Method and device for determining damage to cement sheath of wellbore and storage medium

Abstract

The invention relates to the technical field of oil gas, in particular to a method and device for determining damage to a cement sheath of a shaft and a storage medium. Comprising the following steps: acquiring a plurality of set cement samples and compression stress thereof; determining the elastic modulus and the compression inelastic strain of each set cement sample; determining a compression damage factor of each set cement sample; determining the compression plastic strain of each set cement sample according to the compression inelastic strain, the compression stress, the elastic modulus and the compression damage factor of each set cement sample; constructing a finite element model based on the structural data of the shaft; inputting the compression stress, the compression inelastic strain and the compression damage factor of any set cement sample into the finite element model, and setting the cycle index and the cycle internal pressure; and according to the processed finite element model, determining the compression damage of the cement sheath and the width of the first interface micro-annular gap so as to accurately determine the compression damage and the width of the micro-annular gap of the cement sheath, and the method has relatively high practicability.

Description

Technical Field

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

[0002] Deep shale oil and gas is the main area of ​​natural gas resource exploration in the future. In the process of deep shale oil and gas development, multi-stage fracturing construction with ultra-high pump pressure and ultra-large displacement is the key means to achieve efficient development, which causes the cement sheath to be subjected to extreme environments such as high temperature, high construction pressure and multiple cycles of alternating internal pressure, and its sealing integrity is severely challenged.

[0003] It is generally believed that the multiple alternating internal pressure loads during multi-stage fracturing are the main cause of cement sheath seal failure. However, in actual engineering, the temperature environment of the cement sheath at different locations in the entire well section is different during the solidification process, and the cyclic load forms borne by the cement sheath at different locations are also quite different, all of which will cause cement sheath damage. Existing technologies do not take the above factors into account, 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 cement sheath damage in a wellbore, so as to solve the problem that cement sheath damage cannot be accurately determined in the prior art.

[0005] In order to achieve the above-mentioned object, the first aspect of the present application provides a method for determining cement sheath damage of a wellbore, the method comprising:

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

[0007] Determine the elastic modulus and compressive inelastic strain of each cement paste specimen;

[0008] Determine the compression damage factor of each cement paste sample based on the compression inelastic strain, elastic modulus and compression stress of each cement paste sample;

[0009] Determine the compressive plastic strain of each cement paste sample based on the compressive inelastic strain, compressive stress, elastic modulus, and compressive damage factor of each cement paste sample;

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

[0011] The compressive stress, compressive inelastic strain and compressive damage factor of any cement paste sample are input into the finite element model, and the number of cycles and cyclic internal pressure of the finite element model are set;

[0012] The compression damage of the cement sheath and the width of the micro-annulus at the first interface were determined based on the processed finite element model.

[0013] In an 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 load data and displacement data of each cement stone sample; determining a first relationship curve between stress and strain of each cement stone sample based on the load data and displacement data of each cement stone sample; determining the elastic modulus of each cement stone sample based on the linear elastic segment of each first relationship curve; obtaining the compressive strain of each cement stone sample; determining the compressive elastic strain of each cement stone sample based on the compressive stress and elastic modulus of each cement stone sample; and determining the compressive inelastic strain of each cement stone sample based on the compressive strain and compressive elastic strain of each cement stone sample.

[0014] In an embodiment of the present application, determining the compression 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 simulation data of the processed finite element model; extracting the compression 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.

[0015] In an embodiment of the present application, determining the first interface micro-annular gap width according to the accumulated plastic deformation includes determining the first interface micro-annular gap width 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 annulus, and ε ture，pl is the accumulated plastic deformation.

[0018] In an 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 based on the maximum principal stress and the minimum principal stress of the cement sheath; determining the yield condition of the formation based on the cohesion and internal friction angle of the formation; determining the material properties of the finite element model based on 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.

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

[0020]

[0021] in, 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 compression damage factor.

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

[0023]

[0024] Among them, d c is the compression damage factor, σ c is the compressive stress, E0 is the elastic modulus, is the compressive inelastic strain, b c The value is 0.1.

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

[0026]

[0027] Among them, σ c is the compressive stress, d c is the compression 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 cement sheath damage in a wellbore, comprising:

[0029] a memory configured to store instructions;

[0030] The processor is configured to call instructions from the memory and implement the above method for determining cement sheath damage of a wellbore when executing the instructions.

[0031] A third aspect of the present application provides a machine-readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the above-mentioned method for determining cement sheath damage in a wellbore.

