A method and system for judging the failure of multiple packers based on the calculation of pipe string deformation

Abstract

The present invention discloses a method and system for judging the failure of multiple packers based on the calculation of pipe string deformation, which relates to the technical field of oil and gas well packers. The method includes the following steps: calculating the first change length based on the total axial force change, calculating the second change length based on the radial force received by the pipe string, calculating the third change length based on the temperature change received by the pipe string, calculating the fourth change length based on the virtual force of the buckling effect of the pipe string, and calculating the fifth change length based on the relaxation force received by a single packer. Whether the entire multiple packer string fails is judged by the sum of all change lengths; the system is a virtual device for this method. The judgment method and system calculate the deformation of the pipe string by combining five factors: end face force, radial force, temperature, buckling, and relaxation force. The total deformation obtained by calculation is more real and accurate, and can provide a reliable judgment basis for the deformation failure of the packer.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well packers, and more specifically, to a method and system for judging the failure of multiple packers based on the calculation of string deformation. Background Art

[0002] Currently, the research on multiple packers is not yet mature, and many proposed models are overly simplified. For example, the influence of buckling is ignored, and various frictional forces are ignored. Existing research shows that the influence of buckling, frictional forces, etc. on the string cannot be ignored, otherwise serious calculation errors will occur.

[0003] Therefore, in the prior art, the analysis and calculation of the deformation of multiple packers are either ideal assumptions, such as assuming that the packers do not affect each other, assuming that the single-packer situation is the same as that of some multiple-packer situations, etc., or the influence of key factors is ignored, such as ignoring the buckling factor, resulting in a large error in the final calculation result and being unable to accurately judge the failure situation of the corresponding packer further.

[0004] In view of this, the present application is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for judging the failure of multiple packers based on the calculation of string deformation. The judgment method and system calculate the deformation of the string by combining five factors: end face force, radial force, temperature, buckling, and relaxation force. The total deformation obtained by the calculation is more real and accurate, and can provide a reliable basis for judging the deformation failure of the packer.

[0006] The embodiments of the present invention are implemented as follows:

[0007] In a first aspect, a method for judging the failure of multiple packers based on the calculation of string deformation includes the following steps: calculating the first change length: obtaining the axial additional force F τ,j received by the string to be analyzed, the end face force F a1,j at the packer corresponding to the string to be analyzed, and the end face force F a2,j at the corresponding pipe diameter change, and calculating the total axial force F τ,j and the total axial force change ΔF a1,j of the string based on F a2,j , and calculating the first change length ΔL1 based on the total axial force change ΔF α , where the total axial force change ΔF α is based on the total axial force F α , and the total axial force change ΔF α is based on the total axial force F αObtained by calculating the initial total axial force F0; calculating the second change length: calculating the second change length ΔL2 based on the radial force received by the pipe string; calculating the third change length: calculating the third change length ΔL3 based on the temperature change received by the pipe string; calculating the fourth change length: calculating the fourth change length ΔL4 based on the virtual force F generated by the buckling effect of the pipe string f Calculating the fourth change length ΔL4; wherein, calculating the fourth change length ΔL4 according to the position of the buckling neutral point; calculating the fifth change length: calculating the fifth change length ΔL5 based on the relaxation force F received by the corresponding packer s Calculating the fifth change length ΔL5, wherein the relaxation force F s is obtained by solving respectively when the pipe string is in a straight state or a buckled state; judging whether the entire multi-packer string fails based on the sum of ΔL1, ΔL2, ΔL3, ΔL4 and ΔL5.

[0008] In an alternative embodiment, in calculating the fourth change length, the calculation steps of the buckling neutral point are as follows: when the buckling neutral point is on the pipe string to be analyzed, ΔL4 is obtained by calculating through the following expression (1):

[0009]

[0010] Or, when the buckling neutral point is above the pipe string to be analyzed, ΔL4 is obtained by calculating through the following expression (2):

[0011]

[0012] In expressions (1) and (2), r represents the gap between the pipe string and the casing; E represents the elastic modulus of the pipe string; I represents the moment of inertia of the pipe string; W represents the unit weight of the pipe string; l represents the length of the pipe string.

[0013] In an alternative embodiment, whether the buckling neutral point is located on the pipe string to be analyzed is judged through the following expression (3):

[0014]

[0015] In expression (3), n represents the distance from the neutral point to the bottom of the well; W i and W j respectively represent the unit weights of pipe string i and pipe string j; l represents the length of pipe string j.

[0016] In an alternative embodiment, in calculating the fifth change length:

[0017] If the pipe string is in a straight state, then based on the relaxation force F s Calculating the fifth change length ΔL5 is achieved through the following expression (4):

[0018]

[0019] In formula (4), l represents the length of the pipe string; E represents the elastic modulus of the pipe string; A t represents the cross-sectional area of the pipe string.

