A method for determining the permissible pressure of the casing annulus in high-pressure oil and gas wells and its application

Abstract

The present invention provides a method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well and its application. The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well provided by the present invention systematically considers the safety requirements of various components constituting the casing annulus device, such as the tubing head, tubing string, production casing, and packer, and has better pertinence and reliability. The present invention also provides a device for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well. The implementation scheme of the device to solve the problem includes the above-mentioned method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well, which has the advantages of high efficiency and strong operability. The present invention also provides the application of the method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well in the transformation operation of a high-pressure oil and gas well. According to the range of the permissible pressure value of the casing annulus determined by the method, a curve diagram of the relationship between the permissible pressure value of the casing annulus and the pump pressure during the transformation process can be drawn, which has important guiding significance for on-site transformation operations.

Description

Technical Field

[0001] The invention belongs to the field of gas production engineering, and relates to a method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well and an application thereof. Background Art

[0002] During the high-pressure oil and gas well transformation operation, safety control is of vital importance and runs through the entire transformation process. Once out of control, it will lead to operation failure or even catastrophic consequences.

[0003] The safety of transformation operations depends not only on the quality of equipment and process measures, but also on the management of the transformation process. For example, the pressure control of the casing annulus (the annulus between the tubing string and the production casing) is extremely important for the wellbore safety of high-pressure oil and gas wells.

[0004] In actual production, excessively high casing annulus pressure may lead to potential production safety accidents; if the casing annulus pressure is too low, the casing pressure difference at the wellhead will be too large, the safety factor will be low, and long-term fatigue production will also easily lead to accidents. Therefore, it is very important to predetermine a reasonable casing annulus pressure control value for the operation safety of high-pressure oil and gas wells.

[0005] High-pressure oil and gas wells are usually completed by using a completion string with a packer and filling the annulus with completion fluid. In order to ensure the safety of the operation, it is usually necessary to supplement the pressure of the casing annulus. The operating conditions of high-pressure oil and gas wells are more complicated than those of general low-pressure oil and gas wells. Affected by high temperature and high pressure, even for some low-yield high-pressure gas reservoirs, the construction pressure of the transformation operation will be high. Therefore, the casing annulus pressure has a great impact on the safety of the operating string or production string.

[0006] Therefore, in the design stage before entering the field operation, the permissible pressure values ​​of the casing annulus in each operation link must be comprehensively analyzed to determine the reasonable permissible pressure values ​​of the casing annulus, so as to effectively ensure the safety of the high-pressure oil and gas well transformation operation. In other words, the determined casing annulus pressure control range can ensure that the devices and components constituting the casing annulus in the high-pressure oil and gas well, including the tubing head, production casing, tubing string, packer and other components, are always in a safe state.

[0007] In view of this, determining the permissible pressure of the casing annulus is crucial to ensure the safety of high-pressure oil and gas well reconstruction operations. Summary of the invention

[0008] The present invention provides a method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well. The method systematically considers the safety requirements of various components constituting the casing annulus device, such as a tubing head, a tubing string, a production casing, and a packer, and determines the permissible pressure of the casing annulus according to the actual well conditions and working conditions of the high-pressure oil and gas well, thereby having better pertinence and reliability.

[0009] The present invention also provides a device for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well. The implementation scheme of the device includes the above-mentioned method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well, and has the advantages of high efficiency and strong operability.

[0010] The present invention also provides a method for determining the allowable pressure of the casing annulus of a high-pressure oil and gas well and its application in high-pressure oil and gas well reconstruction operations. A curve diagram of the relationship between the allowable pressure value of the casing annulus of a high-pressure oil and gas well and the pump pressure can be drawn based on the above method for determining the allowable pressure of the casing annulus of a high-pressure oil and gas well, which is very convenient for on-site operations.

[0011] A first aspect of the present invention provides a method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well, comprising the following steps:

[0012] Obtain the maximum allowable pressure value P1 of the first casing annulus according to the rated strength of the tubing head;

[0013] Obtain the maximum allowable pressure value P2 of the second casing annulus according to the internal pressure resistance strength of the production casing;

[0014] Obtain the maximum allowable pressure value P3 of the third casing annulus according to the rated working pressure of the packer;

[0015] Obtain the maximum allowable pressure value P4 of the fourth casing annulus according to the external squeezing force of the tubing string;

[0016] Obtain the minimum allowable pressure value P5 of the first casing annulus according to the rated working pressure of the packer;

[0017] Obtain the minimum allowable pressure value P6 of the second casing annulus according to the internal pressure of the tubing string;

[0018] Determine the maximum allowable pressure value of the casing annulus based on P1, P2, P3, and P4;

[0019] Determine the minimum allowable pressure value of the casing annulus based on P5 and P6.

