Counterflush drilling system

Abstract

The invention discloses a counterflush drilling system to solve the problem of a risk of collapse of a well wall as the mechanical drilling speed is to be increased and the density of a drilling fluidis to be reduced in the prior art. The counterflush drilling system comprises a shaft, a drilling four-way joint, a rotary blowout preventer, a top drive, a vibrating screen, a slurry tank, a slurrypump, an air compressor, a drill pipe, a drill collar and a circulating valve. The drill pipe is connected in series in multiple stages; the circulating valve is provided with a valve body and a valveelement; a runner is arranged inside the valve body, and a mounting hole is formed in the side wall; two ends of the valve body is connected to the drill pipe and the drill collar, the inner part ofthe valve body is connected through the drill pipe and the drill collar, and the valve body rotates synchronously along with the drill pipe and the drill collar; and the valve element can be started under an internal and external pressure difference, so that the internal and external areas of the valve boy connected to two ends of the valve element are connected. The counterflush drilling system disclosed by the invention can reduce a confining pressure of shaft bottom rocks and a pressing effect of the drilling fluid to the shaft bottom rocks effectively so as to increase the mechanical drilling speed. Meanwhile, the system further has the characteristics of being low in shaft bottom pressure, easy to establish circulation, free of rock debris in an annular space, low in jamming risk andthe like.

Description

technical field [0001] The invention relates to the technical field of oil and gas drilling, in particular to a reverse circulation drilling system. Background technique [0002] In drilling, the main function of drilling fluid is to carry cuttings from the bottom of the well to the surface, cool and lubricate the drill bit and drill string, reduce the temperature of the drill bit, reduce the wear of the drill tool, improve the service life of the drill tool, and at the same time balance the rock on the side of the well Lateral pressure, stabilizing the borehole wall. [0003] In drilling, it generally refers to the hydraulic pressure acting on the surrounding rock in the formation, which is called confining pressure. As the confining pressure increases, the strength and plasticity of the rock increase, and the ROP decreases. The holding effect is caused by the excessive positive pressure difference at the bottom of the well, which makes it difficult for the cuttings to le...

AI Technical Summary

Problems solved by technology

[0005] However, underbalanced and gas drilling technologies increase the ROP, but due to the decrease in drilling fluid density, it also reduces the effect on the side pressure of the wellbore rock and stabilizes the wellbore, increasing the risk of wellbore collapse

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