Method, device and storage medium for determining cement sheath damage in a wellbore

Abstract

This application relates to the field of oil and gas technology, and in particular, to a method, device, and storage medium for determining the damage of the cement sheath in a wellbore. The method includes: obtaining a plurality of cement stone samples and their compressive stresses; determining the elastic modulus and compressive inelastic strain of each cement stone sample; determining the compressive damage factor of each cement stone sample; determining the compressive plastic strain of each cement stone sample based on the compressive inelastic strain, compressive stress, elastic modulus, and compressive damage factor of each cement stone sample; constructing a finite element model based on the structural data of the wellbore; inputting the compressive stress, compressive inelastic strain, and compressive damage factor of any one cement stone sample into the finite element model, and setting the number of cycles and the internal pressure within the cycle; and determining the compressive damage of the cement sheath and the width of the first interface micro-annulus according to the processed finite element model, so as to accurately determine the compressive damage of the cement sheath and the width of the micro-annulus, which has high practicability.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas, and particularly to a method, device and storage medium for determining the damage of the cement sheath in a wellbore. Background Art

[0002] Deep shale oil and gas are the main areas for future natural gas resource exploration. During the development of deep shale oil and gas, multi-stage fracturing construction with ultra-high pump pressure and super-large displacement is the key means to achieve efficient development, resulting in the cement sheath being subjected to extreme environments such as high temperature, high construction pressure, and multi-cycle alternating internal pressure, and its sealing integrity is severely challenged.

[0003] Currently, it is generally believed that the multiple alternating internal pressure loads during multi-stage fracturing are the main reasons for the sealing failure of the cement sheath. However, in actual engineering, the temperature environments of the cement sheath at different positions in the entire well section are different during the solidification process, and there are also significant differences in the forms of cyclic loads borne by the cement sheath at different positions, and these differences will all lead to cement sheath damage. The existing technologies do not take into account the above factors, resulting in the inability to accurately determine whether the cement sheath is damaged and the degree of damage. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a method, device and storage medium for determining the damage of the cement sheath in a wellbore, so as to solve the problem in the existing technology that the damage of the cement sheath cannot be accurately determined.

[0005] To achieve the above purpose, the first aspect of the present application provides a method for determining the damage of the cement sheath in a wellbore, the method comprising:

[0006] Obtaining a plurality of cement stone samples and the compressive stress of each cement stone sample in the plurality of cement stone samples, wherein the plurality of cement stone samples are cured based on different temperatures;

[0007] Determining the elastic modulus and compressive inelastic strain of each cement stone sample;

[0008] Determining the compressive damage factor of each cement stone sample according to the compressive inelastic strain, elastic modulus and compressive stress of each cement stone sample;

[0009] Determining the compressive plastic strain of each cement stone sample according to the compressive inelastic strain, compressive stress, elastic modulus and compressive damage factor of each cement stone sample;

[0010] Constructing a finite element model based on the structural data of the wellbore, the finite element model including a casing, a cement sheath and a formation;

[0011] Input the compressive stress, compressive inelastic strain, and compressive damage factor of any cement stone sample into the finite element model, and set the number of cycles and the internal pressure within the cycle of the finite element model.

[0012] Determine the compressive damage of the cement sheath and the width of the micro-annulus at the first interface according to the processed finite element model.

[0013] In the embodiment of the present application, determining the elastic modulus and compressive inelastic strain of each cement stone sample includes: applying a uniaxial compressive load to each cement stone sample to obtain the load data and displacement data of each cement stone sample; determining the first relationship curve between stress and strain of each cement stone sample according to the load data and displacement data of each cement stone sample; determining the elastic modulus of each cement stone sample according to the linear elastic section of each first relationship curve; obtaining the compressive strain of each cement stone sample; determining the compressive elastic strain of each cement stone sample according to the compressive stress and elastic modulus of each cement stone sample; determining the compressive inelastic strain of each cement stone sample according to the compressive strain and compressive elastic strain of each cement stone sample.

