Lifting-free borehole bottom rope freezing coring drilling tool and method

Abstract

The invention relates to a lifting-free borehole bottom rope freezing coring drilling tool and method. The lifting-free borehole bottom rope freezing coring drilling tool comprises a salvaging device, an inner pipe assembly and an outer pipe assembly. According to the coring method, liquid nitrogen is fed into a liquid nitrogen chamber of the salvaging device; the salvaging device is fed into an outer pipe once the roundtrip is ended; the salvaging device is connected with the inner pipe assembly so as to feed the liquid nitrogen into a freezing chamber; and the liquid nitrogen absorbs heat and is gasified so as to freeze the hydrate rock core. By adopting the lifting-free borehole bottom rope freezing coring drilling tool and method, the liquid nitrogen can be prevented from being gasified due to heat dissipation and vibration during drilling, so that the freezing efficiency of the liquid nitrogen can be improved. According to the lifting-free borehole bottom rope freezing coring drilling tool and the coring method, a small drill bit is arranged on the inner pipe assembly and is driven by a large drill bit to drill together, so as to obtain the rock core with required dimension; a drill column does not needed to be integrally lifted from the borehole, so that the lifting-free continuous drilling and coring can be realized; and the small drill bit and a clamp spring seat are disassembled during sampling, a half-closing pipe is drawn out of a rock core pipe together with the rock core, and a rock core sample is stored in a liquid nitrogen storage tank or a high-pressure container.

Description

technical field [0001] The invention relates to a drilling tool, which is especially suitable for a drilling tool and a coring method for natural gas hydrate coring in land permafrost layers. Background technique [0002] With the increasing demand for energy in modern industry, conventional energy such as oil, coal and natural gas can no longer meet the demand. With its abundant resources, natural gas hydrate has become a world-recognized energy source that can become a conventional energy source such as oil, coal and natural gas in the future. Energy alternatives. [0003] Natural gas hydrates form and exist in high-pressure and low-temperature environments. According to the pressure stabilization characteristic curve of natural gas hydrate, if the temperature or pressure condition changes beyond the equilibrium condition, it will lead to the decomposition of natural gas hydrate. At present, natural gas hydrate samplers at home and abroad mainly have two design ideas: on...

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Problems solved by technology

This idea is to store the liquid nitrogen in the inner pipe assembly. The disadvantage is that the liquid nitrogen may be vaporized due to the vibration and heat dissipation of the drilling tool during the drilling process, and the full use of the liquid nitrogen cannot be realized. lead to coring failure

[0004] In addition, both the bottom-hole pressure-holding sampler and the bottom-hole freezing sampler use ordinary samplers before reaching the hydrate reservoir and replace the sampler after reaching the hydrate reservoir. As a result, the core size that the core tube can hold becomes smaller, so it is necessary to lift the drill at this time, lift out all the drill pipes in the hole, and replace the drill bit to reduce the core size, but this will waste man-hours

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