Downhole safety valve performance envelope curve drawing method

Abstract

The invention discloses a subsurface safety valve performance envelope curve drawing method, which is mainly based on API 14A and GB / T28259-2012 standards, and specifically comprises the following steps: establishing a subsurface safety valve three-dimensional model, and measuring material performance parameters of all parts; all parts of the subsurface safety valve are subjected to fault mode, influence and harmfulness analysis, and main failure parts influencing the performance of the subsurface safety valve are obtained; carrying out working principle and stress analysis to obtain all load-bearing parts of the subsurface safety valve; establishing a simulation model of the subsurface safety valve and determining a failure point under an extreme working condition; drawing a subsurface safety valve performance envelope curve; and verifying and correcting the performance envelope curve of the subsurface safety valve. The method provided by the invention can effectively guide the drawing of the performance envelope curve of the subsurface safety valve, accurately characterizes the application limit of the subsurface safety valve under the limit working condition, provides an effective basis for the application of the subsurface safety valve of a deep well, an ultra-deep well, a deep water well and a gas storage, and meets the well completion operation requirements of the subsurface safety valve.

Description

Technical Field

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

[0002] As the scope of oilfield exploration and development expands, the exploration and development of deep wells, ultra-deep wells and deepwater wells has become an important task. Due to the particularity and complexity of the downhole environment, the safe and stable operation of downhole operating tools has become crucial. Downhole safety valves are an important operating tool installed underground in oil and gas wells and gas storage reservoirs. When abnormal conditions occur during production, they can be closed urgently to prevent blowout accidents and ensure the safety of oil and gas well production.

[0003] At present, domestic and foreign oil companies have not yet established a unified and complete standardization system for downhole safety valve performance evaluation, 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 limit of downhole safety valves under extreme working conditions.

[0004] According to API 14A standard, each downhole safety valve must undergo four rigorous tests, including resistance to internal pressure, external squeeze, tension and compression. According to GB / T 28259-2012 standard, the four quadrants of the downhole safety valve performance envelope curve, from the first quadrant to the fourth quadrant, represent the load conditions in accordance with the quadrant regulations of the Cartesian rectangular coordinate system: downhole safety valve internal pressure and axial tension, downhole safety valve internal pressure and axial pressure, downhole safety valve external pressure and axial pressure, downhole safety valve external pressure and axial tension, and the downhole safety valve is graphically represented in the form of a curve to indicate the bearing limit of the downhole safety valve under reasonable internal and external pressures and tension; 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 downhole safety valves for internal pressure resistance, external squeeze resistance, tensile resistance and compression resistance, the application limit of downhole safety valves under extreme working conditions can be accurately characterized, and the safe working area and failure area of ​​downhole safety valves can be predicted, thereby determining the boundary envelope of downhole safety valves, that is, the performance envelope curve of downhole safety valves. The performance envelope curve of downhole safety valves can provide the safe operating area of ​​downhole safety valves, judge the working status of downhole safety valves on site, effectively guide the selection of downhole safety valves, and determine the ultimate load that downhole safety valves can withstand under various complex working conditions. It is of great significance for the practical application of downhole safety valves.

[0006] In order to better guide the application of downhole safety valves in deep wells, ultra-deep wells, deepwater wells and gas storage areas, it is urgent to invent a method for drawing a performance envelope curve of a downhole safety valve, conduct a real-time safety evaluation of the working status of the downhole safety valve, accurately judge its working status, determine whether the downhole safety valve is in a safe operating range, and avoid a series of safety accidents caused by failure of the downhole safety valve. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for drawing a performance envelope curve of a downhole safety valve to solve the technical problem of drawing a performance envelope curve of a downhole safety valve under complex service conditions. The 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-mentioned purpose, the present invention discloses a method for drawing a performance envelope curve of a downhole safety valve, characterized in that the method mainly draws the performance envelope curve of a downhole safety valve according to API 14A and GB / T 28259-2012 standards, specifically: (1) 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 sequence according to 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 in 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 a performance envelope curve of a downhole safety valve, characterized in that the method comprises the following steps:

[0011] S101: Establishment of three-dimensional model and determination of material performance parameters. According to the geometric dimensions of the downhole safety valve components, establish its overall three-dimensional model; carry out tensile / compression tests on the downhole safety valve component materials to obtain the component material performance parameters;

[0012] 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;

[0013] 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;

[0014] 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;

[0015] 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;

[0016] 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.

