Method for calculating casing round thread connection slip strength based on logging inner diameter big data

Abstract

This invention relates to the field of oil well tubing technology, specifically to a method for calculating the slippage strength of casing threaded connections based on big data from well logging. This method obtains the distance between the upper and lower pipe ends at the coupling based on well logging data; and calculates the slippage strength of the thread at the coupling based on the distance between the upper and lower pipe ends. This invention provides a calculation method based on big data from multi-arm caliper logging, and performs accurate calculations by combining simulation analysis or experimental testing based on the calculated well depth range of the threaded connection location, thereby improving the accuracy and reliability of downhole casing strength calculation.

Description

Technical Field

[0001] This invention relates to the field of oil well pipe technology, and specifically to a method for calculating the slippage strength of casing circular thread connection based on big data of well logging inner diameter. Background Technology

[0002] API (American Petroleum Institute) standard specifies round threads as API round threads. They are widely used because they are simple to process, easy to maintain, have good interchangeability and are inexpensive. However, round threads have poor load-bearing capacity and are prone to slippage failure under axial tensile loads. If the engagement length of the round thread is changed, the anti-slippage ability of the round thread connection will change accordingly.

[0003] During the casing installation process in oilfields, round thread casings are typically threaded based on torque values, making it impossible to determine the direct or indirect thread engagement length. Furthermore, the engagement length of the round thread may change during casing string installation, making it impossible to calculate and predict the slippage strength of the round thread connection. Currently, the strength calculation for the casing string uses a fixed standard rated slippage strength, which, because it does not consider the actual thread engagement length, leads to significant errors.

[0004] Chinese patent CN1065018C discloses an oil and sleeve threaded joint. The patent specification states that, according to finite element analysis, the maximum contact stress distribution between the tooth surfaces is uneven. Under the tightening torque specified by API, it generally exceeds the allowable contact stress of the material, causing the threads to stick together first. This means that the slippage strength of the sleeve threaded connection or the strength of the tubing cannot be directly calculated using the parameters specified by API.

[0005] Chinese patent CN119004785A discloses a method, device, and electronic device for calculating the top-thread torque. This calculation method can calculate the top-thread torque of the casing and tubing based on the outer diameter of the casing, the inner diameter of the casing, the thread tightening depth, and pre-set calculation parameters, thus avoiding connection failures caused by excessive or insufficient torque and ensuring the safety and efficiency of downhole operations. However, this method does not take into account the possibility that the engagement length may change when the casing is downhole, which may lead to changes in the thread tightening depth and the axial interference of the thread. If the top-thread torque is used to calculate the strength of the tubing string, the error with the actual situation will be large. Summary of the Invention

[0006] The purpose of this invention is to provide a method for calculating the slippage strength of casing circular thread connection based on big data of well logging inner diameter. This method calculates the actual slippage strength of the thread connection by combining well logging data with simulation analysis or experimental testing.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for calculating the slippage strength of casing threaded connections based on big data from well logging inner diameters, which accurately calculates the slippage strength of downhole casing threaded connections based on the series of inner radii of the downhole casing string measured by a multi-arm caliper, and on the basis of calculating the well depth range of the threaded connection location, combined with finite element simulation analysis or experimental testing, includes the following steps:

[0009] Step 1: Calculate the position of the coupling.

[0010] Acquire logging data from multi-arm caliper to form a depth-inner diameter curve. Figure 1 Because the upper external threaded pipe 2 and the lower external threaded pipe 4 connected by the coupling do not contact each other, there is a distance L2 between the upper and lower pipe ends. The inner surface of the coupling forms a groove with the upper and lower pipe ends. The inner diameter measured by the multi-arm caliper at this position will show a sudden change, forming a peak. Therefore, at intervals of pipe length on the depth-inner diameter curve, a peak value fluctuation of the inner diameter will appear near the well depth position of the coupling center. Selecting a peak value for data calculation, the peak width of the coupling inner diameter L1 = H4 - H3, and the well depth at the center of the peak width H5 = (H3 + H4) / 2.

[0011] The well depth at the center of the coupling is H = H5; the distance between the upper and lower pipe ends is L2 = L1.

