Method and device for determining bearing boundary of shaft before formation testing

Abstract

The invention discloses a method and device for determining the bearing boundary of a shaft before oil testing. The method comprises the steps that the stress state of a drill column unit is determined, the contact force between the drill column unit and a casing pipe is determined according to the stress state, and the drill column unit comprises a drill column connector and drill column sections located at the two ends of the connector; the sleeve abrasion depth of the sleeve is determined according to the contact force, the sleeve residual strength of the abrasion area of the sleeve is determined according to the sleeve abrasion depth, and the sleeve residual strength comprises residual internal pressure resistance strength, residual external extrusion resistance strength and residual tensile strength; according to the internal pressure, the external pressure, the axial force, the wear depth of the sleeve and the residual strength of the sleeve, a biaxial stress ellipse of the sleeve is drawn under a target coordinate system, and the biaxial stress ellipse is displayed, so that the problems that the wear condition of the sleeve is evaluated depending on manpower and experience and the residual strength of the sleeve is inaccurate in related technologies are solved; and the safety, the reliability and the operation efficiency of drilling operation are improved.

Description

Technical Field

[0001] This invention relates to the field of petroleum exploration technology, and in particular to a method and apparatus for determining the bearing capacity limit of a wellbore before oil testing. Background Technology

[0002] As shallow oil and gas resources are gradually depleted, oil and gas well development is increasingly moving towards deep wells, ultra-deep wells, and high-temperature, high-pressure oil and gas wells. However, with the increase in drilling depth, drilling time, and downhole temperature, the contact force between the drill string and casing also increases, leading to increasingly severe casing wear and consequently reducing the safety of subsequent well testing and completion operations.

[0003] In most related technologies, the stress state of the drill string unit is determined by experience or estimation, and often only a single strength index is considered, failing to fully consider the complex mechanical relationship between the drill string and the casing. This results in a lack of accuracy in the estimation process, making it impossible to accurately quantify the degree of casing wear, and thus difficult to comprehensively assess the remaining strength of the casing. Underestimating or overestimating the degree of casing wear not only affects the safety of drilling operations but also affects operational efficiency. Summary of the Invention

[0004] This invention provides a method and apparatus for determining the bearing capacity limit of the wellbore before oil testing, in order to solve the problem that related technologies have difficulty in accurately determining the wear condition and remaining strength of the casing, resulting in inaccurate assessment of the bearing capacity limit of the wellbore before oil testing.

[0005] According to one aspect of the present invention, a method for determining the wellbore bearing capacity limit before oil testing is provided, comprising:

[0006] Determine the stress state of the drill string unit, and determine the contact force between the drill string unit and the casing based on the stress state. The drill string unit includes a drill string joint and drill string sections located at both ends of the joint.

[0007] The wear depth of the sleeve is determined based on the contact force, and the remaining strength of the sleeve in the wear area is determined based on the wear depth, wherein the remaining strength of the sleeve includes the remaining internal pressure resistance, the remaining external extrusion resistance, and the remaining tensile strength.

[0008] Based on the internal pressure, external pressure, axial force, wear depth, and remaining strength of the casing, a biaxial stress ellipse of the casing is plotted in the target coordinate system, and the biaxial stress ellipse is displayed.

[0009] According to another aspect of the present invention, a device for determining the wellbore bearing capacity limit before oil testing is provided, the device comprising:

[0010] A drill string contact force determination module is used to determine the stress state of the drill string unit and determine the contact force between the drill string unit and the casing based on the stress state. The drill string unit includes a drill string joint and drill string sections located at both ends of the joint.

[0011] The casing remaining strength determination module is used to determine the casing wear depth of the casing based on the contact force, and to determine the casing remaining strength of the wear area of ​​the casing based on the casing wear depth, wherein the casing remaining strength includes remaining internal pressure resistance, remaining external extrusion resistance, and remaining tensile strength.

[0012] The wellbore bearing capacity determination module is used to draw a biaxial stress ellipse of the casing in the target coordinate system based on the internal pressure, external pressure, axial force, wear depth of the casing, and remaining strength of the casing, and to display the biaxial stress ellipse.

[0013] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising:

[0014] At least one processor; and

[0015] A memory communicatively connected to the at least one processor; wherein,

[0016] The memory stores a computer program that can be executed by the at least one processor, which enables the at least one processor to perform the method for determining the wellbore bearing limit before oil testing as described in any embodiment of the present invention.

[0017] According to another aspect of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium storing computer instructions for causing a processor to execute and implement the method for determining the wellbore bearing limit before oil testing as described in any embodiment of the present invention.

[0018] According to another aspect of the present invention, a computer program product is provided, the computer program product comprising a computer program that, when executed by a processor, implements the method for determining the wellbore bearing limit before oil testing as described in any embodiment of the present invention.

[0019] The technical solution of this invention firstly determines the stress state of the drill string unit and then determines the contact force between the drill string unit and the casing based on the stress state. Since the drill string unit includes a drill string joint and drill string sections located at both ends of the joint, the contact force between the drill string unit and the casing can be quantified, improving the accuracy of the overall mechanical analysis and providing data support for subsequent analysis. Next, the casing wear depth is determined based on the contact force, and the remaining casing strength in the wear area is determined based on the casing wear depth. Since the remaining casing strength includes remaining internal pressure resistance and remaining external pressure resistance... Extrusion strength and remaining tensile strength can comprehensively evaluate the overall mechanical properties of the casing under wear conditions, ensuring that multiple strengths are included in the analysis. Finally, based on the internal pressure, external pressure, axial force, wear depth, and remaining strength of the casing, a biaxial stress ellipse of the casing is plotted in the target coordinate system and displayed. This visually demonstrates the stress distribution of the casing under different pressures and wear conditions, solving the problem of inaccurate assessment of casing wear and remaining casing strength relying on manual and experience in related technologies, and improving the safety, reliability, and efficiency of drilling operations.

[0020] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of a method for determining the bearing capacity limit of a wellbore before oil testing, according to Embodiment 1 of the present invention.

[0023] Figure 2 This is a flowchart of a method for determining the wellbore bearing capacity limit before oil testing, according to Embodiment 2 of the present invention.

[0024] Figure 3 This is a flowchart of a method for determining the wellbore bearing capacity limit before oil testing, provided by Embodiment 3 of the present invention.

[0025] Figure 4 This is a schematic diagram of a device for determining the bearing capacity of a wellbore before oil testing, according to Embodiment 4 of the present invention.

[0026] Figure 5This is a three-dimensional schematic diagram of the stress state of a drill string unit in a wellbore, based on a method for determining the bearing capacity of a wellbore before oil testing, according to Embodiment 1 of the present invention.

[0027] Figure 6 This is a schematic diagram of the casing wear cross-sectional morphology and stress state of a method for determining the bearing limit of a wellbore before oil testing according to Embodiment 1 of the present invention.

[0028] Figure 7 This is a schematic diagram of the casing stress state in a curved section of a well, according to a method for determining the bearing capacity limit of a wellbore before oil testing provided in Embodiment 1 of the present invention.

[0029] Figure 8 This is a schematic diagram of the casing wear prediction results of a method for determining the bearing limit of a wellbore before oil testing according to Embodiment 1 of the present invention.

[0030] Figure 9 This is a schematic diagram of the biaxial stress ellipse of the casing at different wear depths, according to a method for determining the bearing limit of the wellbore before oil testing provided in Embodiment 1 of the present invention.

[0031] Figure 10 This is a schematic diagram of the structure of an electronic device for implementing the method of determining the wellbore bearing limit before oil testing according to an embodiment of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0034] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0035] The names of messages or information exchanged between multiple devices in the embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of such messages or information.

[0036] It is understood that before using the technical solutions disclosed in the various embodiments of this disclosure, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in this disclosure in an appropriate manner in accordance with relevant laws and regulations, and user authorization should be obtained.

