Pressure reducing device for lowering tail pipe

Abstract

The invention relates to the technical field of downhole tools and discloses a pressure reducing device for lowering a tail pipe. The pressure reducing device comprises an upper joint, an upper sleeve, a lower sleeve, a lower joint, a valve cavity hood, a valve seat, a blade valve and a center pipe. The outer side of the lower portion of the upper joint and the inner side of the upper portion of the upper sleeve are fixedly mounted together; a sleeve annular table is arranged on the inner side of the lower end of the upper sleeve; and the outer side of the sleeve annular table and the inner side of the upper portion of the lower sleeve are fixedly mounted together. The pressure reducing device provided by the invention is reasonable in structure and convenient to use, and automatic grouting is formed by means of a valve clack through hole in the blade valve; the center pipe moves upward to open a lower circulating hole to communicate the inner side and the outer side; the blade valve is opened by injecting a drilling fluid, so that the center pipe moves downward to cut off a shear pin and the lower circulating hole is closed for follow-up construction, thereby playing a role of a float collar. Surge pressures generated by a leaker stratum and a ground floor of an oil well are prevented as a result of too quick lowering while the drilling speed is accelerated to promote the construction progress, the damage on the tail pipe and the fed drilling tool is reduced, and the pressure reducing device has the characteristics of being reliable, safe and simple and convenient.

Description

technical field [0001] The invention relates to the technical field of downhole tools, and relates to a decompression device for a lower liner. Background technique [0002] In the liner cementing operation in oil and gas fields, the normal running speed of the liner will affect the construction progress due to the large liner running depth. When the running speed is accelerated, it is easy to leak the formation, damage the liner and the drilling tool and the oil well The bottom layer will generate exciting pressure; when the lowering speed is reduced, it will cause the sticking of the tail pipe, which will lead to serious engineering accidents. Contents of the invention [0003] The invention provides a decompression device for the lower liner, which overcomes the above-mentioned deficiencies in the prior art, and can effectively avoid the pressure leakage formation and the bottom layer of the oil well caused by the excessively fast lowering speed while accelerating the d...

AI Technical Summary

Problems solved by technology

[0002] In the liner cementing operation in oil and gas fields, the normal running speed of the liner will affect the construction progress due to the large liner running depth. When the running speed is accelerated, it is easy to leak the formation, damage the liner and the drilling tool and the oil well The bottom layer will generate exciting pressure; when the lowering speed is reduced, it will cause the sticking of the tail pipe, which will lead to serious engineering accidents

Images