A novel telescopic pipe structure for high-temperature and high-pressure wells and its optimized tubing configuration method

Abstract

This invention discloses a novel telescopic pipe structure for high-temperature and high-pressure wells and its optimized tubing configuration method, belonging to the field of oil and gas extraction technology. It aims to solve the problem of tubing string buckling failure caused by piston force load under high-temperature and high-pressure conditions in existing telescopic pipes. The novel telescopic pipe consists of inner and outer cylinder mechanisms and a balancing chamber mechanism. The inner and outer cylinder mechanisms are connected by threads, ensuring structural integrity and reliable connection. The balancing chamber mechanism includes inner and outer pressure chambers and hydraulic holes, respectively connected to the internal and external pressures of the tubing, dynamically balancing the piston force. The optimized tubing configuration involves three steps: S1, analysis of the telescopic pipe's mechanical behavior to provide a mechanical basis for configuration optimization; S2, design of the telescopic pipe's position to determine the well depth range in which the telescopic pipe functions and iteratively calculate and lock in the optimal position; and S3, design of the number of telescopic pipes to determine the optimal number of telescopic pipes to meet compensation requirements. This invention can significantly improve the stability of tubing strings in high-temperature and high-pressure wells, providing technical support for the safe and efficient development of ultra-deep oil and gas wells.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction technology, specifically relating to a novel telescopic pipe structure for high-temperature and high-pressure wells and its optimized configuration method for the tubing string. Background Technology

[0002] Driven by both the global energy structure transformation and the rigid growth in oil and gas demand, oil and gas resource development has entered a new stage characterized by "ultra-deep, complex, and unconventional" characteristics. Downhole tubing faces severe challenges from high temperatures (180-200℃), high pressures (140MPa), and complex geostress environments. Under these harsh conditions, tubing failures are frequent, seriously affecting the safe and efficient extraction of oil and gas wells. Currently, the common engineering approach is to install telescopic tubes within the tubing. This aims to alleviate thermal stress caused by temperature changes during fracturing operations through the telescopic deformation characteristics of the tubes, while also compensating for uneven deformation of the tubing, thereby protecting wellhead equipment, the tubing, and downhole tools such as packers.

[0003] However, field applications in multiple ultra-deep wells in western China have shown that permanent buckling failures occur in test tubing with telescopic tubes, with buckling deformation concentrated near the telescopic tube. Research has revealed limitations in existing telescopic tube technology: when the telescopic tube compensation exceeds the actual deformation of the tubing, the telescopic tube is in a partially stretched state; under this state, the internal and external pressures acting on the variable cross-section of the telescopic tube generate additional piston force loads, which are the main cause of tubing buckling failure; furthermore, traditional tubing mechanical analysis models fail to fully consider the dynamic compensation characteristics of the telescopic tube, leading to an unclear understanding of the tubing failure mechanism, thus making it difficult for existing technologies to effectively solve the tubing stability problem under complex operating conditions. Summary of the Invention

[0004] When the telescopic pipe is in a partially stretched state, an additional piston force load will be generated at the variable cross-section of the telescopic pipe under the action of high pressure fluid downhole; the piston force load acting on the upper and lower ends of the telescopic pipe string can easily cause the string string to buckle and fail.

[0005] To address the shortcomings of existing telescopic pipe technology, the present invention aims to provide a novel telescopic pipe structure for high-temperature and high-pressure wells and an optimized configuration method for the tubing string, thereby improving the stability of the tubing string through structural innovation and mechanical model optimization.

[0006] This invention provides a novel telescopic pipe structure for high-temperature and high-pressure wells, which mainly consists of an outer cylinder mechanism, an inner cylinder mechanism, and a balance chamber mechanism. By adding two pressure chambers, the novel telescopic pipe significantly reduces the piston force acting on the telescopic pipe when there is a pressure difference between the inside and outside.

[0007] The outer cylinder mechanism includes an upper connector, an upper outer cylinder, an outer cylinder connecting section, a section end cap, a lower outer cylinder, a sealing section, and a sealing end cap. The upper connector is connected to the upper oil pipe via an internal thread and to the upper outer cylinder via an external thread. The upper outer cylinder is connected to the outer cylinder connecting section via an external thread. The outer cylinder connecting section is connected to the lower outer cylinder via an external thread and to the section end cap via an internal thread. The lower outer cylinder is connected to the sealing section via an internal thread. The sealing section is connected to the sealing end cap via an internal thread.

[0008] The inner cylinder mechanism includes a lower connector, a lower inner cylinder, an inner cylinder connecting section, an inner cylinder end cap, an upper inner cylinder, and a sealing end. The lower connector is connected to the lower oil pipe via an external thread and to the lower inner cylinder via an internal thread. The lower inner cylinder is connected to the inner cylinder connecting section via an external thread. The inner cylinder connecting section is connected to the inner cylinder end cap via an external thread and to the upper inner cylinder via an internal thread. The upper inner cylinder is connected to the sealing end via an external thread.

[0009] The balance chamber mechanism includes an inner pressure chamber, an outer pressure chamber, an inner hydraulic hole, and an outer hydraulic hole; the inner pressure chamber is connected to the inner pressure of the oil pipe through the inner hydraulic hole designed in the lower inner cylinder, and the outer pressure chamber is connected to the outer pressure of the oil pipe through the outer hydraulic hole designed in the lower outer cylinder.