[0037] For example, upon receiving a user's active request, a prompt message is sent to the user to explicitly inform them that the requested operation will require the acquisition and use of the user's personal information. This allows the user to independently choose whether to provide personal information to the software or hardware, such as the electronic device, application, server, or storage medium performing the operations of this disclosed technical solution, based on the prompt message.

[0038] As an optional but non-limiting implementation, in response to a user's active request, sending a prompt message to the user can be done via a pop-up window, where the prompt message can be presented in text format. Furthermore, the pop-up window can also include a selection control allowing the user to choose "agree" or "disagree" to provide personal information to the electronic device.

[0039] It is understood that the above notification and user authorization process are merely illustrative and do not constitute a limitation on the implementation of this disclosure. Other methods that comply with relevant laws and regulations may also be applied to the implementation of this disclosure.

[0040] It is understood that the data involved in this technical solution (including but not limited to the data itself, the acquisition or use of the data) shall comply with the requirements of relevant laws, regulations and related provisions.

[0041] Example 1

[0042] Figure 1 The flowchart of a method for determining the bearing capacity limit of the wellbore before oil testing is provided in Embodiment 1 of the present invention. This embodiment can be applied to the situation of evaluating casing wear and remaining strength in oil and gas well drilling. The method can be executed by a device for determining the bearing capacity limit of the wellbore before oil testing. The device for determining the bearing capacity limit of the wellbore before oil testing can be implemented in hardware and / or software. Optionally, it can be implemented by electronic devices, such as mobile terminals, PCs, or servers.

[0043] like Figure 1 As shown, the method may specifically include:

[0044] S110. Determine the stress state of the drill string unit, and determine the contact force between the drill string unit and the casing based on the stress state, wherein the drill string unit includes a drill string joint and drill string sections located at both ends of the joint.

[0045] The drill string unit can be understood as a connecting steel pipe section used in oil drilling. For example, the drill string unit may include, but is not limited to, a drill string joint and drill string sections located at both ends of the joint. The joint can be understood as a component connecting two drill string sections. The drill string section can be understood as the basic unit constituting the drill string, which can be a steel pipe of a specific length. The stress state can be understood as the mechanical state of the drill string unit in the operating environment. For example, the stress state may include, but is not limited to, pressure, tension, and bending stress, and the stress state is one of the key factors determining whether the drill string can work safely and effectively. The casing can be understood as a steel pipe lowered into the wellbore and fixed in place with cement, used to prevent wellbore collapse and isolate different formations.

[0046] Based on the above scheme, optionally, determining the contact force between the drill string and the casing according to the force state includes: determining the first component of the contact force in the principal normal direction based on the unit length of the drill string unit, the axial force at both ends, the effective weight of the drill string in the drilling fluid, the unit principal normal vector, and the rate of change of the total angle; determining the second component of the contact force in the secondary normal direction based on the effective weight of the drill string unit, the unit length, and the unit secondary normal vector; and determining the contact force between the drill string and the casing based on the first component and the second component.

[0047] The unit length can be understood as the length of a single drill string segment. The axial force at both ends can be understood as the force applied to both ends of the drill string unit along the drill string axis. The effective weight of the drill string can be understood as the effective gravity experienced by the drill string in a well filled with drilling fluid. It is understood that the actual weight of the drill string will be reduced due to the buoyancy of the drilling fluid. The unit principal normal vector can be understood as the direction perpendicular to the wellbore curve, pointing to the wellbore surface at a given location, and is used to determine the direction of the contact force. The rate of change of total angle can be understood as an index measuring the curvature of the wellbore trajectory, used to represent the change angle of the wellbore direction within a unit length. The first component force can be understood as the component of the contact force in the principal normal direction calculated based on the unit length, axial force, effective weight, and unit principal normal vector of the drill string unit. The unit secondary normal vector can be understood as a unit length vector relative to the principal normal vector in the direction perpendicular to the principal normal, used to define another direction of the contact force. The second component force can be understood as the component of the contact force in the secondary normal direction calculated based on the effective weight, unit length, and unit secondary normal vector of the drill string unit. The contact force can be understood as the magnitude and direction of the contact force between the drill string and the casing, determined by combining the first and second component forces. It is understood that both the unit principal normal vector and the unit secondary normal vector of the drill string unit are associated with the well inclination angle and azimuth angle corresponding to the two endpoints of the drill string unit. The well inclination angle can be understood as the angle between the drill string and the vertical line. The azimuth angle can be understood as the angle of the drill string unit projected onto the horizontal plane.

[0048] For example, the stress state of the drill string unit in the three-dimensional wellbore is as follows: Figure 5 As shown, 51 represents the casing, 52 represents the drill string section, and 53 represents the drill string joint. The following assumptions are made: ① The curvature of the drill string unit is constant; ② The curvature of the drill string unit is consistent with the wellbore curvature; ③ The wellbore curvature of the drill string sections at both ends lies within a single spatial plane; ④ The bending of the drill string unit is elastic deformation; ⑤ The axial tensile force of the downhole drill string unit is positive, and the axial compressive force is negative. Based on the force state of the drill string unit and the principle of force composition, the contact force F between the drill string section and the casing is... s It can be determined using the following formula:

[0049]

[0050] Among them, F s F represents the contact force between the drill string and the casing. n F is the component of the contact force in the direction of the principal normal vector; m This is the component of the contact force in the direction of the principal normal vector.

[0051] The component of the contact force in the direction of the principal normal vector can be determined based on the following formula:

[0052]

[0053] Among them, F n θ is the component of the contact force in the direction of the principal normal vector; L is the element length of the drill string; q is the effective weight of a unit length of drill string in the drilling fluid; n is the unit principal normal vector of the drill string; T1 is the axial force at the upper end of the drill string; T2 is the axial force at the lower end of the drill string; θ is the total angle change rate of the drill string.

[0054] The component of the contact force in the direction of the secondary normal vector can be determined based on the following formula:

[0055] F m =Lq·m; (3)

[0056] Among them, F m q is the component of the contact force in the direction of the principal normal vector; L is the element length of the drill string element; q is the effective weight of the drill string in the drilling fluid; m is the unit secondary normal vector of the drill string element, which is "+" (positive) when the drill string moves upward and "-" (negative) when the drill string moves downward.

[0057] The unit pair normal vector m of the drill string element can be determined based on the following formula:

[0058]

[0059] Where θ is the rate of change of the full angle of the drill string element; α1 and These are the well inclination angle and azimuth angle of the upper end of the drill string unit, respectively; α2 and These are the well inclination angle and azimuth angle at the lower end of the drill string unit, respectively.

[0060] The unit principal normal vector n of the drill string element can be determined based on the following formula:

[0061] n = m × τ0; (5)

[0062] Where m is the unit subnormal vector of the drill string element, and τ0 is the tangential vector at the midpoint of the drill string element.

[0063] The tangential vector τ0 at the midpoint of the drill string element can be determined based on the following formula:

[0064]

[0065] Where τ1 and τ2 are unit tangential vectors, which can be determined based on the following formula:

[0066]

[0067] Where i, j, k are unit vectors; α1 and These are the well inclination angle and azimuth angle of the upper end of the drill string unit, respectively; α2 and These are the well inclination angle and azimuth angle at the lower end of the drill string unit, respectively.

[0068] The above scheme, by accurately calculating the stress state and contact force components of the drill string unit, can more accurately assess the interaction between the drill string and the casing, improve the quantification accuracy of the contact force, thereby optimizing the prediction and management of casing wear and enhancing the safety and reliability of drilling operations.

[0069] S120. Determine the wear depth of the sleeve based on the contact force, and determine the remaining strength of the sleeve in the wear area based on the wear depth, wherein the remaining strength of the sleeve includes the remaining internal pressure resistance, the remaining external extrusion resistance, and the remaining tensile strength.