[0014] In the embodiment of the present application, determining the compressive damage of the cement sheath and the width of the micro-annulus at the first interface according to the processed finite element model includes: simulating the damage of the cement sheath at different positions of the wellbore based on the processed finite element model to obtain the simulation data of the processed finite element model; extracting the compressive damage of the cement sheath from the simulation data; extracting the cumulative plastic deformation of the cement sheath from the simulation data; determining the width of the micro-annulus at the first interface according to the cumulative plastic deformation.

[0015] In the embodiment of the present application, determining the width of the micro-annulus at the first interface according to the cumulative plastic deformation includes determining the width of the micro-annulus at the first interface according to formula (1):

[0016] ΔL = ε ture，pl ·D (1)

[0017] where ΔL is the width of the micro-annulus at the first interface, D is the width of the cement sheath, and ε ture，pl is the cumulative plastic deformation.

[0018] In the embodiment of the present application, constructing a finite element model based on the structural data of the wellbore includes: determining the yield condition of the casing according to the maximum principal stress and minimum principal stress of the cement sheath; determining the yield condition of the formation according to the cohesion and internal friction angle of the formation; determining the material properties of the finite element model according to the elastic parameters of the cement sheath, the yield condition of the casing, and the yield condition of the formation; constructing the finite element model based on the material properties.

[0019] In an embodiment of the present application, determining the compressive plastic strain of each cement stone sample based on the compressive inelastic strain, compressive stress, elastic modulus, and compressive damage factor of each cement stone sample includes determining the compressive plastic strain of each cement stone sample according to formula (2):

[0020]

[0021] Wherein, is the compressive plastic strain, is the compressive inelastic strain, σ c is the compressive stress, E0 is the elastic modulus, d c is the compressive damage factor.

[0022] In an embodiment of the present application, determining the compressive damage factor of each cement stone sample based on the compressive inelastic strain, elastic modulus, and compressive stress of each cement stone sample includes determining the compressive damage factor according to formula (3):

[0023]

[0024] Wherein, d c is the compressive damage factor, σ c is the compressive stress, E0 is the elastic modulus, is the compressive inelastic strain, b c takes a value of 0.1.

[0025] In an embodiment of the present application, the method further includes: generating a relationship between the compressive stress and compressive strain of each cement stone sample based on the elastic modulus, compressive plastic strain, compressive strain, compressive stress, and compressive damage factor of each cement stone sample; wherein, the relationship is as shown in formula (4):

[0026]

[0027] Wherein, σ c is the compressive stress, d c is the compressive damage factor, E0 is the elastic modulus, ε c is the compressive strain, is the compressive plastic strain.

[0028] A second aspect of the present application provides a device for determining the damage of a cement sheath in a wellbore, including:

[0029] A memory configured to store instructions;

[0030] A processor configured to call instructions from the memory and capable of implementing the above method for determining the damage of a cement sheath in a wellbore when executing the instructions.

[0031] A third aspect of the present application provides a machine-readable storage medium, on which instructions are stored for causing a machine to execute the above method for determining the damage of the cement sheath in the wellbore.

[0032] Through the above technical solutions, a plurality of cement stone samples and the compressive stress of each cement stone sample in the plurality of cement stone samples are obtained, wherein the plurality of cement stone samples are cured based on different temperatures; the elastic modulus and compressive inelastic strain of each cement stone sample are determined; the compressive damage factor of each cement stone sample is determined according to the compressive inelastic strain, elastic modulus and compressive stress of each cement stone sample; the compressive plastic strain of each cement stone sample is determined according to the compressive inelastic strain, compressive stress, elastic modulus and compressive damage factor of each cement stone sample; a finite element model is constructed based on the structural data of the wellbore, and the finite element model includes a casing, a cement sheath and a formation; the compressive stress, compressive inelastic strain and compressive damage factor of any one cement stone sample are input into the finite element model, and the number of cycles and the internal pressure within the cycle of the finite element model are set; the compressive damage of the cement sheath and the width of the first interface micro-annulus are determined according to the processed finite element model, so as to accurately determine the compressive damage of the cement sheath and the width of the micro-annulus, which has high practicability.

