] σ h represents the minimum horizontal principal stress, MPa;

[0077] θ represents the angle between the natural fracture and the maximum horizontal principal stress, in degrees.

[0078] Combined with the above analysis, the shear stress τ parallel to the natural fracture surface NF is taken as the critical peak shear strength τ of the natural fracture f_min .

[0079] Calculate or retrieve the critical peak shear strength data corresponding to the current fracturing interval through the means of the embodiments of the present invention. As Figure 4 shown, further, perform the critical fluid pressure analysis step, and calculate the critical fluid pressure of the natural fracture that causes shear slip of the natural fracture in the interval based on the determined critical peak shear strength of the natural fracture and the fracture property parameters.

[0080] Specifically, taking the shear stress parallel to the natural fracture surface as the critical shear strength of the natural fracture, combined with the basic friction angle of the natural fracture, the compressive strength of the natural fracture, and the roughness parameter of the natural fracture in the corresponding interval, use the calculation formula of the peak shear strength of the natural fracture to inversely analyze the fluid pressure data as the critical fluid pressure of the natural fracture that causes shear slip of the natural fracture, that is, the maximum in-fracture fluid pressure that causes shear slip of the natural fracture.

[0081] Optionally, in one embodiment, use the calculation formula of the critical peak shear strength of the natural fracture to inversely calculate the critical fluid pressure of the natural fracture:

[0082]

[0083] In the formula: τ f_min represents the critical peak shear strength of the natural fracture, in MPa;

[0084] σ NF represents the normal stress perpendicular to the natural fracture surface, in MPa;

[0085] represents the critical fluid pressure of the natural fracture, in MPa;

[0086] JRC represents the roughness of the natural fracture, dimensionless;

[0087] JCS represents the compressive strength of the natural fracture, in MPa, generally equal to the tensile strength of the target formation rock;

[0088] represents the basic friction angle of the natural fracture, in degrees, generally equal to the internal friction angle of the target formation rock.

[0089] In actual application, if there are multiple natural fractures, calculate the critical fluid pressure of each fracture respectively.

[0090] Considering the need to control the risk of casing deformation in actual fracturing operations, when there are multiple natural fracture critical fluid pressures with different values, the smallest one is selected as the final natural fracture critical fluid pressure.

[0091] After calculating the natural fracture critical fluid pressure corresponding to the current fracturing interval for shear slip of natural fractures by means of the embodiments of the present invention, a critical pump pressure inversion step is further carried out to determine the construction operation parameters corresponding to the fracturing interval, and based on the construction operation parameters, the corresponding fracturing construction pump pressure data is inversely analyzed using the natural fracture critical fluid pressure.

[0092] Among them, in a preferred embodiment, the process of determining the construction operation parameters corresponding to the fracturing interval includes:

[0093] According to the fracturing design and construction conditions of each fracturing interval of the target fracturing well, the construction operation parameters of the fracturing construction of the target fracturing well are obtained, including parameters such as the density of the fracturing fluid, the wellbore friction pressure drop during the fracturing construction in the interval with natural fractures, and the perforation hole friction pressure drop.

[0094] In an alternative embodiment, the corresponding fracturing construction pump pressure data is inversely analyzed using the wellbore flow system calculation model shown in the following formula:

[0095]

[0096] In the formula: represents the critical construction pump pressure that can reduce the risk of casing deformation, MPa;

[0097] represents the critical fluid pressure in the natural fracture, MPa;

[0098] △p wb represents the wellbore friction pressure drop, MPa;

[0099] △p h represents the perforation hole friction pressure drop, MPa.

[0100] ρ represents the density of the fracturing fluid, kg / m 3 ;

[0101] h represents the vertical depth of the interval with natural fractures, m;

[0102] g represents the acceleration of gravity, m / s 2 .

