Double-wall drill pipe

Abstract

The invention discloses a double-wall drill pipe which comprises an upper pup joint, an outer pipe, a lower pup joint and an inner pipe, wherein the upper pup joint, the outer pipe and the lower pup joint are sequentially connected in a threaded manner from top to bottom, and the inner pipe is arranged in a center duct of the outer pipe. Center ducts and eccentric ducts are axially formed in the upper pup joint and the lower pup joint, the inner pipe is mounted in the outer pipe in a gapped mode to form a double-wall pipe with a center duct and an annular duct, two ends of the double-wall pipeare fixed onto walls of the center ducts of the upper pup joint and the lower pup joint, the center ducts of the upper pup joint and the lower pup joint are communicated with the center duct of the inner pipe to form a first liquid passing channel, the eccentric ducts of the upper pup joint and the lower pup joint are communicated with the annular duct formed between walls of the inner pipe and the outer pipe to form a second liquid passing channel, and a shoulder seal is formed between two components in threaded connection, so that the first liquid passing channel is not connected with the second liquid passing channel. According to the double-wall drill pipe, up-down bounce of the inner pipe in the use process is effectively prevented, and sealing pressure-bearing capacity and reliability between the inner pipe and the outer pipe which are long can be greatly improved.

Description

technical field [0001] The invention relates to the technical field of drilling, in particular to a double-wall drill pipe. Background technique [0002] The double-wall drill pipe drilling method refers to the method of drilling with double-wall drill pipe and other auxiliary equipment, mainly including low-pressure drilling, central sampling drilling, RDM technology and double-wall gas-filled drilling. This method has been paid attention to and popularized in the fields of geology and mining and oil drilling. [0003] At present, the double-wall drill pipe commonly used in the double-wall drill pipe drilling method is composed of an inner pipe and an outer pipe. They are connected by threads, and the inner tubes are connected by inserting a radial sealing structure to prevent fluid communication between the two channels. However, the double-walled drill pipe with this structure has the following problems: ① Both the inner and outer drill pipes are relatively long, and th...

AI Technical Summary

Problems solved by technology

However, the double-walled drill pipe with this structure has the following problems: ① Both the inner and outer drill pipes are relatively long, and their length can reach about 10 m. If the gap between the joints is too large, the sealing ring under high pressure will be easily damaged by the assembly sealing ring squeezed into the gap between the male joint and the female joint, which will reduce the pressure bearing capacity and reliability of the seal; ② Frequent disassembly and assembly of the drill pipe may cause the sealing ring to curl and crushing damage, reducing the pressure bearing capacity and reliability of the seal; ③Due to the space limitation between the inner and outer pipes, the inner pipe needs to be suspended on the upper step of the outer pipe. Due to the small step surface and the double-walled drill pipe, the inner pipe vibrates up and down during the process It is easy to cause the suspension step to fail, and the inner and outer tubes are misaligned up and down; the up and down vibration of the inner tube will also greatly reduce the service life of the sealing ring

The failure of the sealing ring will lead to the failure of the double-wall drill pipe drilling method, which seriously hinders the popularization and application of the double-wall drill pipe drilling technology

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