[0070] The casing wear depth can be understood as the thickness lost due to friction between the casing and the drill string. This wear depth directly affects the integrity and service life of the casing. The wear area can be understood as the specific area where the casing suffers wear due to contact with the drill string; this area may vary with time and operating conditions. The remaining casing strength can be understood as the mechanical strength retained by the casing after wear. For example, the remaining casing strength may include, but is not limited to, remaining internal pressure resistance, remaining external extrusion resistance, and remaining tensile strength. The remaining internal pressure resistance can be understood as the casing's ability to resist deformation or fracture under internal pressure. The remaining external extrusion resistance can be understood as the casing's ability to resist deformation under external extrusion, which can be formation pressure or external mechanical forces. The remaining tensile strength can be understood as the casing's strength under tensile load, i.e., its ability to withstand longitudinal tension without fracture. It is understood that a worn casing will have a thinner wall, thereby reducing its internal pressure resistance and resistance to external pressure, and making it more susceptible to damage under tensile conditions.

[0071] Based on the above scheme, optionally, the remaining strength of the casing includes the remaining internal pressure resistance; determining the remaining strength of the casing in the worn area based on the casing wear depth includes: determining the remaining internal pressure resistance of the worn area of ​​the casing in its original state based on the inner wall radius of the casing, the casing wear depth, the casing wall thickness of the unworn area of ​​the casing, and the casing yield strength corresponding to the worn area; determining the remaining internal pressure resistance of the worn area of ​​the casing under bending stress based on the remaining internal pressure resistance of the worn area in its original state, the bending stress of the casing, the inner wall radius, the outer wall radius, and the casing yield strength.

[0072] The inner wall radius of the casing can be understood as the radius of the inner side of the casing. The casing yield strength can be understood as the maximum stress value of the casing material before it begins to undergo plastic deformation, used to measure the strength of the casing material. The bending stress can be understood as the stress generated when the casing is subjected to bending load. It is understood that during drilling or production, the casing may undergo bending deformation due to geological structures or mechanical operations. The outer wall radius of the casing can be understood as the radius of the outer side of the casing.

[0073] For example, considering the combined effects of wear and wellbore curvature, it is assumed that the circumferential stress σ2 at the worn part of the casing reaches the casing yield strength σ. s If the bushing fails, then the remaining internal pressure resistance P of the worn area in its original state... b It can be determined based on the following formula:

[0074]

[0075] Among them, P b σ represents the remaining internal compressive strength of the worn area in its original state; s R is the yield strength of the casing; h0 is the casing wall thickness in the unworn area; h is the casing wear depth; ci The inner wall radius is denoted by 0.875. The tolerance of the casing wall thickness being 12.5% ​​smaller than the nominal wall thickness is expressed by a factor of 0.875.

[0076] Understandably, due to the curvature of the wellbore trajectory, severely worn casing sections are typically located in curved sections with significant wellbore curvature. The bending stress applied to the worn casing will affect the assessment of casing safety and remaining internal pressure resistance. The bending stress of the casing in curved sections mainly consists of two parts: the stress caused by the bending load and the stress caused by the weight of the lower casing section. The bending stress in the curved section can be determined based on the following method:

[0077]

[0078] Where, σ z F represents the bending stress of the casing. z The force generated by the weight of the lower section of the casing; A s E is the cross-sectional area of ​​the casing; D is the elastic modulus; R is the outer diameter of the casing, i.e., the diameter of the outer circumference of the casing; and R is the radius of curvature of the curved section.

[0079] In the absence of wear on the casing, the radial and circumferential stresses of the casing can be determined using the Lame formula for a cylindrical model, based on the following method:

[0080]

[0081] Where, σr R represents the radial stress of the casing. ci p is the inner wall radius of the pipe. i For internal pressure; R co R is the outer radius of the pipe; r is the radius of the casing wall thickness range. ci ≤r≤R co ;p o External pressure; σ θ This refers to the circumferential stress of the casing.

[0082] The stress state of the casing in the curved section is as follows Figure 7 As shown, according to the von Mises yield criterion, the equivalent stress σ of the casing at yield failure is... M It can be determined based on the following method:

[0083]

[0084] Where, σ M σ represents the equivalent stress of the casing at yield failure; r The radial stress of the casing; σ θ σ represents the circumferential stress of the casing. z This refers to the bending stress of the sleeve.

[0085] The remaining resistance to external extrusion in the bending section of the casing can be determined as follows:

[0086]

[0087] Among them, P bT To account for the residual internal pressure strength of the worn sleeve under bending stress; P b R represents the remaining internal compressive strength of the worn area in its original state; ci R is the inner wall radius of the pipe; co σ is the outer radius of the pipe; z For the casing bending stress; σ s The sleeve yield strength;

[0088] The above scheme determines the remaining internal pressure resistance of the wear zone by comprehensively evaluating the casing wear depth, casing wall thickness and casing yield strength, and further considers the influence of bending stress. This allows for a more accurate assessment of the mechanical properties of the casing under different working conditions, improves the prediction accuracy of casing safety, and thus enhances the safety of drilling operations.

[0089] Based on the above scheme, optionally, the remaining strength of the casing includes the remaining resistance to external extrusion; determining the remaining strength of the casing in the worn area based on the casing wear depth includes: determining the yield pressure of the casing based on the inner wall radius of the casing, the casing wear depth, the casing yield strength corresponding to the worn area of ​​the casing, and the casing wall thickness of the unworn area of ​​the casing; determining the remaining resistance to external extrusion of the worn area of ​​the casing in its original state based on the yield pressure, outer wall diameter, elastic modulus, initial ellipticity, yield strength, and casing wall thickness of the unworn area of ​​the casing; and determining the remaining resistance to external extrusion of the worn area of ​​the casing under bending stress based on the remaining resistance to external extrusion of the worn area in its original state, the bending stress of the casing, and the casing yield strength.

[0090] The elastic modulus can be understood as the ability of the casing to resist deformation within its elastic range, and can be represented by Young's modulus. The initial ellipticity can be understood as the slight non-roundness present during the manufacturing or installation of the casing, which affects the stress state of the casing. The residual external extrusion strength can be understood as the external extrusion force that the worn area can withstand when it is not affected by bending stress, taking into account factors such as the wall thickness of the worn and unworn areas and the yield strength of the casing.

[0091] Understandably, considering only the wear defects in the casing, the casing being an isotropic ideal elastoplastic material, and the casing not undergoing plastic deformation, the residual external extrusion strength P of the worn area of ​​the casing in its original state is affected by the casing's external extrusion strength ratio, yield pressure, elastic modulus, and initial ellipticity. c It can be determined based on the following formula:

[0092]

[0093] In the formula, P p σ is the yield pressure; s R is the yield strength of the casing; h0 is the casing wall thickness in the unworn area; h is the casing wear depth; ci P is the inner wall radius of the pipe; c R represents the residual resistance to external extrusion in the worn area under its original state; E is the elastic modulus; R co D is the outer radius of the pipe. co Let Δ be the outer diameter of the pipe, and Δ0 be the initial ellipticity. The constant values ​​are a = -1.478, b = 0.611, c = 0.379, d = 2.436, e = -0.094, f = -0.047, and g = 0.049, respectively.

[0094] The remaining resistance to external extrusion of the worn sleeve, considering bending stress, can be determined based on the following formula:

[0095]

[0096] Among them, P cT To account for the residual external extrusion strength of the worn casing under bending stress; P c σ represents the remaining resistance to external extrusion in the worn area under its original state; z For the casing bending stress; σ s This represents the yield strength of the casing.

[0097] For example, the dogleg degree (i.e., the rate of change of the full angle), lateral force, wear depth, and casing strength distribution along the well depth can be visualized, such as... Figure 8 As shown.

