A method for drawing the performance envelope curve of a downhole safety valve

Abstract

The present invention discloses a method for drawing the performance envelope curve of a downhole safety valve. This method is mainly based on the API 14A and GB / T 28259-2012 standards, and specifically includes: establishing a three-dimensional model of the downhole safety valve and measuring the material performance parameters of all components; conducting a failure mode, effects, and criticality analysis on all components of the downhole safety valve to obtain the main failed components that affect the performance of the downhole safety valve; performing a working principle and force analysis to obtain all components of the downhole safety valve that bear loads; establishing a simulation model of the downhole safety valve and determining the failure points under extreme conditions; drawing the performance envelope curve of the downhole safety valve; and verifying and correcting the performance envelope curve of the downhole safety valve through tests. The method proposed by the present invention can effectively guide the drawing of the performance envelope curve of the downhole safety valve, accurately characterize the application limit of the downhole safety valve under extreme conditions, provide an effective basis for the application of downhole safety valves in deep wells, ultra-deep wells, deep water wells, and gas storage reservoirs, and meet their well completion operation requirements.

Description

Technical Field

[0001] The present invention relates to the fields of well completion and production operations for deep wells, ultra-deep wells, deep water wells, gas storage caverns, etc., and particularly relates to a method for drawing the performance envelope curve of a downhole safety valve. Background Art

[0002] With the increasing scope of oilfield exploration and development, the exploration and development of oil and gas reservoirs in deep wells, ultra-deep wells, and deep water wells have become an important task. Due to the particularity and complexity of the downhole environment, the safe and stable operation of downhole operation tools has become crucial. A downhole safety valve is an important operation tool installed in the downhole of oil and gas wells and gas storage caverns. When abnormal conditions occur during production, it can be urgently closed to prevent blowout accidents and ensure the production safety of oil and gas wells.

[0003] Currently, relevant oil companies at home and abroad have not yet established a unified and complete standardized system for the performance evaluation of downhole safety valves, which brings many difficulties to the design, selection, and operation of downhole safety valves. Therefore, it is urgent to carry out research on the performance envelope curve of downhole safety valves to accurately characterize the application limits of downhole safety valves under extreme conditions.

[0004] According to API 14A standard, each downhole safety valve must undergo four strict tests, including internal pressure resistance, external collapse resistance, tensile strength, and compression resistance. According to GB / T 28259-2012 standard, the load conditions represented by the four quadrants of the performance envelope curve of the downhole safety valve, from the first quadrant to the fourth quadrant, in accordance with the quadrant regulations of the Cartesian rectangular coordinate system, are: internal pressure and axial tension of the downhole safety valve, internal pressure and axial pressure of the downhole safety valve, external pressure and axial pressure of the downhole safety valve, and external pressure and axial tension of the downhole safety valve, and the load-bearing limits of the downhole safety valve under reasonable internal and external pressures and tensile and compressive forces are represented in the form of a curve diagram; the positive half-axis of the X-axis represents the tensile load, the negative half-axis of the X-axis represents the compressive load, the positive half-axis of the Y-axis represents the internal pressure, and the negative half-axis of the Y-axis represents the external pressure; at least one failure point should be tested in each quadrant.

[0005] According to API 14A and GB / T 28259-2012 standards, by conducting separate and combined load tests on the downhole safety valve for internal pressure resistance, external collapse resistance, tensile strength, and compression resistance, the application limits of the downhole safety valve under extreme conditions can be accurately characterized, the safe working area and failure area of the downhole safety valve can be predicted, and thus the boundary envelope line of the downhole safety valve, that is, the performance envelope curve of the downhole safety valve, can be determined. The performance envelope curve of the downhole safety valve can provide the safe operation area of the downhole safety valve, judge the working state of the downhole safety valve on-site, and effectively guide the selection of the downhole safety valve, and determine the ultimate load that the downhole safety valve can withstand under various complex conditions, which is of great significance for the actual application of the downhole safety valve.

[0006] To better guide the application of downhole safety valves in the fields of deep wells, ultra-deep wells, deep water wells, and gas storage reservoirs, to conduct a safety assessment of the working state of downhole safety valves in real time, accurately judge their working state, determine whether the downhole safety valves are within the safe operation range, and avoid a series of safety accidents caused by the failure of downhole safety valves, it is urgent to invent a method for drawing the performance envelope curve of downhole safety valves. Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for drawing the performance envelope curve of downhole safety valves, so as to solve the technical problem of drawing the performance envelope curve of downhole safety valves under complex service conditions. This method is simple to operate and is fully applicable to different service conditions and different types of downhole safety valves.

