Method for loosening drill rod by utilizing explosion superimposed effect

Abstract

The invention discloses a method for loosening a drill rod by utilizing an explosion superimposed effect, and relates to the technical field of oil and gas well drilling equipment. According to the method, the finite element model is established for the threaded connection joint of the drill rod, and the explosion loosening action mechanism of the drill rod under the working conditions of a deep well and an ultra-deep well is simulated, so that the structural design, the explosive loading amount, the explosive loading number, the explosive loading position and the explosion interval of an explosion cylinder are determined. According to the method for loosening the drill rod by utilizing the explosion superimposed effect, the explosion loosening mechanism research of a deep well and an ultra-deep well under different working conditions is developed, and theoretical guidance is provided for explosion loosening explosive quantity selection, explosion position establishment and an operation method. According to the research of the method, small-equivalent explosive is applied, vibration force is generated in an underground structure, and inherent friction torque between threads is broken, so that the unbuckling effect is achieved, and the success rate of unbuckling of deep well and ultra-deep well drill rod packages is increased.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas well drilling equipment, in particular to the technical field of a drill pipe loosening design after being stuck in an oil and gas well, and more specifically to a method for loosening a drill pipe by utilizing an explosion superposition effect. Background Art

[0002] With the continuous deepening of exploration and development, the depth structure of deep wells and ultra-deep wells has become more and more complex, and some layers are prone to leakage and collapse, with a high risk of drill stuck. The types of drill stuck accidents include sticking, collapse, sand bridge, necking, keyway, mud bag, dry drilling, falling objects and cement consolidation. To deal with drill stuck, generally use circular rotation, up and down movement of drill tools, soaking in salt water, acid bath and other methods. Explosive loosening is a process that uses explosive vibration to loosen the thread of a drill coupling above the stuck point when other measures cannot be used to release the stuck drill.

[0003] Explosive loosening is to use a cable to lower a tool equipped with explosives to above the stuck point, to the thread of the first coupling of the drill bit, to raise the drill and apply enough counter-torque to the drill bit, so that the stuck point is the neutral point and the counter-torque is sufficient, and then ignite and detonate. The high-speed impact force generated by the explosion of the explosive instantly causes the friction and self-locking property between the thread teeth to disappear or greatly reduce instantly, so that the joint thread is loosened under the action of the pre-applied counter-torque, so as to achieve the purpose of loosening the buckle.

[0004] The explosive loosening operation mainly consists of the following steps: 1) The drilling tool is tightly fastened; 2) Lower detonating cord explosive rod or explosive tube; 3) Increase tonnage; 4) Apply counter torque and ensure that the counter torque is delivered to the stuck point; 5) Align the center of the explosive rod or explosive tube with the loose coupling and ignite the loose coupling.

[0005] Due to the complexity of deep and ultra-deep wells, existing explosive loosening technologies often have problems such as excessive charge damaging the drill bit, or too little charge failing to loosen the thread. The study of the mechanism of explosive loosening is essentially a study of the microscopic response characteristics of threaded connection structures under the conditions of explosive impact loads. Under the action of explosive impact loads, most threaded connection structures are not only subject to circumferential tension, but also to the combined force of forces and moments in all directions, as well as to non-periodic transient effects and the comprehensive effects of plastic deformation failure of materials.

[0006] Limited by the special working environment of explosive loosening operations, the mechanism of explosive loosening cannot be restored through experiments. At this stage, most of the process exploration work of explosive loosening is based on operating experience. Summary of the invention

[0007] In order to overcome the defects and shortcomings in the above-mentioned prior art, the present invention provides a method for loosening drill pipes by using the explosion superposition effect. The purpose of the present invention is to solve the problem that most of the current process exploration work of explosive loosening is based on operating experience, and it is easy to cause excessive amount of explosives to damage the drill tools, or too little amount of explosives to loosen the drill pipes. The method for loosening drill pipes by using the explosion superposition effect provided by the present invention has carried out research on the explosive loosening mechanism under different working conditions of deep wells and ultra-deep wells, and provided theoretical guidance for the selection of explosive loosening dosage, establishment of explosion location and operating methods. Through the research of the method of the present invention, a small equivalent explosive is used to generate a vibration force in the underground structure to break the inherent friction torque between the threads, thereby achieving a loosening effect and improving the success rate of loosening drill pipe packaging in deep wells and ultra-deep wells.