[0098] The above scheme, by comprehensively evaluating casing wear depth, casing wall thickness, casing yield strength and elastic modulus, determines the yield pressure and residual resistance to external extrusion in the wear area, and considers the influence of bending stress. This allows for a more accurate assessment of the mechanical properties of the casing under different working conditions, improves the accuracy of casing safety prediction, and thus enhances the safety of drilling operations.

[0099] Based on the above scheme, optionally, when the remaining strength of the sleeve includes the remaining tensile strength, the step of determining the remaining strength of the sleeve in the wear area of ​​the sleeve according to the wear depth of the sleeve includes: determining the remaining tensile strength of the wear area of ​​the sleeve according to the surface area of ​​the wear area of ​​the sleeve, the yield strength of the sleeve, the inner wall radius of the sleeve and the outer wall radius of the sleeve.

[0100] The surface area can be understood as the surface area of ​​the specific region on the casing where wear occurs. By considering the surface area of ​​the wear region, the yield strength of the casing, and the radii of the inner and outer walls of the casing, it is possible to comprehensively assess how much tensile force the casing can withstand under wear conditions without plastic deformation.

[0101] For example, such as Figure 6 As shown, the remaining tensile strength is mainly affected by the curved surface area S of the wear region of the sleeve, and the remaining tensile strength T of the wear region of the sleeve is... t It can be determined based on the following formula:

[0102] T t =σ s [π(R co 2 -R ci 2 )-S]; (18)

[0103] Among them, T t σ represents the remaining tensile strength of the worn area of ​​the casing; s R is the yield strength of the casing;ci R is the inner wall radius of the pipe; co Where is the outer radius of the pipe; S is the surface area of ​​the wear region of the casing.

[0104] The surface area S of the worn region of the sleeve can be determined based on the following formula:

[0105]

[0106] Where S is the surface area of ​​the sleeve wear region; γ0 is the half angle on the wear circle of the joint at the wear point; R tj R is the radius of the drill string joint; ci Where is the inner wall radius of the pipe; P is Figure 6 In the left image, the perimeter of ΔO1M1O2 is half; e d for Figure 6 The eccentricity of O1O2 in the left figure; θ0 is the half angle on the sleeve circle at the wear point.

[0107] Among them, half the perimeter P of ΔO1M1O2 and the eccentricity e d It can be determined based on the following formula:

[0108]

[0109] e d =R ci -R tj +h; (21)

[0110] Where P is Figure 6 In the left figure, the perimeter of ΔO1M1O2 is half; R ci R is the inner wall radius of the pipe; tj e is the radius of the drill string joint; d for Figure 6 The eccentricity of O1O2 in the left figure; h is the wear depth of the sleeve.

[0111] The above scheme, by comprehensively evaluating the surface area of ​​the wear zone, the yield strength of the casing, and the inner and outer wall radii of the casing, can accurately calculate the remaining tensile strength of the wear zone, thereby improving the accuracy of the assessment of the mechanical properties of the casing and enhancing the safety of drilling operations.

[0112] S130. Based on the internal pressure, external pressure, axial force, wear depth, and remaining strength of the casing, draw a biaxial stress ellipse of the casing in the target coordinate system and display the biaxial stress ellipse.

[0113] The internal pressure can be understood as the pressure acting on the inside of the casing, typically caused by the fluid pressure within the well. This internal pressure exerts an outward expansion pressure on the casing. The external pressure can be understood as the pressure acting on the outside of the casing, which can be caused by formation pressure or cement sheath pressure, etc. This external pressure exerts an inward compression pressure on the casing. The axial force can be understood as the force along the casing's axis; this axial force acts along the length of the casing, causing it to elongate or shorten. The biaxial stress ellipse can be understood as a graphical representation of the stress distribution of a material under biaxial stress. The biaxial stress ellipse can be used to represent the stress states experienced by the casing in different directions.

[0114] For example, based on the equivalent stress at different wear depths when the casing reaches yield failure, and the corresponding internal and external pressures, the bearing capacity of the casing under axial, internal, and external pressures can be represented by a biaxial stress ellipse. The vertical axis represents the pressure difference between the inside and outside of the casing, and the horizontal axis represents the axial load of the casing, such as... Figure 9 As shown, with the increase of the casing wear depth, the area of ​​the biaxial stress ellipse of the casing gradually decreases, indicating that the casing's ability to withstand external and internal pressures is gradually decreasing.

[0115] Based on the above scheme, optionally, after drawing and displaying the biaxial stress ellipse of the casing according to the internal and external pressure difference, axial force, casing wear depth, and remaining strength of the casing, the method further includes: determining the circumferential stress of the worn part according to a pre-constructed force balance equation and moment balance equation, wherein the force balance equation and moment balance equation are constructed based on the circumferential stress of the unworn area of ​​the casing, the circumferential stress of the worn part, the internal pressure of the casing, the external pressure, the outer wall radius of the casing, the casing wall thickness of the unworn area, the half angle on the wear circle corresponding to the drill string joint at the worn area, and the half angle force on the wear circle corresponding to the casing; determining the critical remaining strength of the worn area of ​​the casing according to the circumferential stress of the worn part, and marking the critical remaining strength in the target coordinate system, so as to determine the wellbore bearing index based on the relative positional relationship between the biaxial stress ellipse and the critical remaining strength, wherein the wellbore bearing index is used to indicate whether the bearing limit of the wellbore is exceeded.

[0116] The force balance equation can be understood as a mathematical expression describing the drill string unit's equilibrium state under all external forces, i.e., the sum of all external forces acting on the drill string unit is zero. Similarly, the moment balance equation can be understood as a mathematical expression describing the drill string unit's equilibrium state under all external moments, i.e., the sum of all external moments acting on the drill string unit is zero. The circumferential stress can be understood as the stress along the circumference of the casing, typically generated by the combined action of internal and external pressures. The circumferential stress in the unworn area can be understood as the circumferential stress borne by the casing under internal and external pressures in the unworn area. The circumferential stress in the worn area can be understood as the circumferential stress borne by the casing under internal and external pressures in the worn area. It is understood that wear leads to a reduction in casing wall thickness, thus affecting the distribution of circumferential stress. The casing wall thickness in the unworn area can be understood as the wall thickness of the casing in its original, unworn state. The half-angle on the wear circle can be understood as the angle between the tangent at a point on the wear profile formed in the wear area and the casing axis. The critical residual strength can be understood as the maximum stress value that the casing can withstand in the wear area, i.e., the maximum stress without plastic deformation. The wellbore load-bearing index can be understood as an index used to evaluate whether the wellbore can safely bear the expected load under given conditions. For example, by comparing the relative positions of the biaxial stress ellipse and the critical residual strength, it can be determined whether the wellbore has exceeded its load-bearing limit.

[0117] For example, such as Figure 6 As shown, considering only the wear defects of the casing, the casing being an isotropic ideal elastic-plastic material, and the casing not undergoing plastic deformation, the wear of the casing under external pressure p is investigated. o and internal pressure p i Analyzing the force state under action, the force balance equation and moment balance equation can be determined based on the following formulas:

[0118]

[0119] In the formula, σ1 is the circumferential stress in the unworn area of ​​the casing; σ2 is the circumferential stress in the worn area of ​​the casing; Δt1 is the casing wall thickness in the unworn area; Δt2 is the casing wall thickness in the worn area; γ0 is the half-angle on the wear circle corresponding to the drill string joint in the worn area; p i For internal pressure; R tj R is the radius of the drill string joint; θ0 is the half-angle on the wear circle corresponding to the casing; ci p is the inner wall radius of the pipe. o External pressure; R co The radius of the outer wall of the pipe is denoted as .