[0020] In a possible implementation, the method for obtaining the maximum allowable pressure value P2 of the second oil casing annulus according to the internal pressure resistance strength of the production casing includes:

[0021] According to formula 1, P2 is obtained;

[0022] P2=P 内 / S1﹢ρ b gh×10 -3 ﹣ρ a gh×10 -3 Formula 1

[0023] In formula 1: P 内 is the internal pressure resistance strength of the production casing, MPa; S1 is the safety factor of the production casing against internal pressure; ρ ais the completion fluid density in the casing annulus, g / cm 3 ρ b is the brine density of the annulus between the production casing and the inner technical casing, g / cm 3 ; g is the acceleration of gravity, N / kg; h is the depth of the danger point, m.

[0024] In a possible implementation, the method for obtaining the maximum allowable pressure value P3 of the third casing annulus according to the rated working pressure of the packer includes:

[0025] According to formula 2, P3 is obtained;

[0026] P3=P t ﹢ρ t gh p ×10 -3 ﹢P pe ﹣ρ a gh p ×10 -3 Formula 2

[0027] In formula 2: P t is the pump pressure, MPa; ρ t is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; P pe is the rated working pressure of the packer, MPa; ρ a is the completion fluid density in the casing annulus, g / cm 3 ;h p is the packer setting depth, m.

[0028] In a possible implementation, the method for obtaining the maximum allowable pressure value P4 of the fourth casing annulus according to the external squeezing force of the oil pipe string includes:

[0029] According to formula 3, P4 is obtained;

[0030] P4=P t0 ﹣ρ p gh×10 -3 Formula 3

[0031] In formula 3: P t0 is the external squeeze force of the tubing string, MPa; ρ p is the completion fluid density in the annulus between the tubing and the production casing, g / cm 3 ; g is the acceleration due to gravity, N / kg; h is the depth of the calculation point, m.

[0032] In a possible implementation, the method for obtaining the minimum allowable pressure value P5 of the first casing annulus according to the rated working pressure of the packer includes:

[0033] According to formula 4, P5 is obtained;

[0034] P5=P t ﹢ρ t gh p ×10 -3 -P pe ﹣ρ a gh p ×10 -3 Formula 4

[0035] In formula 4: P t is the pump pressure, MPa; ρ t is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; P pe is the rated working pressure of the packer, MPa; ρ a is the completion fluid density in the casing annulus, g / cm 3 ;h p is the packer setting depth, m.

[0036] In a possible implementation, the method for obtaining the minimum allowable pressure value P6 of the second casing annulus according to the internal pressure of the tubing string includes:

[0037] According to formula 5, P6 is obtained;

[0038] P6=P ti ﹣ρ p gh×10 -3 Formula 5

[0039] In formula 5: P ti is the external squeeze force of the tubing string, MPa; ρ p is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; h is the depth of the calculation point, m.

[0040] In a possible implementation, determining the maximum allowable pressure value of the casing annulus according to P1, P2, P3, and P4 includes:

[0041] The maximum allowable pressure of the casing annulus is determined based on the minimum value of P1, P2, P3, and P4.

[0042] In a possible implementation, determining the minimum allowable pressure value of the casing annulus according to P5 and P6 includes:

[0043] The minimum allowable pressure value of the casing annulus is determined based on the maximum value of P5 and P6.

[0044] A second aspect of the present invention provides a device for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well, the device comprising:

[0045] A first acquisition unit, the first acquisition unit is used to acquire a maximum allowable pressure value P1 of the first casing annulus according to the rated strength of the tubing head;

[0046] A second acquisition unit, the second acquisition unit is used to obtain the maximum allowable pressure value P2 of the second oil casing annulus according to the internal pressure resistance strength of the production casing;

[0047] A third acquisition unit, the third acquisition unit is used to acquire a third maximum allowable pressure value P3 of the casing annulus according to the rated working pressure of the packer;

[0048] A fourth acquisition unit, the fourth acquisition unit is used to acquire a fourth maximum allowable pressure value P4 of the casing annulus according to the external squeezing force of the oil pipe string;

[0049] A fifth acquisition unit, the fifth acquisition unit is used to acquire the minimum allowable pressure value P5 of the first oil casing annulus according to the rated working pressure of the packer;

[0050] A sixth acquisition unit, the sixth acquisition unit is used to acquire the minimum allowable pressure value P6 of the second oil casing annulus according to the internal pressure of the oil pipe string;

[0051] A first determining unit, the first determining unit is used to determine the maximum allowable pressure value of the casing annulus according to P1, P2, P3, and P4;

[0052] The second determining unit is used to determine the minimum allowable pressure value of the casing annulus according to P5 and P6.

[0053] A third aspect of the present invention provides a method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well and its application in high-pressure oil and gas well reconstruction operations.

