Well cementation cement sheath integrity failure evaluation method and system based on strain measurement

Abstract

The invention discloses a well cementation cement sheath integrity failure evaluation method and system based on strain measurement, and relates to the technical field of oil drilling engineering well cementation, and the method comprises the steps: carrying out the parameter initialization of a shaft simulation system, and maintaining a to-be-evaluated cement sheath; adjusting the in-pipe pressure value of the cement sheath to be evaluated after maintenance to change along with time based on a shaft simulation system, and acquiring time-varying data of an end face radial strain value of the cement sheath to be evaluated and time-varying data of an inner wall circumferential strain value; respectively generating an in-pipe pressure value change curve, an end face radial strain value change curve and an inner wall circumferential strain value change curve; respectively calculating a first curve goodness of fit and a second curve goodness of fit; and based on the first curve goodness of fit and the second curve goodness of fit, evaluating the integrity failure of the cement sheath to be evaluated. Whether the integrity of the cement sheath fails or not can be judged by analyzing the strain of the cement sheath.

Description

Technical Field

[0001] The invention relates to the technical field of cementing in petroleum drilling and production engineering, and in particular to a method and system for evaluating failure of cement ring integrity based on strain measurement. Background Art

[0002] The integrity of cement sheath is crucial for the safe and efficient exploitation of oil and gas wells. On the one hand, cement sheath can support the formation and casing, weaken the uneven force of the formation on the casing, and on the other hand, it can isolate the formation fluid channeling longitudinally. During the operation and production of oil and gas wells, under the pressure in the pipe, the cement sheath is subjected to compressive stress in the radial direction to produce radial strain, and is subjected to tensile stress or compressive stress in the circumferential direction to produce circumferential strain. Before the integrity failure of the cement sheath, the strain will increase with the increase of the pressure in the pipe, and the strain will also recover after the pressure is restored; but after the integrity failure of the cement sheath, due to the irreversible deformation of the cement sheath, the strain will not recover with the recovery of the pressure in the pipe. Based on the above principle, the integrity failure of the cement sheath can be evaluated by its strain. At present, the analysis of cement sheath integrity failure in China is generally judged by fluid channeling, and there is no related report on evaluating the integrity failure of the cement sheath by cement sheath strain. Summary of the invention

[0003] The purpose of the present invention is to provide a method and system for evaluating cement ring integrity failure based on strain measurement in order to solve at least one of the above technical problems.

[0004] In a first aspect, an embodiment of the present invention provides a cement ring integrity failure evaluation method based on strain measurement, comprising: placing a cement ring to be evaluated into a wellbore simulation system, initializing parameters of the wellbore simulation system and maintaining the cement ring to be evaluated; adjusting the pressure value in the pipe to which the cement ring to be evaluated is subjected to after maintenance based on the wellbore simulation system, and obtaining the end face radial strain value change data and the inner wall circumferential strain value change data of the cement ring to be evaluated over time; normalizing the inner pipe pressure value, the end face radial strain value and the inner wall circumferential strain value change data over time, respectively, and generating an inner pipe pressure value change curve, an end face radial strain value change curve and an inner wall circumferential strain value change curve; respectively calculating a first curve fit between the inner pipe pressure value change curve and the end face radial strain value change curve, and a second curve fit between the inner pipe pressure value change curve and the inner wall circumferential strain value change curve; based on the first curve fit and the second curve fit, evaluating the integrity failure of the cement ring to be evaluated.

[0005] Furthermore, parameters of the wellbore simulation system are initialized and the cement ring to be evaluated is maintained, including: obtaining the initial in-pipe pressure, initial downhole temperature and initial formation confining pressure when the target oil and gas well is cemented to form a cement ring; setting the in-pipe pressure value of the wellbore simulation system to the initial in-pipe pressure, setting the simulated temperature of the wellbore simulation system to the initial downhole temperature, and setting the out-pipe pressure of the wellbore simulation system to the initial formation confining pressure; and maintaining the cement ring to be evaluated for a preset time period.

[0006] Furthermore, the data of the end face radial strain value changing with time and the data of the inner wall circumferential strain value changing with time of the cement ring to be evaluated are obtained, including: respectively setting a first strain gauge and a second strain gauge on the upper end face and the inner wall surface of the cement ring to be evaluated; based on the first strain gauge and the second strain gauge, respectively, obtaining the data of the end face radial strain value changing with time and the data of the inner wall circumferential strain value changing with time.

