Analysis of conditions of formation of middle-and deep-level gas accumulations in the Yinggehai basin west of Hainan Island and their comparison with those of shallow-level gas accumulations.

The level of shallow gas exploration and research in the Yinggehai basin is relatively high, and the gas reserves discovered by most exploratory wells in the area are also concentrated in the shallow strata. Up to now, however, the good exploration targets and large-scale local structures at shallow depths have been mostly drilled and there are scarce remaining good targets. So gas exploration potential is not optimistic. Limited gas geological reserves have been found and identified in the area mainly because of few exploratory wells and low exploration and research level in middle- and deep-level strata in the area. By a comprehensive analysis, comparison and evaluation of the geological conditions of gas accumulation formation in the shallow-level strata and the middle- and deep-level strata, the authors explicitly point out and emphasize that the geological conditions of gas accumulation formation and the middle- and deep-level strata are better than in the shallow-level strata, and the middle- and deep-level strata should be exploration targets for looking for large and medium-sized gas fields.