[0054] The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well provided by the present invention systematically considers the safety requirements of various components constituting the casing annulus device, such as the tubing head, tubing string, production casing, and packer, and determines the permissible pressure of the casing annulus according to the actual well conditions and working conditions of the high-pressure oil and gas well, and has better pertinence and reliability. The device for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well provided by the present invention, the implementation scheme of the device includes the above-mentioned method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well, and has the advantages of high efficiency and strong operability. According to the method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well provided by the present invention, a curve diagram of the relationship between the permissible pressure value of the casing annulus and the pump pressure during the transformation process can be drawn, which has important guiding significance for on-site transformation operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A flow chart of a method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well according to the present invention;

[0056] Figure 2The present invention is a flow chart of a device for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] A first aspect of the present invention provides a method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well. Figure 1 The flowchart of the method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well according to the present invention is shown in FIG. Figure 1 As shown, the method comprises the following steps:

[0059] S101: Obtaining the maximum allowable pressure value P1 of the first casing annulus according to the rated strength of the tubing head;

[0060] S102: Obtain the maximum allowable pressure value P2 of the second casing annulus according to the internal pressure resistance strength of the production casing;

[0061] S103: Obtain the maximum allowable pressure value P3 of the third casing annulus according to the rated working pressure of the packer;

[0062] S104: Obtain the maximum allowable pressure value P4 of the fourth casing annulus according to the external squeezing force of the tubing string;

[0063] S105: Obtain the minimum allowable pressure value P5 of the first casing annulus according to the rated working pressure of the packer;

[0064] S106: Obtain the minimum allowable pressure value P6 of the second casing annulus according to the internal pressure of the tubing string;

[0065] S107: Determine the maximum allowable pressure value of the casing annulus based on P1, P2, P3, and P4;

[0066] S108: Determine the minimum allowable pressure value of the casing annulus based on P5 and P6.

[0067] The above S101 to S106 are in no particular order, and S107 and S108 are also in no particular order.

[0068] When S101 to S104 are completed, S107 can be completed according to the results obtained; when S105 to S106 are completed, S108 can be completed according to the results obtained.

[0069] When the annular pressure of the casing and oil casing is abnormal, the safety limit value of the annular pressure of the casing and oil casing needs to be considered. The maximum allowable pressure value of the annular pressure of the casing and oil casing is the upper limit of the safety limit value, and the minimum allowable pressure value of the annular pressure of the casing and oil casing is the lower limit of the safety limit value. When the annular pressure of the casing and oil casing exceeds the maximum allowable pressure value of the annular pressure of the casing and oil casing, pressure relief measures need to be taken; when the annular pressure of the casing and oil casing is lower than the minimum allowable pressure value of the annular pressure of the casing and oil casing, pressure replenishment measures need to be taken.

[0070] The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well provided by the present invention determines the final maximum permissible pressure value of the casing annulus by comprehensively comparing the first maximum permissible pressure value P1 of the casing annulus, the second maximum permissible pressure value P2 of the casing annulus, the third maximum permissible pressure value P3 of the casing annulus, and the fourth maximum permissible pressure value P4 of the casing annulus obtained according to the rated strength of the tubing head, the internal pressure resistance of the production casing, the rated working pressure of the packer, and the external squeezing force of the tubing string.

[0071] The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well provided by the present invention determines the final minimum permissible pressure value of the casing annulus by comprehensively comparing the first minimum permissible pressure value P5 of the casing annulus and the second minimum permissible pressure value P6 of the casing annulus obtained according to the rated working pressure of the packer and the internal pressure of the oil tubing.

[0072] The pressure range between the maximum allowable pressure value of the casing annulus and the minimum allowable pressure value of the casing annulus is the allowable pressure of the casing annulus of the high-pressure oil and gas well determined by the present invention.

[0073] The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well provided by the present invention systematically considers the safety requirements of various components constituting the casing annulus device including the tubing head, the tubing string, the production casing, the packer, etc., and determines the range of the permissible pressure of the casing annulus according to different well conditions and transformation conditions encountered by the high-pressure oil and gas well. The method has strong pertinence and good reliability, and is of great significance for the transformation construction of high-pressure oil and gas wells.

[0074] In a possible implementation, the maximum allowable pressure value P1 of the first oil casing annulus can be directly taken as the rated strength of the tubing head. The rated strength of the tubing head is determined by the material properties of the tubing head itself and does not need to be obtained through calculation.

[0075] In a possible implementation, a method for obtaining the maximum allowable pressure value P2 of the second casing annulus according to the internal pressure resistance strength of the production casing includes:

[0076] According to formula 1, P2 is obtained;

[0077] P2=P 内 / S1﹢ρ b gh×10 -3 ﹣ρ a gh×10-3 Formula 1

[0078] In formula 1: P 内 is the internal pressure resistance strength of the production casing, MPa; S1 is the safety factor of the production casing against internal pressure; ρ a is the completion fluid density in the casing annulus, g / cm 3 ρ b is the brine density of the annulus between the production casing and the inner technical casing, g / cm 3 ; g is the acceleration of gravity, N / kg; h is the depth of the danger point, m.

[0079] When the present invention is implemented, the internal pressure resistance strength P of the production casing is 内 The safety factor S1 against internal pressure is determined by the material properties of the production casing itself and does not need to be obtained through calculation; the brine density ρ of the completion fluid in the oil casing annulus and the annulus between the production casing and the inner technical casing a and ρ b It can be measured according to the commonly used density meter method; the value of gravity acceleration g can be 9.8N / kg; the danger point depth h is the maximum value of the production casing depth.