[0020] In an alternative embodiment, when calculating the fifth change length: if the pipe string is in a buckled state, the sum of the relaxation force F s it receives and the virtual force F f it receives is used as the resultant force F to calculate the fifth change length ΔL5.

[0021] In an alternative embodiment, the end face force F a1,j at the packer is expressed by formula (5) as:

[0022] F a1,j =(A p,j -A i，j )P i，j -(A p，j -A o，j )P o，j (5);

[0023] The end face force F a2,j at the pipe diameter change is expressed by formula (6) as:

[0024] F a2,j =(A i,j+1 -A i，j )P i，j -(A o,j+1 -A o，j )P o,j (6)

[0025] In formulas (5) and (6), A p,j represents the area corresponding to the inner diameter of the packer at packer j, A i,j represents the area corresponding to the inner diameter of the pipe at packer j, A o,j represents the area corresponding to the outer diameter of the pipe at packer j, P i,j represents the internal pressure at packer j, P o,j represents the external pressure at packer j.

[0026] In an alternative embodiment, based on the total axial force change ΔF α the first change length ΔL1 is calculated through formula (7) as follows:

[0027]

[0028] In formula (7), E represents the elastic modulus of the pipe string; A t represents the cross-sectional area of the pipe string; l represents the length of the pipe string.

[0029] In an optional embodiment, the second change length ΔL2 is calculated based on the radial force on the pipe string by expression (8):

[0030]

[0031] In formula (8), l represents the length of the string consisting of all pipe strings; u represents the Poisson's ratio; Δρ i Indicates the change in density of the liquid in the tube; Δρ o represents the change in density of the liquid outside the pipe string; δ represents the pressure drop in the pipe caused by the flow rate per unit length; Δp i Indicates the pressure change in the pipe string; Δp o It represents the change of external pressure of the pipe string; R represents the ratio of the outer diameter to the inner diameter of the pipe string; E represents the elastic modulus of the pipe string.

[0032] In an optional embodiment, the third change length ΔL3 is calculated based on the temperature change of the column by expression (9):

[0033] ΔL3=lα△T (9);

[0034] In formula (9), α represents the thermal expansion coefficient; ΔT represents the average temperature change; l represents the length of the pipe string composed of all pipe strings.

[0035] In a second aspect, a multi-packer failure judgment system based on string deformation calculation includes:

[0036] The first calculation unit is used to calculate the first variable length: obtain the additional axial force F on the pipe string to be analyzed τ,j , the end force F at the packer corresponding to the pipe string to be analyzed a1,j And the corresponding end force F at the point where the pipe diameter changes a2,j , based on F τ,j 、F a1,j and F a2,j Calculate the total axial force F of the pipe string α And the total axial force change ΔF α , based on the total axial force change ΔF α Calculate the first change length ΔL1, where the total axial force change ΔF α is based on the total axial force F α Calculated with the initial total axial force F0;

[0037] A second calculation unit, which is used to calculate a second change length: calculate the second change length ΔL2 based on the radial force exerted on the pipe string;

[0038] A third calculation unit, which is used to calculate a third change length: the third change length ΔL3 is calculated based on the temperature change of the pipe string;

[0039] A fourth calculation unit, which is configured to calculate a fourth change length: based on the virtual force F of the buckling effect of the pipe string f Calculate the fourth change length ΔL4; wherein, the fourth change length ΔL4 is calculated according to the position of the buckling neutral point;

[0040] A fifth calculation unit, which is configured to calculate a fifth change length: based on the relaxation force F received by the corresponding packer s Calculate the fifth change length ΔL5, wherein the relaxation force F s is obtained by solving respectively when the pipe string is in a straight state or a buckling state;

[0041] A judgment unit, which is configured to judge whether the entire multi-packer string fails based on the sum of ΔL1, ΔL2, ΔL3, ΔL4 and ΔL5.

[0042] The beneficial effects of the embodiments of the present invention are:

[0043] The method and system for judging the failure of multi-packers based on the calculation of pipe string deformation provided by the embodiments of the present invention can calculate the total deformation length or all axial forces of the pipe string by comprehensively considering the factors affecting the pipe string deformation, such as end face force, radial force, temperature, buckling effect and relaxation force, etc. The five influencing factors are used to calculate the deformation length of the pipe string. The correction term is used to solve some factors that cannot be quantitatively calculated in the prior art, and thus judge whether the packer fails, so as to obtain a more accurate and reliable judgment result. Description of the Drawings

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0045] Figure 1 It is a schematic structural diagram of an n-multi-packer string in a vertical well provided by the embodiments of the present invention;

[0046] Figure 2 It is a calculation flow chart of the failure judgment method provided by the embodiments of the present invention. Detailed Embodiments

[0047] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0048] Accordingly, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0049] It should be understood that the "system", "device" and / or "module" used in the present invention is a way to distinguish different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the said words can be replaced by other expressions.