[0120] The casing wall thickness Δt1 in the unworn area and Δt2 in the worn area can be determined based on the following formula:

[0121] Δt1=h0; (24)

[0122] Δt2=h0-h; (25)

[0123] In the formula, h0 is the sleeve wall thickness in the unworn area; h is the sleeve wear depth.

[0124] The half-angle γ0 on the wear circle corresponding to the drill string joint and the half-angle θ0 on the wear circle corresponding to the casing in the wear zone can be determined based on the following formula:

[0125]

[0126] Where h is the wear depth of the casing; R ci R is the inner wall radius of the pipe; tj The radius of the drill string joint.

[0127] The circumferential stress σ1 in the unworn area of ​​the casing and the circumferential stress σ2 in the worn area of ​​the casing can be determined based on the following formula:

[0128]

[0129] Where, p i For internal pressure; R tj R is the radius of the drill string joint; γ0 is the half-angle on the wear circle corresponding to the wear area of ​​the drill string joint; ci θ is the inner wall radius of the pipe; θ0 is the half angle on the wear circle corresponding to the sleeve; p o External pressure; R co Δt1 is the outer radius of the pipe; Δt2 is the wall thickness of the casing in the unworn area; Δt3 is the wall thickness of the casing in the worn area.

[0130] The above scheme determines the circumferential stress of the worn area by constructing force balance equations and moment balance equations, and further evaluates the critical residual strength of the worn area and marks it in the target coordinate system. Combined with biaxial stress ellipse analysis of the wellbore bearing index, it can more accurately evaluate the mechanical properties of the casing under wear conditions, improve the prediction accuracy of casing safety, thereby enhancing the safety of drilling operations, ensuring that the wellbore does not exceed the bearing limit under various working conditions, and guaranteeing the smooth progress of drilling operations.

[0131] The technical solution of this invention firstly determines the stress state of the drill string unit and then determines the contact force between the drill string unit and the casing based on the stress state. Since the drill string unit includes a drill string joint and drill string sections located at both ends of the joint, the contact force between the drill string unit and the casing can be quantified, improving the accuracy of the overall mechanical analysis and providing data support for subsequent analysis. Next, the casing wear depth is determined based on the contact force, and the remaining casing strength in the wear area is determined based on the casing wear depth. Since the remaining casing strength includes remaining internal pressure resistance, remaining external extrusion resistance, and remaining internal pressure resistance, the remaining internal pressure resistance is determined. Tensile strength analysis can comprehensively evaluate the overall mechanical properties of the casing under wear conditions, ensuring that multiple strengths are included in the analysis and improving the accuracy of the remaining casing strength analysis. Finally, based on the internal pressure, external pressure, axial force, casing wear depth, and remaining casing strength, a biaxial stress ellipse of the casing is plotted in the target coordinate system and displayed. This provides a visual representation of the stress distribution of the casing under different pressures and wear conditions, solving the problem of inaccurate assessment of casing wear and remaining casing strength relying on manual and experience-based methods in related technologies. This improves the safety, reliability, and efficiency of drilling operations.

[0132] Example 2

[0133] Figure 2 This is a flowchart of a method for determining the bearing capacity limit of a wellbore before oil testing, provided in Embodiment 2 of the present invention. Based on the above embodiments, this embodiment further refines how to determine the casing wear depth of the casing based on the contact force. Optionally, determining the casing wear depth based on the contact force includes: determining the wear volume of the casing based on the contact force; determining a first cross-sectional area of ​​the wear region of the casing based on the wear volume and the unit casing length; determining a second cross-sectional area based on a preset maximum wear depth and the wear boundary point of the wear region, wherein the wear boundary point is the boundary point of the wear region in the extension direction of the drill string unit; and taking the preset maximum wear depth as the casing wear depth when the area difference between the first cross-sectional area and the second cross-sectional area is less than or equal to a preset area error. For detailed implementation, please refer to the description of this embodiment. Technical features that are the same as or similar to those in the foregoing embodiments will not be repeated here.

[0134] like Figure 2 As shown, the method may specifically include:

[0135] S210. Determine the stress state of the drill string unit, and determine the contact force between the drill string unit and the casing based on the stress state, wherein the drill string unit includes a drill string joint and drill string sections located at both ends of the joint.

[0136] S220. Determine the wear volume of the sleeve based on the contact force, and determine the first cross-sectional area of ​​the wear region of the sleeve based on the wear volume and the unit sleeve length.

[0137] Wherein, the wear volume can be understood as the volume of the sleeve removed from the surface due to external force. The unit sleeve length can be understood as the standard length of the sleeve. For example, the unit sleeve length can be 1m. The first cross-sectional area can be understood as the cross-sectional area of ​​the sleeve affected by wear.

[0138] Based on the above scheme, optionally, determining the wear volume of the casing based on the contact force includes: determining the wear volume of the casing based on the contact force, casing wear coefficient, drill pipe rotation speed, mechanical drilling speed, initial drilling depth, final drilling depth, circumferential friction coefficient between drill string and casing, and diameter of drill pipe joint.

[0139] The casing wear coefficient can be understood as a coefficient representing the degree of casing wear. This coefficient is temperature-dependent, meaning that temperature changes affect the degree of wear. The drill pipe rotation speed can be understood as the number of rotations of the drill pipe per unit time. For example, the unit time can be per minute. It is understood that the drill pipe rotation speed affects the friction and wear between the drill string and the casing. The mechanical drilling rate can be understood as the speed at which the drill bit penetrates the formation per unit time. It is understood that the mechanical drilling rate affects drilling efficiency and the frequency of contact between the drill string and the casing, thus indirectly affecting the casing wear condition. The initial drilling depth can be understood as the depth at the start of drilling, i.e., the starting position of drilling. Correspondingly, the final drilling depth can be understood as the depth reached when drilling is completed, i.e., the ending position of drilling. The circumferential friction coefficient can be understood as the ratio of the frictional resistance on the contact surface between the drill string and the casing to the pressure perpendicular to the contact surface. A larger circumferential friction coefficient indicates stronger friction, which will exacerbate wear.

[0140] For example, by using a linear "wear-efficiency" energy model to predict casing wear and considering the effect of temperature on casing wear, the wear volume of the casing can be determined based on the following formula:

[0141]

[0142] Among them, V W The wear volume of the casing is denoted by l; l0 is the initial drilling depth; l is the final drilling depth; k(T) is the temperature-dependent casing wear coefficient; RPM is the drill pipe rotation speed; ROP is the mechanical drilling rate; μ t F is the coefficient of circumferential friction between the drill string and the casing. S D represents the contact force between the drill string and the casing. tj This refers to the diameter of the drill pipe joint.

[0143] Furthermore, the first cross-sectional area A1 of the wear region can be determined by the wear volume V. w Divide by the unit sleeve length to obtain.

[0144] S230. Determine the second cross-sectional area based on the preset maximum wear depth and the wear boundary point of the wear area, wherein the wear boundary point is the boundary point of the wear area in the extension direction of the drill string unit.

[0145] The preset maximum wear depth can be understood as the maximum wear level assumed in the wear analysis, i.e., the maximum reduction in casing wall thickness under the most severe wear condition, used to evaluate the casing strength under the most unfavorable conditions. The wear boundary point can be understood as the edge point of the wear region along the extension direction of the drill string unit, i.e., the start and end point of the wear region. The extension direction of the drill string unit can be understood as the axial direction of the drill string unit, i.e., the length direction of the drill string. The extension direction of the drill string unit, combined with the wear boundary point, can determine the range of the wear region.

[0146] Based on the above scheme, optionally, the second cross-sectional area is determined according to the preset maximum wear depth and the wear boundary point of the wear area, including: determining the abscissa corresponding to the wear boundary point according to the joint radius of the drill string joint, the inner wall radius of the casing, and the preset maximum wear depth corresponding to the casing; and determining the second cross-sectional area corresponding to the wear area according to the abscissa corresponding to the wear boundary point, the joint radius, the inner wall radius of the casing, and the preset maximum wear depth.