[0080] If the production casing is tied back after completion, the wear of the upper tie-back casing will not be considered, and the maximum allowable pressure value P2 of the second casing annulus will be calculated directly according to the internal pressure resistance of the new casing using Formula 1; if the production casing is worn due to drilling or workover operations, it is necessary to calculate the maximum allowable pressure value P2 of the second casing annulus according to the internal pressure resistance of the worn casing using Formula 1.

[0081] In actual field applications, the production casing included in the wellbore of a high-pressure oil and gas well may be a multi-stage casing. The size, wall thickness, internal pressure resistance and other parameters of each stage of casing may be different. In specific calculations, it is necessary to calculate the maximum allowable pressure value P2 of the second oil casing annulus separately according to each stage of casing.

[0082] In a possible implementation, a method for obtaining the maximum allowable pressure value P3 of the third casing annulus according to the rated working pressure of the packer includes:

[0083] According to formula 2, P3 is obtained;

[0084] P3=P t ﹢ρ t gh p ×10 -3 ﹢P pe ﹣ρ a gh p ×10 -3 Formula 2

[0085] In formula 2: P t is the pump pressure, MPa; ρ tis the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; P pe is the rated working pressure of the packer, MPa; ρ a is the completion fluid density in the casing annulus, g / cm 3 ;h p is the packer setting depth, m.

[0086] The pump pressure is the pressure of the transformation fluid injected into the wellhead. In the specific implementation of the present invention, the specific pump pressure P t The value can be read from the pressure gauge at the wellhead.

[0087] To ensure the sealing effect of the packer, the upper and lower pressure difference of the packer is required to be no greater than its rated working pressure P pe , that is, it needs to satisfy Formula 6:

[0088] |P 上 -P 下 |≤P pe Formula 6

[0089] In formula 6: P 上 is the pressure acting on the upper part of the packer (the sum of the annular pressure and the annular protection liquid column pressure), MPa; P 下 It is the pressure acting on the lower part of the packer (the sum of the pump pressure and the reforming fluid column pressure).

[0090] In a possible implementation, a method for obtaining the maximum allowable pressure value P4 of the fourth casing annulus according to the external squeezing force of the tubing string includes:

[0091] According to formula 3, P4 is obtained;

[0092] P4=P t0 ﹣ρ p gh×10 -3 Formula 3

[0093] In formula 3: P t0 is the external squeeze force of the tubing string, MPa; ρ p is the completion fluid density in the annulus between the tubing string and the production casing, g / cm 3 ; g is the acceleration due to gravity, N / kg; h is the depth of the calculation point, m.

[0094] Among them, the external squeeze force P of the oil pipe string t0 can be calculated by the following three formulas:

[0095]

[0096]

[0097] σz =G / AF formula 9

[0098] In formulas 7, 8, and 9: r is the radial stress, MPa; σ θ is the circumferential stress, MPa; σ z is the axial stress, MPa; P t0 is the external squeeze force of the tubing string, MPa; P ti is the internal pressure of the tubing string, MPa; r t0 is the outer radius of the tubing string, mm; r t0 is the inner radius of the tubing string, mm; r is the average value of the outer radius and the inner radius of the tubing string, mm; G is the weight of the tubing string, N; F is the buoyancy of the tubing string, MPa; A is the cross-sectional area of ​​the tubing string, m 2 .

[0099] The outer radius r of the above tubing string t0 、Inner radius of tubing string r t0 All are known values. The internal pressure of the tubing string P ti It can be calculated by formula 10:

[0100] P ti =P t +ρ t gh p ×10 -3 Formula 10

[0101] In formula 10: P ti is the internal pressure of the tubing string, MPa; P t is the pump pressure, MPa; ρ t is the density of the fluid in the tubing string; g is the acceleration due to gravity, N / kg; h p To calculate the point depth.

[0102] Using the fourth strength theory, the radial stress σ in equations 7, 8, and 9 is r , circumferential stress σ θ , axial stress σ z Three values ​​and the von Mises stress σ of the tubing string VME There is an equation relationship as shown in formula 11:

[0103]

[0104] In formula 11: z is the axial stress, MPa; σ θ is the circumferential stress, MPa; σ r is the radial stress, MPa.

[0105] In field applications, according to the Von-Mises yield strength criterion, the von Mises stress should satisfy equation 12:

[0106]

[0107] In formula 12: VME is the von Mises stress of the oil pipe string, MPa; Y e is the yield strength of the tubing string, MPa; S is the von Mises stress safety factor of the tubing string.

[0108] The yield strength of the tubing string can be calculated using formula 13 or formula 14:

[0109]

[0110] In formula 13, F a is the tensile strength of the tubing string, kN; D is the outer diameter of the tubing string, mm; d is the inner diameter of the tubing string, mm.

[0111]

[0112] In formula 13, P b is the internal pressure strength of the tubing string, kN; D is the outer diameter of the tubing string, mm; d is the inner diameter of the tubing string, mm.