[0008] To achieve the above purpose, a method for drawing the performance envelope curve of downhole safety valves according to the present invention is characterized in that the method mainly draws the performance envelope curve of downhole safety valves according to API 14A and GB / T 28259-2012 standards. Specifically: (1) For the four quadrants of the performance envelope curve of the downhole safety valve, the load conditions represented in sequence from the first quadrant to the fourth quadrant according to the quadrant regulations of the Cartesian rectangular coordinate system are: the internal pressure and axial tension of the downhole safety valve, the internal pressure and axial pressure of the downhole safety valve, the external pressure and axial pressure of the downhole safety valve, and the external pressure and axial tension of the downhole safety valve, and the load-bearing limit of the downhole safety valve under reasonable internal and external pressures and tensile and compressive forces is represented in the form of a curve diagram; (2) The positive half-axis of the X-axis represents the tensile load, the negative half-axis of the X-axis represents the compressive load, the positive half-axis of the Y-axis represents the internal pressure, and the negative half-axis of the Y-axis represents the external pressure; (3) At least one failure point should be tested in each quadrant.

[0009] The specific technical solutions adopted are as follows:

[0010] A method for drawing the performance envelope curve of downhole safety valves is characterized in that the method includes the following steps:

[0011] S101: According to the design drawings of the downhole safety valve components or the geometric dimensions of the measured downhole safety valve components, use 3D modeling software to establish 3D models of all components of the downhole safety valve. Prepare standard tensile / compressive specimens of the materials of all components of the downhole safety valve, ensure that the specimen surfaces are smooth and have no obvious defects. Select a tensile / compressive testing machine and ensure its calibration and normal operation. Install specimen fixtures to ensure that the specimens can be correctly clamped. According to the material characteristics of the components and the test requirements, set the test load loading method. Correctly install the specimens on the testing machine to ensure that the specimen axes are consistent with the loading direction. Tighten the specimen fixtures to prevent the specimens from sliding or falling off during the test. Before the formal loading, perform pre-loading to eliminate the gap between the specimens and the fixtures. According to the test requirements, terminate the test when the specimens are damaged. Process and analyze the test data, and calculate the elastic modulus, tensile / compressive strength of the materials of the downhole safety valve components;

[0012] S102: Failure mode, effects, and criticality analysis. Analyze all possible failure modes, failure causes, and failure consequences of all components of the downhole safety valve to obtain the main failed components that affect the performance of the downhole safety valve;

[0013] S103: Working principle and force analysis. According to the working principle of the downhole safety valve and various production conditions, analyze the force conditions when the downhole safety valve is working to obtain all components of the downhole safety valve that bear loads;

[0014] S104: Establishment of the downhole safety valve simulation model and determination of the failure points under extreme conditions. Simplify the 3D model of the downhole safety valve according to the main failed components that affect the performance of the downhole safety valve and all components of the downhole safety valve that bear loads to obtain the simulation model; Use numerical simulation methods to obtain the failure points of the downhole safety valve under extreme conditions;

[0015] S105: Plot the performance envelope curve of the downhole safety valve. According to API 14A and GB / T 28259-2012 standards, combined with the failure points of the downhole safety valve under extreme conditions, plot the performance envelope curve of the downhole safety valve;

[0016] S106: Experimental verification and correction of the performance envelope curve of the downhole safety valve. Conduct separate and combined load tests on the downhole safety valve, and verify and correct the performance envelope curve of the downhole safety valve according to the test results.

[0017] Further, in the step S102, the steps of failure mode, effects, and criticality analysis are as follows:

[0018] S201: Conduct failure mode, effects, and criticality analysis on all components of the downhole safety valve to determine the boundaries and levels of the analysis;

[0019] S202: Identify possible failure modes by understanding the functions, structures, and working principles of downhole safety valves.

[0020] S203: Evaluate the direct and indirect impacts of each failure mode on downhole safety valves, including impacts on functions, performances, safety, reliability, etc.

[0021] S204: Evaluate the hazard levels of each failure mode based on the severity, occurrence probability, and detection difficulty of the failure impacts.

[0022] S205: Based on the failure mode, impact, and hazard analysis results, obtain the main failed components affecting the performance of downhole safety valves.

[0023] Furthermore, in step S103, the methods for working principle and force analysis are as follows:

[0024] S301: The working principle of the downhole safety valve is based on the balance relationship between the elastic force of the spring and the pressure in the wellbore. When the wellhead pressure exceeds the set value, the spring will be compressed, causing the valve core to move downward to close the wellhead. When the wellhead pressure returns to the normal range, the spring will return to its original state, causing the valve core to move upward to open the wellhead.

[0025] S302: Use static and dynamic analysis methods to conduct a force analysis on the downhole safety valve under extreme conditions to obtain all the components of the downhole safety valve that bear loads.