[0008] In order to solve the above problems existing in the prior art, the present invention is implemented through the following technical solutions.

[0009] The present invention provides a method for loosening a drill pipe by utilizing the explosion superposition effect, the method comprising the following steps: S1. Establish a finite element model of a drill pipe threaded connection joint, and set the material, elastic modulus, Poisson's ratio, yield limit and strength limit parameters of the finite element model; S2. Simplify the thread stress of the drill pipe threaded connection joint, set one end of the drill pipe as a fixed constraint, apply a preload to the drill pipe threaded connection joint in the form of a paired tension, and keep it in a neutral state in the axial direction, and set the friction mode and friction coefficient of the drill pipe threaded connection joint; S3. Calculate the established finite element model according to the design working conditions. The detonation point of the charge is set at the end of the explosive near the wellhead, which is simplified to instantaneous top detonation. S4, simulate and calculate the thread response state under the condition of 5000m-7000m well depth, set different preset charging amount, charging number, charging position and explosion interval respectively, calculate and record the thread response state of different charging amount, charging number, charging position and explosion interval; S5. Determine the required charge quantity, charge number, charge position and explosion interval based on the thread response state obtained in step S4, and design the explosion tube structure according to the determined charge quantity, charge number, charge position and explosion interval.

[0010] Further preferably, in step S4, the preset charge amount is 230g-300g, the number of charges is 2-5, the charging position is single-side charging or center charging, and the explosion interval is 5μs-60μs.

[0011] Further preferably, the charging position is preferably single-side charging, the number of charging rounds is 3, the explosion interval is 50μs, and when the well depth exceeds 6000m, the total charging amount is 230g; when the well depth exceeds 6500m, the total charging amount is ≤250g.

[0012] More preferably, the thread response state refers to the displacement oscillation of the thread nodes in the X direction of the drill pipe threaded connection joint under simulated explosion impact.

[0013] Further preferably, in step S5, after the designed explosive tube is lowered into the bottom of the well, the depth is adjusted and positioned to the upper end of the drill pipe thread, and it is excited by electric ignition, multiple explosive cakes are used to provide the explosion power source, and a 50μs gunpowder delay device is used to achieve the timing interval of the explosion.

[0014] More preferably, the explosion tube structure comprises an explosion tube body, in which three explosive cakes are arranged in an upper and lower manner, and adjacent explosive cakes are connected by a gunpowder delay device.

[0015] Further preferably, in step S1, the finite element model of the drill pipe threaded connector established is a finite element model of an NC40 threaded connector.

[0016] Further preferably, in the finite element model of the NC40 threaded connector, a special steel material is given to the model, with an elastic modulus of 206 GPa and a Poisson's ratio of , the yield limit of the material MPa, ultimate strength MPa.

[0017] More preferably, in the finite element model of the NC40 threaded connector, the material model adopts an ideal elastic-plastic model.

[0018] More preferably, in step S2, the friction mode of the drill pipe threaded connection joint is set to sliding friction, and the friction coefficient is 0.17.

[0019] Compared with the prior art, the beneficial technical effects brought by the present invention are as follows: 1. The present invention has carried out research on the explosive loosening mechanism under different working conditions in ultra-deep wells and ultra-deep wells, and provided theoretical guidance for the selection of explosive loosening charges, the establishment of explosion positions and the operation methods.