[0147] The joint radius can be understood as the radius of the drill string joint, which is crucial for determining the contact surface and wear condition. The second cross-sectional area can be understood as the area of ​​the cross-section of the wear region at a preset maximum wear depth.

[0148] For example, considering the crescent-shaped wear marks formed on the inner wall of the casing after wear, the cross-sections of the drill pipe joint and the casing are taken as the research object. A geometric model and a two-dimensional coordinate system for calculating the maximum wear depth are established, such as... Figure 6 As shown.

[0149] x1 and x2 are the x-coordinates of the wear boundary point, which can be determined based on the following formula:

[0150]

[0151] Among them, R tj R is the radius of the drill string joint. ci h is the inner wall radius of the pipe. max The maximum wear depth is preset for the casing.

[0152] Therefore, the maximum wear depth h is determined. max In this case, the area A of the second cross section can be determined based on the following formula:

[0153]

[0154] Where x1 and x2 are the x-coordinates of the wear boundary points; R tj R is the radius of the drill string joint; ci h is the inner wall radius of the pipe. max The maximum wear depth is preset for the casing.

[0155] S240. When the area difference between the first cross-sectional area and the second cross-sectional area is less than or equal to a preset area error, the preset maximum wear depth is taken as the wear depth of the sleeve, and the remaining strength of the sleeve in the wear area of ​​the sleeve is determined according to the wear depth, wherein the remaining strength of the sleeve includes the remaining internal pressure resistance, the remaining external extrusion resistance, and the remaining tensile strength.

[0156] The preset area error can be understood as a pre-defined allowable error range, used to determine whether the reduction in cross-sectional area caused by wear is within an acceptable range. The preset area error can be set based on engineering experience and specific requirements, and is not limited here.

[0157] For example, determine whether the result of |A1-A| is less than the allowable error. If it is, the wear depth of the sleeve is obtained. If it is not, a new wear depth is selected until the condition is met, and the final wear depth is obtained.

[0158] S250. Based on the internal pressure, external pressure, axial force, wear depth, and remaining strength of the casing, draw a biaxial stress ellipse of the casing in the target coordinate system and display the biaxial stress ellipse.

[0159] The technical solution of this invention determines the casing wear depth by calculating the contact force and predicting the wear volume, combined with the geometric relationship between the preset maximum wear depth and the wear boundary, thus ensuring the accuracy and reliability of the assessment. By controlling the error between the first and second cross-sectional areas, the determination of wear depth is made more scientific and reasonable, reducing safety hazards caused by inaccurate wear assessment. In addition, the influence of environmental factors such as temperature on wear is considered, enhancing the practical application value of the assessment model and ensuring the safe and efficient operation of drilling operations.

[0160] Example 3

[0161] Figure 3 The method for determining the wellbore bearing capacity limit before oil testing, provided in Embodiment 3 of the present invention, is an optional embodiment of the above embodiments. Figure 3 As shown, the method may specifically include

[0162] First, data was collected. After data collection, on the one hand, the contact force between the drill string unit and the casing was calculated based on the stress state of the drill string unit. Then, casing wear was predicted using a linear "wear-efficiency" energy model, considering the influence of temperature on casing wear, and the wear volume of the casing was calculated. The cross-sectional area A1 of the wear region was then obtained by dividing the calculated wear volume Vw by the unit casing length. On the other hand, based on the crescent-shaped wear geometry model of the casing, the relationship between wear width and wear depth was obtained. Then, different wear depths were selected to obtain different wear widths, and the geometric area A of the casing wear was calculated based on the wear width.

[0163] Next, determine whether the difference between the geometric area A of the casing wear and A1 is less than the allowable error. If not, recalculate the geometric area A of the casing wear by selecting the wear depth. If it is satisfied, the casing wear depth is obtained.

[0164] Considering wear and curvature, the axial stress of the curved section of the casing, the circumferential stress of the unworn section, and the circumferential stress of the worn section are calculated. Assuming casing failure occurs when the circumferential stress at the worn section reaches the casing's yield strength, the remaining internal pressure resistance 1, remaining external extrusion resistance 2, and remaining tensile strength of the casing under natural conditions are first calculated based on the wear depth. For the curved section of the casing, the remaining internal pressure resistance 2 and remaining external extrusion resistance 2 are calculated based on the yield strength, remaining internal pressure resistance 1, and remaining external extrusion resistance 2.

[0165] Finally, based on the equivalent stress and corresponding internal and external pressures at different wear depths when the worn casing reaches yield failure, the bearing capacity of the casing under axial force and internal and external pressure can be represented by a biaxial stress ellipse. The vertical axis represents the internal and external pressures of the casing, and the horizontal axis represents the axial load of the casing. The combination of internal and external pressures and axial loads inside the ellipse does not produce equivalent stresses exceeding the allowable stress, which meets the requirements. The combination of internal and external pressures and axial loads outside the ellipse produces equivalent stresses exceeding the allowable stress, which does not meet the requirements.

[0166] The technical solution of this invention calculates contact force and predicts wear volume, and determines a reasonable wear depth by combining a wear geometry model to ensure that the wear area meets the error requirements. It further analyzes the stress distribution under the influence of wear and curvature, and calculates the remaining internal pressure resistance, remaining external extrusion resistance and remaining tensile strength of the casing. It also conducts a special evaluation of the bent section of the casing. Finally, it ensures structural safety through remaining strength evaluation and load limit analysis, improves the accuracy of casing condition assessment, and guarantees operational safety and efficiency.

[0167] Example 4

[0168] Figure 4 This is a schematic diagram of a device for determining the bearing capacity limit of a wellbore before oil testing, provided in Embodiment 3 of the present invention. Figure 4 As shown, the device may include: a drill sleeve contact force determination module 410, a casing residual strength determination module 420, and a wellbore bearing limit determination module 430. The drill sleeve contact force determination module 410 is used to determine the stress state of the drill string unit and, based on the stress state, determine the contact force between the drill string unit and the casing. The drill string unit includes a drill string joint and drill string sections located at both ends of the joint. The casing residual strength determination module 420 is used to determine the casing wear depth of the casing based on the contact force and, based on the casing wear depth, determine the remaining casing strength of the worn area of ​​the casing. The remaining casing strength includes remaining internal pressure resistance, remaining external extrusion resistance, and remaining tensile strength. The wellbore bearing limit determination module 430 is used to draw a biaxial stress ellipse of the casing in a target coordinate system based on the internal pressure, external pressure, axial force, casing wear depth, and remaining casing strength, and to display the biaxial stress ellipse.

[0169] The technical solution of this invention firstly determines the stress state of the drill string unit through the drill bushing contact force determination module 410, and determines the contact force between the drill string unit and the casing based on the stress state. Since the drill string unit includes a drill string joint and drill string sections located at both ends of the joint, the contact force between the drill string unit and the casing can be quantified, improving the accuracy of the overall mechanical analysis and providing data support for subsequent analysis. Next, the casing residual strength determination module 420 determines the casing wear depth of the casing based on the contact force, and determines the casing residual strength of the worn area of ​​the casing based on the casing wear depth. Since the casing residual strength includes residual internal pressure resistance and residual external extrusion resistance... The remaining tensile strength and other parameters can comprehensively evaluate the overall mechanical properties of the casing under wear conditions, ensuring that multiple strength aspects are included in the analysis and improving the accuracy of the remaining strength analysis. Finally, the wellbore bearing limit determination module 430 draws a biaxial stress ellipse of the casing in the target coordinate system based on the internal pressure, external pressure, axial force, casing wear depth, and remaining strength of the casing, and displays the biaxial stress ellipse. This can intuitively show the stress distribution of the casing under different pressure and wear conditions, solving the problem of inaccurate assessment of casing wear and remaining casing strength relying on manual and experience in related technologies, and improving the safety, reliability, and efficiency of drilling operations.