[0050] As shown in the present invention and the claims, unless the context clearly indicates an exception, words such as "a", "an", "one" and / or "the" are not specifically singular and may also include plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the clearly identified steps and elements, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements.

[0051] Flowcharts are used in the present invention to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the operations before or after do not necessarily need to be executed precisely in sequence. On the contrary, they can be executed in reverse order or simultaneously. At the same time, other operations can also be added to these processes, or one or several operations can be removed from these processes.

[0052] Embodiment

[0053] Currently, the research on multiple packers is not comprehensive. In previous research, there was a problem that the model assumptions were too ideal, resulting in unreliable conclusions or inapplicability to general downhole systems. For example, when analyzing the forces on a horizontal double-packer well, it was assumed that there was no direct influence between the packers, and it was considered that the force applied to the string at the upper packer was similar to that on a single-packer system; another example is the research on double packers in horizontal wells, where the axial stress of the pipe string was calculated and it was concluded that the packer at the intersection of the curved cross-section column and the horizontal cross-section column was most likely to lose its seal, but the influence of buckling was ignored.

[0054] Therefore, in view of the lack of a complete research system and plan in the current research on multiple packers, and the existing research on multiple packers being relatively one-sided, with rather stringent assumptions that are difficult to conform to reality and unable to reveal the general laws of multiple packers, and there are also problems such as overly simplified models and ignored key influencing factors resulting in serious calculation errors, this embodiment provides a method for judging the failure of multiple packers based on the calculation of tubing deformation, which can calculate the deformation of the tubing by considering multiple factors, that is, using the overall method as the basic method and the general formula for solving multiple packers, and obtaining a reliable basis for judging whether the packer fails by calculating the deformation length and all axial forces of the tubing.

[0055] Specifically, a method for judging the failure of multiple packers based on the calculation of tubing deformation provided in this embodiment includes the following calculation steps, which are respectively used to obtain the first change length ΔL1, the second change length ΔL2, the third change length ΔL3, the fourth change length ΔL4, and the fifth change length ΔL5 of the tubing to be analyzed. It should be noted that the object studied in this embodiment is, for example, a uniform-diameter tubing and a vertical well with multiple packers and fixed hydraulic packers. Exceptionally, if there is a compressive force on the tubing string, it is negative, and if there is a tensile force, it is positive; the axial shortening of the tubing string is negative, while the axial elongation is positive.

[0056] Please refer to Figure 1 , which shows a schematic diagram of an n-multiple packer string in a vertical well. The packers are numbered from the bottom of the well to the wellhead in sequence as "Packer 1", "Packer 2", and so on; the tubing part between the bottom of the well and Packer 1 is denoted as L1 (corresponding length is l1), similarly, the tubing part between Packer 1 and Packer 2 is denoted as L2 (corresponding length is l2), and continuing, the tubing part between Packer n and the wellhead is denoted as L n+1 (corresponding length is l n+1 ). It should be noted that when the packer is sealed, it is assumed that the well is filled with water, and in the acid fracturing operation, the well is filled with acid liquid; in addition, it is assumed that the piston force exerted by any downhole tool on the tubing string except the packer can be ignored.

[0057] This embodiment calculates the deformation of the tubing string with five influencing factors. The first factor is the end face force factor. At the packer and the diameter change of the tubing, due to the different cross-sectional areas, end face forces are generated in the liquid, thereby compressing or stretching the tubing string.

[0058] S1 Calculate the first change length: Obtain the axial additional force F τ,j received by the tubing string to be analyzed (usually the tubing), the end face force F a1,j at the corresponding packer of the tubing string to be analyzed, and the end face force F a2,j at the corresponding diameter change of the tubing string. Based on F τ,j , F a1,j and Fa2,j Calculate the total axial force F of the pipe string α and the change in total axial force ΔF α , based on the change in total axial force ΔF α calculate the first change in length ΔL1, where the change in total axial force ΔF α is calculated based on the total axial force F α and the initial total axial force F0. In this step S1, by calculating the deformation effect of the end face force generated at the packer and the pipe diameter change at the corresponding position of the pipe string to be analyzed, the calculation result of the first influence factor is obtained.