[0020] 2. Use small equivalent explosives to generate vibration force in the underground structure, break the inherent friction torque between the threads, thereby achieving the loosening effect and improving the success rate of explosive loosening of deep and ultra-deep well drill pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The explosive tube structure designed by the present invention is suitable for the NC40 threaded connector; Figure 2 The displacement oscillation of the thread node in the X direction of the drill pipe threaded connection joint under the impact of the center charge explosion; Figure 3 The displacement oscillation of the thread node in the X direction of the drill pipe threaded connection joint under the impact of the explosion of three charges on one side with a time interval of 10μs; Figure 4 The displacement oscillation of the thread node in the X direction of the drill pipe threaded connection joint under the impact of the explosion of three charges on one side with a time interval of 50μs; Figure numerals: 1. Explosion tube, 2. Explosive cake, 3. Gunpowder delay device. DETAILED DESCRIPTION

[0022] The following is an exemplary embodiment of the present invention that helps to fully understand the claims and their equivalents in conjunction with the accompanying drawings, wherein the specific details will be considered only as exemplary, and do not limit the scope of the present invention. Therefore, those of ordinary skill in the art can make various changes and modifications to the embodiments without departing from the scope and spirit of the present invention.

[0023] Example 1 As a preferred embodiment of the present invention, this embodiment discloses a method for loosening a drill pipe by utilizing the explosion superposition effect, the method comprising the following steps: S1. Establish a finite element model of a drill pipe threaded connection joint, and set the material, elastic modulus, Poisson's ratio, yield limit and strength limit parameters of the finite element model; S2. Simplify the thread stress of the drill pipe threaded connection joint, set one end of the drill pipe as a fixed constraint, apply a preload to the drill pipe threaded connection joint in the form of a paired tension, and keep it in a neutral state in the axial direction, and set the friction mode and friction coefficient of the drill pipe threaded connection joint; S3. Calculate the established finite element model according to the design working conditions. The detonation point of the charge is set at the end of the explosive near the wellhead, which is simplified to instantaneous top detonation. S4, simulate and calculate the thread response state under the condition of 5000m-7000m well depth, set different preset charging amount, charging number, charging position and explosion interval respectively, calculate and record the thread response state of different charging amount, charging number, charging position and explosion interval; S5. Determine the required charge quantity, charge number, charge position and explosion interval based on the thread response state obtained in step S4, and design the explosion tube structure according to the determined charge quantity, charge number, charge position and explosion interval.

[0024] Example 2 As another preferred embodiment of the present invention, this embodiment is a further detailed supplement and elaboration of the technical solution of the present invention based on the above-mentioned embodiment 1. In this embodiment, in step S4, the preset charge amount is 230g-300g, the number of charge rounds is 2-5 rounds, the charge position is single-side charge or center charge, and the explosion interval is 5μs-60μs.

[0025] In this embodiment, the finite element model of the drill pipe threaded connector is a finite element model of the NC40 threaded connector. In the finite element model of the NC40 threaded connector, a special steel material is assigned to the model, with an elastic modulus of 206 GPa and a Poisson's ratio of , the yield limit of the material MPa, ultimate strength MPa. In the finite element model of the NC40 threaded connector, the material model adopts the ideal elastic-plastic model. The friction mode of the drill pipe threaded connector is set to sliding friction, and the friction coefficient is 0.17.

[0026] After simulation, it was finally determined that for the NC40 threaded connector, the charging position is preferably single-sided charging, the number of charging rounds is 3, the explosion interval is 50μs, and when the well depth exceeds 6000m, the total charging amount is 230g; when the well depth exceeds 6500m, the total charging amount is ≤250g.

[0027] The thread response state refers to the displacement oscillation of the thread node in the X direction of the threaded connection joint of the drill pipe under the simulated explosion impact. During the simulation, after the designed explosive tube is lowered into the bottom of the well, the depth is adjusted and positioned to the upper end of the drill pipe thread, and it is excited by electric ignition, relying on multiple explosive cakes to provide the explosion power source, and relying on a 50μs gunpowder delay device to achieve the timing interval of the explosion.