[0017] Furthermore, in step S101, the method steps for establishing the three-dimensional model and determining the material performance parameters are as follows:

[0018] S201: Establish a three-dimensional model of all parts of the downhole safety valve using three-dimensional modeling software according to the design drawings of the downhole safety valve parts or the measured geometric dimensions of the downhole safety valve parts;

[0019] S202: Prepare standard tensile / compression specimens of all components of downhole safety valves to ensure that the surface of the specimens is smooth and has no obvious defects;

[0020] S203: Select the tensile / compression testing machine and ensure that it is calibrated and operating normally, install the specimen fixture and ensure that the specimen can be clamped correctly;

[0021] S204: Set the test load loading method according to the material characteristics of the parts and test requirements;

[0022] S205: Install the specimen correctly on the testing machine, ensure that the specimen axis is consistent with the loading direction, and tighten the specimen fixture to prevent the specimen from sliding or falling off during the test;

[0023] S206: Before formal loading, pre-load to eliminate the gap between the specimen and the fixture;

[0024] S207: According to the test requirements, terminate the test when the specimen is damaged;

[0025] S208: Process and analyze the test data, and calculate the elastic modulus and tensile / compressive strength of the downhole safety valve component materials.

[0026] Furthermore, in step S102, the steps of failure mode, impact and criticality analysis are as follows:

[0027] S301: Analyze the failure modes, impacts and criticality of all components of downhole safety valves and determine the boundaries and levels of the analysis;

[0028] S302: Identify possible failure modes by understanding the function, structure and working principle of downhole safety valves;

[0029] S303: Evaluate the direct and indirect impact of each failure mode on the downhole safety valve, including the impact on function, performance, safety, reliability, etc.;

[0030] S304: Evaluate the degree of criticality of each failure mode based on the severity, probability of occurrence, and difficulty of detection of the failure;

[0031] S305: 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;

[0032] Furthermore, in step S103, the working principle and the method of force analysis are as follows:

[0033] S401: 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;

[0034] S402: Use static and dynamic analysis methods to perform stress analysis on the downhole safety valve under extreme working conditions, and obtain all the load-bearing components of the downhole safety valve.

[0035] Furthermore, 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:

[0036] S501: 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;

[0037] S502: setting material property parameters of the downhole safety valve simulation model according to the material tensile / compression test results;

[0038] S503: Meshing the downhole safety valve simulation model;

[0039] S504: 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;

[0040] S505: 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);

[0041] S506: 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);

[0042] S507: 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 );

[0043] S508: 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 );

[0044] S509: 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 );

[0045] S510: 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 );

[0046] S511: 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 , PE7 );

[0047] S512: 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 ).

[0048] Furthermore, in step S105, the method steps for drawing the downhole safety valve performance envelope curve are as follows:

[0049] S601: The four quadrants of the downhole safety valve performance envelope curve, from the first quadrant to the fourth quadrant, represent the load conditions in accordance with the quadrant regulations of the Cartesian rectangular coordinate system: downhole safety valve internal pressure and axial tension, downhole safety valve internal pressure and axial pressure, downhole safety valve external pressure and axial pressure, downhole safety valve external pressure and axial tension, and the downhole safety valve load limit under reasonable internal and external pressure and tensile pressure 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;

[0050] S602: In the 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;

[0051] S603: 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.

[0052] Furthermore, in step S106, the method steps for testing and verifying and correcting the downhole safety valve performance envelope curve are as follows:

[0053] S701: 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;

[0054] S702: 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 5 cycles of opening and closing before the test;

[0055] S703: setting a safety factor for the boundary envelope limit value 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;

[0056] S704: Open and close the downhole safety valve 5 times again without any pressure inside the downhole safety valve to determine whether the downhole safety valve performance 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. Record the hydraulic control pressure of the 5 cycles of opening and closing after the test. If the difference between the average hydraulic control pressures before and after the test is within ±10% or 0.7MPa (±100psi), the downhole safety valve passes the test.

[0057] S705: Downhole safety valve performance envelope curve obtained by simulation of downhole safety valve limit load correction obtained through single and combined load tests.

[0058] The beneficial effects of the present invention are:

[0059] (1) Research on the performance envelope curve of downhole safety valves was carried out, and the performance envelope curve of downhole safety valves under complex working conditions was established. This can accurately characterize the application limit of downhole safety valves under extreme working conditions and provide an effective basis for the application of downhole safety valves;

[0060] (2) It solves the problem that the performance evaluation of downhole safety valves of domestic and foreign oil companies has not formed a unified and complete standardized system, which provides 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 deep wells, ultra-deep wells and deepwater wells, providing an effective basis for the application of downhole safety valves;

[0061] (3) On-site staff can use the envelope curve to determine whether the downhole safety valve is safe to ensure effective operation; designers can use the envelope curve to improve the design and selection of the structure and materials of the downhole safety valve. Replacing the corresponding parts and selecting materials with appropriate strength for the corresponding components according to the stress conditions of the critical points of the envelope curve can reduce operating costs and effectively improve economic benefits.