[0103] Bring the critical fluid pressure in the natural fractures, the well depth and vertical depth of the well section with natural fractures, as well as the parameters such as the density of the fracturing fluid obtained in step (3), the wellbore friction pressure drop, and the perforation hole friction pressure drop during the fracturing construction process in the well section with natural fractures into the wellbore flow system calculation model, and calculate the critical construction pump pressure that will cause the natural fractures to shear and slip and induce casing deformation in the well section with natural fractures in the target layer of the target fracturing well, that is, the critical construction pump pressure that can reduce the risk of casing deformation.

[0104] In the construction decision-making step, use the obtained fracturing construction pump pressure data as the upper limit of the critical construction pump pressure for the fracturing operation to implement the construction configuration decision.

[0105] During the actual fracturing construction process, it is necessary to control the actual construction pump pressure to be less than the critical construction pump pressure. This critical construction pump pressure provides a technical reference for fracturing designers and implementers. When guiding the construction, technicians can choose to actively control the real-time construction pump pressure below the overall pressure. During the fracturing construction process, the construction pump pressure changes in real time. In practical applications, specifically, it can be controlled by the on-site fracturing operators through any feasible means such as displacement, sand volume, and friction reducer. The present invention does not limit this aspect.

[0106] Adopt the critical construction pump pressure decision-making method based on casing deformation risk analysis provided by the embodiment of the present invention. By respectively establishing a wellbore flow calculation model and a "formation-natural fracture-cement sheath-casing" combined system mechanics calculation model during the hydraulic fracturing process of shale gas horizontal wells, focus on the critical peak shear strength of natural fractures and conduct a critical state discrimination of casing deformation induced by natural fracture shear slip. At the same time, combined with the relevant hydraulics calculation of the wellbore flow system during the hydraulic fracturing process, predict the critical construction pump pressure that can reduce the risk of casing deformation. This method has a simple principle, reliable conclusions, and is easy to operate, and has important guiding significance and practical significance for guiding the prevention and control of casing shear deformation and reducing the risk of casing deformation during the hydraulic fracturing process of shale gas horizontal wells.

[0107] The following further describes the present invention in combination with implementation cases. The scope of the present invention is not limited by the embodiments, and the scope of the present invention is set forth in the claims.

[0108] Take a certain hydraulic fracturing horizontal well section as an example, and implement the critical construction pump pressure decision-making method based on casing deformation risk analysis provided by the embodiment of the present invention according to the following operations:

[0109] 1. According to the in-situ stress distribution in the work area where the target fracturing well is located, obtain the in-situ stress parameters of the target layer drilled by the horizontal section of the target fracturing well, including the maximum horizontal principal stress and the minimum horizontal principal stress, as shown in Table 1.

[0110] Table 1 In-situ Stress and Rock Mechanics Parameters

[0111] Parameter Maximum horizontal principal stress Minimum horizontal principal stress Value 106.7 MPa 93.4 MPa

[0112] 2. According to the development of natural fractures in the target layer drilled by the horizontal section of the fracturing well, relevant parameters related to the development of natural fractures are obtained, including the well depth and vertical depth of the well section with natural fractures, the angle between the natural fractures and the maximum horizontal principal stress, the basic friction angle of the natural fractures, the compressive strength of the natural fractures, and the roughness of the natural fractures, etc. The parameters are shown in Table 2.

[0113] Table 2 Relevant parameters of natural fracture development

[0114]

[0115] 3. Establish a mechanical calculation model for the "formation - natural fracture - cement sheath - casing" combined system, and conduct plane stress analysis on the model. Substitute the obtained maximum horizontal principal stress and minimum horizontal principal stress into the plane stress analysis calculation formula, and calculate the changes in the normal stress perpendicular to the natural fracture plane and the shear stress parallel to the natural fracture plane respectively within the range of 0° to 180° of the angle between the natural fracture and the maximum horizontal principal stress, as Figure 3 shown.

