Near drill local low pressure drilling tool

Abstract

A well drilling tool able to generate local low pressure near the drill bit for increasing drilling speed is composed of commutating jointer, internal tube, casing, slide valve with spring, and limited blocking head. It features that the channel of drilling liquid is periodically blocked to generate negative pressure and the negative pressure is delivered to well bottom.

Description

technical field

[0001] The invention belongs to a supporting device for oil and natural gas drilling. technical background

[0002] As the well depth increases, the drilling speed gradually decreases. The reasons can be summarized as the following two aspects. (1) Under the action of the pressure difference between the bottom hole liquid column pressure and the formation pore fluid pressure, the cuttings generated by the rock broken by the drill bit are crushed. Pressed in place and repeatedly cut by the drill bit, it hinders the exposure of the new broken surface of the rock and reduces the efficiency of the drill bit in rock-breaking drilling, that is, the "holding effect". (2) The rock at the bottom of the well is subjected to the pressure σ of the overlying strata h e and the normal stress σ of the bottom hole fluid column n e The role of , generally 0<σ n e <σ h e , according to the three-dimensional Griffith strength criterion, the...

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