The lithologic and stratigraphic gas reservoirs in the north slope of the sanhu area,Qaidam basin:a study on their genetic conditions and characterization techniques

The north slope of the Sanhu area of the Qaidam basin,with its characteristic geologic features such as strong fold,rapid lithofacies variation,promising geologic setting,is prone to have stratigraphic and lithologic gas pools.However,as the reservoir beds are extremely thin(1～3 meters),and lack of 3D seismic data,it is very difficult to identify the sand bodies and trace them laterally,resulting in a very low discovery rate of stratigraphic-lithologic reservoirs.Studies on producing gas trap and theoretical reasoning indicate that abnormal seismic response will be observed when the reservoir is gas accumulated.As a result,based on abnormal seismic response analysis,accompanied by studies on structural,sedimentary,and accumulation conditions,the Tuoxi belt was recognized as a lithologic trap region.A well,Tzh2,drilled afterwards in this belt,showed commercial gas,indicating promising potential of lithologic gas pool in this region.