[0113] In a possible implementation, a method for obtaining the minimum allowable pressure value P5 of the first casing annulus according to the rated working pressure of the packer includes:

[0114] According to formula 4, P5 is obtained;

[0115] P5=P t ﹢ρ t gh p ×10 -3 -P pe ﹣ρ a gh p ×10 -3 Formula 4

[0116] In formula 4: P t is the pump pressure, MPa; ρ t is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; P pe is the rated working pressure of the packer, MPa; ρ a is the completion fluid density in the casing annulus, g / cm 3 ;h p is the packer setting depth, m.

[0117] In a possible implementation, a method for obtaining the minimum allowable pressure value P6 of the second casing annulus according to the internal pressure of the tubing string includes:

[0118] According to formula 5, P6 is obtained;

[0119] P6=P ti ﹣ρ p gh×10 -3 Formula 5

[0120] In formula 5: P ti is the internal pressure of the tubing string, MPa; ρ p is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; h is the depth of the calculation point, m.

[0121] When determining the maximum allowable pressure value of the casing annulus, the strength value of the weakest section in the annulus between the production casing and the tubing string should be considered. Therefore, the minimum value among the first casing annulus maximum pressure value P1, the second casing annulus maximum pressure value P2, the third casing annulus maximum pressure value P3, and the fourth casing annulus maximum pressure value P4 is taken as the maximum allowable pressure value of the casing annulus.

[0122] If the annular pressure is too low, the oil-casing pressure difference at the wellhead will be too large, the safety factor will be too low, and accidents are prone to occur. When taking the minimum allowable pressure value of the oil-casing annulus, the maximum value of the first oil-casing annulus minimum allowable pressure value P5 and the second oil-casing annulus minimum allowable pressure value P6 is taken as the minimum allowable pressure value of the oil-casing annulus.

[0123] A second aspect of the present invention provides a device for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well. Figure 2 The flow chart of the device for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well according to the present invention is as follows: Figure 2 As shown, the device comprises:

[0124] A1: first acquisition unit;

[0125] The first acquisition unit is used to acquire the maximum allowable pressure value P1 of the first casing annulus according to the rated strength of the tubing head;

[0126] A2: second acquisition unit;

[0127] The second acquisition unit is used to acquire the maximum allowable pressure value P2 of the second oil casing annulus according to the internal pressure resistance strength of the production casing;

[0128] A3: The third acquisition unit;

[0129] The third acquisition unit is used to acquire the third maximum allowable pressure value P3 of the casing annulus according to the rated working pressure of the packer;

[0130] A4: The fourth acquisition unit;

[0131] The fourth acquisition unit is used to acquire the fourth maximum allowable pressure value P4 of the casing annulus according to the external squeezing force of the oil pipe string;

[0132] A5: The fifth acquisition unit;

[0133] The fifth acquisition unit is used to acquire the minimum allowable pressure value P5 of the first oil casing annulus according to the rated working pressure of the packer;

[0134] A6: Sixth acquisition unit;

[0135] The sixth acquisition unit is used to acquire the minimum allowable pressure value P6 of the second casing annulus according to the internal pressure of the oil pipe string;

[0136] A7: First determination part;

[0137] The first determination unit is used to determine the maximum allowable pressure value of the casing annulus according to P1, P2, P3, and P4;

[0138] A8: The second determination part;

[0139] The second determining unit is used to determine the minimum allowable pressure value of the casing annulus according to P5 and P6.

[0140] Since the implementation scheme of the above-mentioned device for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well is similar to the method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well, the implementation of the specific device can refer to the implementation of the aforementioned method, and the repeated parts will not be repeated.

[0141] A third aspect of the present invention provides a method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well and its application in high-pressure oil and gas well reconstruction operations.

[0142] In specific construction and renovation operations, the casing annulus pressure control range corresponding to different pump pressure values ​​can be calculated based on the method for determining the permissible pressure of the casing annulus of high-pressure oil and gas wells, and a curve diagram of the relationship between the permissible pressure value of the casing annulus of high-pressure oil and gas wells and the pump pressure can be drawn to form a chart. Through the chart, the changing pattern of the permissible pressure of the casing annulus of high-pressure oil and gas wells can be analyzed and determined more clearly and simply, which is very convenient for on-site operations.

[0143] The present invention is further described in detail below in conjunction with specific embodiments.

[0144] Example 1

[0145] The pressure level of the tubing head of the high-pressure oil and gas well in this embodiment is 105 MPa, and the density of the completion fluid is 1.3 g / cm 3The packer is 6887.07m deep and its rated working pressure is 105MPa. The temperature gradient of the well is 2.33℃ / 100m. The formation temperature at 7145m in the middle of the production layer is 167℃. The pressure coefficient is 1.75. The middle of the production layer is 7145m. The formation pressure is 123MPa. The transformation displacement is 4.2m 3 / min, the fluid density in the oil pipe is 1.04g / cm 3 The brine density in the annulus between the production casing and the inner technical casing is 1.03 g / cm 3 The basic data of production casing at each level are shown in Table 1, and the basic parameters of oil tubing at each level are shown in Table 2.