[0116] 4. According to the obtained changes in the shear stress parallel to the natural fracture plane under different angles between the natural fracture and the maximum horizontal principal stress, combined with the angle between the natural fracture and the maximum horizontal principal stress in the well section with natural fractures, identify the normal stress perpendicular to the natural fracture plane and the shear stress parallel to the natural fracture plane corresponding to the well section with natural fractures. Among them, the shear stress parallel to the natural fracture plane is regarded as the critical minimum value corresponding to the peak shear strength of the natural fracture, that is, the critical peak shear strength, as Figure 4 and Table 3 shown.

[0117] Table 3 Stress distribution of natural fractures

[0118]

[0119] 5. According to the obtained normal stress perpendicular to the natural fracture plane and the critical peak shear strength of the corresponding natural fracture in the well section with natural fractures, combined with the obtained basic friction angle of the natural fracture, compressive strength of the natural fracture, and roughness of the natural fracture, substitute them into the natural fracture peak shear strength calculation formula, and calculate the maximum internal fluid pressure of the natural fracture that causes shear slip of the natural fracture in the well section with natural fractures, that is, the critical fluid pressure in the natural fracture, as shown in Table 4.

[0120] Table 4 Critical fluid pressure in natural fractures

[0121]

[0122] 6. According to the fracturing design and construction conditions of each fracturing stage of the target fracturing well, obtain the density of the fracturing fluid for the fracturing construction of the target fracturing well, and parameters such as the wellbore friction pressure drop and perforation hole friction pressure drop during the fracturing construction in the well sections with natural fractures, as shown in Table 5.

[0123] Table 5 Parameters such as fracturing construction conditions

[0124]

[0125] 7. Substitute the critical fluid pressure in the natural fractures obtained, the well depth and vertical depth of the well sections with natural fractures obtained, the density of the fracturing fluid obtained, and the wellbore friction pressure drop and perforation hole friction pressure drop during the fracturing construction in the well sections with natural fractures into the wellbore flow system calculation model, and calculate the critical fracturing construction pump pressure at which the natural fractures in the well sections with natural fractures in the target layer of the target fracturing well will cause shear slip of the natural fractures and induce casing deformation, that is, the highest fracturing construction pump pressure that can reduce the risk of casing deformation, as shown in Table 6.

[0126] Table 6 The highest fracturing construction pump pressure to reduce the risk of casing deformation

[0127]

[0128] 8. As shown in Table 7, compare the predicted critical fracturing construction pump pressure at which the natural fractures will cause shear slip and induce casing deformation, that is, the highest fracturing construction pump pressure that can reduce the risk of casing deformation, with the actual highest fracturing construction pump pressure, and combine the actual casing deformation condition records to verify the effectiveness and reliability of the critical construction pump pressure decision-making method based on casing deformation risk analysis in the embodiment of the present invention:

[0129] For the well section NO.Ⅰ with natural fractures and the well section NO.Ⅲ with natural fractures, the corresponding critical fracturing construction pump pressures are both greater than the actual highest fracturing construction pump pressure, indicating that the phenomenon of casing deformation induced by shear slip of natural fractures will not occur during the fracturing process;

[0130] While for the well section NO.Ⅱ with natural fractures, the corresponding critical fracturing construction pump pressure is less than the actual highest fracturing construction pump pressure, indicating that the phenomenon of casing deformation induced by shear slip of natural fractures will occur during the fracturing process.

[0131] The actual situation shows that in this implementation case, the casing shear deformation phenomenon did indeed occur in the well section NO.Ⅱ with natural fractures, and the measured casing shear deformation displacement was 55.3 mm.

[0132] It can be seen that the critical construction pump pressure decision-making method based on casing deformation risk analysis in the embodiments of the present invention is effective. During actual construction, by controlling the actual maximum fracturing construction pump pressure to be less than the predicted critical construction pump pressure, the occurrence probability of casing deformation can be effectively reduced, and even the occurrence of casing deformation can be prevented.

[0133] For the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0134] It should be noted that in other embodiments of the present invention, the method can also be combined with one or several of the above embodiments to obtain a new critical construction pump pressure decision-making method based on casing deformation risk analysis, so as to effectively guide the fracturing construction operation parameters and improve the fracturing transformation effect.