[0059] It should be noted that F τ,j represents the additional force of the axial force received by the j-th section of the pipe string and is an unknown (see the subsequent solution process). In step S1, the end face force F at the packer a1,j The expression (5) is:

[0060] F a1,j =(A p,j -A i，j )P i，j -(A p,j -A o，j )P o，j (5);

[0061] The end face force F at the pipe diameter change a2,j The expression (6) is:

[0062] F a2,j =(A i，j+1 -A i，j )P i，j -(A o，j+1 -A o，j )P o, j (6);

[0063] In equations (5) and (6), A p,j represents the area corresponding to the inner diameter of the packer at the packer j, A i,j represents the area corresponding to the inner diameter of the pipe at the packer j, A o,j represents the area corresponding to the outer diameter of the pipe at the packer j, P i,j represents the internal pressure at the packer j, P o,j represents the external pressure at the packer j.

[0064] Both of the above forces are components of the total axial force F α . The change in total axial force ΔF is obtained by the ratio of the total axial force F α to the initial total axial force F0 α . Based on this change in total axial force ΔF αThe calculation of the first change length ΔL1 is achieved through Expression (7):

[0065]

[0066] In Expression (7), E represents the elastic modulus of the pipe string; A t represents the cross-sectional area of the pipe string; l represents the length of the pipe string.

[0067] The second aspect is the radial force factor. The pipe string is subjected to a radial force and thus is squeezed or expanded, so it will also be elongated or compressed axially accordingly.

[0068] S2 calculates the second change length: Calculate the second change length ΔL2 based on the radial force received by the pipe string. In step S2, the aspect of the radial force affecting the deformation of the pipe string is considered. More specifically, the calculation of the second change length ΔL2 based on the radial force received by the pipe string is achieved through Expression (8):

[0069]

[0070] In Expression (8), l represents the length of the pipe string composed of all pipe columns; u represents the Poisson's ratio; Δρ i represents the change in the density of the liquid inside the pipe; Δρ o represents the change in the density of the liquid outside the pipe string; δ represents the pressure drop of the pipeline caused by the flow rate per unit length; Δp i represents the change in the pressure inside the pipe string; Δp o represents the change in the pressure outside the pipe string; R represents the ratio of the outer diameter to the inner diameter of the pipe string; E represents the elastic modulus of the pipe column.

[0071] The third aspect is the temperature factor. The pipe string will expand and contract due to temperature changes, that is, S3 calculates the third change length: Calculate the third change length ΔL3 based on the temperature change received by the pipe string; in this embodiment, the calculation of the third change length ΔL3 based on the temperature change received by the pipe string is achieved through Expression (9):

[0072] △L3 = lα△T (9);

[0073] In Expression (9), α represents the coefficient of thermal expansion; ΔT represents the average temperature change; l represents the length of the pipe string composed of all pipe columns.

[0074] The fourth aspect is the buckling effect factor. The pipe string will buckle due to the compressive force in the well, and the compressive force needs to reach a certain critical value. In addition, the force that causes the pipe string to buckle is called the virtual force F f Regarding the understanding of the virtual force F f if the force required to overcome the deformation caused by the self-weight of the pipe string is ignored, then the virtual force is the axial force received minus part of the liquid acting force.

[0075] S4 Calculate the fourth change length: Based on the virtual force F of the buckling effect of the pipe string f Calculate the fourth change length ΔL4; wherein, the fourth change length ΔL4 is calculated according to the position of the buckling neutral point; in this step S4, based on the virtual force F f Calculating ΔL4 needs to be calculated separately according to the position of the buckling neutral point.

[0076] Furthermore, when the buckling neutral point is on the pipe string to be analyzed, ΔL4 is calculated by the following expression (1):

[0077]

[0078] Or, when the buckling neutral point is above the pipe string to be analyzed, ΔL4 is calculated by the following expression (2):

[0079]

[0080] In expressions (1) and (2), r represents the gap between the pipe string and the casing; E represents the elastic modulus of the pipe string; I represents the moment of inertia of the pipe string; W represents the unit weight of the pipe string; l represents the length of the pipe string.

[0081] It should be noted that the buckling neutral point refers to the place where the bending strain on the pipe string is the smallest, that is, the place where bending just occurs. Below the buckling neutral point, the pipe string begins to bend, and above the pipe string, the pipe string does not bend. Since the research object is the entire pipe string, if the buckling neutral point is on the pipe string being analyzed, this section of the pipe string undergoes incomplete helical buckling, and all the pipe strings below this pipe string undergo complete helical buckling, and all the pipe strings above it do not buckle.