[0007] Furthermore, the first curve fit includes:

[0008] ψ 1i =[1-(λ 1i -λ 2i )]*100%

[0009] The second curve fit includes:

[0010] ψ 2i =[1-(λ 1i -λ 3i )]*100%

[0011] In the formula, ψ 1i and ψ 2i are the first curve fit degree and the second curve fit degree at the i-th moment, respectively, 1i , 2i and λ 3i They are respectively the ordinate value of the tube internal pressure value change curve, the ordinate value of the end face radial strain value change curve and the ordinate value of the inner wall circumferential strain value change curve corresponding to the i-th moment.

[0012] Furthermore, based on the first curve fit and the second curve fit, the integrity failure of the cement ring to be evaluated is evaluated, including: judging whether the first curve fit exceeds a first preset threshold; if so, the radial mechanical integrity of the cement ring to be evaluated has not failed; if not, the radial mechanical integrity of the cement ring to be evaluated has failed; judging whether the second curve fit exceeds a second preset threshold; if so, the circumferential mechanical integrity of the cement ring to be evaluated has not failed; if not, the circumferential mechanical integrity of the cement ring to be evaluated has failed.

[0013] In a second aspect, an embodiment of the present invention further provides a cement ring integrity failure evaluation system based on strain measurement, comprising: a simulation module, an acquisition module, a generation module, a calculation module and an evaluation module; wherein the simulation module is used to place the cement ring to be evaluated into a wellbore simulation system, initialize the parameters of the wellbore simulation system and maintain the cement ring to be evaluated; the acquisition module is used to adjust the pressure value of the cement ring to be evaluated after maintenance based on the wellbore simulation system to change with time, and at the same time obtain the end face radial strain value change data of the cement ring to be evaluated and the inner wall circumferential strain value change data; the generation module is used to calculate the value of the cement ring to be evaluated after maintenance based on the wellbore simulation system. The module is used to normalize the time-varying data of the inner-tube pressure value, the end-face radial strain value and the inner-wall circumferential strain value, and generate an inner-tube pressure value variation curve, an end-face radial strain value variation curve and an inner-wall circumferential strain value variation curve; the calculation module is used to calculate a first curve fit between the inner-tube pressure value variation curve and the end-face radial strain value variation curve, and a second curve fit between the inner-tube pressure value variation curve and the inner-wall circumferential strain value variation curve; the evaluation module is used to evaluate the integrity failure of the cement ring to be evaluated based on the first curve fit and the second curve fit.

[0014] Furthermore, the simulation module is also used to: obtain the initial in-pipe pressure, initial downhole temperature and initial formation confining pressure when the target oil and gas well is cemented to form a cement ring; set the in-pipe pressure value of the wellbore simulation system to the initial in-pipe pressure, set the simulation temperature of the wellbore simulation system to the initial downhole temperature, and set the out-pipe pressure of the wellbore simulation system to the initial formation confining pressure; and maintain the cement ring to be evaluated for a preset time period.

[0015] Furthermore, the evaluation module is also used to: determine whether the fit of the first curve exceeds a first preset threshold; if so, the radial mechanical integrity of the cement ring to be evaluated has not failed; if not, the radial mechanical integrity of the cement ring to be evaluated has failed; determine whether the fit of the second curve exceeds a second preset threshold; if so, the circumferential mechanical integrity of the cement ring to be evaluated has not failed; if not, the circumferential mechanical integrity of the cement ring to be evaluated has failed.

[0016] In a third aspect, an embodiment of the present invention further provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method provided in the embodiment of the present invention when executing the computer program.

[0017] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and when the computer instructions are executed by a processor, the method provided in the embodiment of the present invention is implemented.

