Natural gas hydrate rotary freezing and pressure-holding wireline coring tool and coring method

Abstract

The invention relates to a natural gas hydrate rotary type freezing pressure maintaining rope coring drilling-tool and method. The coring drilling-tool comprises an outer pipe, an inner pipe assemblyand a drill bit. The outer pipe is arranged on the outer side of the inner pipe assembly in a sleeving mode. The drill bit is arranged at the bottom of the outer pipe, and the inner pipe assembly comprises a fishing spearhead, a screw rod, a screw tube, a first torsion spring, an elastic clamp, an exhaust valve body, an exhaust valve spring, an exhaust valve core, a cavity tube insulating layer, an inner insulating layer, a control rod, a flap valve, a second torsion spring, a coring barrel, a core barrel, a movable valve, a pulling spring, cutting teeth, a cavity pipe and a recovery pipe. Thescrew rod is driven by hydraulic pressure, so that the natural gas hydrate rotary type freezing pressure maintaining rope coring drilling-tool and method can realize rotary coring, and drilling fluidis not in contact with a natural gas hydrate core in the coring process to prevent the natural gas hydrate core from being polluted. The stability of the natural gas hydrate core is ensured by adopting heat preservation and pressure maintaining sampling technology. Freezing sampling technology is used for assisting the heat preservation and pressure maintaining sampling technology. When the pressure maintaining fails, the natural gas hydrate core is frozen to -40 DEG C through the phase-change heat absorption effect of low-temperature phase-change liquid to ensure that the natural gas hydratedoes not decompose.

Description

technical field [0001] The invention relates to a natural gas hydrate rotary freezing and pressure-holding wireline coring tool and a coring method, which is especially suitable for fidelity drilling and coring of deep-sea natural gas hydrate. Background technique [0002] With the rapid development of the economy, the consumption of energy is also increasing day by day. Conventional energy sources such as oil, coal, and natural gas are consumed in large quantities. Judging from their remaining reserves, conventional energy sources cannot continue to support modern industry for a long time, and the amount of natural gas hydrate resources is extremely high. Natural gas hydrate is abundant, and it produces carbon dioxide and water after combustion, which is a kind of clean energy, so natural gas hydrate is regarded as the main energy source in the future. Natural gas hydrates exist in high-pressure and low-temperature environments, and when the temperature-pressure equilibrium...

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Problems solved by technology

However, using this method will change the original basic physical properties of the gas hydrate core, resulting in changes in the test data of the gas hydrate core such as acoustic waves and resistivity.

[0005] To sum up, in order to improve the efficiency of natural gas hydrate fidelity sampling, it is necessary to improve the mechanical seal of the pressure-holding core tool, but this is almost impossible for the structure of the pressure-holding core tool; The sampling method will affect the later test and analysis of the gas hydrate core

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