[0026] Furthermore, in step S104, the method steps for establishing the downhole safety valve simulation model and determining the failure points under extreme conditions are as follows:

[0027] S401: Establish a simplified downhole safety valve simulation model based on the main failed components affecting the performance of the downhole safety valve and all the components of the downhole safety valve that bear loads.

[0028] S402: Set the material property parameters of the downhole safety valve simulation model according to the material tensile / compression test results.

[0029] S403: Conduct mesh division on the downhole safety valve simulation model.

[0030] S404: Determine the boundary conditions and load application of the downhole safety valve simulation model according to the working principle and force analysis results of the downhole safety valve.

[0031] S405: Set a fixed constraint on the lower end face of the lower sub and establish a coupling constraint on the upper end face. Apply a tensile load to the downhole safety valve simulation model. When the internal pressure / external pressure is zero at the same time, calculate the ultimate tensile load F when the downhole safety valve simulation model fails. T-Max , denoted as A(FT-Max , 0);

[0032] S406: Set a fixed constraint on the lower end face of the lower sub, establish a coupling constraint on the upper end face, apply a compressive load to the downhole safety valve simulation model. When the internal pressure / external pressure is zero simultaneously, calculate the ultimate compressive load F when the downhole safety valve simulation model fails. C-Max , denoted as C(F C-Max , 0);

[0033] S407: Since the performance envelope curve of the downhole safety valve refers to the curve under 100% rated performance, therefore, the ultimate internal pressure is the rated internal pressure P I-Max , denoted as B(0, P I-Max );

[0034] S408: Set fixed constraints on the end faces of the upper sub and the lower sub, only apply external pressure to the downhole safety valve simulation model, keep the axial load zero, and calculate the ultimate external pressure P when the downhole safety valve simulation model fails. E-Max , denoted as D(0, P E-Max );

[0035] S409: When the downhole safety valve simulation model simultaneously bears tensile load and internal pressure load, through numerical simulation method, calculate the failure points between A and B, denoted as A1(F T1 , P I1 ), A2(F T2 , P I2 );

[0036] S410: When the downhole safety valve simulation model simultaneously bears compressive load and internal pressure load, through numerical simulation method, calculate the failure points between B and C, denoted as B1(F C3 , P I3 ), B2(F C4 , P I4 );

[0037] S411: When the downhole safety valve simulation model simultaneously bears compressive load and external pressure load, through numerical simulation method, calculate the failure points between C and D, denoted as C1(F C5 , P E5 ), C2(F C6 , P E6 ), C3(F C7 , P E7 );

[0038] S412: When the downhole safety valve simulation model simultaneously bears tensile load and external pressure load, through numerical simulation method, calculate the failure points between D and A, denoted as D1(F T8 , P E8)、D2(F T9 ,P E9 )、D3(F T10 ,P E10 )、D4(F T11 ,P E11 )。

[0039] Furthermore, in the step S105, the method steps for drawing the performance envelope curve of the downhole safety valve are as follows:

[0040] S501: For the four quadrants of the performance envelope curve of the downhole safety valve, the load conditions represented in sequence from the first quadrant to the fourth quadrant according to the quadrant regulations of the Cartesian rectangular coordinate system are: the internal pressure and axial tension of the downhole safety valve, the internal pressure and axial pressure of the downhole safety valve, the external pressure and axial pressure of the downhole safety valve, and the external pressure and axial tension of the downhole safety valve, and the bearing limit of the downhole safety valve under reasonable internal and external pressures and tensile and compressive forces is represented in the form of a curve diagram; the positive half-axis of the X-axis represents the tensile load, the negative half-axis of the X-axis represents the compressive load, the positive half-axis of the Y-axis represents the internal pressure, and the negative half-axis of the Y-axis represents the external pressure; at least one failure point should be tested in each quadrant;

[0041] S502: Divide the X-axis into intervals at 500 KN intervals and the Y-axis into intervals at 50 MPa intervals in the rectangular coordinate system. Determine the maximum tensile / compressive load and the maximum internal / external pressure load according to the calculated failure points, and draw the failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3, D4 of the performance envelope curve of the downhole safety valve;

[0042] S503: Connect the failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3, D4 in a counterclockwise order with straight lines to obtain the performance envelope curve of the downhole safety valve. The area inside the envelope curve belongs to the safe operating area of the downhole safety valve, the area outside the envelope curve belongs to the non-safe operating area of the downhole safety valve, and the points on the envelope curve belong to the critical working state of the downhole safety valve.