[0010] Furthermore, three V-shaped packing seals are designed between the outer cylinder mechanism and the inner cylinder mechanism. Under normal operating conditions, fluororubber is used, while perfluoroether rubber is used when the well temperature exceeds 180℃. The sealing gap is strictly controlled to ≤0.1mm to ensure sealing performance under high pressure.

[0011] Furthermore, a torque transmission key is installed between the outer cylinder connecting section and the upper inner cylinder, which is made of spring steel to ensure stable torque transmission efficiency during the operation of the telescopic pipe and meet the torque transmission requirements of downhole tools.

[0012] Furthermore, a shear pin is installed between the lower outer cylinder and the inner cylinder connecting short section. The shearing characteristics of the shear pin enable precise start-up control of the telescopic tube. When the axial load on the tube column reaches the rated shearing value of the shear pin, the pin shears off, and the telescopic tube starts up and enters the working state, ensuring that the telescopic tube participates in the deformation compensation of the tube column as needed.

[0013] Furthermore, the piston force of a conventional telescopic tube The calculation formula is:

[0014] ,

[0015] in, For a conventional telescopic pipe piston force load, N; The pressure inside the oil pipe, in MPa; External pressure of the oil pipe, MPa; The outer diameter of the oil pipe is in mm; The inner diameter of the oil pipe is in mm; The diameter of the sealing surface of a standard telescopic tube is in mm.

[0016] Furthermore, the piston force of the new telescopic tube The calculation formula is:

[0017] ,

[0018] in, For the piston force load of the new type of telescopic tube, N; The outer diameter of the inner tube of the new type of telescopic tube is mm; The inner diameter of the outer tube of the new type of telescopic pipe is in mm.

[0019] This invention also provides a method for optimizing the configuration of tubing strings suitable for novel telescopic tubes, comprising the following steps:

[0020] S1, Mechanical behavior analysis of a novel telescopic tube column;

[0021] S2, new telescopic tube positioning design;

[0022] S3, a new design for the number of telescopic tubes.

[0023] Further, step S1 includes the following sub-steps:

[0024] S101, Calculation of axial force in the packer string before setting:

[0025] After the tubing is lowered to the expected depth, it reaches static equilibrium under the combined effects of gravity, buoyancy, and Coulomb friction. At this point, at any position... Axial force on the oil pipe It can be represented as:

[0026] ,

[0027] in, From the bottom of the well The length of the oil pipe at the location, in meters (m). The weight per unit length of the oil pipe, in N; The inclination angle is expressed in rad. The fluid density inside the tubing. ; The density of the annular fluid. ; The area enclosed by the inner diameter of the oil pipe. ; The area enclosed by the outer diameter of the oil pipe. ; It is the acceleration due to gravity. ; denoted as the axial Coulomb friction coefficient between the inner walls of the tubing and casing, dimensionless; The positive pressure of the tubing on the casing is in N.

[0028] S102, Calculation of axial force in the tubing after packer setting:

[0029] During the setting process of the hydraulic packer, the setting steel ball first blocks the pressure connection between the oil pipe and the oil sleeve annulus. Then, pressure is applied to the oil pipe. When the pressure reaches the packer's setting pressure, the axial hydraulic pressure compresses the rubber sleeve to achieve a seal. Simultaneously, the cone pushes the lower slip to extend and anchor in the sleeve. At this point, at any position... Axial force on the oil pipe It can be represented as:

[0030] ,

[0031] in, The starting setting pressure for the packer is measured in Pa.

[0032] S103, Calculation of axial force in tubing under fracturing conditions:

[0033] During fracturing operations, changes in temperature and pressure can cause the tubing to be affected by factors such as temperature effect, piston effect, bulging effect and buckling effect.

[0034] Deformation of the tubular string under the influence of temperature effect The calculation formula is: ,

[0035] in, The coefficient of thermal expansion of the tubular material; For the first The length of the test string, in meters; For the first The temperature change of the test tubing relative to the temperature before fracturing, in °C.

[0036] The effect of bulging effect on the deformation of the tubular string The calculation formula is:

[0037] ,

[0038] in, Test the Poisson's ratio of the test column; To test the elastic modulus of the tubular column, in MPa; For the first The change in internal pressure of the test tubing relative to the pre-fracturing pressure, in Pa; For the first The change in external pressure of the test tubing relative to the pre-fracturing pressure, in Pa; For the first The inner cross-sectional area of ​​the test tubing. ; For the first The outer cross-sectional area of ​​the test column, ; For the first The cross-sectional area of ​​the test tubing. .

[0039] The effect of piston effect on the deformation of the tubular column The calculation formula is:

[0040] ,

[0041] in, For the first Level 1 test string relative to the first The change in the internal cross-sectional area of ​​the test tubing. ; For the first Level 1 test string relative to the first Change in the outer cross-sectional area of ​​the test tubing. .

[0042] Deformation of the tubular string under the influence of buckling effect The calculation formula is:

[0043] ,

[0044] in, For the first The effective axial force on the stage test string, in N; For the first The annular space clearance between the test tubing and the casing at this location, in meters; For the first The moment of inertia of the test tubing. .

