Structural characteristics of Shahezi Formation beneath the Well SK-2 and its periphery: An analysis of logging and seismic data

During implementation of the Deep Continental Scientific Drilling Engineering Project Well SK-2 in Songliao Basin, the most integrated core data of Shahezi Formation was obtained. And 43 abnormal strata of deep shale gas were preliminarily identified, with a cumulative thickness of 102 meters, indicating that Shahezi Formation has good deep energy prospect. For further analysis of oil and gas resources potential of Shahezi Formation in Songliao basin, in this paper, on the basis of previous studies and in combination with well logging, core data of Well SK-2 and the newly acquired 2-d seismic data in the north-south direction crossing Well SK-2, the spatial distribution and sequence characteristics of Shahezi formation in the vicinity of Well SK-2 well were analyzed. At the same time, based on gas abnormal data acquired form logging during drilling, the authors studied logging and seismic responses of oil and gas perspective reservoirs in Shahezi Formation. It is shown that the Shahezi Formation adjacent to Well SK-2 has large thickness but small lateral extension, and hence the authors divided it into 4 stratigraphic sequences based on well logging as well as seismic and core data, i.e., SQ1, SQ2, SQ3 and SQ4. Among the 4 stratigraphic sequences, SQ4 has a better energy prospect. Its lithology is dominated by mudstone and has the characteristics of high porosity and low wave impedance on logging curves, with continuous strong amplitude on seismic section. Impedance inversion section shows the characteristics of large wave impedance alternated with many smaller wave impedances. Thus, the occurrence conditions of deep natural gas resources of Shahezi Formation in this area are revealed.