[0032] Through the above technical scheme, the compressive stress of multiple cement stone samples and each of the multiple cement stone samples is obtained, wherein the multiple 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 casing, cement ring and formation; the compressive stress, compressive inelastic strain and compressive damage factor of any cement stone sample are input into the finite element model, and the number of cycles and the cyclic internal pressure of the finite element model are set; the compressive damage of the cement ring and the micro-annulus width of the first interface are determined according to the processed finite element model, so as to accurately determine the compressive damage and micro-annulus width of the cement ring, which has high practicality.

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

[0034] The accompanying 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 implementations, they are used to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings:

[0035] Figure 1 A schematic diagram of a process flow of a method for determining cement sheath damage of a wellbore according to an embodiment of the present application is schematically shown;

[0036] Figure 2 A schematic diagram schematically shows a first relationship curve between stress and strain of a cement paste sample under different temperature curing according to an embodiment of the present application;

[0037] Figure 3 A schematic diagram schematically shows the elastic modulus of cement paste samples under different temperature curing according to an embodiment of the present application;

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

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

[0040] Figure 6 The internal structure diagram of a computer device according to an embodiment of the present application is schematically shown. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the specific implementation methods 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. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0042] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0043] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0044] Figure 1 The following schematically shows a flow chart of a method for determining cement sheath damage in a wellbore according to an embodiment of the present application. Figure 1 As shown, an embodiment of the present application provides a method for determining cement sheath damage in a wellbore, which method may include the following steps.

[0045] Step 101: obtaining a plurality of cement paste samples and the compressive stress of each of the plurality of cement paste samples, wherein the plurality of cement paste samples are cured at different temperatures.

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

[0047] The processor can obtain multiple cement stone samples and the compressive stress of each cement stone sample in the multiple cement stone samples, wherein 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 locations, and cure multiple cement stone samples based on multiple different temperatures. For example, it is calculated that the temperature corresponding to the vertical well section at 2200m is 80°C, the temperature corresponding to the vertical well section at 3400m is 110°C, and the temperature corresponding to the horizontal section at 4600m is 140°C. Different cement stone samples are obtained based on the above-mentioned temperature curing, and the diameter, height, and mass 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 an 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 load data and displacement data of each cement stone sample; determining a first relationship curve between stress and strain of each cement stone sample based on the load data and displacement data of each cement stone sample; determining the elastic modulus of each cement stone sample based on the linear elastic segment of each first relationship curve; obtaining the compressive strain of each cement stone sample; determining the compressive elastic strain of each cement stone sample based on the compressive stress and elastic modulus of each cement stone sample; and determining the compressive inelastic strain of each cement stone sample based on the compressive strain and compressive elastic strain of each cement stone sample.

[0049] The processor can determine the elastic modulus and the compressive inelastic strain of each cement paste sample. Specifically, a uniaxial compressive load is applied to each cement paste sample to obtain load data and displacement data of each cement paste sample. After obtaining the load data and displacement data of each cement paste sample, the processor can determine a first relationship curve between stress and strain of each cement paste sample according to the load data and displacement data of each cement paste sample. Figure 2 The first relationship curve between stress and strain of the cement paste sample cured at T (temperature) 25°C (i.e., uniaxial compression stress-strain curve), the first relationship curve between stress and strain of the cement paste sample cured at T80°C, the first relationship curve between stress and strain of the cement paste sample cured at T110°C, and the first relationship curve between stress and strain of the cement paste sample cured at T140°C.

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

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

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

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

[0054]

[0055] Among them, d c is the compression damage factor, σ c is the compressive stress, E0 is the elastic modulus, is the compressive inelastic strain, b c The value is 0.1, where b c Calibration can be obtained through experiments.

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

[0057]

[0058] in, 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 compression damage factor.

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

[0060]

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

[0062] Figure 4 Schematic diagram showing the compressive stress (σ) of cement paste samples under uniaxial compression load. c ) and compressive strain (ε c ) is the curve corresponding to the relationship between cu is the uniaxial compressive strength, σ c0 is the uniaxial compressive yield stress.

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

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

[0065] In an 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 based on the maximum principal stress and the minimum principal stress of the cement sheath; determining the yield condition of the formation based on the cohesion and internal friction angle of the formation; determining the material properties of the finite element model based on 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 based on the cohesion and internal friction angle of the formation, such as the yield condition of the formation Among them, σ1 is the maximum principal stress, σ3 is the minimum principal stress, C is the cohesion, is the internal friction angle, for The sine function of for After obtaining the yield condition of the casing and the yield condition of the formation, the processor can determine 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 construct the finite element model based on the material properties.