[0082] In addition, on the basis of the above scheme, the determination method of the buckling neutral point can adopt the hypothesis method. If the condition is satisfied, the position of the buckling neutral point can be determined, otherwise, continue to verify. Specifically, assume that the buckling neutral point is located on L1. We can establish a condition where n is less than the ratio of the applied force F f to the weight W1, that is, n = F f / W1 < 1l. If this condition is satisfied, the hypothesis is correct; if this condition is not satisfied, the hypothesis is not established and needs to be verified continuously.

[0083] Similarly, assume that the buckling neutral point is located on L2, then it needs to be satisfied And so on. Assume that the neutral point is located on L n Then, it can be judged by the following expression (3):

[0084]

[0085] In Equation (3), n represents the distance from the neutral point to the bottom of the well; W i and W j respectively represent the unit weights of tubing string i and tubing string j; l represents the length of tubing string j.

[0086] When calculating the fourth change length ΔL4 based on the virtual force F f , the virtual force F f can be obtained through the following solution proof: When there is liquid both inside and outside the tubing string, the liquid acting force that needs to be overcome when solving for the virtual force F f is F l,j =A o,j *P o,j -A i,j *P i,j . This expression can be understood as: To bend the tubing, at least a force of size F l,j is required, without considering the critical buckling force required by the tubing due to its own weight. Therefore, other axial forces (i.e., F τ,j ) also need to be obtained. Here, a correction term for solving the virtual force F f will be introduced to reduce errors.

[0087] Due to the influence of casing wall friction and fluid friction on the force acting on the tubing string, the equivalent axial force acting on the L j part of the tubing string is denoted as F τ,j , and they will change with the changes in the internal and external environments of the tubing string. Then a system of equations is established to determine the F τ,j value for the packer sealing time and the fracturing and acidizing time. F τ,j can be regarded as the equivalent axial force generated by other factors affecting the axial change. Next, the virtual force and axial force are obtained, and thus ΔL1 - ΔL4 can be calculated:

[0088] For L1, there is no packer below it. Therefore, it is subjected to an upward bottom force F l,0 and an equivalent axial force F τ,1 . Therefore, the total axial force received is F a,1 =F l,0 . F τ,j is not included in F a,j because F τ,j is an expression used to correct F f,j . When the string is in a straight and stable state, the conditions are relatively simple, such as no friction with the casing wall. When the tubing buckles, due to the presence of the fixed packer, the force analysis is more complex. Therefore, a correction item F τ,j needs to be added; for the deformation of the tubing, after overcoming the critical force F l,1 , there is a virtual force expression below: F f,1 =F l,0 -Fl,1 +F τ,1 。

[0089] For L2, L2 exerts a force F on L1 2-1 to balance L1, so L1 exerts a reaction force -F on L2 2-1 。F 2-1 =-(F l,0 +F τ,1 +L1W s ). Incorporating the end force at packer 1, the end force that may be caused by the change in tubing diameter, and the equivalent axial force F τ,2 , there is the following expression:

[0090]

[0091]

[0092] Similarly:

[0093]

[0094]

[0095]

[0096]

[0097] Establish an equation to solve for F τ,j :

[0098] After obtaining the axial length change of the string, calculate the force of the string on the packer according to Hooke's law and set it as F t , and then obtain:

[0099]

[0100] Since the packer cannot move, the force exerted on the packer by each part of the string is set as F t,i , for L2 there is:

[0101]

[0102] Similarly:

[0103]

[0104] In summary, the two virtual force expressions are equal. The former considers that the packer can move freely, so the deformation length of the pipe string is calculated and then the force of the packer on the string is calculated through Hooke's law (when considering the packer moving freely, the pipe string will be compressed, but actually the packer is fixed, so it will pull the pipe string downward). However, since the virtual force contains the unknown Fτ,j , there is also an unknown in the calculation formula of the deformed length. Therefore, a second expression is needed. The latter considers the packer fixed, regards each section of the pipe string as an independent system, and the force of the packer on the pipe string needs to be substituted according to the first case, and F can be solved τ,j , thus the virtual force and axial force of each section of the pipe string can be obtained, and then the length changes ΔL1-ΔL4 of each section of the pipe string can be obtained.

[0105] In addition, it should be noted that due to the existence of multiple packers, there is an unknown force F of the packer on the pipe string at each packer t , this force is the same as F τ,j , and it will affect the first length change and the fourth length change. The purpose of the above process is to solve F τ,j and F t , F τ,j is used to improve the accuracy and find some important forces that cannot be directly solved by the formula, F t is to find the force of the packer on the pipe string (the idea of solving the unknown is to establish a system of equations. One is to consider that all multiple packers disappear, so the first virtual force expression is obtained; the other is to directly consider that multiple packers exist, so the second virtual force expression is obtained, and the two are equal).

