A test bench for combined compression and torsion loading of flexible drill pipe under bending conditions

Abstract

This invention relates to a test bench for combined pressure and torsion loading of flexible drill pipes under bending conditions, comprising a bench, a combined loading mechanism, a support and buffer limiting mechanism, and a fully fixed mechanism. The bench includes a frame, with a pressure cylinder fixedly connected to the top of the frame. The combined loading mechanism includes a loading frame located directly below the pressure cylinder. A torsion motor and a drill pipe clamp are sequentially mounted inside the loading frame from top to bottom; the drill pipe clamp is used to hold the upper connector of the flexible drill pipe. The support and buffer limiting mechanism is located below the loading frame, with the bottom end of the loading frame fitted within it. The fully fixed mechanism is located on one side of the frame and is used to fix the lower connector of the flexible drill pipe. This invention, through the combined design of the combined loading mechanism, the support and buffer limiting mechanism, and the fully fixed mechanism, enables more realistic and accurate combined loading test data for flexible drill pipes.

Description

Technical Field

[0001] This invention relates to the field of drill pipe performance testing technology, and in particular to a test bench for combined compression and torsion loading of flexible drill pipes under bending conditions. Background Technology

[0002] Flexible drill pipe is one of the core components of ultra-short radius sidetracking horizontal well technology, and its mechanical strength directly affects the success of drilling operations. Flexible drill pipe is composed of multiple drill pipe sections connected end-to-end, with sections that can be bent at certain angles. By superimposing the bending angles of multiple drill pipe sections, the transition from vertical to horizontal sections can be achieved, enabling ultra-short radius radial horizontal well drilling operations. It is generally located at the bottom of the drill string assembly, connected to the drill bit or flexible drill string, and serves to transmit drilling pressure and torque.

[0003] During drilling operations, flexible drill pipes must withstand the dual loads of drilling pressure and torque simultaneously, posing safety risks such as drill pipe breakage and seal failure in the field. Therefore, composite loading tests must be conducted during the development of flexible drill pipes to verify their mechanical properties. However, current testing methods mostly involve single-force loading: single compression, single tension, or single torsion. Moreover, the test objects are mostly straight rods, or flexible drill pipes are used to simulate straight conditions. But flexible drill pipes bend at a certain angle during operation, so commonly used composite loading testing machines cannot perform combined compression and torsion loading tests on flexible drill pipes under bending conditions, and cannot be used for accurate verification of numerical simulations.

[0004] The Chinese invention patent CN104764576B, "Vibration Testing Machine for Combined Tension, Torsion, and Bending of Flexible Rods," although utilizing a tension cylinder to apply tensile and compressive loads to the upper and lower ends of the flexible rod, a torsion motor to apply torsional loads to the bottom end of the flexible rod, and a combined swing device to achieve back-and-forth and left-and-right swinging of the bottom end of the flexible rod, cannot meet the displacement boundary conditions (only lateral displacement constraints at the upper joint of the flexible drill rod, and full constraints at the lower joint) and load boundary conditions (torque and axial force at the upper joint of the flexible drill rod, and the flexible drill rod bearing its own weight) for the combined compression and torsion loading test of the flexible drill rod. In other words, it cannot simulate the actual working conditions of the flexible drill rod, resulting in distorted compression and torsion test data of the flexible drill rod in bending state, ultimately reducing the accuracy of predicting the mechanical properties of the flexible drill rod in working state. Summary of the Invention

[0005] In view of this, it is necessary to provide a test bench for combined compression and torsion loading under bending conditions of flexible drill pipe, so as to solve the technical problem that the existing technology cannot effectively simulate the actual working conditions of flexible drill pipe, which leads to a decrease in the accuracy of mechanical performance prediction.