[0146] Table 1 Parameters of production casing at all levels

[0147]

[0148] Table 2 Parameters of tubing strings at all levels

[0149]

[0150]

[0151] According to the parameters of the tubing head, production casing, packer and tubing string described above, the maximum allowable pressure value of the casing annulus and the minimum allowable pressure value of the casing annulus of the high-pressure oil and gas well are determined as follows:

[0152] S101: Obtaining the maximum allowable pressure value P1 of the first casing annulus according to the rated strength of the tubing head;

[0153] The pressure rating of the tubing head used in the high-pressure oil and gas well of Example 1 is 105 MPa, that is, the rated strength value of the tubing head is 105 MPa, so the maximum allowable pressure value P1 of the first casing annulus can be determined to be 105 MPa;

[0154] S102: According to formula 1: P2 = P 内 / S1﹢ρ b gh×10 -3 ﹣ρ a gh×10 -3 Determine the maximum allowable pressure value P2 of the second casing annulus;

[0155] As shown in Table 1, the high-pressure oil and gas well in Example 1 has five levels of production casings, and the maximum casing annulus pressure value needs to be calculated for each level of production casing, and the minimum value is the maximum allowable pressure value P2 of the second casing annulus;

[0156] P in Formula 1 内It is the internal pressure resistance strength in Table 1; S1 is the safety factor of the internal pressure resistance strength of the production casing, and the value of the five-level casing is 1.25; ρ b The density of brine in the annulus between the production casing and the inner technical casing is 1.03 g / cm 3 ρ a is the completion fluid density mentioned above, which is 1.3 g / cm 3 ; The value of h is the lower depth value in Table 1. The maximum allowable pressure value P2 of the second casing annulus is 56MPa calculated by formula 1;

[0157] S103: According to formula 2: P3 = P t ﹢ρ t gh p ×10 -3 ﹢P pe ﹣ρ a gh p ×10 -3 Determine the maximum allowable pressure value P3 of the third casing annulus;

[0158] P in Formula 2 t is the pump pressure, which is 61MPa; t is the fluid density in the tubing string, which is 1.04; h p is the packer setting depth, which is consistent with the packer lower depth, 6887.07m; P pe is the rated working pressure of the packer, which is 105MPa; ρ a is the completion fluid density in the casing annulus, which is 1.3 g / cm 3 According to formula 2, the maximum allowable pressure value P3 of the third casing annulus is 112.4MPa;

[0159] S104: According to formula 3: P4 = P t0 ﹣ρ p gh×10 -3 Determine the maximum allowable pressure value P4 of the fourth casing annulus;

[0160] As shown in Table 2, the oil pipe used in the high-pressure oil and gas well of Example 1 is composed of 6 different oil pipe strings, which are numbered as oil pipe 1 to oil pipe 6. It is necessary to calculate the maximum casing annulus pressure value of the 6 oil pipe strings, and the minimum value is taken as the maximum allowable pressure value P4 of the fourth casing annulus;

[0161] In formula 3, P t0 is the external squeeze force of the oil pipe string, which needs to be calculated by equation 7-13;

[0162] Formula 7 is:

[0163] Formula 8 is:

[0164] Formula 9 is: z =G / AF

[0165] Formula 10 is: ti =P t +ρ t gh p ×10 -3

[0166] Formula 11 is:

[0167] Formula 12 is:

[0168] Formula 13 is:

[0169] Among them, in the calculation of formula 9, the parameters required for calculation are G, A, and F. G is the weight of the tubing string, which can be obtained by multiplying the linear weight of the tubing string in Table 2 by the depth of the tubing string. A is the cross-sectional area of ​​the tubing string, which can be obtained according to the outer diameter of the tubing string given in Table 2. F is the buoyancy of the tubing string, and the calculation formula is ρgh, where ρ is the density of the fluid in the tubing string, which is 1.04 g / cm 3 , h is the depth of the oil pipe string, which is given in Table 1. The axial stress σ is calculated from this z ;

[0170] In the calculation of formula 13, F a The value is the tensile strength in Table 2, D is the outer diameter in Table 2, and the inner diameter can be obtained by subtracting twice the wall thickness from the outer diameter, thus obtaining Y e ;

[0171] Since the maximum allowable pressure of the casing annulus is calculated at this time, the equal sign in formula 12 is used to calculate σ VME Calculation is performed and Y is obtained in formula 13 e , the value of S is 1.5, from which we can get σ VME ;

[0172] σ VME Substituting into formula 11, and combining formula 7 and formula 8, the axial stress σ z It has been calculated by formula 9. P in formula 7 and 8 ti is the internal pressure of the tubing string, through formula 10: P ti =P t +ρ t gh p ×10 -3 Calculated, P in formula 10 t is the pump pressure, which is 61MPa, ρ t is the density of the fluid in the tubing string, which is 1.04 g / cm3 ,h p To calculate the point depth, the value is the tubing depth of each specification above the packer depth, and its values ​​are listed in Table 2; r t0 is the outer radius of the tubing string, and its value is half of the outer diameter of the tubing string in Table 2; r t0 is the inner radius of the tubing string, which is the outer radius of the tubing string minus the wall thickness. The outer diameter and wall thickness of the tubing string are given in Table 2. Substituting the above values ​​into equations 7, 8, and 11, P can be calculated. t0 ;