[0045] The combined effect of various factors can cause tubing deformation and generate additional axial stress; at this time, the formula for calculating the total deformation of the tubing string is:

[0046] ,

[0047] in, The value is the total deformation of the tubing string under fracturing conditions, expressed in meters (m).

[0048] The formula for calculating the axial force of the tubular string is:

[0049] ,

[0050] in, For fracturing conditions The axial force of the tubular column at point N; The first effect is the combined effect of all factors. Deformation of the test tubing, in meters (m).

[0051] S104, Analysis of the Start-up Process of the New Type of Telescopic Pipe:

[0052] Expansion joints are typically activated during fracturing operations to alleviate thermal stress caused by temperature changes and compensate for uneven deformation of the tubing string. The formula for calculating the load on the pins of the new expansion joint under fracturing conditions is as follows:

[0053] ,

[0054] in, The shear load of the first expansion joint pin is N; To test the actual axial load (N) on the tubing at the expansion joint.

[0055] When multiple new telescopic tubes are installed in the tubing column, the front After the first telescopic pipe is started, the first The formula for calculating the load on the expansion joint pin is as follows: ,

[0056] in, The displacement compensation amount for a single telescopic pipe is expressed in meters (m).

[0057] When the axial load on the shear pin at the new type of telescopic pipe exceeds its rated shear value, the telescopic pipe will start and enter the working state.

[0058] ,

[0059] in, The rated shear value (N) for the shear pin of the new type of telescopic pipe.

[0060] S105, Status assessment after startup of the new type of telescopic pipe:

[0061] The new type of telescopic tube has three main working states after startup: fully closed, partially stretched, and fully stretched.

[0062] like If the telescopic pipe is in a fully closed state, it will have no effect on the overall stress on the pipe column.

[0063] like If the expansion joint is in a partially stretched or fully stretched state, it is necessary to further calculate the critical expansion amount for the partially stretched and fully stretched states to determine the state of the expansion joint. The formula for calculating the critical expansion amount of the expansion joint is:

[0064] ,

[0065] in, The critical expansion / contraction of the telescopic tube is expressed in meters (m).

[0066] like If the telescopic tube is in a partially stretched state, there is no interaction force between the inner and outer cylinders of the telescopic tube. The mechanical behavior of the upper and lower parts of the telescopic tube needs to be analyzed and calculated separately.

[0067] in, The compensation amount for the expansion joint is specified in meters (m).

[0068] like When the telescopic tube is fully stretched, it can be considered as a complete tubing string.

[0069] S106, Calculation of axial force in the tube column after startup of the new type of telescopic tube:

[0070] If the telescopic tube is in a fully closed state, the formula for calculating the axial force of the test tube string is: ,

[0071] If the telescopic tube is under full tension, the formula for calculating the axial force of the test tube column is:

[0072] ,

[0073] If the telescopic tube is under partial tension, the formula for calculating the axial force of the test tube column is:

[0074] ,

[0075] Furthermore, step S2, the design of the new telescopic tube position, includes the following sub-steps:

[0076] S201, Calculate the well depth range within which the expansion joint cannot be activated when the packer is set:

[0077] Under packer setting conditions, the pin is under load when the expansion joint is in different positions. The calculation formula is:

[0078] ,

[0079] in, The axial force of the tubing string under setting conditions is N; The value is N, which represents the piston force at the variable cross-section of the telescopic pipe under the setting condition.

[0080] According to the rated shear value of the shear pin of the new telescopic tube Calculate the well depth range where the telescopic pipe cannot be started under the setting and sealing conditions. :

[0081] ,

[0082] S202, When calculating fracturing stimulation conditions, the well depth range that allows the telescopic pipe to be activated is as follows:

[0083] Under fracturing conditions, the pin is subjected to load when the expansion joint is in different positions. The calculation formula is:

[0084] ,

[0085] in, The axial force of the tubing string under fracturing conditions is expressed in N. The value is N, which represents the piston force at the variable cross-section of the telescopic tube under fracturing conditions.

[0086] According to the rated shear value of the shear pin of the new telescopic tube Calculate the well depth range within which the telescopic pipe can be activated under fracturing stimulation conditions. :

[0087] ,

[0088] S203, Effective well depth range determined:

[0089] The following conditions must be met simultaneously, meaning the well depth range in which the telescopic pipe is effective is: ,

[0090] like If the problem persists, the number of pins needs to be adjusted or other types of shear pins need to be replaced, and the calculation needs to be recalculated following the steps above.

[0091] S204, iterative calculation to determine the optimal position:

[0092] The axial force of the tubing string under different positions of the telescopic pipe is calculated iteratively within the well depth range where the telescopic pipe is effective. The optimal position is determined by comprehensively considering the overall load conditions of the telescopic pipe, packer, and tubing string.

[0093] Furthermore, step S3, the design of the number of novel telescopic tubes, includes the following sub-steps:

[0094] S301, Calculate the total deformation of the tubing string under the combined effects of various effects during the fracturing process. .

[0095] S302, Calculate the critical expansion / contraction amount of the expansion joint. .

[0096] S303, the number of expansion joints must meet the following formula: ,

[0097] in, The quantity of the new type of telescopic tube is [number].