[0106] The fifth aspect is the relaxation force factor. After the packer is sealed, a part of the weight of the pipe string will be applied to the packer, and the packer will react with the axial force on the pipe string to become the "relaxation force", denoted as F s . The relaxation force refers to the load that drops in weight, and its value is equal to the gravity of part of the tubing string. When the packer is sealed, the direction of the relaxation force on the rope is upward. If it is assumed that the packer does not exist, the pipe string is equal to bearing the same force in the opposite direction, and the length change caused by it is denoted as L5. Assuming that the packer can move freely, the distance that should be moved after setting is but in fact it cannot move, so a corresponding axial force is needed to restore it to the original position (however, there is still a relaxation force to continue deforming at this time). When the pipe string does not buckle, at least the same magnitude and opposite direction of force need to be applied to make the pipe string buckle; when the pipe string buckles, any additional positive force will cause it to buckle more severely. Thus, through the relaxation force F s of the corresponding packer for further calculation:

[0107] S5 calculates the fifth change length: Based on the relaxation force F s received by the packer (the packer here refers to the packer corresponding to the pipe string to be analyzed) to calculate the fifth change length ΔL5, where the relaxation force F s is calculated respectively when the pipe string of the pipe string is in a straight state or a buckled state.

[0108] It should be noted that for any part of the pipe string, if the pipe string is in a straight state after sealing, then based on the relaxation force F s The calculation of the fifth change length ΔL5 is achieved through the following expression (4):

[0109]

[0110] In formula (4), l represents the length of the pipe string; E represents the elastic modulus of the pipe string; A t represents the cross-sectional area of the pipe string.

[0111] If the pipe string of the pipe column is in a buckled state, then the sum of the relaxation force F s it receives and the virtual force F f it receives is used as the resultant force F to calculate the fifth change length ΔL5. Specifically, for L2, there is an expression: F = F f,2 + F s,1 . Substituting this expression into the buckling calculation formula, ΔL'5 can be obtained; substituting F f,2 into the buckling calculation formula, ΔL”5 can be obtained, then ΔL5 = -(ΔL'5 - ΔL”5);

[0112] For L3, since the transfer of the relaxation force F s,1 to L3 will affect the buckling of L3, therefore, in order to obtain the individual influence of F s,2 on L3, the influence of F s,1 must be subtracted. Substituting F = F f,3 + F s,1 into the buckling calculation formula to obtain ΔL'5; substituting F = F f,3 + F s,1 + F s,2 into the buckling calculation formula to obtain ΔL”5; then ΔL5 = -(ΔL'5 - ΔL”5), and similarly, ΔL5 of L i can also be calculated.

[0113] Through the above technical solutions, the influencing factors of the deformation of the pipe string to be analyzed in five aspects are obtained, so that it is possible to judge whether the pipe string exceeds the failure threshold based on the sum of the ΔL1, ΔL2, ΔL3, ΔL4 and ΔL5, and then judge whether the entire multi-packer string fails through at least one pipe string. The judgment result obtained based on this is more real and reliable.

[0114] In other embodiments, for example, the following specific method for failure judgment (based on the judgment of F t ) can also be adopted: According to the calculated unknown F τ,j , substitute it into the following formula:

[0115]

[0116] Thus, there is a judgment condition, F t ≤F max Fmax refers to the maximum axial force that the packer can withstand;

[0117] If Ft is less than or equal to Fmax, the packer will not lose its seal; if Ft is greater than Fmax, it indicates that the packer will lose its seal.

[0118] Therefore, a short tubing joint can be added to protect the packer, that is, increase ΔLt until Ft is less than or equal to Fmax. Finally, there is also a way to relieve seal loss, which is to add a short tubing joint (expansion joint) to relieve the deformation of the pipe string. Therefore, the formula becomes: (ΔLt is the length of the short tubing joint, and finally compare it with Fmax.)

[0119]

[0120] In this embodiment, a multi-packer failure judgment system based on pipe string deformation calculation is also provided, mainly used for dividing the functional modules of the multi-packer failure judgment system based on pipe string deformation calculation according to the embodiments of the above method. For example, each functional module can be divided, or two or more functions can be integrated into one processing module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the present invention is illustrative, only a logical function division, and there can be other division methods in actual implementation. For example, in the case of dividing each functional module according to the corresponding functions, among them, the multi-packer failure judgment system based on pipe string deformation calculation may include a first calculation unit, a second calculation unit, a third calculation unit, a fourth calculation unit, a fifth calculation unit, and a judgment unit. The functions of each unit module will be elaborated below.