[0173] ρ in Formula 3 p is the completion fluid density, which is 1.3 g / cm 3 ; h is the depth of the calculation point, which is the depth of the tubing of each specification above the packer depth, and its value is listed in Table 2; According to Formula 3, the maximum allowable pressure value P4 of the fourth casing annulus is 108.5MPa;

[0174] S105: According to formula 4: P5 = P t ﹢ρ t gh p ×10 -3 -P pe ﹣ρ a gh p ×10 -3 Determine the minimum allowable pressure value P5 of the first casing annulus;

[0175] The values ​​of the parameters in Formula 4 are the same as the values ​​of the parameters in Formula 2 in S103. According to Formula 4, the minimum allowable pressure value P5 of the first casing annulus is calculated to be 0 MPa;

[0176] S106: According to Formula 5: P6 = P ti ﹣ρ p gh×10 -3 Get the minimum allowable pressure value of the second casing annulus as P6;

[0177] In formula 5, P ti is the internal pressure of the tubing string, the calculation method of which has been described in S104; ρ p is the fluid density in the tubing string, which is 1.04 g / cm 3 ; h is the depth of the calculation point, which is taken as the lower depth of the tubing of each specification above the lower depth of the packer. Its values ​​are listed in Table 2. According to Formula 5, the minimum allowable pressure value P6 of the second casing annulus is calculated to be 5MPa;

[0178] S107: Compare the maximum allowable pressure value of the first casing annulus P1 (105 MPa), the maximum allowable pressure value of the second casing annulus P2 (56 MPa), the maximum allowable pressure value of the third casing annulus P3 (112.4 MPa), and the maximum allowable pressure value of the fourth casing annulus P4 (108.5 MPa), and take the minimum value of 56 MPa as the maximum allowable pressure value of the casing annulus during the transformation of the high-pressure oil and gas well;

[0179] S108: Compare the first minimum allowable pressure value of the casing annulus P5 (0 MPa) and the second minimum allowable pressure value of the casing annulus P6 (5 MPa), and take the maximum value of 5 MPa as the minimum allowable pressure value of the casing annulus during the transformation of the high-pressure oil and gas well.

[0180] From the above results, it can be determined that when the pump pressure is 61MPa, the allowable pressure range of the casing annulus of the high-pressure oil and gas well is 5-56MPa. Based on this range, the casing annulus pressure of the high-pressure oil and gas well is strictly monitored. When the pressure exceeds 56MPa, pressure relief measures need to be taken. When the pressure is lower than 5MPa, pressure replenishment measures need to be taken.

[0181] Based on the above process, a series of different pump pressure values ​​can be assumed to obtain the maximum and minimum allowable pressure values ​​of the casing annulus under different pump pressures, forming a database of the correspondence between pump pressure and the allowable pressure value of the casing annulus, thereby drawing a curve of the relationship between the allowable pressure value of the casing annulus and the pump pressure during the renovation process. The casing annulus pressure value can be referred to this graph during the renovation construction process to ensure the safety of the construction operation.

[0182] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0183] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well, characterized in that: The following steps are involved: Obtain the maximum allowable pressure value P1 of the first casing annulus according to the rated strength of the tubing head; Obtain the maximum allowable pressure value P2 of the second casing annulus according to the internal pressure resistance strength of the production casing; According to the rated working pressure of the packer, the maximum allowable pressure value P of the third casing annulus is obtained. 3； Obtain the maximum allowable pressure value P4 of the fourth casing annulus according to the external squeezing force of the tubing string; Obtain the minimum allowable pressure value P5 of the first casing annulus according to the rated working pressure of the packer; Obtain the minimum allowable pressure value P6 of the second casing annulus according to the internal pressure of the tubing string; Determine the maximum allowable pressure value of the casing annulus based on P1, P2, P3, and P4; Determine the minimum permissible pressure value of the casing annulus based on P5 and P6; The method for obtaining the maximum allowable pressure value P3 of the third oil casing annulus according to the rated working pressure of the packer comprises: According to formula 2, P3 is obtained; P3 = P t + ρ t gh p × 10 -3 + P pe − ρ a gh p × 10 -3 Equation 2 In formula 2: P t is the pump pressure, MPa; ρ t is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; P pe is the rated working pressure of the packer, MPa; ρ a is the completion fluid density in the casing annulus, g / cm 3 ;h p is the packer setting depth, m; The method for obtaining the minimum allowable pressure value P5 of the first casing annulus according to the rated working pressure of the packer comprises: According to formula 4, P5 is obtained; P5= P t ﹢ρ t gh p ×10 -3 -P pe ﹣ρ a gh p ×10 -3 Formula 4 In formula 4: P t is the pump pressure, MPa; ρ t is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; P pe is the rated working pressure of the packer, MPa; ρ a is the completion fluid density in the casing annulus, g / cm 3 ;h p is the packer setting depth, m; The method further comprises: calculating the casing annulus pressure control range corresponding to different pump pressure values, and drawing a curve diagram of the relationship between the casing annulus allowable pressure value of the high-pressure oil and gas well and the pump pressure.