[0043] Furthermore, in the step S106, the method steps for experimental verification and correction of the performance envelope curve of the downhole safety valve are as follows:

[0044] S601: Install the physical test prototype of the downhole safety valve on the downhole safety valve performance test device and ensure that its connection and sealing are good; check whether the equipment pressure gauges, recorders, pipelines, valves, pumps, oil cylinders, motors, etc. are in normal working conditions;

[0045] S602: Under the premise that the inside of the downhole safety valve does not bear any pressure, open and close the downhole safety valve 5 times in a cycle to check and verify the operating performance of the downhole safety valve, and record the hydraulic control pressure for the first 5 cycles of opening and closing before the test;

[0046] S603: Set a safety factor for the limit values of the boundary envelope curve of the performance envelope curve of the downhole safety valve drawn by simulation, and conduct separate and combined load tests for internal pressure resistance, external extrusion resistance, tensile resistance, and compressive resistance. Open and close the downhole safety valve under the load conditions at failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3, and D4, and apply the load to the downhole safety valve in a gradually decreasing manner, and record the hydraulic control pressure for opening and closing the downhole safety valve under each load application;

[0047] S604: Once again, under the premise that the inside of the downhole safety valve does not bear any pressure, open and close the downhole safety valve 5 times in a cycle to determine whether the performance of the downhole safety valve is affected when conducting separate and combined load tests for internal pressure resistance, external extrusion resistance, tensile resistance, and compressive resistance, and record the hydraulic control pressure for the 5 cycles of opening and closing after the test. If the difference between the average values of the hydraulic control pressures obtained before and after the test is within ±10% or 0.7 MPa (±100 psi), the downhole safety valve passes the test;

[0048] S605: Modify the performance envelope curve of the downhole safety valve obtained by simulation through the ultimate load of the downhole safety valve obtained from separate and combined load tests.

[0049] The beneficial effects of the present invention are as follows:

[0050] (1) Conduct research on the performance envelope curve of the downhole safety valve, realize the establishment of the performance envelope curve of the downhole safety valve under complex working conditions, and can accurately characterize the application boundary of the downhole safety valve under extreme working conditions, providing an effective basis for the application of the downhole safety valve;

[0051] (2) Solve the problem that there is no unified and complete standardized system for the performance evaluation of downhole safety valves in domestic and foreign oil companies at present, provide convenience for the design, selection, and operation of downhole safety valves, and can effectively guide the optimization design, selection, and replacement of downhole safety valves in the fields of deep wells, ultra-deep wells, and deep water wells, providing an effective basis for the application of downhole safety valves;

[0052] (3) Field workers can judge whether the downhole safety valve is safe through the envelope curve to ensure effective operation; designers can improve the design and selection of the structure and materials of the downhole safety valve through the envelope curve, replace the corresponding components according to the stress conditions at the critical points of the envelope curve, and select materials with appropriate strength for the corresponding components, which can reduce the operation cost and effectively improve the economic benefits;

[0053] (4) It can conduct safety evaluations on the working status of downhole safety valves in real time, accurately judge their working status, and take timely measures to prevent a series of safety accidents such as blowouts. Description of the Drawings

[0054] Figure 1 It is a schematic diagram of the performance envelope curve of a downhole safety valve determined by the present invention;

[0055] Figure 2 It is a schematic diagram of the flow chart of the drawing method of the present invention. Detailed Embodiments

[0056] The present invention will be described in detail below with reference to the drawings and embodiments.

[0057] Referring to the drawings, the present invention proposes a method for drawing the performance envelope curve of a downhole safety valve, and the method mainly includes the following steps:

[0058] S1: Establish a three-dimensional model and determine material property parameters. According to the geometric dimensions of the components of the downhole safety valve, establish its overall three-dimensional model; conduct tensile / compression tests on the materials of the components of the downhole safety valve to obtain the material property parameters of the components, specifically including:

[0059] S11: According to the design drawings of the components of the downhole safety valve or the measured geometric dimensions of the components of the downhole safety valve, use three-dimensional modeling software to establish the three-dimensional models of all components of the downhole safety valve;

[0060] S12: Prepare standard tensile / compression specimens for the materials of all components of the downhole safety valve to ensure that the surfaces of the specimens are smooth and there are no obvious defects;

[0061] S13: Select a tensile / compression testing machine, ensure its calibration and normal operation, install specimen fixtures to ensure that the specimens can be correctly clamped;

[0062] S14: Set the test load loading method according to the material characteristics of the components and the test requirements;

[0063] S15: Correctly install the specimens on the testing machine to ensure that the specimen axes are consistent with the loading direction, and tighten the specimen fixtures to prevent the specimens from sliding or falling off during the test;

[0064] S16: Before the formal loading, conduct pre-loading to eliminate the gap between the specimens and the fixtures;

[0065] S17: Terminate the test when the specimens are damaged according to the test requirements;

[0066] S18: Process and analyze the test data, and calculate the elastic modulus, tensile / compressive strength of the materials of the components of the downhole safety valve;

[0067] S2: Failure mode, effects, and criticality analysis. Analyze all possible failure modes, causes, and consequences of all components of the downhole safety valve to obtain the main failed components affecting the performance of the downhole safety valve, specifically including:

[0068] S21: Conduct failure mode, effects, and criticality analysis on all components of the downhole safety valve to determine the boundaries and levels of the analysis;

[0069] S22: Identify possible failure modes by understanding the function, structure, and working principle of the downhole safety valve;

[0070] S23: Evaluate the direct and indirect impacts of each failure mode on the downhole safety valve, including impacts on functions, performance, safety, reliability, etc.;

[0071] S24: Evaluate the criticality level of each failure mode based on the severity, occurrence probability, and detection difficulty of the failure impact;

[0072] S25: Obtain the main failed components affecting the performance of the downhole safety valve based on the results of the failure mode, effects, and criticality analysis;

[0073] S3: Working principle and force analysis. Analyze the force conditions during the operation of the downhole safety valve according to its working principle and various production conditions to obtain all components of the downhole safety valve that bear loads, specifically including:

[0074] S31: The working principle of the downhole safety valve is based on the balance between the elastic force of the spring and the pressure in the wellbore. When the wellhead pressure exceeds the set value, the spring will be compressed, causing the valve core to move downward and close the wellhead. When the wellhead pressure returns to the normal range, the spring will return to its original state, causing the valve core to move upward and open the wellhead;

[0075] S32: Use static and dynamic analysis methods to conduct force analysis on the downhole safety valve under extreme conditions to obtain all components of the downhole safety valve that bear loads;

[0076] S4: Establish a simulation model of the downhole safety valve and determine the failure points under extreme conditions. Simplify the 3D model of the downhole safety valve according to the main failed components affecting its performance and all components that bear loads of the downhole safety valve to obtain a simulation model. Use numerical simulation methods to obtain the failure points of the downhole safety valve under extreme conditions, specifically including:

[0077] S41: Establish a simplified simulation model of the downhole safety valve according to the main failed components affecting its performance and all components that bear loads of the downhole safety valve;

[0078] S42: Set the material property parameters of the downhole safety valve simulation model according to the results of the material tensile / compression test;

[0079] S43: Mesh the downhole safety valve simulation model;

[0080] S44: Determine the boundary conditions and load application of the downhole safety valve simulation model according to the working principle and force analysis results of the downhole safety valve;

[0081] S45: Set a fixed constraint on the lower end face of the lower sub, establish a coupling constraint on the upper end face, apply a tensile load to the downhole safety valve simulation model, and when the internal pressure / external pressure is zero at the same time, calculate the ultimate tensile load F at which the downhole safety valve simulation model fails T-Max , denoted as A(F T-Max , 0);

[0082] S46: Set a fixed constraint on the lower end face of the lower sub, establish a coupling constraint on the upper end face, apply a compression load to the downhole safety valve simulation model, and when the internal pressure / external pressure is zero at the same time, calculate the ultimate compression load F at which the downhole safety valve simulation model fails C-Max , denoted as C(F C-Max , 0);

[0083] S47: Since the performance envelope curve of the downhole safety valve refers to the curve under 100% rated performance, therefore, the ultimate internal pressure is the rated internal pressure P I-Max , denoted as B(0, P I-Max );

[0084] S48: Set fixed constraints on the upper and lower sub end faces, only apply an external pressure to the downhole safety valve simulation model, keep the axial load zero, and calculate the ultimate external pressure P at which the downhole safety valve simulation model fails E-Max , denoted as D(0, P E-Max );

[0085] S49: When the downhole safety valve simulation model bears both tensile load and internal pressure load at the same time, through numerical simulation method, calculate the failure points between A and B, denoted as A1(F T1 , P I1 ), A2(F T2 , P I2 );

[0086] S410: When the downhole safety valve simulation model bears both compression load and internal pressure load at the same time, through numerical simulation method, calculate the failure points between B and C, denoted as B1(F C3 , P I3 ), B2(F C4 , P I4 );

[0087] S411: When the downhole safety valve simulation model is simultaneously subjected to compressive load and external pressure load, the failure points between C and D are calculated through numerical simulation method and denoted as C1(F C5 , P E5 ), C2(F C6 , P E6 ), C3(F C7 , P E7 );

[0088] S412: When the downhole safety valve simulation model is simultaneously subjected to tensile load and external pressure load, the failure points between D and A are calculated through numerical simulation method and denoted as D1(F T8 , P E8 ), D2(F T9 , P E9 ), D3(F T10 , P E10 ), D4(F T11 , P E11 );

[0089] S5: Drawing the performance envelope curve of the downhole safety valve. According to API 14A and GB / T 28259-2012 standards, combining with the failure points of the downhole safety valve under extreme working conditions, draw the performance envelope curve of the downhole safety valve, specifically including:

[0090] S51: The four quadrants of the performance envelope curve of the downhole safety valve. The load conditions represented in sequence from the first quadrant to the fourth quadrant according to the quadrant regulations of the Cartesian rectangular coordinate system are: the internal pressure and axial tension of the downhole safety valve, the internal pressure and axial pressure of the downhole safety valve, the external pressure and axial pressure of the downhole safety valve, the external pressure and axial tension of the downhole safety valve, and the bearing limit of the downhole safety valve under reasonable internal and external pressures and tensile and compressive forces is represented in the form of a curve diagram; the positive half-axis of the X-axis represents the tensile load, the negative half-axis of the X-axis represents the compressive load, the positive half-axis of the Y-axis represents the internal pressure, and the negative half-axis of the Y-axis represents the external pressure; at least one failure point should be tested in each quadrant;

[0091] S52: Divide the X-axis into intervals at 500 KN intervals and the Y-axis into intervals at 50 MPa intervals in the rectangular coordinate system. Determine the maximum tensile / compressive load and the maximum internal / external pressure load according to the calculated failure points, and draw the failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3, D4 of the performance envelope curve of the downhole safety valve;

[0092] S53: Connect the failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3, D4 in a counterclockwise straight line in sequence to obtain the performance envelope curve of the downhole safety valve. The area inside the envelope curve belongs to the safe operation area of the downhole safety valve, the area outside the envelope curve belongs to the non-safe operation area of the downhole safety valve, and the points on the envelope curve belong to the critical working state of the downhole safety valve;

[0093] S6: Experimental verification and correction of the performance envelope curve of the downhole safety valve. Conduct separate and combined load tests on the downhole safety valve, and verify and correct the performance envelope curve of the downhole safety valve according to the test results. Specifically, it includes:

[0094] S61: Install the physical test prototype of the downhole safety valve on the downhole safety valve performance test device and ensure good connection and sealing; check whether the equipment pressure gauges, recorders, pipelines, valves, pumps, oil cylinders, motors, etc. are in normal working conditions;

[0095] S62: On the premise that there is no pressure inside the downhole safety valve, open and close the downhole safety valve 5 times in a cycle, check and verify the operating performance of the downhole safety valve, and record the hydraulic control pressure for the first 5 cycles of opening and closing before the test;

[0096] S63: Set safety factors for the limit values of the boundary envelope line of the performance envelope curve of the downhole safety valve drawn by simulation, and conduct separate and combined load tests for internal pressure resistance, external extrusion resistance, tensile resistance, and compressive resistance. Open and close the downhole safety valve under the load conditions of the failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3, D4, and apply load to the downhole safety valve in a gradually decreasing manner, and record the hydraulic control pressure for opening and closing the downhole safety valve under each load application;

[0097] S64: Open and close the downhole safety valve 5 times in a cycle again on the premise that there is no pressure inside the downhole safety valve to determine whether the performance of the downhole safety valve is affected during the separate and combined load tests for internal pressure resistance, external extrusion resistance, tensile resistance, and compressive resistance, and record the hydraulic control pressure for the last 5 cycles of opening and closing after the test. If the average value of the hydraulic control pressure obtained before and after the test differs within ±10% or 0.7 MPa (±100 psi), the downhole safety valve passes the test;

[0098] S65: Correct the performance envelope curve of the downhole safety valve obtained by simulation through the ultimate load of the downhole safety valve obtained from the separate and combined load tests.

[0099] In summary, the present invention discloses a method for drawing the performance envelope curve of a downhole safety valve; this method mainly follows the API 14A and GB / T 28259-2012 standards, and specifically includes: establishing a three-dimensional model of the downhole safety valve and measuring the material performance parameters of all components; conducting a failure mode, effects, and criticality analysis on all components of the downhole safety valve to obtain the main failed components affecting the performance of the downhole safety valve; conducting a working principle and force analysis to obtain all components of the downhole safety valve that bear loads; establishing a simulation model of the downhole safety valve and determining the failure points under extreme conditions; drawing the performance envelope curve of the downhole safety valve; testing and verifying and correcting the performance envelope curve of the downhole safety valve. The method proposed by the present invention can effectively guide the drawing of the performance envelope curve of the downhole safety valve, accurately characterize the application limit of the downhole safety valve under extreme conditions, provide an effective basis for the application of downhole safety valves in deep wells, ultra-deep wells, deep water wells, and gas storage reservoirs, and meet their well completion operation requirements.

[0100] At this point, those skilled in the art will recognize that although the embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived from the disclosed content of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all these other variations or modifications.