[0006] This invention provides a test bench for combined compression and torsion loading of flexible drill pipe under bending conditions, including a bench, a combined loading mechanism, a support buffer limiting mechanism, and a fully fixed mechanism;

[0007] The platform includes a frame, and a pressure cylinder is fixedly connected to the top of the frame;

[0008] The composite loading mechanism includes a loading frame located directly below the pressure cylinder, which is used to allow the pressure cylinder to abut against the top of the loading frame and apply a load. A torsion motor and a drill rod clamp are sequentially mounted inside the loading frame from top to bottom. The drill rod clamp is used to hold the upper joint of the flexible drill rod, and the torsion motor is used to apply torque to the drill rod clamp.

[0009] The support buffer limiting mechanism is located below the loading frame. The bottom end of the loading frame is sleeved in the support buffer limiting mechanism, and the support buffer limiting mechanism has a limiting hole in the center to sleeve the flexible drill rod and limit the horizontal displacement of the upper joint of the flexible drill rod.

[0010] The fully fixed mechanism is located on one side of the frame and is used to fix the lower connector of the flexible drill rod.

[0011] In one embodiment of the present invention, the platform further includes a base, the top of which is fixedly connected to the fully fixed mechanism, the support buffer limiting mechanism and the bottom of the frame.

[0012] In one embodiment of the present invention, the loading frame includes a housing having a downward-facing receiving cavity, and at least three pillars extending downward from the outer wall of the housing, each of the three pillars extending into and being adapted to the support buffer limiting mechanism.

[0013] In one embodiment of the present invention, both the torsion motor and the drill pipe clamp are installed in the upper part of the receiving cavity, and the torsion motor and the drill pipe clamp are detachably connected by the torsion clamp.

[0014] In one embodiment of the present invention, the output end of the torsion motor is sleeved inside the torsion clamp, and a transmission shaft is also sleeved below the torsion clamp. The bottom end of the transmission shaft extends out of the torsion clamp and is fixedly connected to the drill pipe clamp.

[0015] In one embodiment of the present invention, a thrust bearing and a pressure clamp are fixed in sequence from top to bottom in the middle of the transmission shaft, and the upper end face and lower end face of the thrust bearing abut against the inner wall of the receiving cavity and the pressure clamp in sequence.

[0016] In one embodiment of the present invention, the support buffer limiting mechanism includes a support frame, an inner liner and an outer liner are provided inside the support frame, hydraulic oil is provided in both the inner liner and the outer liner, the bottom end of the loading frame extends into the inner liner and abuts against the hydraulic oil, and reflux holes are provided on the upper and lower parts of the side wall of the inner liner.

[0017] In one embodiment of the present invention, an elastic component is provided at the inner bottom of the inner liner.

[0018] In one embodiment of the present invention, the elastic component includes a spring and a piston, one end of the spring being fixedly connected to the inner bottom of the inner liner, and the other end of the spring being fixedly connected to the piston.

[0019] In one embodiment of the present invention, the fully fixed mechanism includes an internally threaded drill chuck for threaded connection with the lower connector of the flexible drill rod.

[0020] Compared with the prior art, the flexible drill pipe bending state pressure-torsion combined loading test bench provided by the present invention has the following beneficial effects:

[0021] In this invention, a structural foundation for a pressure-torsion composite loading test of a flexible drill rod is constructed by setting up a composite loading mechanism, a support buffer limiting mechanism, and a fully fixed mechanism. Specifically, a pressure cylinder is fixedly connected to the frame, and the pressure cylinder abuts against the top of the loading frame to apply a load. A torsion motor and a drill rod clamp are installed inside the loading frame. The drill rod clamp further clamps the upper joint of the flexible drill rod, causing the upper joint of the flexible drill rod to generate torque and axial force, and the flexible drill rod to bear its own weight (i.e., meeting the load boundary conditions). At the same time, the bottom end of the loading frame is fitted into the support buffer limiting mechanism, and a limiting hole is opened in the center of the support buffer limiting mechanism to fit the flexible drill rod and limit the horizontal displacement of the upper joint of the flexible drill rod. That is, the horizontal displacement of the loading frame and the upper joint of the flexible drill rod are limited by the support buffer limiting mechanism and the limiting hole, respectively, meaning that the upper joint of the flexible drill rod is only constrained by lateral displacement. The lower joint of the flexible drill rod is fixed by the fully fixed mechanism, which also makes the lower joint of the flexible drill rod fully constrained (i.e., meeting the displacement boundary conditions). Therefore, through the combined design of the above structures, the flexible drill rod can simulate the actual working conditions on the pressure-torsion composite loading test bench, thereby improving the accuracy of predicting the mechanical properties of the flexible drill rod under working conditions.

