A weak point short section for pump-out logging and its assembly method

Abstract

The present invention discloses a weak point short section for pump-out logging and an assembly method thereof. The short section comprises an upper joint, a piston cylinder and a lower joint. One end of the piston cylinder is fixedly connected to the upper joint, and two keyways are arranged on the other end. Two anti-rotation keys are arranged on the lower joint. The two keyways of the piston cylinder can be respectively installed in the two anti-rotation keys of the lower joint. A weak point mandrel is arranged in the piston cylinder, and a compression spring and a piston capable of compressing the compression spring are sequentially mounted on the weak point mandrel. The weak point short section disclosed by the present invention is installed at the lower end of a radioactive instrument and is easy to get stuck at the upper end of the instrument. When the instrument gets stuck and the tension exceeds the limit value, the weak point short section breaks first, effectively protecting the radioactive short section, allowing the radioactive instrument to be first out of the well, reducing the risk of construction and salvage of the radioactive instrument and the impact of the radiation source on the environment.

Description

Technical Field

[0001] The invention belongs to the field of through-drill bit or pump-out logging technology in petroleum logging, and particularly relates to a weak point short section for pump-out logging and an assembly method thereof in the field. Background Art

[0002] The pump-out logging construction process is suitable for complex wells and horizontal wells. Compared with the direct drilling method of drilling tools, its reliability is greatly improved. The pump-out logging system consists of gamma, continuous inclination, radioactivity, lateral, sonic wave, induction and other projects. The length of the whole string of instruments after connection is about 60 meters. In order to ensure the curve quality of sonic wave, induction and other logging projects, multiple stabilizers are required to ensure the centering effect. When the well conditions of complex wells are poor, the risk of the instrument string being stuck is greatly increased due to factors such as the length of the instrument string and the stabilizer. Due to the many intermediate connection links of the instrument string, the system weakness is also uncertain when the stress state is complex. When applying tension to unblock the instrument string, it is easy to cause multiple fractures and damage to the instrument string. In this case, the fracture position is uncertain and the ultimate tensile force value is uncertain. In the system with radioactive projects, it brings great risks to the control of radioactive sources. Therefore, it is particularly important to set a certain weak point position in the pump-out logging system and determine a reasonable ultimate tensile force value. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a weak point short section for pump-out logging and an assembly method thereof, which can realize safe and controllable pulling force when salvaging radioactive instruments.

[0004] The present invention adopts the following technical solution:

[0005] A weak point short joint for pump-out logging, the improvement of which lies in: comprising an upper joint, a piston cylinder and a lower joint, one end of the piston cylinder is fixedly connected to the upper joint, and the other end is provided with two keyways, and two anti-rotation keys are provided on the lower joint, and the two keyways of the piston cylinder can be respectively installed in the two anti-rotation keys of the above-mentioned lower joint, a weak point core shaft is arranged in the piston cylinder, one end of the weak point core shaft is connected to the lower joint through a thread and fixed by a set screw, a compression spring and a piston capable of compressing the compression spring are sequentially mounted on the weak point core shaft, the piston and the piston cylinder and the weak point core shaft are sealed by a sealing ring, a hole is opened on the piston cylinder at a position opposite to the compression spring, the other end of the weak point core shaft is pressed on the inner wall convex ring of the piston cylinder by a clamping nut, a retaining ring is installed on the clamping nut, a hole is opened on the above-mentioned inner wall convex ring, a one-way valve and an overflow valve communicating with the inner core of the weak point core shaft are installed on the lower joint, silicone oil is injected into the piston cylinder from the weak point core shaft through the one-way valve, so that the silicone oil fills the inner space of the piston cylinder.

[0006] Furthermore, a topping screw hole corresponding to the set screw is arranged on the weak point core shaft.

[0007] Furthermore, apply 3145 glue on the set screws.

[0008] Furthermore, a gap is provided between the piston and the weak point core shaft, both ends of the gap are sealed by sealing rings respectively, and a hole is opened at the end of the piston to make the above gap communicate with the internal space of the piston cylinder.

[0009] Furthermore, the weak point sub is installed at the lower end of the radioactive instrument, and the ultimate tension value is greater than the maximum safety tension of the pump-out logging system, and less than the ultimate tension of all instruments at the upper end of the weak point sub.

[0010] An assembly method is applicable to the above-mentioned weak point short joint for pump-out logging, and the improvement thereof lies in: installing a compression spring and a piston on the weak point core shaft, and then connecting the weak point core shaft with a lower joint through a thread, opening a punching thread hole on the weak point core shaft after the installation is in place, fixing the weak point core shaft and the lower joint with a set screw matched with the punching thread hole, and applying 3145 glue to prevent loosening, inserting the weak point core shaft into a piston cylinder, and respectively installing two keyways at one end of the piston cylinder into two anti-rotation keys of the lower joint, installing a clamping nut with a socket wrench, pressing the weak point core shaft against the inner wall convex ring of the piston cylinder, and installing a retaining ring on the clamping nut, the other end of the piston cylinder is fixedly connected with the upper joint, and silicone oil is injected from the weak point core shaft into the piston cylinder through a one-way valve until the silicone oil overflows from the overflow valve, so that the silicone oil fills the internal space of the piston cylinder.

