Laboratory Experimental Study on Sampling Method for Gas Hydrates by Hole Bottom Freezing/

Abstract:

Exploiting gas hydrate is based on the evaluation, and sample drilling is the most direct method. The sampling method for gas hydrate by hole bottom freezing is the way that the temperature of the gas hydrate core is decreased by cold source. Active cooling can reduce the critical dissociated pressure of gas hydrate to inhibit gas hydrate dissociating by passive decompression. The result of temperature decreasing is the same as pressure increasing to retain the core of gas hydrates. But it is easy to decrease temperature of core by external cold source at the well bottom. Firstly, the feasibility of freezing method for sampling gas hydrates is verified by the analysis on the temperaturepressure property; secondly, dry ice is confirmed as coolant, alcohol as positive freezing catalyst and cooling medium by means of indoor freezing simulation; and finally, based on the above experiment, the prototype of FCS hole bottom freezing sampler for gas hydrates was developed. Freezing loess sample is achieved by freezing sample experiment. The research puts forward freezing method for sampling gas hydrates, and provides a new idea for the design of gas hydrates core sampler.