[0098] Compared with the prior art, the beneficial effects of the present invention are:

[0099] Significantly reduced piston force: By connecting the internal and external pressure of the oil pipe through a dual-balance chamber structure, the piston force load of the new telescopic tube is significantly reduced compared with the traditional structure, effectively avoiding tubing buckling failure caused by concentrated piston force.

[0100] Enhanced dynamic compensation capability: Through the precise design of the shear pin, the telescopic tube can be activated as needed during fracturing, and the compensation amount is controllable, avoiding piston force caused by redundant compensation and ensuring the overall stress balance of the tubing string.

[0101] Improved tubing stability: Based on the mechanical behavior analysis model, the optimized telescopic tubing configuration makes the axial stress distribution of the tubing more uniform under fracturing conditions, which is suitable for the complex working conditions of ultra-deep, high-temperature and high-pressure wells. Attached Figure Description

[0102] Figure 1 This is a cross-sectional view of the novel telescopic tube structure of the present invention;

[0103] Figure 2 This is a schematic diagram of the forces acting on a conventional telescopic tube in a semi-stretched state.

[0104] Figure 3 This is a schematic diagram of the forces acting on a novel telescopic tube in a semi-stretched state.

[0105] Figure 4 This is a schematic diagram of the wellbore structure and tubing assembly of well X1 in Example 1;

[0106] Figure 5 This is a graph showing the acid fracturing operation curve of well X1 in Example 1;

[0107] Figure 6 This is a comparison curve of the piston force of the conventional telescopic tube and the new telescopic tube under acid fracturing conditions in well X1 in Example 1.

[0108] Reference numerals: 1-Upper connector, 2-Upper outer cylinder, 3-Sealing end, 4-Packing seal I, 5-Upper inner cylinder, 6-Outer cylinder connecting stub, 7-Transmission key, 8-Stub end cap, 9-Outer pressure chamber, 10-Outer hydraulic hole, 11-Shear pin, 12-Packing seal II, 13-Inner cylinder connecting stub, 14-Inner cylinder end cap, 15-Inner hydraulic hole, 16-Inner pressure chamber, 17-Lower outer cylinder, 18-Packing seal III, 19-Sealing stub, 20-Sealing end cap, 21-Lower inner cylinder, 22-Lower connector, 23-Oil pipe 1, 24-Conventional telescopic pipe inner cylinder assembly, 25-Oil pipe external pressure, 26-Sleeve, 27-Sealing device, 28-Oil pipe internal pressure, 29-Conventional telescopic pipe outer cylinder assembly, 30-Oil pipe 2, 31-New telescopic pipe inner cylinder assembly, 32-Hydraulic hole, 33-New telescopic pipe outer cylinder assembly. Detailed Implementation

[0109] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments; it should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0110] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the conventional meaning as understood by those skilled in the art to which this disclosure pertains; the words “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components; the words “including,” etc., mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but do not exclude other elements or objects; “upper,” “lower,” “inner,” “outer,” etc., are used only to indicate relative positional relationships, and such relative positional relationships may also change accordingly when the absolute position of the described object changes.

[0111] The application principle of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0112] like Figure 1 The diagram shown is a schematic diagram of a novel telescopic pipe structure for high-temperature and high-pressure wells according to the present invention. The novel telescopic pipe structure includes an outer cylinder mechanism, an inner cylinder mechanism, and a balance chamber mechanism.

[0113] The outer cylinder mechanism includes an upper connector 1, an upper outer cylinder 2, an outer cylinder connecting section 6, a section end cap 8, a lower outer cylinder 17, a sealing section 19, and a sealing end cap 20. The upper connector 1 is connected to the upper oil pipe via an internal thread and to the upper outer cylinder 2 via an external thread. The upper outer cylinder 2 is connected to the outer cylinder connecting section 6 via an external thread. The outer cylinder connecting section 6 is connected to the lower outer cylinder 17 via an external thread and to the section end cap 8 via an internal thread. The lower outer cylinder 17 is connected to the sealing section 19 via an internal thread, and the sealing section 19 is connected to the sealing end cap 20 via an internal thread.

[0114] The inner cylinder mechanism includes a lower connector 22, a lower inner cylinder 21, an inner cylinder connecting section 13, an inner cylinder end cap 14, an upper inner cylinder 5, and a sealing end 3. The lower connector 22 is connected to the lower oil pipe via an external thread and to the lower inner cylinder 21 via an internal thread. The lower inner cylinder 21 is connected to the inner cylinder connecting section 13 via an external thread. The inner cylinder connecting section 13 is connected to the inner cylinder end cap 14 via an external thread and to the upper inner cylinder 5 via an internal thread. The upper inner cylinder 5 is connected to the sealing end 3 via an external thread.

[0115] The balance chamber mechanism includes an inner pressure chamber 16, an outer pressure chamber 9, an inner hydraulic hole 15, and an outer hydraulic hole 10; the inner pressure chamber 16 is connected to the inner pressure of the oil pipe through the inner hydraulic hole 15 designed in the lower inner cylinder 21, and the outer pressure chamber 9 is connected to the outer pressure of the oil pipe through the outer hydraulic hole 10 designed in the lower outer cylinder 17.