[0135] It should be noted that based on the method in any one or more of the above embodiments of the present invention, the present invention also provides a storage medium on which program codes capable of implementing the methods described in any one or more of the above embodiments are stored. When the codes are executed by an operating system, the critical construction pump pressure decision-making method based on casing deformation risk analysis as described above can be implemented.

[0136] Embodiment 2

[0137] In the above embodiments disclosed by the present invention, the method is described in detail. The method of the present invention can be implemented by various forms of devices or systems. Therefore, based on other aspects of the method in any one or more of the above embodiments, the present invention also provides a critical construction pump pressure decision-making system based on casing deformation risk analysis, which is used to execute the critical construction pump pressure decision-making method based on casing deformation risk analysis described in any one or more of the above embodiments. Specific embodiments are given below for detailed description.

[0138] Specifically, Figure 5 shows a schematic structural diagram of the critical construction pump pressure decision-making system based on casing deformation risk analysis provided in the embodiments of the present invention. As Figure 5 shown, the system includes:

[0139] A data preparation module configured to determine the in-situ stress parameters of the target fracturing interval when it encounters the target formation in the horizontal section and obtain the fracture attribute parameters related to the development of natural fractures in each fracturing interval;

[0140] A stress analysis module configured to establish a multi-scale combined system mechanical calculation model and determine plane stress data matching different well sections based on the combined in-situ stress parameters.

[0141] A critical fluid pressure analysis module configured to calculate the critical fluid pressure that causes shear slip of natural fractures in a well section based on the plane stress data in combination with fracture attribute parameters.

[0142] A critical pump pressure inversion module configured to determine the construction operation parameters corresponding to a fracturing well section, and inversely analyze the corresponding fracturing construction pump pressure data based on the construction operation parameters in combination with the critical fluid pressure of the natural fractures, and use it as the critical construction pump pressure to implement construction configuration decision-making.

[0143] Optionally, in one embodiment, the formation stress parameters determined by the data preparation module include the maximum horizontal principal stress and the minimum horizontal principal stress of the target layer drilled by the horizontal section of the target fracturing well; the obtained fracture attribute parameters include: the well depth and vertical depth of the fracturing well section with natural fractures, the angle between the natural fractures and the maximum horizontal principal stress, the basic friction angle of the natural fractures, the compressive strength of the natural fractures, and the roughness of the natural fractures.

[0144] Furthermore, in one embodiment, the stress analysis module is configured as follows:

[0145] First, the entire "formation-natural fracture-cement sheath-casing" combined system of the fracturing well section is modeled to establish a combined physical model, and then mechanical analysis is performed based on it to establish the corresponding "formation-natural fracture-cement sheath-casing" combined system mechanical calculation model as the multi-scale combined system mechanical calculation model.

[0146] Specifically, in a preferred embodiment, the stress analysis module determines the plane stress data matching different well sections according to the following operations:

[0147] For different target layers drilled by the fracturing well section, respectively based on the cases where the angle between the natural fractures and the maximum horizontal principal stress is different, in combination with the maximum horizontal principal stress and the minimum horizontal principal stress of the target layer drilled during the fracturing well construction, use the plane stress analysis calculation formula corresponding to the combined system mechanical calculation model to calculate and determine the plane stress data distribution corresponding to different angles between the natural fractures and the maximum horizontal principal stress;

[0148] Associate and store the plane stress data with the corresponding ground stress data and angle parameters to form a plane stress parameter list or chart for query and call when plane stress analysis is required.

[0149] In actual application, in an optional embodiment, the plane stress parameters calculated by the stress analysis module include the normal stress perpendicular to the natural fracture surface and the shear stress parallel to the natural fracture surface.