[0018] The present invention provides a cement ring integrity failure evaluation method and system based on strain measurement. The strain value change of the cement ring is obtained through a wellbore simulation system, and whether the integrity of the cement ring has failed is judged according to the strain change of the cement ring. The mechanical integrity of the cement ring in a specific force direction can be judged according to the strain direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A flow chart of a cement sheath integrity failure evaluation method based on strain measurement provided by an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of the structure of a wellbore simulation system provided by an embodiment of the present invention;

[0022] Figure 3 A top view of a strain gauge bonding position provided by an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of a normalized curve of pipe internal pressure and cement sheath radial strain provided by an embodiment of the present invention;

[0024] Figure 5 A schematic diagram of a normalized curve of the internal pressure of a pipe and the circumferential strain of a cement ring provided in an embodiment of the present invention;

[0025] Figure 6 A schematic diagram of a cement sheath integrity failure evaluation system based on strain measurement provided by an embodiment of the present invention.

[0026] In the figure: 1. kettle body, 2. heating outer cylinder, 3. simulated pipe column, 4. rubber sleeve, 5. kettle body upper cover, 6. kettle body lower cover, 7. first booster pump, 8. second booster pump, 9. temperature controller, 10. first strain gauge, 11. second strain gauge, 12. internal pressure application pipeline, 13. confining pressure application pipeline, 14. first pressure sensor, 15. first pressure control valve, 16. second pressure sensor, 17. second pressure control valve, 18., 19. strain measuring instrument. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Embodiment 1

[0029] Figure 1 FIG. 1 is a flow chart of a cement sheath integrity failure evaluation method based on strain measurement according to an embodiment of the present invention. Figure 1 As shown, the method specifically comprises the following steps:

[0030] Step S102, placing the cement sheath to be evaluated into the wellbore simulation system, initializing the parameters of the wellbore simulation system and maintaining the cement sheath to be evaluated. Specifically, the steps include:

[0031] Step S1021, obtaining the initial pipe pressure, initial downhole temperature and initial formation confining pressure when the target oil and gas well is cemented to form a cement sheath;

[0032] Step S1022, setting the inner tube pressure value of the wellbore simulation system to the initial inner tube pressure, setting the simulation temperature of the wellbore simulation system to the initial downhole temperature, and setting the outer tube pressure of the wellbore simulation system to the initial formation confining pressure;

[0033] Step S1023, curing the cement sheath to be evaluated for a preset time period, for example, curing for 48 hours.

[0034] Step S104, based on the wellbore simulation system, the pressure value of the cement sheath to be evaluated after maintenance changes with time, and the end face radial strain value and inner wall circumferential strain value of the cement sheath to be evaluated change with time data are obtained.

[0035] Step S106, normalizing the time-varying data of the inner tube pressure value, the end face radial strain value, and the inner wall circumferential strain value, and generating an inner tube pressure value variation curve, an end face radial strain value variation curve, and an inner wall circumferential strain value variation curve.

[0036] Step S108, respectively calculating a first curve fit between the tube pressure value variation curve and the end face radial strain value variation curve, and a second curve fit between the tube pressure value variation curve and the inner wall circumferential strain value variation curve.

[0037] Step S110, evaluating the integrity failure of the cement sheath to be evaluated based on the first curve fit and the second curve fit.

[0038] Figure 2 Schematic diagram of a wellbore simulation system provided according to an embodiment of the present invention. Figure 2 As shown, the wellbore simulation system includes a kettle body 1, a heating outer tube 2, a simulation pipe string 3, a rubber sleeve 4 for simulating the well wall, a kettle body upper cover 5 and a kettle body lower cover 6; it also includes a temperature control system, a pressure control system and a data acquisition system. Specifically, the temperature control system includes a temperature controller 9; the pressure control system includes a first booster pump 7, a second booster pump 8, a first pressure control valve 15 and a second pressure control valve 17; the data acquisition system includes a first strain gauge 10, a second strain gauge 11, a strain gauge 19, a first pressure sensor 14 and a second pressure sensor 16. The device can simulate the temperature and pressure conditions of the cement ring in the well to maintain the cement ring, and at the same time measure the radial strain and circumferential strain of the cement ring generated by the increase of the pressure in the pipe.

[0039] like Figure 2 As shown in the figure, when conducting the experiment, we first analyze and determine the initial pipe pressure P0 and initial downhole temperature T when the target oil and gas well is cemented to form a cement ring. d and initial formation confining pressure P c Then assemble the kettle body lower cover 6, then place the simulated pipe string 3 and rubber sleeve 4 in the kettle body, connect the internal pressure application pipeline 12, connect the confining pressure application pipeline 13 on the side of the kettle body 1, prepare cement slurry and inject it into the annulus formed by the simulated pipe string 3 and rubber sleeve 4. After the cement slurry is injected, assemble the kettle body upper cover 5, set the pressure of the second booster pump 8 to P0 to simulate the initial pipe pressure, and set the pressure of the first booster pump 7 to P c Simulate the initial formation confining pressure and set the temperature of temperature controller 9 to T d Simulate the initial downhole temperature and maintain for 48 hours.

