Offshore Drilling Pressure-holding Coring Method

Abstract

The invention relates to a pressure-keeping coring method for marine drilling. The pressure-keeping coring method comprises the following steps that (1) inner pipe assemblies are put into an outer pipe assembly located at the hole bottom through a spear-head; (2) circulating of well drilling liquid is kept, a piston compensation balance mechanism pushes a core barrel to extend forwards through thewell drilling liquid, a penetrating tool bit only is pressed downwards and does not rotate, after the penetrating tool bit penetrates into a stratum, the outer pipe assembly starts to be rotated, thepenetrating tool bit extrudes and trims a core to enter the core barrel along with the footage per bit, and hole bottom rotating-while-drilling penetrating coring is conducted; (3) the inner pipe assembly b is driven to slide upwards along the inner pipe assembly a through the spear-head, the core barrel filled with core samples slide upwards to enter the inner pipe assembly a, and the core barrel triggers a counterweight pipe of a gravity pipe driving mechanism to slide downwards through a self-weight driving ball valve and to be overturned by 90 degrees; and (4) the inner pipe assemblies are de-jammed from an elastic jamming chamber and lifted out of a wellhead through the spear-head, the core samples are taken out, and the pressure-keeping coring process is completed. According to thepressure-keeping coring method, pressure-keeping sampling of a coring device is achieved, and the coring success rate is increased.

Description

technical field [0001] The invention relates to the technical field of drilling, in particular to a pressure-holding and coring method for marine drilling. Background technique [0002] Obtaining gas hydrate samples through ocean drilling is a commonly used technology at present, and because gas hydrate is located in the harsh and inaccessible polar and deep-sea marine environment, especially because when it is brought to the surface, it will quickly decompose into gas hydrate The two components of the substance, namely liquid water and methane gas, are affected by this, usually the success rate of coring is not high, and even lead to coring failure, which also indirectly affects the efficiency of coring, so in order to ensure the success of coring, it is necessary to use a The coring operation is carried out by means of pressure. However, the marine environment is changeable, and the more times of coring failures, the longer the construction time and the greater the constr...

AI Technical Summary

Problems solved by technology

[0002] Obtaining gas hydrate samples through ocean drilling is a commonly used technology at present, and because gas hydrate is located in the harsh and inaccessible polar and deep-sea marine environment, especially because when it is brought to the surface, it will quickly decompose into gas hydrate The two components of the substance, namely liquid water and methane gas, are affected by this, usually the success rate of coring is not high, and even lead to coring failure, which also indirectly affects the efficiency of coring, so in order to ensure the success of coring, it is necessary to use a coring

However, the marine environment is changeable, and the more times of coring failures, the longer the construction time and the greater the construction risk. Therefore, in the face of complex and changeable marine environments, how to improve the success rate of coring is a problem for those skilled in the art. question

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