Claims

1. A method for drawing a performance envelope curve of a downhole safety valve, characterized in that: The method comprises the following steps: S101: According to the design drawings of downhole safety valve parts or the measured geometric dimensions of downhole safety valve parts, use 3D modeling software to establish 3D models of all parts of the downhole safety valve, prepare standard tensile / compression specimens of all parts of the downhole safety valve, ensure that the surface of the specimen is smooth and has no obvious defects, select a tensile / compression testing machine, and ensure its calibration and normal operation, install the specimen fixture, ensure that the specimen can be clamped correctly, set the test load loading method according to the material characteristics of the parts and test requirements, correctly install the specimen on the testing machine, ensure that the axis of the specimen is consistent with the loading direction, tighten the specimen fixture to prevent the specimen from sliding or falling off during the test, preload before formal loading to eliminate the gap between the specimen and the fixture, terminate the test when the specimen is damaged according to the test requirements, process and analyze the test data, and calculate the elastic modulus and tensile / compressive strength of the downhole safety valve parts material; S102: Failure mode, impact and criticality analysis: analyze all possible failure modes, causes and consequences of all components of the downhole safety valve to obtain the main failure components that affect the performance of the downhole safety valve; S103: Working principle and stress analysis: According to the working principle of the downhole safety valve and various production conditions, the stress of the downhole safety valve during operation is analyzed to obtain all the load-bearing parts of the downhole safety valve; S104: Establishing a simulation model of the downhole safety valve and determining the failure point under extreme working conditions. According to the main failure components that affect the performance of the downhole safety valve and all the components of the downhole safety valve that bear the load, simplify the three-dimensional model of the downhole safety valve to obtain a simulation model; using a numerical simulation method, obtain the failure point of the downhole safety valve under extreme working conditions; S105: Draw the performance envelope curve of the downhole safety valve. According to API 14A and GB / T 28259-2012 standards, combined with the failure point of the downhole safety valve under extreme working conditions, draw the performance envelope curve of the downhole safety valve; S106: Test verification and correction of downhole safety valve performance envelope curve. Perform individual and combined load tests on downhole safety valves, and verify and correct the downhole safety valve performance envelope curve based on the test results.

2. A method for drawing a downhole safety valve performance envelope curve according to claim 1, characterized in that: In step S102, the steps of failure mode, impact and criticality analysis are as follows: S201: Analyze the failure modes, impacts and criticality of all components of downhole safety valves and determine the boundaries and levels of analysis; S202: Identify possible failure modes by understanding the function, structure and working principle of downhole safety valves; S203: Evaluate the direct and indirect impact of each failure mode on the downhole safety valve, including the impact on function, performance, safety, reliability, etc.; S204: Evaluate the degree of criticality of each failure mode based on the severity, probability of occurrence and difficulty of detection of the failure; S205: According to the failure mode, impact and criticality analysis results, the main failure components that affect the performance of the downhole safety valve are obtained.

3. A method for drawing a downhole safety valve performance envelope curve according to claim 1, characterized in that: In step S103, the working principle and force analysis method are as follows: S301: The working principle of the downhole safety valve is based on the balance between the elastic force of the spring and the pressure in the wellbore; when the wellhead pressure exceeds the set value, the spring will be compressed, so that the valve core moves downward and closes the wellhead; when the wellhead pressure returns to the normal range, the spring will return to its original state, so that the valve core moves upward and opens the wellhead; S302: Using static and dynamic analysis methods, perform stress analysis on the downhole safety valve under extreme working conditions to obtain all load-bearing components of the downhole safety valve.

4. A method for drawing a downhole safety valve performance envelope curve according to claim 1, characterized in that: In step S104, the method steps for establishing the downhole safety valve simulation model and determining the failure point under extreme working conditions are as follows: S401: Establish a simplified simulation model of the downhole safety valve based on the main failure components that affect the performance of the downhole safety valve and all the components of the downhole safety valve that bear the load; S402: setting material property parameters of the downhole safety valve simulation model according to the material tensile / compression test results; S403: Meshing the downhole safety valve simulation model; S404: Determine the boundary conditions and load application of the downhole safety valve simulation model according to the downhole safety valve working principle and force analysis results; S405: Set a fixed constraint on the lower end face of the lower joint, establish a coupling constraint on the upper end face, apply a tensile load to the downhole safety valve simulation model, and calculate the ultimate tensile load F when the downhole safety valve simulation model fails when the internal pressure / external pressure is zero at the same time. T-Max , denoted as A(F T-Max , 0); S406: Set a fixed constraint on the lower end face of the lower joint, establish a coupling constraint on the upper end face, apply a compressive load to the downhole safety valve simulation model, and calculate the ultimate compressive load F when the downhole safety valve simulation model fails when the internal pressure / external pressure is zero at the same time. C-Max , denoted as C(F C-Max , 0); S407: Since the performance envelope curve of the downhole safety valve refers to the curve at 100% rated performance, the ultimate internal pressure is the rated internal pressure P I-Max , denoted as B(0,P I-Max ); S408: Set fixed constraints on the upper joint and the lower joint end faces, apply external pressure only to the downhole safety valve simulation model, keep the axial load at zero, and calculate the limit external pressure P when the downhole safety valve simulation model fails. E-Max , denoted as D(0,P E-Max ); S409: When the downhole safety valve simulation model is subjected to tensile load and internal pressure load at the same time, the failure point between A and B is calculated by numerical simulation method and recorded as A1(F T1 , P I1 )、A2(F T2 , P I2 ); S410: When the downhole safety valve simulation model is subjected to compression load and internal pressure load at the same time, the failure point between B and C is calculated by numerical simulation method and recorded as B1(F C3 , P I3 )、B2(F C4 , P I4 ); S411: When the downhole safety valve simulation model is subjected to compression load and external pressure load at the same time, the failure point between C and D is calculated by numerical simulation method and recorded as C1(F C5 , P E5 )、C2(F C6 , P E6 )、C3(F C7 , P E7 ); S412: When the downhole safety valve simulation model is subjected to tensile load and external pressure load at the same time, the failure point between D and A is calculated by numerical simulation method and recorded as D1(F T8 , P E8 )、D2(F T9 , P E9 )、D3(F T10 , P E10 )、D4(F T11 , P E11 ).