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

[0068] Step 107: Determine the compression damage of the cement sheath and the width of the first interface micro-annular gap 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 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 the processed finite element model. In a specific embodiment, the processor can determine the upper limit value of the cyclic internal pressure (P max ) and the lower limit (P min ), P max =P pump +ρ fluid HkDJi , P min =ρ fluid HkDJ i , where P pump is the construction pump pressure of the gas well, ρ fluid is the density of the fracturing fluid and can be taken as 1.25 g / cm 3 , g is the acceleration due to gravity and its value is 0.00981g / cm 3 In a specific embodiment, the processor may set different numbers of cycles of the finite element model for different positions of the gas well, such as Figure 5 As shown, for the horizontal section of the gas well, the number of cycles can decrease from the heel end to the toe end, from n (positive integer) cycles to 1 cycle.

[0070] The processor can determine the compression damage of the cement sheath and the first interface micro-annulus width according to the processed finite element model, wherein the first interface micro-annulus width can refer to the micro-annulus width of the interface where the casing and the cement sheath meet.

[0071] In an embodiment of the present application, determining the compression 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 simulation data of the processed finite element model; extracting the compression 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 compression damage of the cement sheath and the width of the first interface micro-annulus based on 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 simulation data of the processed finite element model. After obtaining the simulation data, the processor can extract the compression 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 based on the cumulative plastic deformation. In an embodiment of the present application, determining the width of the first interface micro-annulus based on the cumulative plastic deformation includes determining the width of the first interface micro-annulus based on formula (1):

[0073] ΔL=ε ture，pl ·D (1)

[0074] Where ΔL is the width of the micro-annulus at the first interface, D is the width of the cement annulus, 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 (1+ε nom ) is the logarithmic function of .

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

[0076] Figure 1 FIG. 1 is a flow chart of a method for determining cement sheath damage in a wellbore in one embodiment. Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0077] The present application also provides a device for determining cement sheath damage in a wellbore, comprising:

[0078] a memory configured to store instructions;

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

[0080] An embodiment of the present application further provides a machine-readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the above-mentioned method for determining cement sheath damage in a wellbore.

[0081] In one embodiment, a computer device is provided. The computer device may be a server, and its internal structure diagram may be as follows: Figure 6As shown. 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, a method for determining cement sheath damage in a wellbore is implemented.

[0082] Those skilled in the art will understand that Figure 6 The structure shown in the figure is only a block diagram of a part of the structure 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 certain components, or have a different arrangement of components.

[0083] An embodiment of the present application provides a device, which includes a processor, a memory, and a program stored in the memory and executable on the processor, wherein the processor implements the following steps when executing the program: obtaining a plurality of cement stone samples and the compressive stress of each of the plurality of cement stone samples, wherein the plurality of cement stone samples are cured at 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 casing, cement ring, and formation; inputting the compressive stress, compressive inelastic strain, and compressive damage factor of any 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 ring 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 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 segment 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 compression damage of the cement sheath and the first interface micro-annulus width 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 simulation data of the processed finite element model; extracting the compression 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 first interface micro-annulus width according to the cumulative plastic deformation.

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

[0087] ΔL=ε ture，pl ·D (1)

[0088] Where ΔL is the width of the micro-annulus at the first interface, D is the width of the cement annulus, and ε ture，pl is the accumulated 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 based on the maximum principal stress and the minimum principal stress of the cement sheath; determining the yield condition of the formation based on the cohesion and internal friction angle of the formation; determining the material properties of the finite element model based on 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 paste sample according to the compressive inelastic strain, compressive stress, elastic modulus, and compressive damage factor of each cement paste sample includes determining the compressive plastic strain of each cement paste sample according to formula (2):

[0091]

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

[0093] In one embodiment, determining the compression damage factor of each cement paste sample according to the compressive inelastic strain, elastic modulus, and compressive stress of each cement paste sample includes determining the compression damage factor according to formula (3):

[0094]

[0095] Among them, d c is the compression damage factor, σ c is the compressive stress, E0 is the elastic modulus, is the compressive inelastic strain, b c The value is 0.1.

[0096] In one embodiment, the method further includes: generating a relationship between the compressive stress and the compressive strain of each cement paste sample according to the elastic modulus, the compressive plastic strain, the compressive strain, the compressive stress and the compressive damage factor of each cement paste sample; wherein the relationship is shown in formula (4):

[0097]

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

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

[0100] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment in combination with software and hardware. Moreover, the present application may adopt 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.) that contain computer-usable program code.