[0011] The beneficial effects of the present invention are:

[0012] The weak point short section disclosed in the present invention is installed at the lower end of the radioactive instrument and is easy to get stuck at the upper end of the instrument. When the instrument gets stuck and the tension exceeds the limit value, the weak point short section breaks first, effectively protecting the radioactive short section, allowing the radioactive instrument to be taken out of the well first, reducing the risk of radioactive instrument construction and salvage and the impact of radiation sources on the environment. The weak point short section makes the logging system have a certain weakness, and the tensile limit value is determined, which is conducive to the driller to control the maximum safe tension, effectively protecting the instruments above the weak point short section, and not easily damaged when stuck.

[0013] The weak point short joint disclosed in the present invention mainly bears the downhole mud pressure, the axial tension pressure of the instrument string and the bending and torsion force of the instrument string. The downhole mud pressure is offset by the silicone oil and piston balance structure, so that the internal and external pressures of the weak point core shaft are balanced, and the weak point does not bear absolute pressure; by straightening the two ends of the weak point core shaft, the bending moment is transferred to the piston cylinder as much as possible, and the torque is transferred to the lower joint through the anti-rotation key. It is ensured that during normal construction of the weak point core shaft, the influence of other forces except axial tension pressure on its limit value is minimized to ensure that the limit value is constant. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the installation position of the weak point short section disclosed in Example 1 of the present invention;

[0015] Figure 2It is a schematic diagram of the structure of the weak point short section disclosed in Example 1 of the present invention;

[0016] Figure 3 yes Figure 2 A partial enlarged view of part A;

[0017] Figure 4 It is a schematic structural diagram of the upper joint in the weak point short section disclosed in Example 1 of the present invention;

[0018] Figure 5 It is a schematic structural diagram of the lower joint in the weak point short section disclosed in Example 1 of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] Embodiment 1, as Figure 1 As shown in the figure, in the pump-out logging system, a weak point short section is set, and the weak point short section is installed at the lower end of the radioactive instrument. The ultimate tensile force value is greater than the maximum safety tensile force of the system, which meets the normal construction tensile force requirements, and is less than the ultimate tensile force of all instruments on the upper end of the weak point short section. When the instrument is stuck, if the normal unblocking measures and the maximum safety tensile force of the system still cannot unblock the instrument, a larger tensile force can be applied to break the weak point short section, and the upper end radioactive instrument can be recovered out of the well to ensure the safety of the radioactive source and reduce the subsequent salvage risk.

[0021] like Figure 2-5 As shown, this embodiment discloses a weak point short joint for pump-out logging, including an upper joint, a piston cylinder 1 and a lower joint 2, one end of the piston cylinder is fixedly connected to the upper joint, and two keyways are arranged on the other end, and two anti-rotation keys 3 are arranged on the lower joint, and the two keyways of the piston cylinder can be respectively installed in the two anti-rotation keys of the above-mentioned lower joint, and a weak point core shaft 4 is arranged in the piston cylinder, one end of the weak point core shaft is connected to the lower joint through a thread and fixed by a set screw 5, and a compression spring 6 and a piston 7 that can compress the compression spring are sequentially mounted on the weak point core shaft, and the piston and the piston cylinder and the weak point core shaft are sealed by a sealing ring, and a hole is opened on the piston cylinder at a position opposite to the compression spring so that the mud in the well can enter the piston cylinder and apply pressure to the piston. The other end of the weak point core shaft is pressed on the inner wall convex ring of the piston cylinder through a clamping nut 8, and a retaining ring 9 is installed on the clamping nut to prevent the clamping nut from buckling, and a hole is opened on the inner wall convex ring so that the internal space of the piston cylinder is connected to the inner core of the weak point core shaft. A one-way valve 10 and an overflow valve 11 which are connected to the inner core of the weak point core shaft are installed on the lower joint, and silicone oil is injected from the weak point core shaft into the piston cylinder through the one-way valve to fill the inner space of the piston cylinder with silicone oil.

[0022] In this embodiment, a top screw hole corresponding to the set screw is set on the weak point core shaft. 3145 glue is applied to the set screw. A gap is set between the piston and the weak point core shaft, and both ends of the gap are sealed by sealing rings respectively. A hole is opened at the end of the piston to make the above gap communicate with the internal space of the piston cylinder so that the piston can slide along the weak point core shaft. The weak point short section is installed at the lower end of the radioactive instrument, and the ultimate tensile force value is greater than the maximum safety tensile force of the pump-out logging system, and less than the ultimate tensile force of all instruments at the upper end of the weak point short section.