5. A method for drawing a downhole safety valve performance envelope curve according to claim 1, characterized in that: In step S105, the method steps for drawing the downhole safety valve performance envelope curve are as follows: S501: The four quadrants of the performance envelope curve of the downhole safety valve, from the first quadrant to the fourth quadrant, represent the load conditions in accordance with the quadrant regulations of the Cartesian rectangular coordinate system: the internal pressure and axial tension of the downhole safety valve, the internal pressure and axial pressure of the downhole safety valve, the external pressure and axial pressure of the downhole safety valve, and the external pressure and axial tension of the downhole safety valve, and the bearing limit of the downhole safety valve under reasonable internal and external pressures and tensile pressures is represented by a curve diagram; the positive half axis of the X axis represents the tensile load, the negative half axis of the X axis represents the compressive load, the positive half axis of the Y axis represents the internal pressure, and the negative half axis of the Y axis represents the external pressure; at least one failure point should be tested in each quadrant; S502: In a rectangular coordinate system, the X-axis is divided into intervals of 500KN and the Y-axis is divided into intervals of 50MPa, and the maximum tensile / compressive load and the maximum internal pressure / external pressure load are determined according to the calculated failure points, and the failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3, and D4 of the downhole safety valve performance envelope curve are drawn; S503: Use a straight line to connect the failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3, and D4 in a counterclockwise direction to obtain the performance envelope curve of the downhole safety valve. The area inside the envelope curve belongs to the safe operating area of ​​the downhole safety valve, the area outside the envelope curve belongs to the unsafe operating area of ​​the downhole safety valve, and the area on the envelope curve belongs to the critical working state of the downhole safety valve.

6. A method for drawing a downhole safety valve performance envelope curve according to claim 1, characterized in that: In step S106, the method steps for testing and verifying and correcting the downhole safety valve performance envelope curve are as follows: S601: Install the downhole safety valve physical test prototype on the downhole safety valve performance test device and ensure that its connection and sealing are in good condition; check whether the equipment pressure gauge, recorder, pipeline, valve, pump, cylinder, motor, etc. are in normal working condition; S602: On the premise that the downhole safety valve is not under any pressure, open and close the downhole safety valve 5 times in a cycle to check and verify the operating performance of the downhole safety valve, and record the hydraulic control pressure of the opening and closing cycles before the test for 5 times; S603: setting a safety factor for the limit value of the boundary envelope of the downhole safety valve performance envelope curve drawn by simulation, and conducting individual and combined load tests of internal pressure resistance, external squeeze resistance, tension resistance and compression resistance. The downhole safety valve is opened and closed under the load conditions of failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3 and D4, and the load is applied to the downhole safety valve in a step-by-step manner, and the hydraulic control pressure for opening and closing the downhole safety valve under each load is recorded; S604: Open and close the downhole safety valve 5 times again under the premise that the downhole safety valve is not subjected to any pressure inside, and determine whether the performance of the downhole safety valve is affected when the downhole safety valve is subjected to the individual and combined load tests of internal pressure resistance, external squeeze resistance, tensile resistance and compression resistance, and record the hydraulic control pressure of the 5 cycles of opening and closing after the test. If the difference between the average value of the hydraulic control pressure obtained before and after the test is within ±10% or 0.7MPa (±100psi), the downhole safety valve passes the test; S605: Downhole safety valve performance envelope curve obtained by simulation of downhole safety valve limit load correction obtained through single and combined load tests.

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