[0033] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings are used to provide a further understanding of the embodiments of the present application, and constitute a part of the specification. Together with the following specific implementation, they are used to explain the embodiments of the present application, but do not constitute a limitation to the embodiments of the present application. In the drawings:

[0035] Figure 1 Schematically shows a flowchart of a method for determining the damage of the cement sheath in the wellbore according to an embodiment of the present application;

[0036] Figure 2 Schematically shows a schematic diagram of a first relationship curve between the stress and strain of a cement stone sample cured at different temperatures according to an embodiment of the present application;

[0037] Figure 3 Schematically shows a schematic diagram of the elastic modulus of a cement stone sample cured at different temperatures according to an embodiment of the present application;

[0038] Figure 4 Schematically shows a schematic diagram of a curve between the compressive stress and compressive strain of a cement stone sample under uniaxial compressive load according to an embodiment of the present application;

[0039] Figure 5A schematic diagram showing the number of cycles of a finite element model according to an embodiment of the present application;

[0040] Figure 6 A schematic internal structure diagram of a computer device according to an embodiment of the present application. Detailed implementation manners

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. It should be understood that the specific implementation manners described herein are only used to illustrate and explain the embodiments of the present application, and are not used to limit the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0042] It should be noted that if there are directional indications (such as up, down, left, right, front, back,...) involved in the embodiments of the present application, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0043] In addition, if there are descriptions such as "first" and "second" involved in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0044] Figure 1 A schematic flowchart of a method for determining the damage of a cement sheath in a wellbore according to an embodiment of the present application is schematically shown. As Figure 1 shown, an embodiment of the present application provides a method for determining the damage of a cement sheath in a wellbore, and the method may include the following steps.

[0045] Step 101: Obtain a plurality of cement stone samples and the compressive stress of each cement stone sample in the plurality of cement stone samples, where the plurality of cement stone samples are cured at different temperatures.

[0046] Step 102: Determine the elastic modulus and compressive inelastic strain of each cement stone sample.

[0047] The processor can obtain multiple cement stone samples and the compressive stress of each cement stone sample among the multiple cement stone samples. Among them, the multiple cement stone samples are cured based on different temperatures. For example, the processor can determine multiple different temperatures based on the geothermal gradient and the well depths at different positions, and cure multiple cement stone samples based on the multiple different temperatures. For example, it is calculated that the temperature corresponding to the vertical well section at 2200 m is 80 °C, the temperature corresponding to the vertical well section at 3400 m is 110 °C, and the temperature corresponding to the horizontal well section at 4600 m is 140 °C. Different cement stone samples are cured based on the above temperatures, and the diameter, height, mass, etc. of each cement stone sample are recorded. The processor can determine the elastic modulus and compressive inelastic strain of each cement stone sample.

[0048] In the embodiment of the present application, determining the elastic modulus and compressive inelastic strain of each cement stone sample includes: applying a uniaxial compressive load to each cement stone sample to obtain the load data and displacement data of each cement stone sample; determining the first relationship curve between the stress and strain of each cement stone sample according to the load data and displacement data of each cement stone sample; determining the elastic modulus of each cement stone sample according to the linear elastic section of each first relationship curve; obtaining the compressive strain of each cement stone sample; determining the compressive elastic strain of each cement stone sample according to the compressive stress and elastic modulus of each cement stone sample; and determining the compressive inelastic strain of each cement stone sample according to the compressive strain and compressive elastic strain of each cement stone sample.

[0049] The processor can determine the elastic modulus and compressive inelastic strain of each cement stone sample. Specifically, a uniaxial compressive load is applied to each cement stone sample to obtain the load data and displacement data of each cement stone sample. After obtaining the load data and displacement data of each cement stone sample, the processor can determine the first relationship curve between the stress and strain of each cement stone sample according to the load data and displacement data of each cement stone sample. As Figure 2 shown in the first relationship curve (i.e., the uniaxial compressive stress-strain curve) between the stress and strain of the cement stone sample cured at T (temperature) 25 °C, the first relationship curve between the stress and strain of the cement stone sample cured at T 80 °C, the first relationship curve between the stress and strain of the cement stone sample cured at T 110 °C, and the first relationship curve between the stress and strain of the cement stone sample cured at T 140 °C.