[0040] Figure 3 FIG. 1 is a top view of a strain gauge bonding position provided according to an embodiment of the present invention. Figure 3 As shown, step S104 also includes:

[0041] Step S1041, respectively setting a first strain gauge and a second strain gauge on the upper end surface and the inner wall surface of the cement sheath to be evaluated;

[0042] Step S1042, based on the first strain gauge and the second strain gauge, respectively, obtain the data of the radial strain value of the end face changing with time and the data of the circumferential strain value of the inner wall changing with time.

[0043] Specifically, after the curing is completed, the upper cover 5 of the kettle body is opened, and the first strain gauge 10 is pressed Figure 3The method shown in the figure is applied to the upper end surface of the cement ring 18 to be evaluated, and the second strain gauge 11 is pressed Figure 3 The method shown is fitted to the inner wall of the cement ring 18 to be evaluated, the kettle cover 5 is assembled, and the pressure change in the pipe is adjusted by the second booster pump 8 according to the pressure change plan of the subsequent cementing operation. During the experiment, the radial strain value ε of the end face of the cement ring 18 to be evaluated is monitored by the strain measuring instrument 19 i and the inner wall circumferential strain value ε t .

[0044] The analysis determined that the casing pressure change scheme in the subsequent cementing operation is P0→P1→P2→P3→…→P n , through the second booster pump 8 according to P0→P1→P2→P3→…→P n The pressure change scheme is used to apply the pressure in the casing, and at the same time, the strain value of the first strain gauge 10 during the application and change of the pressure in the casing is recorded by the strain measuring instrument 19 as the radial strain value ε of the end face of the cement sheath to be evaluated. i The strain value of the second strain gauge 11 during the application and change of the pressure in the casing is recorded as the circumferential strain value ε of the inner wall of the cement sheath to be evaluated. t .

[0045] Then the pressure value P in the tube is i Data changing with time, radial strain value of end face ε i Time-varying data and inner wall circumferential strain value ε t The time-varying data are normalized, and the corresponding time-varying curves are drawn respectively. The curve fit is defined to quantitatively analyze the fit between different curves.

[0046] Specifically, the first curve fit includes:

[0047] ψ 1i =[1-(λ 1i -λ 2i )]*100%

[0048] The second curve fit includes:

[0049] ψ 2i =[1-(λ 1i -λ 3i )]*100%

[0050] In the formula, ψ 1i and ψ 2i are the first curve fit and the second curve fit at the i-th moment, respectively, 1i , 2i and λ 3iThey are respectively the ordinate value of the tube internal pressure value change curve corresponding to the i-th moment, the ordinate value of the end face radial strain value change curve, and the ordinate value of the inner wall circumferential strain value change curve.

[0051] Specifically, step S110 also includes the following steps:

[0052] Step S1101, determining whether the first curve fit exceeds a first preset threshold; if yes, the radial mechanical integrity of the cement sheath to be evaluated has not failed; if no, the radial mechanical integrity of the cement sheath to be evaluated has failed;

[0053] For example, the first preset threshold is 90%, if the first curve matching degree ψ of the tube pressure value change curve and the end face radial strain value change curve at a certain moment is 1i >90%, indicating that the radial mechanical integrity of the cement sheath has not failed at this moment; if the first curve of the two curves at a certain moment agrees with each other ψ 1i When it is less than 90%, it indicates that the radial strain generated by the cement sheath can no longer be restored. It is judged that the cement sheath to be evaluated may have undergone plastic deformation or compression failure.

[0054] Step S1102, determining whether the second curve fit exceeds a second preset threshold; if yes, the circumferential mechanical integrity of the cement sheath to be evaluated has not failed; if no, the circumferential mechanical integrity of the cement sheath to be evaluated has failed.