[0150] The plane stress parameters calculated in the stress analysis step include the normal stress perpendicular to the natural fracture plane and the shear stress parallel to the natural fracture plane;

[0151] The following plane stress analysis calculation formula corresponding to the combined system mechanics calculation model is used to calculate the plane stress parameters:

[0152]

[0153]

[0154] In the formula: σ NF represents the normal stress perpendicular to the natural fracture plane, MPa; τ NF represents the shear stress parallel to the natural fracture plane, MPa; σ H represents the maximum horizontal principal stress, MPa; σ h represents the minimum horizontal principal stress, MPa; θ represents the angle between the natural fracture and the maximum horizontal principal stress, °;

[0155] Take the shear stress τ NF parallel to the natural fracture plane as the critical peak shear strength τ f_min .

[0156] Furthermore, in one embodiment, the critical fluid pressure analysis module calculates the critical fluid pressure of the natural fracture according to the following formula:

[0157]

[0158] In the formula: τ f_min represents the critical peak shear strength of the natural fracture, MPa;

[0159] σ NF represents the normal stress perpendicular to the natural fracture plane, MPa;

[0160] represents the critical fluid pressure in the natural fracture, MPa;

[0161] JRC represents the natural fracture roughness, dimensionless;

[0162] JCS represents the compressive strength of the natural fracture, MPa, generally equal to the tensile strength of the target layer rock;

[0163] represents the basic friction angle of the natural fracture, °, generally equal to the internal friction angle of the target layer rock.

[0164] In an alternative embodiment, in the critical pump pressure inversion step, the determined construction operation parameters include: the density of the fracturing fluid, the wellbore friction pressure drop during the fracturing construction in the well section, and the perforation friction pressure drop.

[0165] Preferably, in one embodiment, the critical pump pressure inversion module is configured to inversely analyze the corresponding fracturing construction pump pressure data by using a wellbore flow system calculation model, and the wellbore flow system calculation model used is as follows:

[0166]

[0167] In the formula: represents the critical construction pump pressure that can reduce the risk of casing deformation, MPa; represents the critical fluid pressure in the natural fracture, MPa; △p wb represents the wellbore friction pressure drop, MPa; △p h represents the perforation friction pressure drop, MPa, ρ represents the density of the fracturing fluid, kg / m 3 ; h represents the vertical depth of the well section with natural fractures, m; g represents the acceleration of gravity, m / s 2 .

[0168] In the critical construction pump pressure decision-making system based on casing deformation risk analysis provided by the embodiments of the present invention, each module or unit structure can operate independently or in combination according to actual data acquisition requirements and actual operation and analysis requirements to achieve corresponding technical effects.

[0169] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments and do not mean limitation.

[0170] The phrase "one embodiment" mentioned in the specification means that the specific features, structures or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrase "one embodiment" that appears throughout the specification does not necessarily refer to the same embodiment.

[0171] Although the disclosed embodiments of the present invention are as above, the content described above is only an embodiment adopted for the convenience of understanding the present invention and is not used to limit the present invention. Any person skilled in the technical field to which the present invention pertains may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A critical construction pump pressure decision-making method and system based on casing deformation risk analysis, characterized in that, the method includes: Data preparation step: For the target fracturing well section, determine the in-situ stress parameters of the target layer drilled by the horizontal section, and obtain the fracture attribute parameters related to the development of natural fractures in each fracturing well section; Stress analysis step: Establish a multi-scale combined system mechanics calculation model, and based on it, determine the plane stress data matching different well sections in combination with the in-situ stress parameters; Critical fluid pressure analysis step: Calculate the critical fluid pressure that causes shear slip of the natural fractures in the well section based on the plane stress data in combination with the fracture attribute parameters; Critical pump pressure inversion step: Determine the construction operation parameters corresponding to the fracturing well section, and based on the construction operation parameters, inversely analyze the corresponding fracturing construction pump pressure data in combination with the critical fluid pressure of the natural fractures, and use it as the critical construction pump pressure to realize the construction configuration decision.