[0050] After obtaining the first relationship curve between the stress and strain of each cement stone sample, the processor can determine the elastic modulus of each cement stone sample according to the linear elastic section of each first relationship curve. For example, the processor can select the stress and strain corresponding to an initial point of 5 MPa and an end point of 10 MPa from the linear section of any one of the first relationship curves, determine the stress change amount and strain change amount corresponding to the straight line section according to the initial point and the end point, and determine the elastic modulus of the cement stone sample corresponding to the first relationship curve according to the stress change amount and strain change amount, that is, the elastic modulus E0 = Δσ / Δε, where Δε is the strain change amount and Δσ is the stress change amount. Figure 3 Schematically shows the elastic moduli of cement stones cured at different temperatures, which are the elastic moduli of cement stone samples cured at T25°C, the elastic moduli of cement stone samples cured at T80°C, the elastic moduli of cement stone samples cured at T110°C, and the elastic moduli of cement stone samples cured at T140°C. The processor can obtain the compressive strain of each cement stone sample. After obtaining the compressive strain of each cement stone sample, the processor can determine the compressive elastic strain of each cement stone sample according to the compressive stress and elastic modulus of each cement stone sample, that is, the compressive elastic strain where is the compressive elastic strain calculated according to the initial elastic stiffness in the degradation stage; σ c is the compressive stress. After obtaining the compressive elastic strain of each cement stone sample, the processor can determine the compressive inelastic strain of each cement stone sample according to the compressive strain and compressive elastic strain of each cement stone sample, that is, the compressive inelastic strain where is the compressive inelastic strain.

[0051] Step 103: Determine the compressive damage factor of each cement stone sample according to the compressive inelastic strain, elastic modulus, and compressive stress of each cement stone sample.

[0052] Step 104: Determine the compressive plastic strain of each cement stone sample according to the compressive inelastic strain, compressive stress, elastic modulus, and compressive damage factor of each cement stone sample.

[0053] After obtaining the elastic modulus and compressive inelastic strain of each cement stone sample, the processor can determine the compressive damage factor of each cement stone sample according to the compressive inelastic strain, elastic modulus, and compressive stress of each cement stone sample. In the embodiments of the present application, determining the compressive damage factor of each cement stone sample according to the compressive inelastic strain, elastic modulus, and compressive stress of each cement stone sample includes determining the compressive damage factor according to formula (3):

[0054]

[0055] where d c is the compression damage factor, σ c is the compression stress, E0 is the elastic modulus, is the compression inelastic strain, b c takes a value of 0.1, where b c can be calibrated through experiments.

[0056] After determining the compression damage factor of each cement stone sample, the processor can determine the compression plastic strain of each cement stone sample according to the compression inelastic strain, compression stress, elastic modulus, and compression damage factor of each cement stone sample. In the embodiment of the present application, determining the compression plastic strain of each cement stone sample according to the compression inelastic strain, compression stress, elastic modulus, and compression damage factor of each cement stone sample includes determining the compression plastic strain of each cement stone sample according to formula (2):

[0057]

[0058] where is the compression plastic strain, is the compression inelastic strain, σ c is the compression stress, E0 is the elastic modulus, d c is the compression damage factor.

[0059] In the embodiment of the present application, the method further includes: generating a relationship between the compression stress and the compression strain of each cement stone sample according to the elastic modulus, compression plastic strain, compression strain, compression stress, and compression damage factor of each cement stone sample; where the relationship is as shown in formula (4):

[0060]

[0061] where σ c is the compression stress, d c is the compression damage factor, E0 is the elastic modulus, ε c is the compression strain, is the compression plastic strain.

[0062] Figure 4 Schematically shows the curve corresponding to the relationship between the compression stress (σ c ) and the compression strain (ε c ) of the cement stone sample under uniaxial compression load, where σ cu is the uniaxial compression strength, σ c0 is the uniaxial compression yield stress.

[0063] Step 105: Construct a finite element model based on the structural data of the wellbore, and the finite element model includes a casing, a cement sheath, and a formation.

[0064] The processor can construct a finite element model based on the structural data of the wellbore, and the finite element model includes a casing, a cement sheath, and a formation.