[0116] Furthermore, three V-shaped packing seal devices—packing seal I4, packing seal II12, and packing seal III18—are designed between the outer cylinder mechanism and the inner cylinder mechanism. Under normal operating conditions, fluororubber material is used, while perfluoroether rubber material is used when the well temperature exceeds 180℃. The sealing gap is strictly controlled to ≤0.1mm to ensure sealing performance under high pressure.

[0117] Furthermore, a torque transmission key 7 is installed between the outer cylinder connecting section 6 and the upper inner cylinder 5. This key is made of spring steel to ensure stable torque transmission efficiency during the operation of the telescopic pipe, thus meeting the torque transmission requirements of downhole tools.

[0118] Furthermore, a shear pin 11 is installed between the lower outer cylinder 17 and the inner cylinder connecting section 13 in S4. The shearing characteristics of the shear pin 11 enable precise start-up control of the telescopic tube. When the axial load on the tube column reaches the rated shear value of the shear pin 11, the shear pin 11 shears off, and the telescopic tube starts up and enters the working state, ensuring that the telescopic tube participates in the deformation compensation of the tube column as needed.

[0119] Furthermore, when a conventional telescopic pipe is under partial tension, additional piston force loads will be generated at the variable cross-section of the pipe under the action of high-pressure fluid downhole; the piston force load acting on the upper and lower ends of the telescopic pipe string can easily cause the string to buckle and fail; according to Figure 2 The piston force can be obtained from the force analysis of the conventional telescopic tube under semi-stretched state. The calculation formula is:

[0120] ,

[0121] in, For a conventional telescopic pipe piston force load, N; The pressure inside the oil pipe, in MPa; External pressure of the oil pipe, MPa; The outer diameter of the oil pipe is in mm; The inner diameter of the oil pipe is in mm; The diameter of the sealing surface of a standard telescopic tube is in mm.

[0122] Furthermore, the new telescopic tube adds two balancing chambers compared to the conventional telescopic tube, which are respectively connected to the internal and external pressures of the oil pipe. When a pressure difference exists, the balancing chambers significantly reduce the piston force acting on the telescopic tube; according to Figure 3 The piston force can be obtained from the force analysis of the novel telescopic tube under semi-stretched state. The calculation formula is:

[0123] ,

[0124] in, For the piston force load of the new type of telescopic tube, N; The outer diameter of the inner tube of the new type of telescopic tube is mm; The inner diameter of the outer tube of the new type of telescopic pipe is in mm.

[0125] Based on the structural parameters of the conventional and novel telescopic tubes shown in Table 1, the piston force load of the two types of telescopic tubes under semi-stretched state is compared using the piston force formula.

[0126] Table 1. Structural Dimensions of Conventional and New Types of Telescopic Pipes

[0127]

[0128] Table 2 Piston force data of the new telescopic tube and conventional telescopic tube

[0129]

[0130] Table 2 shows the piston force data of the new telescopic tube and the conventional telescopic tube under different operating conditions. The additional piston force generated by the new telescopic tube under different operating conditions is much smaller than that of the conventional telescopic tube. Under six conventional operating conditions, the piston force of the new telescopic tube is reduced by 46.97% to 66.9% compared with the conventional telescopic tube.

[0131] This invention also provides a method for optimizing the configuration of tubing strings suitable for novel telescopic tubes, comprising the following steps:

[0132] S1, Mechanical behavior analysis of a novel telescopic tube column;

[0133] S2, new telescopic tube positioning design;

[0134] S3, a new design for the number of telescopic tubes.

[0135] Further, step S1 includes the following sub-steps:

[0136] S101, Calculation of axial force in the packer string before setting:

[0137] After the tubing is lowered to the expected depth, it reaches static equilibrium under the combined effects of gravity, buoyancy, and Coulomb friction. At this point, at any position... Axial force on the oil pipe It can be represented as:

[0138] ,

[0139] in, From the bottom of the well The length of the oil pipe at the location, in meters (m). The weight per unit length of the oil pipe, in N; The inclination angle is expressed in rad. The fluid density inside the tubing. ; The density of the annular fluid. ; The area enclosed by the inner diameter of the oil pipe. ; The area enclosed by the outer diameter of the oil pipe. ; It is the acceleration due to gravity. ; denoted as the axial Coulomb friction coefficient between the inner walls of the tubing and casing, dimensionless; The positive pressure of the tubing on the casing is in N.

[0140] S102, Calculation of axial force in the tubing after packer setting:

[0141] During the setting process of the hydraulic packer, the setting steel ball first blocks the pressure connection between the oil pipe and the oil sleeve annulus. Then, pressure is applied to the oil pipe. When the pressure reaches the packer's setting pressure, the axial hydraulic pressure compresses the rubber sleeve to achieve a seal. Simultaneously, the cone pushes the lower slip to extend and anchor in the sleeve. At this point, at any position... Axial force on the oil pipe It can be represented as:

[0142] ,

[0143] in, The starting setting pressure for the packer is measured in Pa.

[0144] S103, Calculation of axial force in tubing under fracturing conditions:

[0145] During fracturing operations, changes in temperature and pressure can cause the tubing to be affected by factors such as temperature effect, piston effect, bulging effect and buckling effect.

[0146] Deformation of the tubular string under the influence of temperature effect The calculation formula is:

[0147] ,

[0148] in, The coefficient of thermal expansion of the tubular material; For the first The length of the test string, in meters; For the first The temperature change of the test tubing relative to the temperature before fracturing, in °C.