[0022] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail in the following embodiments and their accompanying drawings. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0024] Figure 1 An isometric view of a test bench for combined compression and torsion loading under bending conditions of a flexible drill pipe, provided by the present invention.

[0025] Figure 2 for Figure 1 Schematic diagram of the connection relationship between the loading frame and the flexible drill pipe;

[0026] Figure 3 for Figure 1 Axonometric drawing of the central support buffer limiting mechanism;

[0027] Figure 4 for Figure 1 Schematic diagram of the connection relationship between the fixed mechanism and the flexible drill pipe body;

[0028] Figure 5 for Figure 4 Enlarged view of point A in the middle;

[0029] Figure 6 for Figure 1 A schematic diagram showing the connection between the loading frame and the support frame.

[0030] The attached figures are labeled as follows:

[0031] 100. Stand; 110. Frame; 120. Base; 200. Composite loading mechanism; 210. Loading frame; 211. Housing; 212. Receiving cavity; 213. Support column; 220. Torsion motor; 221. Output end; 230. Drill rod clamp; 240. Torsion clamp; 250. Transmission shaft; 260. Thrust bearing; 270. Pressure clamp; 300. Support buffer limiting mechanism; 310. Support frame; 320. Inner liner; 330. Outer liner; 340. Hydraulic oil; 350. Elastic component; 351. Spring; 352. Piston; 360. Return hole; 370. Spiral tube; 400. Fully fixed mechanism; 410. Internal thread drill clamp; 420. Internal spline cylinder; 430. External spline; 500. Pressure cylinder; 600. Flexible drill rod body; 700. Limiting hole. Detailed Implementation

[0032] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0033] Please see Figures 1-6This invention provides a test bench for combined pressure and torsion loading of flexible drill pipe under bending conditions, including a bench 100, a combined loading mechanism 200, a support buffer limiting mechanism 300, and a fully fixed mechanism 400; the bench 100 includes a frame 110, with a pressure cylinder 500 fixedly connected above the frame 110; the combined loading mechanism 200 includes a loading frame 210, which is located directly below the pressure cylinder 500, so that the pressure cylinder 500 abuts against the top of the loading frame 210 and applies a load, and a torsion motor 2 is sequentially installed inside the loading frame 210 from top to bottom. The machine includes a 20-type drill rod clamp 230, which holds the upper connector of the flexible drill rod. A torque motor 220 applies torque to the drill rod clamp 230. A support buffer limiting mechanism 300 is located below the loading frame 210, with the bottom end of the loading frame 210 fitted inside the support buffer limiting mechanism 300. A limiting hole 700 is provided in the center of the support buffer limiting mechanism 300 to accommodate the flexible drill rod and limit the horizontal displacement of the upper connector of the flexible drill rod. A fully fixed mechanism 400 is located on one side of the frame 110 and is used to fix the lower connector of the flexible drill rod. It should be noted that the drill rod clamp 230 and the flexible drill rod are clamped by a threaded connection.