[0012] Step 2: Calculate the well depth range for the casing thread connection location.

[0013] The well depth range for the casing circular thread connection position is calculated based on the coupling length L and the well depth H at the center position of the coupling.

[0014] The distance from the end of the external threaded pipe to the center of the coupling is L3 = L2 / 2; the depth of the upper end of the round threaded connection is H1 = HL / 2; the depth of the lower end of the round threaded connection is H2 = H + L / 2.

[0015] Step 3: Finite element simulation calculation or experimental testing of the slippage strength of the sleeve circular thread connection.

[0016] According to GB / T 17745 (Maintenance and Use of Casing and Tubing in the Oil and Gas Industry), it is reasonable for the coupling end face to be flush with or two turns below the vanishing point of the external thread after the thread is tightened. A finite element model is constructed based on the standard dimensions of the casing external thread and the coupling. Simulation calculations are performed to determine the slip strength of the circular thread connection as A1 when the vanishing point of the external thread is exposed two turns above the coupling end face after tightening, and A2 when the vanishing point is located two turns inside the coupling end face. Alternatively, the slip strength of the threaded connection under these two conditions can be directly tested experimentally.

[0017] Step 4: Calculate the slippage strength of the round threaded connection of the downhole casing.

[0018] For API standard sleeve round thread, when the point where the external thread disappears after the first thread is turned out is exposed two threads above the coupling end face, the distance from the external thread end of the sleeve to the center of the coupling is recorded as L4. According to GB / T 17745 standard, the slippage strength of the sleeve round thread connection under this condition is calculated as A3.

[0019] Calculate the slope of the slippage strength of the sleeve circular thread connection: k = (A2 - A1) / 4R.

[0020] Calculate the slippage strength of the round threaded connection of the downhole casing: A = A3 + k·(L4-L3).

[0021] Step 5: Repeat steps 1 to 4 to calculate the slippage strength of the casing threaded connection at other well depths.

[0022] This invention also provides a method for calculating the slippage strength of casing threaded connections based on big data of well logging inner diameter.

[0023] A method for calculating the slippage strength of casing threaded connections based on big data of well logging inner diameter includes the following steps:

[0024] The well logging inner diameter data was obtained through testing;

[0025] Based on the casing round thread data, the external thread dimensions of the casing and the internal thread dimensions of the coupling are obtained;

[0026] The slippage strength of the thread at the coupling is calculated based on the logging inner diameter data and the casing round thread data.

[0027] Further logging inner diameter data includes: multiple inner radius values ​​at different well depths measured by a multi-arm caliper;

[0028] Furthermore, the inner diameter data obtained through well logging includes: the well depth at the center of the coupling and the distance between the upper and lower pipe ends at the coupling.

[0029] Furthermore, by detecting the well depth-inner diameter curve, the well depth at the center of the coupling and the peak width of the coupling's inner diameter are obtained by measuring the upper and lower well depths of the peak fluctuations of the inner diameter in the well depth-inner diameter curve. The peak width of the coupling's inner diameter is the distance between the upper and lower pipe ends at the coupling.

[0030] Furthermore, the well depth at the center of the coupling is the average of the upper well depth and the lower well depth of the peak value.

[0031] Furthermore, the distance between the upper and lower pipe ends at the coupling is the difference between the upper well depth of the peak value and the lower well depth of the peak value.

[0032] Furthermore, the casing round thread data includes the casing external thread size and the coupling internal thread size.

[0033] Furthermore, the formula for calculating the thread slippage strength is: A = A3 + k·(L4 - L3), where A is the actual thread slippage strength, A3 is the slippage strength of the threaded connection when the disappearance point of the external thread is exposed two turns above the end face of the coupling after the casing round thread is threaded, k is the slope of the slippage strength of the casing round thread connection, L4 is the distance from the end of the external thread to the center of the coupling when the API standard casing round thread is threaded to the point where the disappearance point of the external thread is exposed two turns above the end face of the coupling, and L3 is the distance from the end of the external thread to the center of the coupling obtained through well logging data analysis.

[0034] Furthermore, the distance from the externally threaded pipe end to the center of the coupling is half the distance between the upper and lower pipe ends at the coupling.