[0065] In the embodiments of the present application, constructing a finite element model based on the structural data of the wellbore includes: determining the yield condition of the casing according to the maximum principal stress and the minimum principal stress of the cement sheath; determining the yield condition of the formation according to the cohesion and the internal friction angle of the formation; determining the material properties of the finite element model according to the elastic parameters of the cement sheath, the yield condition of the casing, and the yield condition of the formation; and constructing the finite element model based on the material properties.

[0066] The processor can construct a finite element model based on the structural data of the wellbore. Specifically, the processor can determine the yield condition of the casing according to the maximum principal stress and the minimum principal stress of the cement sheath. For example, the yield condition of the casing is σ1 - σ3 = σ s , where σ1 is the maximum principal stress, σ3 is the minimum principal stress, and σ s is the yield stress. The processor can determine the yield condition of the formation according to the cohesion and the internal friction angle of the formation. For example, the yield condition of the formation where σ1 is the maximum principal stress, σ3 is the minimum principal stress, C is the cohesion, is the internal friction angle, is the sine function of is the cosine function of

[0067] Step 106: Input the compressive stress, compressive inelastic strain, and compressive damage factor of any one cement stone sample into the finite element model, and set the number of cycles and the cyclic internal pressure of the finite element model.

[0068] Step 107: Determine the compressive damage of the cement sheath and the width of the first interface micro-annulus according to the processed finite element model.

[0069] After obtaining the finite element model, the processor can input the compressive stress, compressive inelastic strain, and compressive damage factor of any one cement stone sample into the finite element model, and set the number of cycles and the cyclic internal pressure of the finite element model to obtain a processed finite element model. In a specific embodiment, the processor can determine the upper limit value (P max ) and the lower limit value (P min ) of the cyclic internal pressure, P max = P pump + ρ fluid gHi , P min = ρ fluid gH i , where P pump is the construction pump pressure of the gas well, ρ fluid is the density of the fracturing fluid and can take a value of 1.25 g / cm 3 , g is the acceleration due to gravity and takes a value of 0.00981 g / cm 3 . In a specific embodiment, the processor can set different numbers of cycles of the finite element model for different positions of the gas well. As shown in Figure 5 , for the horizontal section of the gas well, the number of cycles can decrease from the heel end to the toe end, decreasing from n (a positive integer) cycles to 1 cycle in sequence.

[0070] The processor can determine the compressive damage of the cement sheath and the width of the first interface micro-annulus according to the processed finite element model, where the width of the first interface micro-annulus can refer to the width of the micro-annulus at the interface where the casing is in contact with the cement sheath.

[0071] In the embodiments of the present application, determining the compressive damage of the cement sheath and the width of the first interface micro-annulus according to the processed finite element model includes: simulating the damage of the cement sheath at different positions of the wellbore based on the processed finite element model to obtain the simulation data of the processed finite element model; extracting the compressive damage of the cement sheath from the simulation data; extracting the cumulative plastic deformation of the cement sheath from the simulation data; and determining the width of the first interface micro-annulus according to the cumulative plastic deformation.

[0072] The processor can determine the compressive damage of the cement sheath and the width of the first interface micro-annulus according to the processed finite element model. Specifically, the processor can simulate the damage of the cement sheath at different positions of the wellbore based on the processed finite element model to obtain the simulation data of the processed finite element model. After obtaining the simulation data, the processor can extract the compressive damage of the cement sheath from the simulation data. And extract the cumulative plastic deformation of the cement sheath from the simulation data. After obtaining the cumulative plastic deformation of the cement sheath, the processor can determine the width of the first interface micro-annulus according to the cumulative plastic deformation. In the embodiments of the present application, determining the width of the first interface micro-annulus according to the cumulative plastic deformation includes determining the width of the first interface micro-annulus according to formula (1):

[0073] ΔL = ε ture，pl ·D (1)

[0074] where ΔL is the width of the first interface micro-annulus, D is the width of the cement sheath, and ε ture，pl is the cumulative plastic deformation, ε ture = ln(1 + ε nom ), σ ture = σ nom (1 + εnom ), ε ture is the true strain, ε nom is the nominal strain, σ ture is the true stress, σ nom is the nominal stress, ε ture，el is the true elastic strain, ε ture，l is the true total strain, E is the elastic modulus of the cement sheath, ln(1 + ε nom ) is the logarithmic function of (1 + ε nom ).

