Performance requirements of wireline drill pipe measured while drilling

The wireline drill pipe is the component with the most complex stress and the worst working condition in the process of directional drilling. In the process of drilling, the central wireline drill pipe should not only bear the push and pull exerted by the drilling rig and the reverse torque of the screw drill, but also serve as a medium channel to transport mud or other pressure media to the hole bottom. At the same time, during the construction of near horizontal long drilling and super long drilling, additional bending stress will be generated when drilling down inclined hole or branch hole, which is very easy to cause fatigue damage of drill pipe. The central wireline drill pipe is also the signal transmission device between the hole bottom inclination measuring unit and the hole orifice inclination measuring equipment. It shall ensure the real-time and safe signal transmission between the hole bottom inclination measuring unit and the hole orifice inclination measuring equipment, and reduce the impact of complex stress, vibration and pressure medium disturbance on the signal transmission reliability of the drill pipe during drilling, so as to ensure the accuracy and safety of directional drilling construction. It can be seen that the central wireline drill pipe must have the characteristics of high strength and high signal transmission reliability.
Main technical parameters
Through the analysis of the working conditions of the central wireline drill pipe, combined with the performance and application requirements of underground supporting equipment in coal mine, the main technical parameters of the central wireline drill pipe are as follows:
① Drill pipe body Φ 73 mm, wall thickness 5.6 mm, joint outer diameter 75 mm;
② Fixed length of drill pipe 3 m;
③ The maximum tensile capacity of drill pipe is 800 kn; ④ The maximum torsional capacity of drill pipe is 6500 n · m;
⑤ The insulation resistance is greater than 10 m Ω; ⑥ The resistance of the central cable passing device is less than 0 5 Ω。
Overall structure design
The central wireline drill pipe is divided into signal transmission device and drill pipe body. The drill pipe body is not only the carrier of other parts of the central wireline drill pipe, but also the primary condition to ensure directional drilling construction. Its performance directly determines the safety of construction. The signal transmission device of the central wireline drill pipe is composed of three parts: Central wireline device, insulation device and support device.
The central cabling device is composed of male connector, conductor, female connector and reducing spring. Its function is to transmit two-way communication signals between the hole bottom and the hole equipment.
The insulation device is composed of plastic male connector, wire pipe and plastic female connector. Its function is to isolate the central conduction device from mud or other pressure media, protect the communication safety of the central conduction device and prevent the loss of communication signal in the transmission process.
The support device is composed of positioning retaining ring and stabilizer. Its purpose is mainly to position the plastic male and female joints in the axial direction of the drill pipe, prevent the central conduction device and insulation device from moving when the drill pipe is connected, and ensure the reliability of signal transmission. In addition, the stabilizer can reduce the disturbance of mud or other media to the pipeline and avoid the conduction between the conduction device and the drilling medium due to the fracture of the pipeline.
1) Structural design. In order to meet the needs of drill pipe for different construction processes, its main structure is not much different from that of ordinary geological drill pipe. The length of drill pipe is 3 m to reduce the connection point of drill pipe and shorten the auxiliary drilling time; Pipe body adopts Φ 73 mm, wall thickness 5.5 6 mm high strength seamless steel pipe to reduce the quality of drill pipe without affecting the strength of drill pipe;
Joint Φ 75 mm to improve the strength of the threaded part of the joint; The welding area of the drill pipe inner hole is machined to ensure the smooth transition between the joint and the rod body, so as to facilitate the installation and disassembly of the signal transmission cable and reduce the pipeline loss in the transmission process of liquid kinetic energy.
The central wireline drill pipe generally adopts medium and low carbon chromium manganese molybdenum alloy structural steel with yield strength greater than 650 MPa and tensile strength greater than 800 MPa. In order to ensure the connection strength of the drill pipe, the male and female threaded joints of the drill pipe shall be made of materials with better performance than the drill pipe body. In comprehensive consideration, the yield strength of the rod body is required to be greater than 835 MPa, the tensile strength is required to be greater than 980 MPa, and the elongation is required to be greater than 12%; The yield strength of the joint is greater than 925mpa, the tensile strength is greater than 1070mpa, and the elongation is greater than 14 5%。
2) Design and verification of drill pipe thread. The central wireline drill pipe thread structure continues the conical trapezoidal thread structure of ordinary wireline coring drill pipe, which is characterized by increasing the cross-sectional area of the thread root, i.e

Increased thread strength; At the same time, the screw pitch is increased, that is, the contact area of the screw connection is increased, the centering accuracy and connection rigidity of the screw connection are improved, so that the screw force is uniform, the transmission torque is large, and the sealing performance is good. The tooth height is determined as 1 5 mm, about twice the tooth height of ordinary rope coring drill pipe, which not only increases the thread strength, but also reduces the risk of drill pipe tripping.