[0121] The first calculation unit is used to calculate the first change length: obtain the axial additional force F of the pipe string to be analyzed τ,j , the end face force F at the packer corresponding to the pipe string to be analyzed a1,j and the end face force F at the corresponding pipe diameter change a2,j , calculate the total axial force F of the pipe string based on F τ,j , F a1,j and F a2,j , and calculate the total axial force change ΔF α , calculate the first change length ΔL1 based on the total axial force change ΔF α , where the total axial force change ΔF α is calculated based on the total axial force F α and the initial total axial force F0; α

[0122] A second calculation unit for calculating a second change length: calculating the second change length ΔL2 based on the radial force received by the pipe string;

[0123] A third calculation unit for calculating a third change length: calculating the third change length Δl3 based on the temperature change received by the pipe string;

[0124] A fourth calculation unit for calculating a fourth change length: calculating the fourth change length ΔL4 based on the virtual force F of the buckling effect of the pipe string f wherein the fourth change length ΔL4 is calculated according to the position of the buckling neutral point;

[0125] A fifth calculation unit for calculating a fifth change length: calculating the fifth change length ΔL5 based on the relaxation force F received by the corresponding packer s wherein the relaxation force F s is obtained by solving respectively when the pipe string is in a straight state or a buckling state;

[0126] A judgment unit for judging whether the entire multi-packer string fails based on the sum of ΔL1, ΔL2, ΔL3, ΔL4 and ΔL5.

[0127] For other contents of the specific implementation of the above functional units, reference may be made to the content of the method embodiments. In the above embodiments, all or part of them may be implemented by software, hardware, firmware or any combination thereof. When implemented by software, all or part of it may be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website, computer, server or data center to another website, computer, server or data center in a wired or wireless manner. The computer-readable storage medium may be any available medium that the computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (such as a floppy disk, a hard disk, a magnetic tape), an optical medium (such as a DVD), or a semiconductor medium (such as a solid state disk (SSD)) and the like.

[0128] Embodiments of the present application are described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a means for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or a means for implementing the functions specified in multiple blocks.

[0129] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction means that implements the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or a means for implementing the functions specified in multiple blocks.

[0130] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or a means for implementing the functions specified in multiple blocks.

[0131] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

1. A method for judging the failure of multiple packers based on the calculation of pipe string deformation, characterized in that, Including the following steps: Calculate the first change length: Obtain the axial additional force F received by the pipe string to be analyzed τ,j , the end face force F at the packer corresponding to the pipe string to be analyzed a1,j and the end face force F at the corresponding pipe diameter change a2,j , based on the F τ,j , the F a1,j and the F a2,j Calculate the total axial force F of the pipe string α and the total axial force change ΔF α , based on the total axial force change ΔF α Calculate the first change length ΔL1, where the total axial force change ΔF α is calculated based on the total axial force F α and the initial total axial force F0; Calculating the second change length: calculating the second change length ΔL2 based on the radial force applied to the pipe string; Calculating the third change length: calculating the third change length ΔL3 based on the temperature change of the pipe string; Calculate the fourth variable length: Based on the virtual force F of the buckling effect of the pipe string f Calculate the fourth variable length ΔL4; wherein, calculate the fourth variable length ΔL4 according to the position of the buckling neutral point Calculate the fifth variable length: based on the relaxation force F received by the corresponding packer s Calculate the fifth variable length ΔL5, where the relaxation force F s is obtained by solving respectively when the string is in a straight state or a buckling state Judging whether the entire multi-packer string fails based on the sum of ΔL1, ΔL2, ΔL3, ΔL4 and ΔL5; When calculating the fifth variable length: If the string of the pipe string is in a buckled state, then use the sum of the relaxation force F s it receives and the virtual force F f it receives as the resultant force F to calculate the fifth variable length ΔL5; The virtual force F f is obtained by calculating F l and F τ , where F l represents the liquid acting force to be overcome; and F τ represents the additional axial force of the pipe string.

2. The multi-packer failure judgment method based on pipe string deformation calculation according to claim 1, wherein, In calculating the fourth change length, the calculation steps of the buckling neutral point are as follows: When the buckling neutral point is on the pipe string to be analyzed, ΔL4 is obtained by calculating through the following expression (1): Or, when the buckling neutral point is above the pipe string to be analyzed, ΔL4 is obtained by calculating through the following expression (2): In expressions (1) and (2), r represents the gap between the pipe string and the casing; E represents the elastic modulus of the pipe string; I represents the moment of inertia of the pipe string; W represents the unit weight of the pipe string; l represents the length of the pipe string.

3. The multi-packer failure judgment method based on pipe string deformation calculation according to claim 2, wherein, Whether the buckling neutral point is located on the pipe string to be analyzed is judged by the following expression (3): In formula (3), n represents the distance from the neutral point to the bottom of the well; W i and W j respectively represent the unit weights of tubing string i and tubing string j; l represents the length of tubing string j.

