Sampling Technique in Gas Hydrate Drilling Test Well in Qiangtang Basin and the Construction Practice

Abstract:

The test well engineering of gas hydrate drilling is located in northwest of Qiangtang basin with altitude about 4998～5100 meters, where the hydrogeological and engineering geological environment is extremely complex with the lowest annual mean ground temperature and thick permafrost in Qinghai Tibet Plateau. The construction is very difficult with cleavage, fracture, small fault and groundwater extremely developed. In this paper, the practice and experience of test well engineering of gas hydrate drilling in Qiangtang basin are summarized on the improvement of coring tool structure, bit design, flushing fluid formulation and borehole structure, which could be reference to the exploration of gas hydrate and other mineral resources in high altitude regions in future.

Key words:gas hydrate; drilling sampling; drilling test well; Qiangtang basin