[0028] Example 3 As another preferred embodiment of the present invention, this embodiment takes the NC40 threaded connector as an example, establishes a finite element model for the NC40 threaded connector, and performs a simulation of the loosening of the drill rod due to the explosion superposition effect. The simulation process of this embodiment is as follows: S1. Establish the finite element model of NC40 threaded connection, and assign special steel material to the NC40 joint. The elastic modulus of the joint material is 206Gpa, and the Poisson's ratio is 0.29, the yield limit of the material Mpa, ultimate strength Mpa, the material model adopts the ideal elastic-plastic model; S2. Simplify the force on the thread. One end of the drill pipe is set as a fixed constraint. The threaded joint is preloaded by applying a pair of tensile forces. The joint is in a neutral state in the axial direction, neither under pressure nor under tensile load. For the contact of the joint, set sliding friction contact and set the friction coefficient to 0.17.

[0029] S3. Calculation work is carried out on the model according to the design conditions. The detonation point of the charge is set at the end of the explosive close to the wellhead, which is simplified to instantaneous top detonation.

[0030] S4. Simulate and calculate the thread response state under the condition of 5000m to 7000m well depth, with the preset charge amount of 230g to 300g. The X-direction displacement of the horizontal and vertical thread nodes of the single-sided three-shot charge (explosion interval of 50 microseconds) is the maximum displacement of 0.06mm. The whole cycle basically shows an oscillating trend, and there is a cycle with a period of 50 microseconds between the peaks and valleys, such as Figure 2 The displacement of the horizontal and vertical thread nodes of the three-round charge on one side in the X direction (explosion interval 10 microseconds) is as follows: The maximum displacement is 0.05mm. The whole cycle basically shows an oscillating trend. There are suspected cycles between the peaks and valleys with a period significantly higher than the explosion interval of 50 microseconds, such as Figure 3 The maximum displacement of the horizontal and vertical nodes in the Y direction of the central charge thread is 0.03mm. The whole cycle is basically stable and oscillating. Figure 4 .

[0031] S5. Under the calculated working conditions, the strain of the thread of 290g-300g charge is close to the failure value due to the large amount of charge and the short action distance, and there is a risk of plastic deformation of the thread caused by explosion, which may make the loosening work more difficult; The calculation conditions of 290g-300g charge all have this situation, and the deeper the well, the higher the residual strain of the thread and the higher the risk of failure. This phenomenon is first considered to be caused by the superposition of static pressure response conditions in deeper wells.

[0032] S6. After the calculation, although the oscillation of the strain response is consistent with that in the loosening environment, it can be observed that the strain oscillation curve does not dissipate with the passage of time, and the oscillation centerline still revolves around the initial strain with only a slight decrease; this situation occurs when the well depth exceeds 6000m and the loosening charge is 230g; when the well depth exceeds 6500m and the charge is less than or equal to 250g.

[0033] S7. From the perspective of the explosive loosening mechanism obtained from the simulation, the explosive loosening is, in principle, to use a small amount of explosives to generate vibration force in the underground structure to break the inherent friction torque between the threads, thereby achieving the loosening effect.

[0034] S8. From the calculation results, the energy released by the loosening explosion is sometimes not enough to loosen the thread, but it is enough to cause relative vibration of the threaded connection surface. Combined with the mass-spring theory, if multiple application points are set for the explosion itself, the amount of explosives is appropriately reduced, the distance between the explosives and the detonation time interval are increased, and the stress wave generated by the explosion impact is transmitted to the joint interface along the drill pipe structure. Then, the strain curve of the threaded contact surface itself has multiple superimposed explosion vibration excitations, which will accelerate the dissipation of the strain curve, that is, increase the vibration irregularity of the contact surface itself, thereby improving the success rate of explosive loosening.

[0035] S9. From the simulation results, we can see that reducing the amount of explosives and lengthening the explosion time and distance interval can effectively utilize the explosion superposition effect and achieve better explosion loosening effects in deep and ultra-deep well operations.

[0036] S10. Design explosive loose charge structure such as Figure 1 As shown in the figure. 1 is an explosion tube, 2 is a high explosive cake, and 3 is a 50μs gunpowder delay device. When the explosive loosening device is lowered into the bottom of the well, the depth is adjusted and positioned to the upper end of the drill pipe thread, and it is excited by electric ignition, relying on multiple high explosive cakes to provide the explosion power source, and relying on the 50μs gunpowder delay device to achieve the timing interval of the explosion. The impact vibration generated can act on the drill pipe thread to be loosened to achieve the loosening effect.