[0034] In use, first, the flexible drill pipe body 600 is passed through the middle (i.e., the limiting hole 700) of the support buffer limiting mechanism 300. Then, the upper connector of the flexible drill pipe body 600 is connected to the drill pipe clamp 230, and the lower connector of the flexible drill pipe body 600 is connected to the fully fixed mechanism 400 (preferably, the bending angle of the flexible drill pipe can simulate the radius of curvature of a side-drilled horizontal well). Then, the pressure cylinder 500 is activated, so that the pressure force of the pressure cylinder 500 is transmitted sequentially to the flexible drill pipe body 600 and the support buffer limiting mechanism 300 through the loading frame 210 and the drill pipe clamp 230. Since the supporting buffer limiting mechanism 300 has a limiting hole 700 in the center, it is used to fit the flexible drill pipe (i.e., the limiting hole 700). Figure 1The flexible drill rod body 600 limits the horizontal displacement of the upper joint of the flexible drill rod, and the bottom end of the loading frame 210 is sleeved within the support buffer limiting mechanism 300. This limits the horizontal displacement of the upper joint of the flexible drill rod by the limiting hole 700, while the support buffer limiting mechanism 300 indirectly limits the horizontal displacement of the upper joint of the flexible drill rod by limiting the loading frame 210. In other words, both of them fully limit the horizontal displacement of the upper joint of the flexible drill rod body 600, while the fully fixed mechanism 400 fixes the lower joint of the flexible drill rod body 600, thus satisfying the displacement boundary. The conditions are as follows: the hydraulic cylinder 500 abuts against the top of the loading frame 210 and applies a load, and a torsion motor 220 and a drill rod clamp 230 are set inside the loading frame 210. The upper joint of the flexible drill rod (i.e., the flexible drill rod body 600) is clamped by the drill rod clamp 230, so that the upper joint of the flexible drill rod also generates torque and axial force, and the flexible drill rod bears its own weight (i.e., meets the load boundary conditions). That is, the above-mentioned pressure-torsion composite loading test bench can simulate the actual working conditions of the flexible drill rod body 600, thereby improving the accuracy of predicting the mechanical properties of the flexible drill rod in the working state.

[0035] In order to better arrange the structure of the above-mentioned compression-torsion composite loading test bench, in one embodiment of the present invention, the bench 100 further includes a base 120, the top of which is fixedly connected to the fully fixed mechanism 400, the support buffer limiting mechanism 300 and the bottom of the frame 110 respectively.

[0036] To limit the horizontal displacement of the flexible drill pipe body 600 by the support buffer limiting mechanism 300, in one embodiment of the present invention, the loading frame 210 includes a housing 211 with a downward-facing receiving cavity 212. At least three support pillars 213 extend downward from the outer wall of the housing 211, each of which extends into and is adapted to the support buffer limiting mechanism 300. It should be noted that the support buffer limiting mechanism 300 can also achieve buffering and overload protection through a sliding connection with the bottom end of the loading frame 210 (one form of adaptation).

[0037] Furthermore, in one embodiment of the present invention, the torsion motor 220 and the drill pipe clamp 230 are both installed in the upper part of the receiving cavity 212, and a torsion clamp 240 is detachably connected between the torsion motor 220 and the drill pipe clamp 230.

[0038] Furthermore, in one embodiment of the present invention, the output end 221 of the torsion motor 220 is sleeved within the torsion clamp 240, and a transmission shaft 250 is also sleeved below the torsion clamp 240. The bottom end of the transmission shaft 250 extends out of the torsion clamp 240 and is fixedly connected to the drill pipe clamp 230. Specifically, the torsion clamp 240 needs to clamp the transmission shaft 250 and the output end 221 to ensure the smoothness of the rotation of the torsion motor 220. Preferably, the transmission shaft 250 and the drill pipe clamp 230 are integrally formed.

[0039] To achieve a combined compression and torque loading, in one embodiment of the present invention, a thrust bearing 260 and a pressure clamp 270 are sequentially fixed from top to bottom at the middle of the transmission shaft 250. The upper end face (rotor) and lower end face (stator) of the thrust bearing 260 abut against the inner wall of the receiving cavity 212 and the pressure clamp 270 in sequence. Specifically, when the pressure cylinder 500 applies a load to the loading frame 210, the load is sequentially transmitted through the loading frame 210 and the inner wall of the receiving cavity 212 to the upper end face (rotor) of the thrust bearing 260, then applied to the pressure clamp 270 through the lower end face (stator) of the thrust bearing 260, and finally transmitted to the flexible drill pipe body 600 through the pressure clamp 270 (at this time, the upper joint of the flexible drill pipe body 600 is connected to the drill pipe clamp 230).