[0149] The effect of bulging effect on the deformation of the tubular string The calculation formula is:

[0150] ,

[0151] in, To test the Poisson's ratio of the tubing; To test the elastic modulus of the tubular column, in MPa; For the first The change in internal pressure of the test tubing relative to the pre-fracturing pressure, in Pa; For the first The change in external pressure of the test tubing relative to the pre-fracturing pressure, in Pa; For the first The inner cross-sectional area of ​​the test tubing. ; For the first The outer cross-sectional area of ​​the test column, ; For the first The cross-sectional area of ​​the test tubing. .

[0152] The effect of piston effect on the deformation of the tubular column The calculation formula is:

[0153] ,

[0154] in, For the first Level 1 test string relative to the first The change in the internal cross-sectional area of ​​the test tubing. ; For the first Level 1 test string relative to the first Change in the outer cross-sectional area of ​​the test tubing. .

[0155] Deformation of the tubular string under the influence of buckling effect The calculation formula is:

[0156] ,

[0157] in, For the first The effective axial force on the stage test string, in N; For the first The annular space clearance between the test tubing and the casing at this location, in meters; For the first The moment of inertia of the test tubing. .

[0158] The combined effect of various factors can cause tubing deformation and generate additional axial stress; at this time, the formula for calculating the total deformation of the tubing string is:

[0159] ,

[0160] in, The value is the total deformation of the tubing string under fracturing conditions, expressed in meters (m).

[0161] The formula for calculating the axial force of the tubular string is:

[0162] ,

[0163] in, For fracturing conditions The axial force of the tubular column at point N; The first effect is the combined effect of all factors. Deformation of the test tubing, in meters (m).

[0164] S104, Analysis of the Start-up Process of the New Type of Telescopic Pipe:

[0165] Expansion joints are typically activated during fracturing operations to alleviate thermal stress caused by temperature changes and compensate for uneven deformation of the tubing string. The formula for calculating the load on the pins of the new expansion joint under fracturing conditions is as follows:

[0166] ,

[0167] in, The shear load of the first expansion joint pin is N; To test the actual axial load (N) on the tubing at the expansion joint.

[0168] When multiple new telescopic tubes are installed in the tubing column, the front After the first telescopic pipe is started, the first The formula for calculating the load on the expansion joint pin is as follows:

[0169] ,

[0170] in, The displacement compensation amount for a single telescopic pipe is expressed in meters (m).

[0171] When the axial load on the shear pin at the new type of telescopic pipe exceeds its rated shear value, the telescopic pipe will start and enter the working state.

[0172] ,

[0173] in, The rated shear value (N) for the shear pin of the new type of telescopic pipe.

[0174] S105, Status assessment after startup of the new type of telescopic pipe:

[0175] The new type of telescopic tube has three main working states after startup: fully closed, partially stretched, and fully stretched.

[0176] like

[0177] ,

[0178] When the telescopic pipe is in a fully closed state, it has no effect on the overall stress on the pipe column.

[0179] like

[0180] ,

[0181] If the telescopic tube is in a partially or fully stretched state, further calculation of the critical expansion and contraction amount for the partially and fully stretched states is needed to determine the state of the telescopic tube. The formula for calculating the critical expansion and contraction amount of the telescopic tube is:

[0182] ,

[0183] in, The critical expansion / contraction of the telescopic tube is expressed in meters (m).

[0184] like If the telescopic tube is in a partially stretched state, there is no interaction force between the inner and outer cylinders of the telescopic tube. The mechanical behavior of the upper and lower parts of the telescopic tube needs to be analyzed and calculated separately.

[0185] in, The compensation amount for the expansion joint is specified in meters (m).

[0186] like When the telescopic tube is fully stretched, it can be considered as a complete tubing string.

[0187] S106, Calculation of axial force in the tube column after startup of the new type of telescopic tube:

[0188] If the telescopic tube is in a fully closed state, the formula for calculating the axial force of the test tube string is: ,

[0189] If the telescopic tube is under full tension, the formula for calculating the axial force of the test tube column is:

[0190] ,

[0191] If the telescopic tube is under partial tension, the formula for calculating the axial force of the test tube column is:

[0192] ,

[0193] Furthermore, step S2, the design of the new telescopic tube position, includes the following sub-steps:

[0194] S201, Calculate the well depth range within which the expansion joint cannot be activated when the packer is set:

[0195] Under packer setting conditions, the pin is under load when the expansion joint is in different positions. The calculation formula is:

[0196] ,

[0197] in, The axial force of the tubing string under setting conditions is N; The value is N, which represents the piston force at the variable cross-section of the telescopic pipe under the setting condition.

[0198] According to the rated shear value of the shear pin of the new telescopic tube Calculate the well depth range where the telescopic pipe cannot be started under the setting and sealing conditions. :

[0199] ,

[0200] S202, When calculating fracturing stimulation conditions, the well depth range that allows the telescopic pipe to be activated is as follows:

[0201] Under fracturing conditions, the pin is subjected to load when the expansion joint is in different positions. The calculation formula is:

[0202] ,

[0203] in, The axial force of the tubing string under fracturing conditions is expressed in N. The value is N, which represents the piston force at the variable cross-section of the telescopic tube under fracturing conditions.