[0055] For example, the second preset threshold is 90%, if the second curve matching degree ψ of the change curve of the pressure value in the tube and the change curve of the circumferential strain value of the inner wall at a certain moment is 2i >90%, indicating that the circumferential mechanical integrity of the cement ring has not failed at this moment; if the second curve of the two curves at a certain moment agrees with each other ψ 2i When it is less than 90%, it indicates that the circumferential strain of the cement sheath can no longer be recovered, and it is judged that the cement sheath to be evaluated may have tensile failure.

[0056] From the above description, it can be seen that the present invention provides a cementing ring integrity failure evaluation method based on strain measurement, which obtains the strain value change of the cement ring through a wellbore simulation system, and judges whether the cement ring integrity has failed according to the strain change of the cement ring, and can judge the mechanical integrity of the cement ring in a specific force direction according to the strain direction.

[0057] Embodiment 2

[0058] The embodiment of the present invention further illustrates the specific process of a cement sheath integrity failure evaluation method based on strain measurement provided by the present invention through a specific embodiment.

[0059] Step 1:

[0060] Establish as Figure 2 The wellbore simulation system is shown.

[0061] Step 2:

[0062] The analysis determined that the initial pipe pressure, initial downhole temperature and initial formation confining pressure of a certain well during cementing to form a cement ring were 40MPa, 60℃ and 60MPa, respectively. During the experiment, the pressure of the second booster pump 8 was set to 40MPa, the pressure of the first booster pump 7 was set to 60MPa, the temperature of the temperature controller 9 was set to 60℃, and the curing was carried out for 48 hours. After the curing was completed, the upper cover 5 of the kettle was opened, and the first strain gauge 10 was pressed Figure 3 The method shown is attached to the upper end face of the cement ring 18 to be evaluated, the second strain gauge 11 is attached to the inner wall surface of the cement ring 18 to be evaluated, and the kettle cover 5 is assembled; the pressure change in the pipe is adjusted by the second booster pump 8 according to the pressure change plan of the subsequent cementing operation, and the radial strain value ε of the end face of the cement ring 18 to be evaluated is monitored by the strain measuring instrument 19 during the experiment i and the inner wall circumferential strain value ε t .

[0063] Step 3:

[0064] The change scheme of casing pressure in a certain well during subsequent cementing operations is analyzed and determined as follows:

[0065] 50MPa→60MPa→70MPa→80MPa→90MPa→100MPa→90MPa→80MPa→70MPa→60MPa→50MPa

[0066] The second booster pump 8 applies the pressure in the pipe according to the above pressure change scheme, and the strain gauge 19 measures the radial strain value ε of the end face of the cement sheath to be evaluated during the pressure application and change process in the casing. i and the inner wall circumferential strain value ε t , the measurement results are shown in Table 1:

[0067] Table 1 Data of cement sheath radial strain and circumferential strain measurement values ​​changing with simulated casing internal pressure

[0068]

[0069]

[0070] Step 4:

[0071] The pressure value P in the tube in Table 1 i The time-varying data and the radial strain value ε of the end surface i The time-varying data are normalized and their time-varying curves are plotted. Figure 4As shown in Table 2, the normalized curve agreement between the pressure inside the pipe and the radial strain of the cement sheath during the change of the pressure inside the pipe is calculated.

[0072] Table 2 The consistency between the normalized value of casing pressure and cement sheath radial strain at different times

[0073] Time(h) Normalized curve fit (%) 1 99.98 2 99.92 3 98.78 4 97.89 5 97.93 6 99.17 7 94.03 8 95.13 9 97.12 10 97.26

[0074] From Table 2 and Figure 4 The minimum value of normalized agreement between the pressure inside the pipe and the radial strain of the cement sheath at different times can be obtained as min =94.03%>90%, so it can be judged that the cement sheath did not produce plastic deformation or compression failure during this pressure change process.

[0075] Step 5:

[0076] The pressure P in the tube in Table 1 i Time-varying data and inner wall circumferential strain value ε t The time-varying data are normalized and their time-varying curves are plotted. Figure 5 As shown in Table 3, the agreement between the normalized curve of the casing pressure and the circumferential strain during the change of the casing pressure is obtained by calculation:

[0077] Table 3 The consistency between the normalized value of casing pressure and cement sheath circumferential strain at different times

[0078] Time(h) Normalized curve fit (%) 1 99.98 2 99.93 3 98.88 4 97.32 5 97.78 6 99.12 7 97.36 8 96.33 9 76.69 10 21.72

[0079] From Table 3 and Figure 5 It can be seen that the circumferential strain remains unchanged after 8 hours, indicating that part of the circumferential strain cannot be recovered after the pressure in the casing is unloaded, further indicating that the cement sheath has undergone circumferential tensile failure during the process of increasing pressure in the casing.