[0062] (4) It can conduct real-time safety evaluation on the working status of the downhole safety valve, accurately judge its working status, and take timely measures to prevent a series of safety accidents such as blowouts. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 A schematic diagram of a downhole safety valve performance envelope curve determined by the present invention;

[0064] Figure 2 It is a schematic diagram of the drawing method flow of the present invention. DETAILED DESCRIPTION

[0065] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0066] Referring to the accompanying drawings, the present invention proposes a method for drawing a downhole safety valve performance envelope curve, and the method mainly includes the following steps:

[0067] S1: Establishment of three-dimensional model and determination of material performance parameters. According to the geometric dimensions of the downhole safety valve components, establish its overall three-dimensional model; carry out tensile / compression tests on the downhole safety valve component materials to obtain the component material performance parameters, including:

[0068] S11: Based on the design drawings of the downhole safety valve components or the measured geometric dimensions of the downhole safety valve components, use 3D modeling software to establish a 3D model of all the components of the downhole safety valve;

[0069] S12: Prepare standard tensile / compression specimens of all components of downhole safety valves to ensure that the surface of the specimens is smooth and has no obvious defects;

[0070] S13: Select the tensile / compression testing machine and ensure that it is calibrated and operating normally, install the specimen fixture and ensure that the specimen can be clamped correctly;

[0071] S14: Set the test load loading method according to the material characteristics of the parts and test requirements;

[0072] S15: Install the specimen correctly on the testing machine, ensure that the specimen axis is consistent with the loading direction, and tighten the specimen fixture to prevent the specimen from sliding or falling off during the test;

[0073] S16: Before formal loading, pre-load to eliminate the gap between the specimen and the fixture;

[0074] S17: According to the test requirements, terminate the test when the specimen is damaged;

[0075] S18: Process and analyze the test data to calculate the elastic modulus and tensile / compressive strength of the downhole safety valve component materials;

[0076] S2: Failure mode, impact and criticality analysis: analyze all possible failure modes, causes and consequences of all components of the downhole safety valve, and obtain the main failure components that affect the performance of the downhole safety valve, including:

[0077] S21: Analyze the failure modes, effects and criticality of all components of downhole safety valves and determine the boundaries and levels of analysis;

[0078] S22: Identify possible failure modes by understanding the function, structure and working principle of downhole safety valves;

[0079] S23: Evaluate the direct and indirect impact of each failure mode on the downhole safety valve, including the impact on function, performance, safety, reliability, etc.;

[0080] S24: Evaluate the criticality of each failure mode based on the severity, probability of occurrence and difficulty of detection of the failure;

[0081] S25: 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;

[0082] S3: Working principle and force analysis. According to the working principle of the downhole safety valve and various production conditions, the force of the downhole safety valve during operation is analyzed to obtain all the load-bearing parts of the downhole safety valve, including:

[0083] 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;

[0084] S32: Use static and dynamic analysis methods to perform stress analysis on the downhole safety valve under extreme working conditions, and obtain all the load-bearing components of the downhole safety valve;

[0085] S4: Establishment of downhole safety valve simulation model and determination of 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; use numerical simulation methods to obtain the failure point of the downhole safety valve under extreme working conditions, including:

[0086] S41: 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;

[0087] S42: setting material property parameters of the downhole safety valve simulation model according to the material tensile / compression test results;

[0088] S43: Meshing the downhole safety valve simulation model;

[0089] S44: 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;

[0090] S45: 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);

[0091] S46: 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);

[0092] S47: 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 );

[0093] S48: Fixed constraints are set on the upper joint and the lower joint end faces, and only external pressure is applied to the downhole safety valve simulation model. The axial load is kept at zero, and the limit external pressure P when the downhole safety valve simulation model fails is calculated. E-Max , denoted as D(0,P E-Max );

[0094] S49: 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(FT1 , P I1 )、A2(F T2 , P I2 );

[0095] 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 );

[0096] 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 );

[0097] 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 );

[0098] S5: 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, including:

[0099] S51: The four quadrants of the downhole safety valve performance envelope curve, 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 in 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;

[0100] S52: In the 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 point, 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;

[0101] S53: 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;

[0102] S6: 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, including:

[0103] S61: 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;

[0104] S62: 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;

[0105] S63: setting a safety factor for the boundary envelope limit value of the downhole safety valve performance envelope curve drawn by simulation, conducting separate and combined load tests of internal pressure resistance, external squeeze resistance, tension resistance and compression resistance, opening and closing the downhole safety valve under the load conditions of failure points A, A1, A2, B, B1, B2, C, C1, C2, C3, D, D1, D2, D3 and D4, and applying load to the downhole safety valve in a step-by-step manner, and recording the hydraulic control pressure of opening and closing the downhole safety valve under each load loading;

[0106] S64: 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, tension resistance and compression resistance. 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;

[0107] S65: Downhole safety valve performance envelope curve obtained by simulation of downhole safety valve limit load correction obtained through single and combined load tests.