[0075] Through the above technical solution, the compressive damage and the width of the micro-annulus of the cement sheath can be accurately determined, which has high practicability.

[0076] Figure 1 is a schematic flowchart of a method for determining the damage of the cement sheath of a wellbore in an embodiment. It should be understood that although Figure 1 the steps in the flowchart are shown in sequence according to the indication of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, Figure 1 at least a part of the steps in

[0077] This application embodiment also provides a device for determining the damage of the cement sheath of a wellbore, including:

[0078] A memory configured to store instructions;

[0079] A processor configured to call instructions from the memory and be able to implement the above method for determining the damage of the cement sheath of a wellbore when executing the instructions.

[0080] This application embodiment also provides a machine-readable storage medium, on which instructions are stored, and these instructions are used to make a machine execute the above method for determining the damage of the cement sheath of a wellbore.

[0081] In one embodiment, a computer device is provided. This computer device can be a server, and its internal structure diagram can be as Figure 6As shown in the figure. The computer device includes a processor A01, a network interface A02, a memory (not shown in the figure), and a database (not shown in the figure) connected through a system bus. Among them, the processor A01 of the computer device is used to provide computing and control capabilities. The memory of the computer device includes an internal memory A03 and a non-volatile storage medium A04. The non-volatile storage medium A04 stores an operating system B01, a computer program B02, and a database (not shown in the figure). The internal memory A03 provides an environment for the operation of the operating system B01 and the computer program B02 in the non-volatile storage medium A04. The database of the computer device is used to store data such as compressive stress, elastic modulus, compressive inelastic strain, compressive damage factor, compressive plastic strain, compressive damage, and the width of the first interface micro-annulus. The network interface A02 of the computer device is used to communicate with an external terminal through a network connection. When the computer program B02 is executed by the processor A01, it implements a method for determining the damage of the cement sheath in a wellbore.

[0082] Those skilled in the art can understand that Figure 6 the structure shown in the figure is only a block diagram of some structures related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0083] The embodiment of the present application provides a device, which includes a processor, a memory, and a program stored on the memory and executable on the processor. When the processor executes the program, the following steps are implemented: obtaining a plurality of cement stone samples and the compressive stress of each cement stone sample in the plurality of cement stone samples, wherein the plurality of cement stone samples are cured based on different temperatures; determining the elastic modulus and compressive inelastic strain of each cement stone sample; determining the compressive damage factor of each cement stone sample according to the compressive inelastic strain, elastic modulus, and compressive stress of each cement stone sample; determining the compressive plastic strain of each cement stone sample according to the compressive inelastic strain, compressive stress, elastic modulus, and compressive damage factor of each cement stone sample; constructing a finite element model based on the structural data of the wellbore, the finite element model including a casing, a cement sheath, and a formation; inputting the compressive stress, compressive inelastic strain, and compressive damage factor of any one of the cement stone samples into the finite element model, and setting the number of cycles and the internal pressure within the cycle of the finite element model; determining the compressive damage of the cement sheath and the width of the first interface micro-annulus according to the processed finite element model.

[0084] In one embodiment, determining the elastic modulus and compressive inelastic strain of each cement stone sample includes: applying a uniaxial compressive load to each cement stone sample to obtain the load data and displacement data of each cement stone sample; determining a first relationship curve between stress and strain of each cement stone sample according to the load data and displacement data of each cement stone sample; determining the elastic modulus of each cement stone sample according to the linear elastic section of each first relationship curve; obtaining the compressive strain of each cement stone sample; determining the compressive elastic strain of each cement stone sample according to the compressive stress and elastic modulus of each cement stone sample; and determining the compressive inelastic strain of each cement stone sample according to the compressive strain and compressive elastic strain of each cement stone sample.