[0080] Embodiment 3

[0081] Figure 6 FIG. 1 is a schematic diagram of a cement sheath integrity failure evaluation system based on strain measurement according to an embodiment of the present invention. Figure 6 As shown, the system includes: a simulation module 10, an acquisition module 20, a generation module 30, a calculation module 40 and an evaluation module 50.

[0082] Specifically, the simulation module 10 is used to place the cement sheath to be evaluated into the wellbore simulation system, initialize the parameters of the wellbore simulation system and maintain the cement sheath to be evaluated;

[0083] The acquisition module 20 is used to adjust the pressure value of the cement sheath to be evaluated after the maintenance based on the wellbore simulation system, and to obtain the end face radial strain value and inner wall circumferential strain value of the cement sheath to be evaluated.

[0084] A generating module 30 is used to normalize the time-varying data of the inner tube pressure value, the end face radial strain value and the inner wall circumferential strain value, and generate an inner tube pressure value variation curve, an end face radial strain value variation curve and an inner wall circumferential strain value variation curve;

[0085] A calculation module 40 is used to calculate a first curve fit between the pressure value change curve in the tube and the radial strain value change curve of the end face, and a second curve fit between the pressure value change curve in the tube and the circumferential strain value change curve of the inner wall;

[0086] The evaluation module 50 is used to evaluate the integrity failure of the cement sheath to be evaluated based on the first curve fit and the second curve fit.

[0087] Specifically, the simulation module 10 is also used for:

[0088] Obtain the initial pipe pressure, initial downhole temperature and initial formation confining pressure when cementing the target oil and gas well to form a cement sheath;

[0089] Set the internal pressure value of the wellbore simulation system to the initial internal pressure, set the simulated temperature of the wellbore simulation system to the initial downhole temperature, and set the external pressure of the wellbore simulation system to the initial formation confining pressure;

[0090] Maintain the cement sheath to be evaluated for a preset time period.

[0091] Specifically, the evaluation module 50 is further used for:

[0092] Determine whether the first curve fit exceeds a first preset threshold; if so, the radial mechanical integrity of the cement sheath to be evaluated has not failed; if not, the radial mechanical integrity of the cement sheath to be evaluated has failed;

[0093] It is determined whether the second curve fit exceeds a second preset threshold; if so, the circumferential mechanical integrity of the cement sheath to be evaluated has not failed; if not, the circumferential mechanical integrity of the cement sheath to be evaluated has failed.

[0094] The present invention further provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method provided in the embodiment of the present invention when executing the computer program.

[0095] The present invention also provides a computer-readable storage medium, which stores computer instructions. When the computer instructions are executed by a processor, the method provided in the embodiment of the present invention is implemented.

[0096] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0097] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A cement sheath integrity failure evaluation method based on strain measurement, characterized in that: include: Placing the cement sheath to be evaluated into a wellbore simulation system, initializing parameters of the wellbore simulation system and maintaining the cement sheath to be evaluated; Based on the change of the pressure value in the pipe of the cement ring to be evaluated after the wellbore simulation system is adjusted and maintained, the change of the radial strain value of the end face of the cement ring to be evaluated and the change of the circumferential strain value of the inner wall with time are obtained; Normalizing the time-varying data of the inner tube pressure value, the end face radial strain value, and the inner wall circumferential strain value, respectively, and generating an inner tube pressure value variation curve, an end face radial strain value variation curve, and an inner wall circumferential strain value variation curve; Calculating respectively a first curve fit between the tube pressure value change curve and the end face radial strain value change curve, and a second curve fit between the tube pressure value change curve and the inner wall circumferential strain value change curve; Based on the first curve fit and the second curve fit, the integrity failure of the cement sheath to be evaluated is evaluated.

