Intermittent shaft bottom pressure difference reduction sub

Abstract

The invention discloses an intermittent shaft bottom pressure difference reduction sub. The sub comprises an outer cylinder, a drill rod joint, a spring and a circular piston. A through axle hole is formed in the outer cylinder axially, the upper end of the outer cylinder is connected with the drill rod joint, part of the drill rod joint is inserted in the axle hole, and a water flow channel is formed in the center of the drill rod joint axially. The spring and the circular piston are sleeved on the lower portion of the drill rod joint and capable of moving along the axis vertically, the upper end of the spring is connected with the drill rod joint, and the lower end of the spring is connected with the upper end of the circular piston. Pressure release holes and reverse nozzles are formed in the side wall of the outer cylinder, the pressure release holes are communicated with a chamber, the upper end of the circular piston is subjected to external annular pressure, the lower end of the circular piston is subjected to drilling liquid pressure in the axial hole, and the reverse nozzles are communicated with the axle hole when the circular piston moves upwards for certain distance under the action of the pressure difference on the upper and lower ends. By means of the sub, the shaft bottom pressure difference reduction effect can be improved, the drilling speed of drilling machinery is improved, and the shaft bottom cleaning auxiliary rock fracture capacity of bit nozzles is improved.

Description

technical field [0001] The invention relates to a pressure-reducing and speed-increasing tool for oil and gas drilling, in particular to an intermittent sub-joint for reducing the pressure difference at the bottom of a well. Background technique [0002] The bottom hole pressure difference refers to the pressure difference between the hydrostatic column pressure in the well and the formation pore pressure, which is one of the important factors affecting the increase of drilling speed. Laboratory experiments and field practice show that the ROP will decrease significantly with the increase of the bottom hole pressure difference. Broken, affecting the rock-breaking efficiency of the drill bit. When drilling in low-permeability rock formations, the bottom hole pressure difference has a greater impact on drilling speed than in high-permeability rock formations, because it is difficult for drilling fluid to enter the pores of low-permeability rock formations and cannot be balanc...

AI Technical Summary

Problems solved by technology

Jet-type hydraulic decompression technology and negative pressure pulse jet decompression technology have not been popularized and applied due to their complex structure, high process requirements, and relatively harsh application conditions.

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