[0085] In one embodiment, determining the compressive damage and the width of the first interface micro-annulus of the cement sheath according to the processed finite element model includes: simulating the damage of the cement sheath at different positions of the wellbore based on the processed finite element model to obtain the simulation data of the processed finite element model; extracting the compressive damage of the cement sheath from the simulation data; extracting the cumulative plastic deformation of the cement sheath from the simulation data; and determining the width of the first interface micro-annulus according to the cumulative plastic deformation.

[0086] In one embodiment, determining the width of the first interface micro-annulus according to the cumulative plastic deformation includes determining the width of the first interface micro-annulus according to formula (1):

[0087] ΔL = ε ture，pl ·D (1)

[0088] where ΔL is the width of the first interface micro-annulus, D is the width of the cement sheath, and ε ture，pl is the cumulative plastic deformation.

[0089] In one embodiment, constructing a finite element model based on the structural data of the wellbore includes: determining the yield condition of the casing according to the maximum principal stress and minimum principal stress of the cement sheath; determining the yield condition of the formation according to the cohesion and internal friction angle of the formation; determining the material properties of the finite element model according to the elastic parameters of the cement sheath, the yield condition of the casing, and the yield condition of the formation; and constructing the finite element model based on the material properties.

[0090] In one embodiment, determining the compressive plastic strain of each cement stone sample according to the compressive inelastic strain, compressive stress, elastic modulus, and compressive damage factor of each cement stone sample includes determining the compressive plastic strain of each cement stone sample according to formula (2):

[0091]

[0092] where is the compressive plastic strain, is the compressive inelastic strain, σ cis the compressive stress, E0 is the elastic modulus, and d c is the compressive damage factor.

[0093] In one embodiment, determining the compressive damage factor for each cement stone sample based on the compressive inelastic strain, elastic modulus, and compressive stress of each cement stone sample includes determining the compressive damage factor according to Equation (3):

[0094]

[0095] where d c is the compressive damage factor, σ c is the compressive stress, E0 is the elastic modulus, is the compressive inelastic strain, and b c has a value of 0.1.

[0096] In one embodiment, the method further includes: generating a relationship between the compressive stress and compressive strain for each cement stone sample based on the elastic modulus, compressive plastic strain, compressive strain, compressive stress, and compressive damage factor of each cement stone sample; where the relationship is as shown in Equation (4):

[0097]

[0098] where σ c is the compressive stress, d c is the compressive damage factor, E0 is the elastic modulus, ε c is the compressive strain, and is the compressive plastic strain.

[0099] The present application also provides a computer program product that, when executed on a data processing device, is adapted to execute a program initialized with method steps for determining the damage of the cement sheath in a wellbore.

[0100] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0101] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, and combinations of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce a means for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or a means for implementing the functions specified in one or more of the blocks.

[0102] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction means that implements the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or a means for implementing the functions specified in one or more of the blocks.

[0103] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are performed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or a means for implementing the functions specified in one or more of the blocks.

[0104] In a typical configuration, a computing device includes one or more processors (CPUs), an input / output interface, a network interface, and memory.

[0105] The memory may include non-permanent memory in the form of computer-readable media, random access memory (RAM), and / or non-volatile memory such as read-only memory (ROM) or flash RAM. The memory is an example of computer-readable media.

[0106] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0107] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0108] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for determining damage to a cement sheath in a wellbore, characterized in that, The method includes: Obtaining a plurality of cement stone samples and the compressive stress of each cement stone sample in the plurality of cement stone samples, wherein the plurality of cement stone samples are cured based on different temperatures; Determining the elastic modulus and compressive inelastic strain of each cement stone sample; Determining the compressive damage factor of each cement stone sample according to the compressive inelastic strain, elastic modulus and compressive stress of each cement stone sample; Determining the compressive plastic strain of each cement stone sample according to the compressive inelastic strain, compressive stress, elastic modulus and compressive damage factor of each cement stone sample; Constructing a finite element model based on the structural data of the wellbore, the finite element model including a casing, a cement sheath and a formation; Inputting the compressive stress, compressive inelastic strain and compressive damage factor of any one cement stone sample into the finite element model, and setting the number of cycles and the cyclic internal pressure of the finite element model; Determining the compressive damage of the cement sheath and the width of the first interface micro-annulus according to the processed finite element model, wherein the width of the first interface micro-annulus refers to the width of the micro-annulus at the interface where the casing is in contact with the cement sheath.