[0035] Furthermore, the formula for calculating the slope of the slippage strength of the sleeve circular thread connection is: k=(A2-A1) / 4R; where A1 is the slippage strength of the circular thread connection when the disappearance point of the external thread after threading is exposed two turns above the end face of the coupling; A2 is the slippage strength of the circular thread connection when the disappearance point of the external thread after threading is located two turns inside the end face of the coupling; and R is the pitch.

[0036] Furthermore, the slippage strength of the circular thread connection when the disappearance point of the external thread after threading is exposed two turns above the end face of the coupling, and the slippage strength of the circular thread connection when the disappearance point of the external thread after threading is located two turns inside the end face of the coupling, are obtained by finite element simulation calculation or experimental testing based on standard thread dimensions.

[0037] The present invention has the following beneficial effects: Based on the logging big data of the multi-arm caliper, the present invention provides a method for calculating the slippage strength of the round thread connection of downhole casing. Based on the calculation of the well depth range of the round thread connection position, the method combines simulation analysis or experimental testing to perform accurate calculation, thereby improving the accuracy and reliability of the downhole casing strength calculation. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a well depth-inner diameter curve generated based on logging data from a multi-arm caliper in a specific embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the circular thread connection structure in a specific embodiment of the present invention;

[0041] In the diagram: 1-Peak inner diameter of coupling; 2-Upper external threaded pipe; 3-Coupling; 4-Lower external threaded pipe; 5-Meshing thread.

[0042] H - Well depth at the center of the coupling; H1 - Well depth at the upper end of the round thread connection; H2 - Well depth at the lower end of the round thread connection; H3 - Well depth at the upper end of the peak value; H4 - Well depth at the lower end of the peak value; H5 - Well depth at the center of the peak value width; L - Coupling length; L1 - Peak width of the coupling inner diameter; L2 - Distance between the upper and lower pipe ends; L3 - Distance from the external thread pipe end to the center of the coupling; L4 - Distance from the external thread pipe end to the center of the coupling when two turns of the API standard casing round thread are exposed on the coupling end face at the point where the external thread disappears. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] A depth-inner diameter curve is generated based on logging data from a multi-arm caliper. See the depth-inner diameter curve diagram below. Figure 1 , Figure 1 In the diagram, 1 represents the peak value of the coupling inner diameter, L1 represents the peak width of the coupling inner diameter, H3 represents the depth at the upper end of the peak value, H4 represents the depth at the lower end of the peak value, and H5 represents the depth at the center of the peak width.

[0046] Example of selecting API Φ139.7mm×9.17mm N80 long round thread casing string. The method of calculating the slippage strength of casing round thread connection based on big data of well logging inner diameter in this invention.

[0047] See the diagram for the circular thread connection structure in the long circular threaded sleeve column. Figure 2 , Figure 2 2 is the upper external threaded pipe; 3 is the coupling; 4 is the lower external threaded pipe; 5 is the meshing thread; H is the well depth at the center of the coupling; H1 is the well depth at the upper end of the round thread connection; H2 is the well depth at the lower end of the round thread connection; L is the length of the coupling; L2 is the distance between the upper and lower pipe ends; L3 is the distance from the end of the external threaded pipe to the center of the coupling; L4 is the distance from the end of the external threaded pipe to the center of the coupling when the API standard casing round thread is turned up to the point where the external thread disappears and two turns are exposed on the end face of the coupling.

[0048] Calculate the location of the coupling:

[0049] Based on the well depth-inner diameter curves generated from the logging big data of the multi-arm caliper, H3 = 999.987m and H4 = 1000.013m were obtained.

[0050] The peak width of the coupling inner diameter L1 = H4 - H3 = 26 mm, and the well depth at the center of the peak width H5 = (H3 + H4) / 2 = 1000 m.

[0051] The well depth at the center of the coupling is H = H5 = 1000m; the distance between the upper and lower pipe ends is L2 = L1 = 26mm.

[0052] Calculate the well depth range for the casing thread connection location:

[0053] The coupling length L = 200 mm;

[0054] The distance from the end of the externally threaded pipe to the center of the coupling is L3 = L2 / 2 = 13mm;

[0055] The well depth at the upper end of the circular threaded connection is H1 = HL / 2 = 999.9m; the well depth at the lower end of the circular threaded connection is H2 = H + L / 2 = 1000.1m.