[0170] Based on the above scheme, optionally, the drill string contact force determination module may include: a first component force determination submodule, a second component force determination submodule, and a contact force determination submodule. The first component force determination submodule is used to determine the first component of the contact force in the principal normal direction based on the unit length of the drill string unit, the axial forces at both ends, the effective weight of the drill string in the drilling fluid, the unit principal normal vector, and the rate of change of the total angle. The second component force determination submodule is used to determine the second component of the contact force in the secondary normal direction based on the effective weight of the drill string unit, the unit length, and the unit secondary normal vector. The contact force determination submodule is used to determine the contact force between the drill string and the casing based on the first component force and the second component force, wherein the unit principal normal vector and the unit secondary normal vector of the drill string unit are both associated with the inclination angle and azimuth angle corresponding to the two endpoints of the drill string unit.

[0171] Based on the above scheme, optionally, the casing remaining strength determination module may include: a first cross-sectional area determination unit, a second cross-sectional area determination unit, and a casing wear depth determination unit. The first cross-sectional area determination unit is used to determine the wear volume of the casing based on the contact force, and to determine a first cross-sectional area of ​​the wear region of the casing based on the wear volume and the unit casing length. The second cross-sectional area determination unit is used to determine a second cross-sectional area based on a preset maximum wear depth and the wear boundary point of the wear region, wherein the wear boundary point is the boundary point of the wear region in the extension direction of the drill string unit. The casing wear depth determination unit is used to take the preset maximum wear depth as the casing wear depth of the casing when the area difference between the first cross-sectional area and the second cross-sectional area is less than or equal to a preset area error.

[0172] Based on the above scheme, optionally, the second cross-sectional area determining unit is specifically used to: determine the abscissa corresponding to the wear boundary point according to the joint radius of the drill string joint, the inner wall radius of the casing, and the preset maximum wear depth corresponding to the casing; and determine the second cross-sectional area corresponding to the wear area according to the abscissa corresponding to the wear boundary point, the joint radius, the inner wall radius of the casing, and the preset maximum wear depth.

[0173] Based on the above scheme, optionally, the first cross-sectional area determining unit may include: a wear volume determining subunit. The wear volume determining subunit is used to determine the wear volume of the casing based on the contact force, casing wear coefficient, drill pipe rotation speed, mechanical drilling speed, initial drilling depth, final drilling depth, circumferential friction coefficient between the drill string and casing, and the diameter of the drill pipe joint, wherein the casing wear coefficient is temperature-related.

[0174] Based on the above scheme, optionally, the remaining strength of the casing includes the remaining internal pressure resistance; the casing remaining strength determination module includes: a first remaining internal pressure resistance determination submodule and a second remaining internal pressure resistance determination submodule. The first remaining internal pressure resistance determination submodule is used to determine the remaining internal pressure resistance of the worn area of ​​the casing in its original state based on the inner wall radius of the casing, the wear depth of the casing, the casing wall thickness of the unworn area of ​​the casing, and the yield strength of the casing corresponding to the worn area; the second remaining internal pressure resistance determination submodule is used to determine the remaining internal pressure resistance of the worn area of ​​the casing under bending stress based on the remaining internal pressure resistance of the worn area in its original state, the bending stress of the casing, the inner wall radius, the outer wall radius, and the yield strength of the casing.

[0175] Based on the above scheme, optionally, the remaining strength of the casing includes the remaining resistance to external extrusion; the casing remaining strength determination module includes: a yield pressure determination submodule, a first remaining resistance to external extrusion determination submodule, and a second remaining resistance to external extrusion determination submodule. Specifically, the yield pressure determination submodule is used to determine the yield pressure of the casing based on the inner wall radius of the casing, the wear depth of the casing, the yield strength of the casing corresponding to the wear area of ​​the casing, and the casing wall thickness of the unwear area of ​​the casing; the first remaining resistance to external extrusion determination submodule is used to determine the remaining resistance to external extrusion of the wear area of ​​the casing in its original state based on the yield pressure of the casing, the outer wall diameter, the elastic modulus, the initial ellipticity, the yield strength, and the casing wall thickness of the unwear area of ​​the casing; the second remaining resistance to external extrusion determination submodule is used to determine the remaining resistance to external extrusion of the wear area of ​​the casing under bending stress based on the remaining resistance to external extrusion of the wear area in its original state, the bending stress of the casing, and the yield strength of the casing.

[0176] Based on the above scheme, optionally, the remaining strength of the sleeve includes the remaining tensile strength; the remaining strength determination module of the sleeve may include: a remaining tensile strength determination submodule. The remaining tensile strength determination submodule is used to determine the remaining tensile strength of the wear area of ​​the sleeve based on the surface area of ​​the wear region of the sleeve, the yield strength of the sleeve, the inner wall radius of the sleeve, and the outer wall radius of the sleeve.

[0177] Based on the above scheme, optionally, the device for determining the wellbore bearing capacity limit before oil testing further includes: a circumferential stress determination module and a wellbore bearing capacity index determination module. The circumferential stress determination module is used to determine the circumferential stress of the worn area after drawing and displaying the biaxial stress ellipse of the casing based on the internal and external pressure difference, axial force, wear depth, and remaining strength of the casing. This determination is based on pre-constructed force balance equations and moment balance equations. The force balance equations and moment balance equations are constructed based on the circumferential stress of the unworn area of ​​the casing, the circumferential stress of the worn area, the internal pressure and external pressure of the casing, the outer wall radius of the casing, the casing wall thickness of the unworn area, the half-angle on the wear circle corresponding to the drill string joint at the worn area, and the half-angle force on the wear circle corresponding to the casing. The wellbore bearing capacity determination module is used to determine the critical remaining strength of the worn area of ​​the casing based on the circumferential stress of the worn area, and to mark the critical remaining strength in the target coordinate system. The wellbore bearing capacity is determined based on the relative positional relationship between the biaxial stress ellipse and the critical remaining strength, indicating whether the bearing capacity limit of the wellbore has been exceeded.

[0178] The device for determining the bearing capacity of the wellbore before oil testing provided in this embodiment of the invention can execute the method for determining the bearing capacity of the wellbore before oil testing provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects of the method.

[0179] Example 4

[0180] Figure 10 A schematic diagram of an electronic device 10 that can be used to implement embodiments of the present invention is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices (e.g., helmets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the invention described and / or claimed herein.

[0181] like Figure 10As shown, the electronic device 10 includes at least one processor 11 and a memory, such as a read-only memory (ROM) 12 or a random access memory (RAM) 13, communicatively connected to the at least one processor 11. The memory stores computer programs executable by the at least one processor. The processor 11 can perform various appropriate actions and processes based on the computer program stored in the ROM 12 or loaded from storage unit 18 into the RAM 13. The RAM 13 may also store various programs and data required for the operation of the electronic device 10. The processor 11, ROM 12, and RAM 13 are interconnected via a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0182] Multiple components in electronic device 10 are connected to I / O interface 15, including: input unit 16, such as keyboard, mouse, etc.; output unit 17, such as various types of displays, speakers, etc.; storage unit 18, such as disk, optical disk, etc.; and communication unit 19, such as network card, modem, wireless transceiver, etc. Communication unit 19 allows electronic device 10 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0183] Processor 11 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of processor 11 include, but are not limited to, central processing unit (CPU), graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, digital signal processors (DSPs), and any suitable processor, controller, microcontroller, etc. Processor 11 performs the various methods and processes described above, such as a method for determining wellbore load limits before oil testing.