[0023] The ultimate tensile force value of the weak point mandrel is controlled by the size, material, heat treatment and tensile test at the weak point. The heat treatment conditions of the weak point mandrel are controlled so that the Rockwell hardness error of the same batch of blank materials is within 1 degree. According to the requirements of the inner hole size of the mandrel, the inner hole is finely processed to ensure the size, coaxiality and roughness. Process the test piece, conduct the ultimate tensile test on the tensile testing machine, calculate the ultimate strength of the batch of materials, determine the outer diameter of the mandrel at the weak point, and after the weak point mandrel is processed, conduct the tensile test again to ensure that the limit value is within the design range, and the sampling quantity is not less than 20% of the processing quantity of this batch. By controlling the material and heat treatment process of the weak point mandrel, the ultimate tensile force value error is guaranteed to be within ±5%.

[0024] The present embodiment also discloses an assembly method, which is applicable to the above-mentioned weak point short joint for pump-out logging. A compression spring and a piston are installed on the weak point core shaft, and then the weak point core shaft is connected to the lower joint through a thread. After installation, a punching thread hole is opened on the weak point core shaft, and the weak point core shaft and the lower joint are fixed with a set screw matched with the punching thread hole, and 3145 glue is applied to prevent loosening. The weak point core shaft is inserted into the piston cylinder, and the two keyways at one end of the piston cylinder are respectively installed in the two anti-rotation keys of the lower joint. The clamping nut is installed with a socket wrench, and the weak point core shaft is pressed against the inner wall convex ring of the piston cylinder, and a retaining ring is installed on the clamping nut. The other end of the piston cylinder is fixedly connected to the upper joint, and silicone oil is injected into the piston cylinder from the weak point core shaft through a one-way valve until the silicone oil overflows from the overflow valve, so that the silicone oil fills the internal space of the piston cylinder.

Claims

1. A weak point short sub for pump-out logging, characterized in that: It includes an upper joint, a piston cylinder and a lower joint, one end of the piston cylinder is fixedly connected to the upper joint, and two key grooves are arranged on the other end, and two anti-rotation keys are arranged on the lower joint, and the two key grooves of the piston cylinder can be respectively installed in the two anti-rotation keys of the above-mentioned lower joint, and a weak point core shaft is arranged in the piston cylinder, one end of the weak point core shaft is connected to the lower joint through a thread and fixed by a set screw, and a compression spring and a piston that can squeeze the compression spring are sequentially mounted on the weak point core shaft, and the piston and the piston cylinder and the weak point core shaft are sealed by a sealing ring, a hole is opened on the piston cylinder at a position opposite to the compression spring, the other end of the weak point core shaft is pressed on the inner wall convex ring of the piston cylinder by a clamping nut, and a retaining ring is installed on the clamping nut, and a hole is opened on the above-mentioned inner wall convex ring, and a one-way valve and an overflow valve connected to the inner core of the weak point core shaft are installed on the lower joint, and silicone oil is injected into the piston cylinder from the weak point core shaft through the one-way valve to fill the internal space of the piston cylinder with the silicone oil; The weak point sub is installed at the lower end of the radioactive instrument, and the ultimate tension value is greater than the maximum safety tension of the pump-out logging system, and less than the ultimate tension of all instruments at the upper end of the weak point sub.

2. The weak point sub for pump-out logging according to claim 1 is characterized in that: A punching screw hole corresponding to the set screw is arranged on the weak point core shaft.

3. The weak point sub for pump-out logging according to claim 1 is characterized in that: Apply 3145 glue to the set screws.

4. The weak point sub for pump-out logging according to claim 1 is characterized in that: A gap is arranged between the piston and the weak point core shaft, and both ends of the gap are sealed by sealing rings respectively. A hole is opened at the end of the piston to make the gap communicate with the inner space of the piston cylinder.

5. An assembly method, applicable to the weak point sub for pump-out logging according to claim 1, characterized in that: Install the compression spring and piston on the weak point core shaft, and then connect the weak point core shaft to the lower joint through threads. After installation, open a punching thread hole on the weak point core shaft, fix the weak point core shaft and the lower joint with a set screw that matches the punching thread hole, and apply 3145 glue to prevent loosening. Insert the weak point core shaft into the piston cylinder, and install the two keyways at one end of the piston cylinder into the two anti-rotation keys of the lower joint respectively. Use a socket wrench to install the clamping nut, press the weak point core shaft against the inner wall convex ring of the piston cylinder, and install a retaining ring on the clamping nut. The other end of the piston cylinder is fixedly connected to the upper joint, and silicone oil is injected into the piston cylinder from the weak point core shaft through the one-way valve until the silicone oil overflows from the overflow valve to fill the internal space of the piston cylinder with silicone oil.

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