4. The multi-packer failure judgment method based on pipe string deformation calculation according to claim 1, wherein In calculating the fifth change length: If the pipe string's pipe string is in a straight state, then based on the relaxation force F s The calculation of the fifth change length ΔL5 is achieved through the following expression (4): In Equation (4), l represents the length of the pipe string; E represents the elastic modulus of the pipe string; A t represents the cross-sectional area of the pipe string.

5. The multi-packer failure judgment method based on pipe string deformation calculation according to claim 1, wherein End face force F at the packer a1,j Expression (5) is as follows: F a1,j = (A p,j - A i,j ) P i,j - (A p,j - A o,j ) P o,j (5); End face force F at the pipe diameter change a2,j The expression (6) is as follows: F a2,j = (A i,j+1 - A i,j ) P i,j - (A o,j+1 - A o,j ) P o,j (6); In formulas (5) and (6), A p,j represents the area corresponding to the inner diameter of the packer at packer j, A i,j represents the area corresponding to the inner diameter of the pipe at packer j, A o,j represents the area corresponding to the outer diameter of the pipe at packer j, P i,j represents the internal pressure at packer j, P o,j represents the external pressure at packer j.

6. The multi-packer failure judgment method based on the calculation of the pipe string deformation according to claim 1 or 5, characterized in that Based on the change in the total axial force ΔF α The calculation of the first change in length ΔL1 is achieved through expression (7): In Equation (7), E represents the elastic modulus of the pipe string; A t represents the cross-sectional area of the pipe string; l represents the length of the pipe string.

7. The multi-packer failure judgment method based on pipe string deformation calculation according to claim 1, wherein Calculating the second change length ΔL2 based on the radial force applied to the pipe string is realized through expression (8): In Equation (8), l represents the length of the pipe string composed of all pipe columns; u represents the Poisson's ratio; Δρ i represents the change in the density of the liquid inside the pipe; Δρ o represents the change in the density of the liquid outside the pipe string; δ represents the pressure drop of the pipeline caused by the flow rate per unit length; Δp i represents the change in the pressure inside the pipe string; Δp o represents the change in the pressure outside the pipe string; R represents the ratio of the outer diameter to the inner diameter of the pipe string; E represents the elastic modulus of the pipe column.

8. The method for judging the failure of multiple packers based on the calculation of string deformation according to claim 1, wherein Calculating the third change length ΔL3 based on the temperature change of the pipe string is realized through expression (9): ΔL3 = lαΔT (9); In expression (9), α represents the coefficient of thermal expansion; ΔT represents the average temperature change; l represents the length of the pipe string composed of all pipe strings.

9. A multi-packer failure judgment system based on pipe string deformation calculation, characterized in that, Including: A first calculation unit, which is used to calculate a first change length: obtaining an axial additional force F applied to the pipe string to be analyzed τ,j , an end face force F at the packer corresponding to the pipe string to be analyzed a1,j , and an end face force F at the corresponding pipe diameter change a2,j , based on the F τ,j , the F a1,j , and the F a2,j to calculate the total axial force F of the pipe string α and the change in total axial force ΔF α , based on the change in total axial force ΔF α to calculate a first change length ΔL1, where the change in total axial force ΔF α is obtained by calculating based on the total axial force F α and the initial total axial force F0; A second calculation unit for calculating the second change length: calculating the second change length ΔL2 based on the radial force applied to the pipe string; A third calculation unit for calculating the third change length: calculating the third change length ΔL3 based on the temperature change of the pipe string; The fourth calculation unit is configured to calculate a fourth change length: based on the virtual force F of the buckling effect occurring in the pipe string f calculate the fourth change length ΔL4; wherein, the fourth change length ΔL4 is calculated according to the position of the buckling neutral point; The fifth calculation unit is configured to calculate a fifth change length: based on the relaxation force F exerted on the corresponding packer s calculate the fifth change length ΔL5, where the relaxation force F s is obtained by solving respectively when the pipe string is in a straight state or a buckling state; A judging unit for judging whether the entire multi-packer string fails based on the sum of ΔL1, ΔL2, ΔL3, ΔL4 and ΔL5; Among them, the fifth calculation unit is further configured to perform the following steps: if the pipe string is in a buckled state, use the sum of the relaxation force F s it receives and the virtual force F f it receives as the resultant force F to calculate the fifth change length ΔL5; the virtual force F f is obtained by calculating from F l and F τ , where F l represents the liquid acting force to be overcome; F τ represents the axial additional force of the pipe string.

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