[0204] According to the rated shear value of the shear pin of the new telescopic tube Calculate the well depth range within which the telescopic pipe can be activated under fracturing stimulation conditions. :

[0205] ,

[0206] S203, Effective well depth range determined:

[0207] The following conditions must be met simultaneously, meaning the well depth range in which the telescopic pipe is effective is: ,

[0208] like If the problem persists, the number of pins needs to be adjusted or other types of shear pins need to be replaced, and the calculation needs to be recalculated following the steps above.

[0209] S204, iterative calculation to determine the optimal position:

[0210] The axial force of the tubing string under different positions of the telescopic pipe is calculated iteratively within the well depth range where the telescopic pipe is effective. The optimal position is determined by comprehensively considering the overall load conditions of the telescopic pipe, packer, and tubing string.

[0211] Furthermore, step S3, the design of the number of novel telescopic tubes, includes the following sub-steps:

[0212] S301, Calculate the total deformation of the tubing string under the combined effects of various effects during the fracturing process. .

[0213] S302, Calculate the critical expansion / contraction amount of the expansion joint. .

[0214] S303, the number of expansion joints must meet the following formula:

[0215] ,

[0216] in, The quantity of the new type of telescopic tube is [number].

[0217] [Example 1] To verify the practical application effect of the novel telescopic pipe structure for high-temperature and high-pressure wells and its optimized tubing configuration method of the present invention, a tubing configuration test was carried out in an X1 ultra-deep high-temperature and high-pressure well in an oilfield. The specific test conditions and results are as follows:

[0218] Well X1 was drilled to a depth of 8699m, which is a typical ultra-deep, high-temperature and high-pressure well. The packer was set at a depth of 7200m. The tubing string was configured with two 3 1 / 2″ telescopic tubes. The actual depth of the telescopic tubes was 7180m, and the design telescopic distance of a single telescopic tube was 3m.

[0219] Based on the schematic diagram of the X1 wellbore structure and tubing assembly (as shown in the diagram) Figure 4 As shown), the acid fracturing construction curve of well X1 (as shown) Figure 5 As shown in the figure, the piston force variation law of "tubing with conventional telescopic pipe" and "tubing with the new telescopic pipe of this invention" under acid pressure conditions is quantitatively calculated through the built-in tubing mechanical analysis module of this invention; among them, the key parameters of the X1 well casing are detailed in Table 3, which provides the basic boundary conditions for mechanical calculation.

[0220] The results of the mechanical analysis calculation of the tubular column are as follows: Figure 6 As shown in the data, during the entire acid fracturing process of Well X1, the piston force on the tubing string using the new telescopic pipe of this invention was significantly lower than that of the conventional telescopic pipe string, with a maximum reduction rate of 55.49%. Especially under low-pressure fracturing fluid conditions, when the new telescopic pipe is in a semi-stretched working state, its tubing piston force is only 177.09 kN, which is 52% lower than that of the conventional telescopic pipe under the same conditions. This effectively avoids the risks of packer seal failure, tubing deformation or movement caused by piston force overload, and significantly improves the safety and reliability of the tubing string in high-temperature and high-pressure well acid fracturing operations.

[0221] Table 3. Oil Casing Data for Well X1

[0222]