[0056] Finite element method (FEM) simulation calculations or experimental testing of the slippage strength of the sleeve circular thread connection

[0057] A finite element model was constructed based on the external thread of the sleeve and the standard dimensions of the coupling. Simulation calculations yielded a slip strength of A1 = 1900 kN when the vanishing point of the external thread is exposed two turns above the coupling end face after the initial threading. Simulation calculations yielded a slip strength of A2 = 1950 kN when the vanishing point of the external thread is located two turns inside the coupling end face after the initial threading. Alternatively, the slip strength of the threaded connection under these two conditions can be tested experimentally.

[0058] Calculate the slippage strength of the round threaded connection of the downhole casing.

[0059] For an API Φ139.7mm×9.17mm N80 long round thread, when the point where the external thread disappears is two turns above the coupling end face, the distance from the external thread end to the coupling center is recorded as L4=12mm. According to GB / T 17745 standard, the slippage strength of the sleeve round thread connection under this condition is calculated to be A3=1903kN.

[0060] R = 5.08 mm, calculate the slope of the slippage strength of the sleeve circular thread connection k = (A2 - A1) / 4R = 2.461.

[0061] The slippage strength of the round threaded connection of the downhole casing is calculated as A = A3 + k·(L4-L3) = 1900.539kN.

Claims

1. A method for calculating the slippage strength of casing circular thread connections based on big data of well logging inner diameter, characterized in that, The slippage strength of the thread at the coupling is calculated based on the logging inner diameter data and the casing round thread data.

2. The method according to claim 1, characterized in that, The well logging inner diameter data was obtained using a multi-arm caliper.

3. The method according to claim 1, characterized in that, By detecting the well depth-inner diameter curve, and by using the well depth at the upper end of the peak fluctuation of the inner diameter in the well depth-inner diameter curve and the well depth at the lower end of the peak, the well depth at the center of the coupling and the peak width of the inner diameter of the coupling are obtained. The peak width of the inner diameter of the coupling is the distance between the upper and lower pipe ends at the coupling.

4. The method according to claim 3, characterized in that, The well depth at the center of the coupling is the average of the upper well depth and the lower well depth of the peak value.

5. The method according to claim 3, characterized in that, The distance between the upper and lower pipe ends at the coupling is the difference between the upper well depth of the peak value and the lower well depth of the peak value.

6. The method according to claim 1, characterized in that, The casing thread data includes the external thread size of the casing and the internal thread size of the coupling.

7. The method according to claim 1, characterized in that, The formula for calculating the slippage strength of the threaded connection is: A = A3 + k·(L4 - L3), where A is the actual slippage strength of the thread, A3 is the slippage strength of the threaded connection when the disappearance point of the external thread is exposed two turns above the end face of the coupling after the casing round thread is turned on, k is the slope of the slippage strength of the casing round thread connection, L4 is the distance from the end of the external thread to the center of the coupling when the API standard casing round thread is turned on to the point where the disappearance point of the external thread is exposed two turns above the end face of the coupling, and L3 is the distance from the end of the external thread to the center of the coupling obtained by well logging data analysis.

8. The method according to claim 7, characterized in that, The distance from the end of the externally threaded pipe to the center of the coupling is half the distance between the upper and lower pipe ends at the coupling.

9. The method according to claim 7, characterized in that, The formula for calculating the slope of the slippage strength of the sleeve circular thread connection is: k=(A2-A1) / 4R; where A1 is the slippage strength of the circular thread connection when the disappearance point of the external thread after threading is exposed two turns above the end face of the coupling; A2 is the slippage strength of the circular thread connection when the disappearance point of the external thread after threading is located two turns inside the end face of the coupling; and R is the pitch.

10. The method according to claim 9, characterized in that, The slippage strength of the circular thread connection when the disappearance point of the external thread after threading is exposed two turns above the end face of the coupling, and the slippage strength of the circular thread connection when the disappearance point of the external thread after threading is located two turns inside the end face of the coupling, are obtained through finite element simulation calculation or experimental testing.

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