2. The method for determining the damage of the cement sheath of a wellbore according to claim 1, wherein, The determining the elastic modulus and compressive inelastic strain of each cement stone sample includes: Applying a uniaxial compressive load to each cement stone sample to obtain the load data and displacement data of each cement stone sample; Determining the first relationship curve between stress and strain of each cement stone sample according to the load data and displacement data of each cement stone sample; Determining the elastic modulus of each cement stone sample according to the linear elastic section of each first relationship curve; Obtaining the compressive strain of each cement stone sample; Determining the compressive elastic strain of each cement stone sample according to the compressive stress and elastic modulus of each cement stone sample; Determining the compressive inelastic strain of each cement stone sample according to the compressive strain and compressive elastic strain of each cement stone sample.

3. The method for determining the damage of the cement sheath of a wellbore according to claim 1, wherein, The determining the compressive damage of the cement sheath and the width of the first interface micro-annulus according to the processed finite element model includes: Simulating the damage of the cement sheath at different positions of the wellbore based on the processed finite element model to obtain the simulation data of the processed finite element model; Extracting the compressive damage of the cement sheath from the simulation data; Extracting the cumulative plastic deformation of the cement sheath from the simulation data; Determining the width of the first interface micro-annulus according to the cumulative plastic deformation.

4. The method for determining the cement sheath damage of a wellbore according to claim 3, characterized in that, The determining the width of the first interface micro-annulus according to the cumulative plastic deformation includes determining the width of the first interface micro-annulus according to formula (1): （1） Among them, is the width of the first interface micro-annulus, and D is the width of the cement sheath, is the cumulative plastic deformation.

5. The method for determining the damage of the cement sheath in a wellbore according to claim 1, characterized in that, The constructing a finite element model based on the structural data of the wellbore includes: Determining the yield condition of the casing according to the maximum principal stress and minimum principal stress of the cement sheath; Determining the yield condition of the formation according to the cohesion and internal friction angle of the formation; Determining the material properties of the finite element model according to the elastic parameters of the cement sheath, the yield condition of the casing and the yield condition of the formation; Constructing the finite element model based on the material properties.

6. The method for determining the damage of the cement sheath of a wellbore according to claim 1, wherein, Determining the compressive plastic strain of each cement stone sample based on the compressive inelastic strain, compressive stress, elastic modulus, and compressive damage factor of each cement stone sample includes determining the compressive plastic strain of each cement stone sample according to formula (2): （2） wherein, is the compressive plastic strain, is the compressive inelastic strain, is the compressive stress, is the elastic modulus, is the compressive damage factor.

7. The method for determining cement sheath damage in a wellbore according to claim 1, characterized in that, Determining the compressive damage factor of each cement stone sample based on the compressive inelastic strain, elastic modulus, and compressive stress of each cement stone sample includes determining the compressive damage factor according to formula (3): （3） wherein, is the compression damage factor, is the compression stress, is the elastic modulus, is the compressive inelastic strain, takes a value of 0.

1.

8. The method for determining cement sheath damage in a wellbore according to claim 1, wherein The method further includes: Generating a relationship between the compressive stress and compressive strain of each cement stone sample based on the elastic modulus, compressive plastic strain, compressive strain, compressive stress, and compressive damage factor of each cement stone sample; wherein, the relationship is as shown in formula (4): （4） wherein, is the compression stress, is the compression damage factor, is the elastic modulus, is the compression strain, is the compression plastic strain.

9. A device for determining the damage of the cement sheath in a wellbore, characterized in that, including: a memory configured to store instructions; a processor configured to call the instructions from the memory and capable of implementing the method for determining the cement sheath damage of a wellbore according to any one of claims 1 to 8 when executing the instructions.

10. A machine-readable storage medium, characterized in that, Instructions are stored on the machine-readable storage medium, and the instructions are used to cause the machine to execute the method for determining the cement sheath damage of a wellbore according to any one of claims 1 to 8.

Images