[0101] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0102] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0103] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

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

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

[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 cement sheath damage in a wellbore, characterized in that: The method comprises: Obtaining a plurality of cement paste samples and a compressive stress of each of the plurality of cement paste samples, wherein the plurality of cement paste samples are cured based on different temperatures; Determine the elastic modulus and compressive inelastic strain of each cement paste specimen; Determine the compression damage factor of each cement paste sample based on the compression inelastic strain, elastic modulus and compression stress of each cement paste sample; Determine the compressive plastic strain of each cement paste sample based on the compressive inelastic strain, compressive stress, elastic modulus, and compressive damage factor of each cement paste sample; Constructing a finite element model based on the structural data of the wellbore, wherein the finite element model includes casing, cement ring and formation; Inputting the compressive stress, compressive inelastic strain and compressive damage factor of any cement paste sample into the finite element model, and setting the number of cycles and cyclic internal pressure of the finite element model; The compression damage of the cement sheath and the width of the first interface micro-annular gap are determined based on the processed finite element model.

2. The method for determining cement sheath damage in a wellbore according to claim 1, characterized in that: Determining the elastic modulus and compressive inelastic strain of each cement paste sample includes: Applying uniaxial compression load to each cement paste sample to obtain load data and displacement data of each cement paste sample; Determine a first relationship curve between stress and strain of each cement paste sample according to the load data and displacement data of each cement paste sample; determining the elastic modulus of each cement paste sample according to the linear elastic segment of each first relationship curve; Obtain the compressive strain of each cement paste sample; determining the compressive elastic strain of each cement paste sample based on the compressive stress and elastic modulus of each cement paste sample; The compressive inelastic strain of each cement paste sample is determined based on the compressive strain and compressive elastic strain of each cement paste sample.

3. The method for determining cement sheath damage in a wellbore according to claim 1, characterized in that: Determining the compression damage of the cement sheath and the width of the first interface micro-annulus according to the processed finite element model includes: Simulating damage of the cement sheath at different positions of the wellbore based on the processed finite element model to obtain simulation data of the processed finite element model; extracting compression damage of the cement sheath from the simulation data; extracting the accumulated plastic deformation of the cement sheath from the simulation data; The first interface micro-annular gap width is determined according to the accumulated plastic deformation.

4. The method for determining cement sheath damage in a wellbore according to claim 3, characterized in that: Determining the first interface micro-annular gap width according to the accumulated plastic deformation includes determining the first interface micro-annular gap width according to formula (1): ΔL=ε ture,pl ·D (1) Wherein, ΔL is the width of the first interface micro-annulus, D is the width of the cement annulus, ε ture，pl is the accumulated plastic deformation.

5. The method for determining cement sheath damage in a wellbore according to claim 1, characterized in that: The constructing of the finite element model based on the structural data of the wellbore comprises: Determining the yield condition of the casing according to the maximum principal stress and the minimum principal stress of the cement sheath; determining a 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; The finite element model is constructed based on the material properties.

6. The method for determining cement sheath damage in a wellbore according to claim 1, characterized in that: Determining the compressive plastic strain of each cement paste sample according to the compressive inelastic strain, compressive stress, elastic modulus and compressive damage factor of each cement paste sample includes determining the compressive plastic strain of each cement paste sample according to formula (2): in, 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 compression damage factor.

7. The method for determining cement sheath damage in a wellbore according to claim 1, characterized in that: Determining the compression damage factor of each cement paste sample according to the compression inelastic strain, elastic modulus and compression stress of each cement paste sample includes determining the compression damage factor according to formula (3): Among them, d c is the compression damage factor, σ c is the compressive stress, E0 is the elastic modulus, is the compressive inelastic strain, b c The value is 0.

1.

8. The method for determining cement sheath damage in a wellbore according to claim 1, characterized in that: The method further comprises: Generate a relationship between the compressive stress and the compressive strain of each cement paste sample according to the elastic modulus, the compressive plastic strain, the compressive strain, the compressive stress and the compressive damage factor of each cement paste sample; The relationship is shown in formula (4): Among them, σ c is the compressive stress, d c is the compression damage factor, E0 is the elastic modulus, ε c is the compressive strain, is the compressive plastic strain.

9. A device for determining cement sheath damage in a wellbore, characterized in that: include: a memory configured to store instructions; A processor is configured to call the instructions from the memory and implement the method for determining 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: The machine-readable storage medium stores instructions for causing a machine to execute the method for determining cement sheath damage of a wellbore according to any one of claims 1 to 8.

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