[0184] In some embodiments, a method for determining the wellbore bearing capacity limit before oil testing can be implemented as a computer program tangibly contained in a computer-readable storage medium, such as storage unit 18. In some embodiments, part or all of the computer program can be loaded and / or installed on electronic device 10 via ROM 12 and / or communication unit 19. When the computer program is loaded into RAM 13 and executed by processor 11, one or more steps of the method for determining the wellbore bearing capacity limit before oil testing described above can be performed. Alternatively, in other embodiments, processor 11 can be configured to perform a method for determining the wellbore bearing capacity limit before oil testing by any other suitable means (e.g., by means of firmware).

[0185] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), payload-programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transmitting data and instructions to the storage system, the at least one input device, and the at least one output device.

[0186] Computer programs used to implement the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, such that when executed by the processor, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be performed. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0187] In the context of this invention, a computer-readable storage medium can be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, apparatus, or device. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination thereof. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0188] To provide interaction with a user, the systems and techniques described herein can be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the electronic device. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0189] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as data servers), or computing systems that include middleware components (e.g., application servers), or computing systems that include frontend components (e.g., user computers with graphical user interfaces or web browsers through which users can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., communication networks). Examples of communication networks include local area networks (LANs), wide area networks (WANs), blockchain networks, and the Internet.

[0190] A computing system can include clients and servers. Clients and servers are generally located far apart and typically interact through communication networks. The client-server relationship is created by computer programs running on the respective computers and having a client-server relationship with each other. The server can be a cloud server, also known as a cloud computing server or cloud host, which is a hosting product within the cloud computing service system to address the shortcomings of traditional physical hosts and VPS services, such as high management difficulty and weak business scalability.

[0191] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0192] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for determining pre-test wellbore load bearing limits, comprising: The method comprises: determining a force state of a drill string unit, and determining a contact force between the drill string unit and a casing according to the force state, wherein the drill string unit comprises a drill string joint and drill string segments located at two ends of the joint; determining a casing wear depth of the casing according to the contact force, and determining a casing residual strength of a worn area of the casing according to the casing wear depth, wherein the casing residual strength comprises a residual internal pressure strength, a residual external pressure strength, and a residual tensile strength; drawing a casing biaxial stress ellipse in a target coordinate system according to an internal pressure of the casing, an external pressure of the casing, an axial force, the casing wear depth, and the casing residual strength, and displaying the biaxial stress ellipse.

2. The method of claim 1, wherein, The determination of the contact force between the drill string and the casing according to the force state comprises: determining a first component of the contact force in a main normal direction according to a unit length of the drill string unit, axial forces at two ends of the drill string unit, an effective weight of the drill string in drilling fluid, a unit main normal vector, and a total angle change rate; determining a second component of the contact force in a secondary normal direction according to the effective weight of the drill string unit, the unit length, and a unit secondary normal vector; determining the contact force between the drill string and the casing according to the first component and the second component, wherein the unit main normal vector and the unit secondary normal vector of the drill string unit are associated with a deviation angle and an azimuth angle corresponding to two end points of the drill string unit.

3. The method of claim 1, wherein, The determination of the casing wear depth of the casing according to the contact force comprises: determining a worn volume of the casing according to the contact force, and determining a first cross-sectional area of the worn area of the casing according to the worn volume and a unit casing length; determining a second cross-sectional area according to a preset maximum wear depth and a wear boundary point of the worn area, wherein the wear boundary point is a boundary point of the worn area in an extension direction of the drill string unit; in a case where an area difference between the first cross-sectional area and the second cross-sectional area is less than or equal to a preset area error, taking the preset maximum wear depth as the casing wear depth of the casing.

4. The method of claim 3, wherein, The determination of the second cross-sectional area according to the preset maximum wear depth and the wear boundary point of the worn area comprises: determining a horizontal coordinate corresponding to the wear boundary point according to a joint radius of the drill string joint, an inner wall radius of the casing, and a preset maximum wear depth corresponding to the casing; determining a second cross-sectional area corresponding to the worn area according to the horizontal coordinate corresponding to the wear boundary point, the joint radius, the inner wall radius, and the preset maximum wear depth.

5. The method of claim 3, wherein, The determination of the worn volume of the casing according to the contact force comprises: determining the worn volume of the casing according to the contact force, a casing wear coefficient, a drill pipe rotation speed, a mechanical drilling speed, a starting drilling depth, a final drilling depth, a circumferential friction coefficient between the drill string and the casing, and a diameter of a drill pipe joint, wherein the casing wear coefficient is related to temperature.

6. The method of claim 1, wherein, The casing residual strength comprises a residual internal pressure strength; and the determination of the casing residual strength of the worn area of the casing according to the casing wear depth comprises: determining the residual internal pressure strength of the worn area of the casing in the original state according to the internal wall radius of the casing, the casing wear depth, the casing wall thickness of the unworn area of the casing, and the casing yield strength corresponding to the worn area of the casing; determining the residual internal pressure strength of the worn area of the casing under bending stress according to the residual internal pressure strength of the worn area of the casing in the original state, the bending stress of the casing, the internal wall radius, the external wall radius of the casing, and the casing yield strength.

7. The method of claim 1, wherein, The casing residual strength includes residual external extrusion strength; the casing residual strength of the worn area of the casing according to the casing wear depth comprises: determining the yield pressure of the casing according to the internal wall radius of the casing, the casing wear depth, the casing wall thickness of the unworn area of the casing, and the casing yield strength corresponding to the worn area of the casing; determining the residual external extrusion strength of the worn area of the casing in the original state according to the yield pressure of the casing, the external wall diameter of the casing, the elastic modulus, the initial ovality, the yield strength, and the casing wall thickness of the unworn area of the casing; determining the residual external extrusion strength of the worn area of the casing under bending stress according to the residual external extrusion strength of the worn area of the casing in the original state, the bending stress of the casing, and the casing yield strength.

8. The method of claim 1, wherein, The casing residual strength includes residual tensile strength; the casing residual strength of the worn area of the casing according to the casing wear depth comprises: determining the residual tensile strength of the worn area of the casing according to the curved surface area of the worn area of the casing, the casing yield strength, the internal wall radius of the casing, and the external wall radius of the casing.

9. The method of claim 1, wherein, After the casing biaxial stress ellipse is drawn and displayed according to the internal and external pressure difference of the casing, the axial force, the casing wear depth, and the casing residual strength, the method further comprises: determining the hoop stress of the worn part according to the pre-constructed force balance equation and the moment balance equation, wherein the force balance equation and the moment balance equation are constructed according to the hoop stress of the unworn area of the casing, the hoop stress of the worn part, the internal pressure of the casing, the external pressure, the external wall radius of the casing, the casing wall thickness of the unworn area, the half angle on the wear circle corresponding to the drill string joint at the worn area, and the half angle force on the wear circle corresponding to the casing; determining the critical residual strength of the worn area of the casing according to the hoop stress of the worn part, and identifying the critical residual strength in the target coordinate system, so as to determine the wellbore bearing index based on the relative position relationship between the biaxial stress ellipse and the critical residual strength, wherein the wellbore bearing index is used to indicate whether the bearing limit of the wellbore is exceeded.

10. An apparatus for determining pre-test wellbore load limits, comprising: Comprise: a drill casing contact force determination module for determining the stress state of a drill string unit, and determining the contact force between the drill string unit and the casing according to the stress state, wherein the drill string unit comprises a drill string joint and drill string segments located at both ends of the joint; a casing remaining strength determination module configured to determine a casing wear depth of the casing according to the contact force, and determine a casing remaining strength of a worn area of the casing according to the casing wear depth, wherein the casing remaining strength comprises a remaining internal pressure resistance strength, a remaining external extrusion resistance strength, and a remaining tensile strength; a wellbore bearing limit determination module configured to draw a casing biaxial stress ellipse in a target coordinate system according to the internal pressure, the external pressure, the axial force, the casing wear depth, and the casing remaining strength of the casing, and display the biaxial stress ellipse.

Images