2. The method according to claim 1, characterized in that: Initializing parameters of the wellbore simulation system and maintaining the cement sheath to be evaluated include: Obtain the initial pipe pressure, initial downhole temperature and initial formation confining pressure when cementing the target oil and gas well to form a cement sheath; The inner tube pressure value of the wellbore simulation system is set to the initial inner tube pressure, the simulation temperature of the wellbore simulation system is set to the initial downhole temperature, and the outer tube pressure of the wellbore simulation system is set to the initial formation confining pressure; Maintain the cement sheath to be evaluated for a preset time period.

3. The method according to claim 1, characterized in that: Obtaining the end face radial strain value variation data and the inner wall circumferential strain value variation data of the cement sheath to be evaluated over time, including: A first strain gauge and a second strain gauge are respectively arranged on the upper end surface and the inner wall surface of the cement ring to be evaluated; Based on the first strain gauge and the second strain gauge, respectively, the data of the radial strain value of the end face varying with time and the data of the circumferential strain value of the inner wall varying with time are obtained.

4. The method according to claim 1, characterized in that: The first curve fit includes: ψ 1i =[1―(λ 1i ―l 2i )]*100% The second curve fit includes: ψ 2i =[1―(λ 1i ―l 3i )]*100% In the formula, ψ 1i and ψ 2i are the first curve fit degree and the second curve fit degree at the i-th moment, respectively, 1i , 2i and λ 3i They are respectively the ordinate value of the tube internal pressure value change curve, the ordinate value of the end face radial strain value change curve and the ordinate value of the inner wall circumferential strain value change curve corresponding to the i-th moment.

5. The method according to claim 1, characterized in that: Based on the first curve fit and the second curve fit, evaluating the integrity failure of the cement sheath to be evaluated includes: Determine whether the first curve fit exceeds a first preset threshold; if yes, the radial mechanical integrity of the cement sheath to be evaluated has not failed; if no, the radial mechanical integrity of the cement sheath to be evaluated has failed; It is determined whether the second curve fit exceeds a second preset threshold; if so, the circumferential mechanical integrity of the cement sheath to be evaluated has not failed; if not, the circumferential mechanical integrity of the cement sheath to be evaluated has failed.

6. A cement sheath integrity failure evaluation system based on strain measurement, characterized in that: include: simulation module, acquisition module, generation module, calculation module and evaluation module; among them, The simulation module is used to place the cement sheath to be evaluated into the wellbore simulation system, initialize the parameters of the wellbore simulation system and maintain the cement sheath to be evaluated; The acquisition module is used to adjust the pressure value of the cement ring to be evaluated after the wellbore simulation system is maintained and change with time, and at the same time obtain the end face radial strain value and inner wall circumferential strain value of the cement ring to be evaluated. Change with time data; The generating module is used to respectively normalize the time-varying data of the inner tube pressure value, the end face radial strain value and the inner wall circumferential strain value, and generate an inner tube pressure value variation curve, an end face radial strain value variation curve and an inner wall circumferential strain value variation curve; The calculation module is used to respectively calculate a first curve fit between the tube pressure value change curve and the end face radial strain value change curve, and a second curve fit between the tube pressure value change curve and the inner wall circumferential strain value change curve; The evaluation module is used to evaluate the integrity failure of the cement sheath to be evaluated based on the first curve fit and the second curve fit.

7. The system according to claim 6, characterized in that: The simulation module is also used for: Obtain the initial pipe pressure, initial downhole temperature and initial formation confining pressure when cementing the target oil and gas well to form a cement sheath; The inner tube pressure value of the wellbore simulation system is set to the initial inner tube pressure, the simulation temperature of the wellbore simulation system is set to the initial downhole temperature, and the outer tube pressure of the wellbore simulation system is set to the initial formation confining pressure; Maintain the cement sheath to be evaluated for a preset time period.

8. The system according to claim 6, characterized in that: The evaluation module is also used for: Determine whether the first curve fit exceeds a first preset threshold; if yes, the radial mechanical integrity of the cement sheath to be evaluated has not failed; if no, the radial mechanical integrity of the cement sheath to be evaluated has failed; Determining whether the second curve fit exceeds a second preset threshold; If yes, the circumferential mechanical integrity of the cement sheath to be evaluated has not failed; If not, the circumferential mechanical integrity of the cement sheath to be evaluated fails.

9. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 5 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and when the computer instructions are executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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