Claims

1. A new type of telescopic pipe structure for high temperature and high pressure wells and a pipe string optimization configuration method thereof, characterized in that, The new telescopic pipe structure and the new telescopic pipe column optimization configuration method are disclosed. The new telescopic pipe structure comprises an outer cylinder mechanism, an inner cylinder mechanism and a balance chamber mechanism; the outer cylinder mechanism comprises an upper joint, an upper outer cylinder, an outer cylinder connecting short section, a short section end cover, a lower outer cylinder, a sealing short section and a sealing end cover, the upper joint is connected with an upper oil pipe through an internal thread and connected with the upper outer cylinder through an external thread, the upper outer cylinder is connected with the outer cylinder connecting short section through an external thread, the outer cylinder connecting short section is connected with the lower outer cylinder through an external thread and connected with the short section end cover through an internal thread, the lower outer cylinder is connected with the sealing short section through an internal thread, and the sealing short section is connected with the sealing end cover through an internal thread; the inner cylinder mechanism comprises a lower joint, a lower inner cylinder, an inner cylinder connecting short section, an inner cylinder end cover, an upper inner cylinder and a sealing end head, the lower joint is connected with a lower oil pipe through an external thread and connected with the lower inner cylinder through an internal thread, the lower inner cylinder is connected with the inner cylinder connecting short section through an external thread, the inner cylinder connecting short section is connected with the inner cylinder end cover through an external thread and connected with the upper inner cylinder through an internal thread, and the upper inner cylinder is connected with the sealing end head through an external thread; the balance chamber mechanism comprises an inner pressure chamber, an outer pressure chamber, an inner hydraulic hole and an outer hydraulic hole, the inner pressure chamber is communicated with the inner pressure of the oil pipe through the inner hydraulic hole arranged in the lower inner cylinder, and the outer pressure chamber is communicated with the outer pressure of the oil pipe through the outer hydraulic hole arranged in the lower outer cylinder. The new telescopic pipe column optimization configuration method comprises the following steps: S1: analysis of the mechanical behavior of the new telescopic pipe column, which comprises the following sub-steps: S101, pipe string axial force before packer setting Calculation: ， in, Before packer setting The axial force of the tubular column at point N; From the bottom of the well The length of the oil pipe at the location, in meters (m). The weight per unit length of the oil pipe, in N; The inclination angle is expressed in rad. The fluid density inside the tubing. ; The density of the annular fluid. ; The area enclosed by the inner diameter of the oil pipe. ; The area enclosed by the outer diameter of the oil pipe. ; It is the acceleration due to gravity. ; denoted as the axial Coulomb friction coefficient between the inner walls of the tubing and casing, dimensionless; The positive pressure of the tubing on the casing, in N; S102, pipe string axial force after packer setting Calculation: ， wherein, is the axial force on the string of pipe at the point, N; is the axial force on the string of pipe at the point, N; is the packer set pressure, Pa; S103, Axial force of pipe string under fracturing working condition Calculation: ， wherein, is the axial force of the pipe string at the point, N; is the axial force of the pipe string at the point, N; is the elastic modulus of the test pipe string, MPa; is the cross-sectional area of the test pipe string of the first is the cross-sectional area of the test pipe string of the first 2 ; is the deformation of the test pipe string of the first is the deformation of the test pipe string of the first is the length of the test pipe string of the first is the length of the test pipe string of the first S104: analysis of the starting process of the new telescopic pipe, New retracting tube piston force The calculation formula is: ， wherein, N is the new telescopic tube piston load, P is the tubing internal pressure, MPa; P is the tubing external pressure, MPa; D is the tubing outside diameter, mm; D is the tubing inside diameter, mm; D is the new telescopic tube inner tube outside diameter, mm; D is the new telescopic tube outer tube inside diameter, mm; When the pipe string is installed with multiple new type stretch pipes, the front After the first The formula for calculating the load of the first stretch pipe pin is: ， wherein, is the Rooted expansion tube pin shear load, N; is the actual axial load on the test string at the expansion tube, N; is the displacement compensation of a single expansion tube, m; If wherein, is the new telescopic tube shear pin rated shear value, N; then the Telescopic tube is activated into the working condition; S105: judgment of the state after the starting of the new telescopic pipe, If then the telescopic tube is in the fully closed condition; If , the critical telescopic amount of the telescopic tube needs to be further calculated ; If wherein, m is the compensation amount for the telescopic tube design; the telescopic tube is in a partially stretched state; If then the telescopic tube is in full extension; S106: calculation of the shaft force of the new telescopic pipe after the starting, If the telescopic pipe is in the fully closed state, the axial force calculation formula of the test pipe string is , If the telescopic pipe is in full stretch state, the axial force calculation formula of the test pipe string is , If the telescopic pipe is in a partially stretched state, the axial force calculation formula of the test pipe string is: , S2: design of the position of the new telescopic pipe, which comprises the following sub-steps: S201: calculation of the range of well depth in which the telescopic pipe cannot be started when the packer is set, According to the new telescopic tube shear pin rated shear value Calculate the well depth range that meets the setting condition under which the telescopic tube cannot be started : ， wherein, N is the load on the pin when the expansion tube is in different positions under the setting condition. S202: calculation of the range of well depth in which the telescopic pipe is started in the fracturing reconstruction working condition, Shear rating of new type of telescopic pipe shear pin Calculating well depth range that meets the condition of telescopic pipe starting under fracturing reconstruction : ， wherein, N is the load on the pin when the extension pipe is in different positions under fracturing conditions. S203, determining the effective well depth range in which the telescopic pipe works ; S204: iterative calculation and determination of the optimal position of the telescopic pipe in the effective well depth range, S3: design of the number of the new telescopic pipe, which comprises the following sub-steps: S301, calculate the total deformation of the pipe string under the comprehensive effect of each effect in the fracturing process ; S302, calculate the critical telescopic amount of the telescopic tube ; S303, determining the number of new telescopic pipes according to the total deformation of the pipe column and the critical telescopic amount: , wherein, is the number of new telescopic pipes, and n is an integer.

2. The new telescopic pipe structure for high temperature and high pressure well and its string optimization configuration method according to claim 1, characterized in that, Three V-type packing seal devices are arranged between the outer cylinder mechanism and the inner cylinder mechanism; the V-type packing seal device adopts fluorine rubber material when the well temperature is ≤180℃, adopts perfluoroether rubber material when the well temperature is >180℃, and the sealing gap of the V-type packing seal device is ≤0.1mm.

3. The new type of telescopic pipe structure for high temperature and high pressure well and the method for optimizing the configuration of the pipe string according to claim 1, characterized in that, A torque transmission key is installed between the outer cylinder connecting short section and the upper inner cylinder, and the torque transmission key adopts spring steel material; a shear pin is installed between the lower outer cylinder and the inner cylinder connecting short section, and when the axial load borne by the pipe column reaches the rated shear value of the shear pin, the shear pin is sheared, and the telescopic pipe is started.

4. The new type of telescopic pipe structure for high temperature and high pressure well and the method for optimizing the configuration of the pipe string according to claim 1, characterized in that, Conventional telescopic tube piston force The calculation formula is: ， wherein, Fp is the conventional telescoping tube piston force load, N; Dp is the conventional telescoping tube piston diameter, mm.

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