[0040] In order to enable the support buffer limiting mechanism 300 to better perform its buffering function, in one embodiment of the present invention, the support buffer limiting mechanism 300 includes a support frame 310, an inner liner 320 and an outer liner 330 are provided inside the support frame 310, and hydraulic oil 340 is provided in both the inner liner 320 and the outer liner 330. The bottom end of the loading frame 210 extends into the inner liner 320 and abuts against the hydraulic oil 340. The upper and lower parts of the side wall of the inner liner 320 are provided with return holes 360. Specifically, when the two pillars 213 move downward under load, they will first squeeze the hydraulic oil 340. Since the lower part of the side wall of the inner liner 320 is provided with a return hole 360, the hydraulic oil 340 will flow out through the variable cross section under pressure and the pressure force will be slowly applied. At this time, the liquid level of the hydraulic oil 340 in the outer liner 330 rises, and once it tends to fill the entire outer liner 330, it will flow back into the inner liner 320 through the return hole 360 ​​located on the upper part of the side wall of the inner liner 320.

[0041] Furthermore, in one embodiment of this utility model, a spiral tube 370 is hung on the outer wall of the inner liner 320. One end of the spiral tube 370 is connected to the return hole 360, and the other end of the spiral tube 370 extends upward, allowing the hydraulic oil 340 to flow back and forth within the spiral tube 370. Additionally, when the load is removed, the three supports 213 will slowly return to their initial positions. It should be noted that, under the same diameter and pressure, when the spiral tube 370 is connected to the orifice of the return hole 360 ​​(outflow from the nozzle), the resistance to fluid movement of the hydraulic oil 340 is greater than that at the orifice of the return hole 360 ​​(outflow from the orifice). It should also be noted that when the three supports 213 continue to move downward and are located below the lower return hole 360, forming a sealed space, they will be unable to continue moving downward due to overload protection.

[0042] In order to increase the buffer and allow the three pillars 213 to reset better (after the load of the hydraulic cylinder 500 is removed), in one embodiment of the present invention, an elastic component 350 is provided at the inner bottom of the inner liner 320.

[0043] Furthermore, in one embodiment of the present invention, the elastic component 350 includes a spring 351 and a piston 352. One end of the spring 351 is fixedly connected to the inner bottom of the inner liner 320, and the other end of the spring 351 is fixedly connected to the piston 352. Specifically, when the three pillars 213 move downward, they not only squeeze the hydraulic oil 340, but also compress the spring 351, thus better achieving buffering and displacement limitation.

[0044] In order to better achieve full constraint of the flexible drill pipe body 600, in one embodiment of the present invention, the full fixing mechanism 400 includes an internal thread drill chuck 410, which is used to be threadedly connected to the lower connector of the flexible drill pipe.

[0045] Furthermore, the fully fixed mechanism 400 also includes an external spline 430 and an internal spline cylinder 420. One end of the external spline 430 is fixedly connected to the internal thread drill chuck 410, and the other end of the external spline 430 is keyedly connected to the internal spline cylinder 420. Preferably, the internal spline cylinder 420 is fixedly mounted on the base 120, and the base 120 is fixedly connected to the ground.

[0046] In practical use, the aforementioned pressure-torsion composite loading test bench first uses the drill rod clamp 230 to constrain the upper joint of the flexible drill rod body 600, and then uses the pressure cylinder 500 to apply axial force to the upper joint of the flexible drill rod body 600 and to allow the flexible drill rod body 600 to bear its own weight. Then, the torsion motor 220, which is sleeved inside the loading frame 210, applies torque to the flexible drill rod body 600. Because the flexible drill rod is constrained by the limiting hole 700, and the three supports 213 extend into the inner liner 320, the flexible drill rod... The horizontal displacement of the upper joint of the rod body 600 is further limited, and the combined design of the internal thread drill chuck 410, external spline 430, and internal spline cylinder 420 makes the lower joint of the flexible drill rod body 600 fully constrained. That is, when the flexible drill rod body 600 is tested on the above-mentioned pressure-torsion composite loading test bench, it meets the load boundary conditions and displacement boundary conditions, which can better simulate the state of the flexible drill rod body 600 under actual working conditions, thereby improving the accuracy of predicting the mechanical properties of the flexible drill rod under working conditions.