2. The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well according to claim 1, characterized in that: The method for obtaining the maximum allowable pressure value P2 of the second casing annulus according to the internal pressure resistance strength of the production casing comprises: According to formula 1, P2 is obtained; P2= P 内 / S1﹢ρ b gh×10 -3 ﹣ρ a gh×10 -3 Formula 1 In formula 1: P 内 is the internal pressure resistance strength of the production casing, MPa; S1 is the safety factor of the production casing against internal pressure; ρ a is the completion fluid density in the casing annulus, g / cm 3 ρ b is the brine density of the annulus between the production casing and the inner technical casing, g / cm 3 ; g is the acceleration of gravity, N / kg; h is the depth of the danger point, m.

3. The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well according to claim 1, characterized in that: The method for obtaining the maximum allowable pressure value P4 of the fourth casing annulus according to the external squeezing force of the oil pipe string comprises: According to formula 3, P4 is obtained; P4= P t0 ﹣ρ p gh×10 -3 Formula 3 In formula 3: P t0 is the external squeeze force of the tubing string, MPa; ρ p is the completion fluid density in the annulus between the tubing and the production casing, g / cm 3 ; g is the acceleration due to gravity, N / kg; h is the depth of the calculation point, m.

4. The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well according to claim 1, characterized in that: The method for obtaining the minimum allowable pressure value P6 of the second casing annulus according to the internal pressure of the tubing string comprises: According to formula 5, P6 is obtained; P6= P ti ﹣r p gh×10 -3 formula 5 In formula 5: P ti is the internal pressure of the tubing string, MPa; ρ p is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; h is the depth of the calculation point, m.

5. The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well according to claim 1, characterized in that: Determining the maximum allowable pressure value of the casing annulus based on P1, P2, P3, and P4 includes: The maximum allowable pressure of the casing annulus is determined based on the minimum value of P1, P2, P3, and P4.

6. The method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well according to claim 1, characterized in that: Determining the minimum allowable pressure value of the casing annulus according to P5 and P6 includes: The minimum allowable pressure value of the casing annulus is determined based on the maximum value of P5 and P6.

7. A device for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well, characterized in that: The device comprises: A first acquisition unit, the first acquisition unit is used to acquire a maximum allowable pressure value P1 of the first casing annulus according to the rated strength of the tubing head; A second acquisition unit, the second acquisition unit is used to obtain the maximum allowable pressure value P2 of the second oil casing annulus according to the internal pressure resistance strength of the production casing; A third acquisition unit, the third acquisition unit is used to acquire a third maximum allowable pressure value P3 of the casing annulus according to the rated working pressure of the packer; A fourth acquisition unit, the fourth acquisition unit is used to acquire a fourth maximum allowable pressure value P4 of the casing annulus according to the external squeezing force of the oil pipe string; A fifth acquisition unit, the fifth acquisition unit is used to acquire the minimum allowable pressure value P5 of the first oil casing annulus according to the rated working pressure of the packer; A sixth acquisition unit, the sixth acquisition unit is used to acquire the minimum allowable pressure value P6 of the second oil casing annulus according to the internal pressure of the oil pipe string; A first determining unit, the first determining unit is used to determine the maximum allowable pressure value of the casing annulus according to P1, P2, P3, and P4; A second determining unit, the second determining unit is used to determine the minimum allowable pressure value of the casing annulus according to P5 and P6; Wherein, the third acquisition unit is specifically used for: According to formula 2, P3 is obtained; P3 = P t + ρ t gh p × 10 -3 + P pe − ρ a gh p × 10 -3 Equation 2 In formula 2: P t is the pump pressure, MPa; ρ t is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; P pe is the rated working pressure of the packer, MPa; ρ a is the completion fluid density in the casing annulus, g / cm 3 ;h p is the packer setting depth, m; The fifth acquisition unit is specifically used for: According to formula 4, P5 is obtained; P5= P t ﹢ρ t gh p ×10 -3 -P pe ﹣ρ a gh p ×10 -3 Formula 4 In formula 4: P t is the pump pressure, MPa; ρ t is the fluid density in the tubing string, g / cm 3 ; g is the acceleration due to gravity, N / kg; P pe is the rated working pressure of the packer, MPa; ρ a is the completion fluid density in the casing annulus, g / cm 3 ;h p is the packer setting depth, m; The second determination unit is further used to calculate the casing annulus pressure control range corresponding to different pump pressure values, and draw a relationship curve between the casing annulus allowable pressure value of the high-pressure oil and gas well and the pump pressure.

8. Application of the method for determining the permissible pressure of the casing annulus of a high-pressure oil and gas well according to any one of claims 1 to 6 in high-pressure oil and gas well reconstruction operations.

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