[0037] While the inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the claims.

Claims

1. A method for loosening a drill pipe by utilizing the explosion superposition effect, characterized in that: The method comprises the following steps, S1. Establish a finite element model of a drill pipe threaded connection joint, and set the material, elastic modulus, Poisson's ratio, yield limit and strength limit parameters of the finite element model; S2. Simplify the thread stress of the drill pipe threaded connection joint, set one end of the drill pipe as a fixed constraint, apply a preload to the drill pipe threaded connection joint in the form of a paired tension, and keep it in a neutral state in the axial direction, and set the friction mode and friction coefficient of the drill pipe threaded connection joint; S3. Calculate the established finite element model according to the design working conditions. The detonation point of the charge is set at the end of the explosive near the wellhead, which is simplified to instantaneous top detonation. S4, simulate and calculate the thread response state under the condition of 5000m-7000m well depth, set different preset charging amount, charging number, charging position and explosion interval respectively, calculate and record the thread response state of different charging amount, charging number, charging position and explosion interval; S5. Determine the required charge quantity, charge number, charge position and explosion interval based on the thread response state obtained in step S4, and design the explosion tube structure according to the determined charge quantity, charge number, charge position and explosion interval.

2. A method for loosening a drill pipe by utilizing the explosion superposition effect as claimed in claim 1, characterized in that: In step S4, the preset charge amount is 230g-300g, the number of charges is 2-5, the charging position is single-side charging or center charging, and the explosion interval is 5μs-60μs.

3. A method for loosening a drill pipe by utilizing the explosion superposition effect as claimed in claim 1 or 2, characterized in that: The charging position is preferably single-side charging, the number of charging rounds is 3, the explosion interval is 50μs, and the total charging amount is 230g when the well depth exceeds 6000m; when the well depth exceeds 6500m, the total charging amount is ≤250g.

4. A method for loosening a drill pipe by utilizing the explosion superposition effect as claimed in claim 1, characterized in that: The thread response state refers to the displacement oscillation of the thread nodes in the X direction of the drill pipe threaded connection joint under the simulated explosion impact.

5. A method for loosening a drill pipe by utilizing the explosion superposition effect as claimed in claim 1, 2 or 4, characterized in that: In step S5, after the designed explosive tube is lowered into the bottom of the well, the depth is adjusted and positioned to the upper end of the drill pipe thread, and it is excited by electric ignition, relying on multiple explosive cakes to provide the explosion power source, and relying on a 50μs gunpowder delay device to achieve the timing interval of the explosion.

6. A method for loosening a drill pipe by utilizing the explosion superposition effect as claimed in claim 1, 2 or 4, characterized in that: The explosion tube structure comprises an explosion tube body, in which three explosive cakes are arranged from top to bottom with intervals, and adjacent explosive cakes are connected by a gunpowder delay device.

7. A method for loosening a drill pipe by utilizing the explosion superposition effect as claimed in claim 1, 2 or 4, characterized in that: In step S1, the finite element model of the drill pipe threaded connector established is a finite element model of the NC40 threaded connector.

8. A method for loosening a drill pipe by utilizing the explosion superposition effect as claimed in claim 7, characterized in that: In the finite element model of the NC40 threaded connector, the model is given a special steel material with an elastic modulus of 206 GPa and a Poisson's ratio of , the yield limit of the material MPa, ultimate strength MPa.

9. A method for loosening a drill pipe by utilizing the explosion superposition effect as claimed in claim 8, characterized in that: In the finite element model of the NC40 threaded connector, the material model adopts the ideal elastic-plastic model.

10. A method for loosening a drill pipe by utilizing the explosion superposition effect as claimed in claim 9, characterized in that: In step S2, the friction mode of the drill pipe threaded connection joint is set to sliding friction, and the friction coefficient is 0.17.

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