2. The method according to claim 1, characterized in that, in the data preparation step, the determined formation stress parameters include the maximum horizontal principal stress and the minimum horizontal principal stress of the target layer drilled by the horizontal section of the target fracturing well; the obtained fracture attribute parameters include: the well depth and vertical depth of the fracturing well section with natural fractures, the angle between the natural fracture and the maximum horizontal principal stress, the basic friction angle of the natural fracture, the compressive strength of the natural fracture, and the roughness of the natural fracture.

3. The method according to claim 1, characterized in that, the stress analysis step includes: First, model the entire "formation-natural fracture-cement sheath-casing" combined system of the fracturing well section, establish a combined physical model, and then perform mechanical analysis based on it to establish a corresponding combined system mechanics calculation model as the multi-scale combined system mechanics calculation model.

4. The method according to claim 1, characterized in that, in the stress analysis step, the process of determining the plane stress data matching different well sections includes: For the target layer drilled by different fracturing well sections, respectively based on the situation where the angle between the natural fracture and the maximum horizontal principal stress is different, in combination with the maximum horizontal principal stress and the minimum horizontal principal stress of the target layer drilled by the fracturing well construction, use the plane stress analysis calculation formula corresponding to the combined system mechanics calculation model to calculate and determine the plane stress data distribution corresponding to different angles between the natural fracture and the maximum horizontal principal stress; Associate and store the plane stress data with the corresponding ground stress data and angle parameters to form a plane stress parameter list or chart for query and call when plane stress analysis is required.

5. The method according to claim 1, characterized in that, the plane stress parameters calculated in the stress analysis step include the normal stress perpendicular to the natural fracture surface and the shear stress parallel to the natural fracture surface; Use the following plane stress analysis calculation formula corresponding to the combined system mechanics calculation model to calculate the plane stress parameters: Where: σ NF represents the normal stress perpendicular to the natural fracture plane, MPa; τ NF represents the shear stress parallel to the natural fracture plane, MPa; σ H represents the maximum horizontal principal stress, MPa; σ h represents the minimum horizontal principal stress, MPa; θ represents the angle between the natural fracture and the maximum horizontal principal stress, °; Take the shear stress τ parallel to the natural fracture plane NF as the critical shear stress τ corresponding to the critical peak shear strength of the natural fracture f_min .

6. The method according to claim 1, characterized in that, in the critical fluid pressure analysis step, calculate the critical fluid pressure of the natural fracture according to the following formula: In the formula: τ f_min represents the critical peak shear strength of the natural fracture, MPa; σ NF represents the normal stress perpendicular to the natural fracture plane, MPa; represents the critical fluid pressure of the natural fracture, MPa; JRC represents the roughness of the natural fracture, dimensionless; JCS represents the compressive strength of the natural fracture, MPa; represents the basic friction angle of the natural fracture, °.

7. The method according to claim 1, characterized in that, In the critical pump pressure inversion step, the determined construction operation parameters include: the density of the fracturing fluid, the wellbore friction pressure drop and the perforation hole friction pressure drop during the fracturing construction in the well section.

8. According to the method described in claim 1, characterized in that, in the critical pump pressure inversion step, the corresponding fracturing construction pump pressure data is inversely analyzed by using the wellbore flow system calculation model, and the wellbore flow system calculation model is as follows: Wherein: represents the critical construction pump pressure, MPa; represents the critical fluid pressure of natural fractures, MPa; △p wb represents the frictional pressure drop in the wellbore, MPa; △p h represents the frictional pressure drop of perforation holes, MPa, ρ represents the density of the fracturing fluid, kg / m 3 ; h represents the vertical depth of the well section with natural fractures developed, m; g represents the acceleration of gravity, m / s 2 .

9. A storage medium, characterized in that, the storage medium stores program codes that can implement the method described in any one of claims 1 to 8.

10. A critical construction pump pressure decision-making system based on casing deformation risk analysis, characterized in that, the system executes the method described in any one of claims 1 to 8.

Images