[0108] In summary, the present invention discloses a method for drawing a performance envelope curve of a downhole safety valve; the method is mainly based on API 14A and GB / T 28259-2012 standards, and specifically includes: establishing a three-dimensional model of a downhole safety valve, determining the material performance parameters of all components; performing failure mode, influence and hazard analysis on all components of the downhole safety valve, and obtaining the main failed components that affect the performance of the downhole safety valve; performing working principle and force analysis, and obtaining all components of the downhole safety valve that bear loads; establishing a simulation model of the downhole safety valve and determining the failure point under extreme working conditions; drawing a performance envelope curve of the downhole safety valve; experimentally verifying and correcting the performance envelope curve of the downhole safety valve. The method proposed in 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 working conditions, and provide an effective basis for the application of downhole safety valves in deep wells, ultra-deep wells, deep water wells, and gas storages, and meet their completion operation requirements.

[0109] At this point, those skilled in the art 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 based on the contents disclosed in 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 such 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: Establishment of three-dimensional model and determination of material performance parameters. According to the geometric dimensions of the downhole safety valve components, establish its overall three-dimensional model; carry out tensile / compression tests on the downhole safety valve component materials to obtain the component material performance parameters; 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 S101, the method steps for establishing a three-dimensional model and determining material performance parameters are as follows: S201: Establish a three-dimensional model of all the components of the downhole safety valve using three-dimensional modeling software according to the design drawings of the downhole safety valve components or the measured geometric dimensions of the downhole safety valve components; S202: Prepare standard tensile / compression specimens of all components of downhole safety valves to ensure that the surface of the specimens is smooth and has no obvious defects; S203: Select the tensile / compression testing machine and ensure that it is calibrated and operating normally, install the specimen fixture and ensure that the specimen can be clamped correctly; S204: Set the test load loading method according to the material characteristics of the parts and test requirements; S205: Install the specimen correctly on the testing machine, ensure that the specimen axis is consistent with the loading direction, and tighten the specimen fixture to prevent the specimen from sliding or falling off during the test; S206: Before formal loading, pre-load to eliminate the gap between the specimen and the fixture; S207: According to the test requirements, terminate the test when the specimen is damaged; S208: Process and analyze the test data, and calculate the elastic modulus and tensile / compressive strength of the downhole safety valve component materials.

3. 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: S301: Analyze the failure modes, impacts and criticality of all components of downhole safety valves and determine the boundaries and levels of the analysis; S302: Identify possible failure modes by understanding the function, structure and working principle of downhole safety valves; S303: Evaluate the direct and indirect impact of each failure mode on the downhole safety valve, including the impact on function, performance, safety, reliability, etc.; S304: Evaluate the degree of criticality of each failure mode based on the severity, probability of occurrence, and difficulty of detection of the failure; S305: 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.

4. 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: S401: 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; S402: Use static and dynamic analysis methods to perform stress analysis on the downhole safety valve under extreme working conditions, and obtain all the load-bearing components of the downhole safety valve.

5. 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: S501: 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; S502: setting material property parameters of the downhole safety valve simulation model according to the material tensile / compression test results; S503: Meshing the downhole safety valve simulation model; S504: 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; S505: 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); S506: 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 when the internal pressure / external pressure are both zero, calculate the ultimate compressive load F when the downhole safety valve simulation model fails. C-Max , denoted as C(F C-Max , 0); S507: 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 ); S508: Fixed constraints are set on the upper joint and the lower joint end faces, and only external pressure is applied to the downhole safety valve simulation model. The axial load is kept at zero, and the limit external pressure P when the downhole safety valve simulation model fails is calculated. E-Max , denoted as D(0,P E-Max ); S509: 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 ); S510: 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 ); S511: 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 ); S512: 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 ).

6. 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: S601: The four quadrants of the downhole safety valve performance envelope curve, from the first quadrant to the fourth quadrant, represent the load conditions in accordance with the quadrant regulations of the Cartesian rectangular coordinate system: downhole safety valve internal pressure and axial tension, downhole safety valve internal pressure and axial pressure, downhole safety valve external pressure and axial pressure, downhole safety valve external pressure and axial tension, and the downhole safety valve load limit under reasonable internal and external pressure and tensile pressure 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; S602: In the 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; S603: 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.

7. 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: S701: 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; S702: 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 5 cycles of opening and closing before the test; S703: setting a safety factor for the boundary envelope limit value 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; S704: Open and close the downhole safety valve 5 times again without any pressure inside the downhole safety valve to determine whether the downhole safety valve performance 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. Record the hydraulic control pressure of the 5 cycles of opening and closing after the test. If the difference between the average hydraulic control pressures before and after the test is within ±10% or 0.7MPa (±100psi), the downhole safety valve passes the test. S705: 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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