[0047] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A test bench for combined compression and torsion loading of flexible drill rods under bending conditions, characterized in that, Includes a platform, a composite loading mechanism, a support buffer limiting mechanism, and a fully fixed mechanism; The platform includes a frame, and a pressure cylinder is fixedly connected to the top of the frame; The composite loading mechanism includes a loading frame located directly below the pressure cylinder, which is used to allow the pressure cylinder to abut against the top of the loading frame and apply a load. A torsion motor and a drill rod clamp are sequentially mounted inside the loading frame from top to bottom. The drill rod clamp is used to hold the upper joint of the flexible drill rod, and the torsion motor is used to apply torque to the drill rod clamp. The support buffer limiting mechanism is located below the loading frame. The bottom end of the loading frame is sleeved in the support buffer limiting mechanism, and the support buffer limiting mechanism has a limiting hole in the center to sleeve the flexible drill rod and limit the horizontal displacement of the upper joint of the flexible drill rod. The fully fixed mechanism is located on one side of the frame and is used to fix the lower connector of the flexible drill rod.

2. The test bench for combined compression and torsion loading of a flexible drill rod under bending state according to claim 1, characterized in that, The platform also includes a base, the top of which is fixedly connected to the fully fixed mechanism, the support buffer limiting mechanism, and the bottom of the frame.

3. The test bench for combined compression and torsion loading of a flexible drill rod under bending state according to claim 1, characterized in that, The loading frame includes a housing having a downward-facing receiving cavity, and at least three support pillars extending downward from the outer wall of the housing, each of the three support pillars extending into and being adapted to the support buffer limiting mechanism.

4. The test bench for combined compression and torsion loading of a flexible drill rod under bending state according to claim 3, characterized in that, The torsion motor and the drill pipe clamp are both installed in the upper part of the receiving cavity, and the torsion clamp is detachably connected between the torsion motor and the drill pipe clamp.

5. The test bench for combined compression and torsion loading of a flexible drill rod under bending state according to claim 4, characterized in that, The output end of the torsion motor is fitted inside the torsion clamp, and a transmission shaft is also fitted inside the torsion clamp. The bottom end of the transmission shaft extends out of the torsion clamp and is fixedly connected to the drill pipe clamp.

6. The test bench for combined compression and torsion loading of a flexible drill rod under bending state according to claim 5, characterized in that, A thrust bearing and a pressure clamp are fixed in sequence from top to bottom in the middle of the transmission shaft. The upper and lower end faces of the thrust bearing abut against the inner wall of the receiving cavity and the pressure clamp in sequence.

7. The test bench for combined compression and torsion loading of a flexible drill rod under bending state according to claim 1, characterized in that, The support buffer limiting mechanism includes a support frame, an inner liner and an outer liner are provided inside the support frame, and hydraulic oil is provided in both the inner liner and the outer liner. The bottom end of the loading frame extends into the inner liner and abuts against the hydraulic oil. Return holes are provided on the upper and lower parts of the side wall of the inner liner.

8. The test bench for combined compression and torsion loading of a flexible drill rod under bending state according to claim 7, characterized in that, A spiral tube is hung on the outer wall of the inner liner. One end of the spiral tube is connected to the reflux hole at the lower part of the side wall of the inner liner, and the other end of the spiral tube extends upward.

9. The test bench for combined compression and torsion loading of a flexible drill pipe under bending state according to claim 7, characterized in that, The inner bottom of the inner liner is provided with an elastic component.

10. A test bench for combined compression and torsion loading of a flexible drill rod under bending state according to claim 9, characterized in that, The elastic component includes a spring and a piston, one end of the spring being fixedly connected to the inner bottom of the inner liner, and the other end of the spring being fixedly connected to the piston.

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