THE SHALE SEQUENCE OF LONGMAXI FORMATION AND SEISMIC PREDICTION OF SWEET SPOTS OF SHALE GAS IN THE JIAOSHIBA AREA, SICHUAN BASIN

A breakthrough in shale-gas exploration and development has been reached over the past few years in the Longmaxi Formation of the Sichuan Basin in China. Specific geophysical methods and techniques are thoroughly studied and applied for detecting sweet spots. Sequence stratigraphic study suggests that the shale segment belongs to a deep-water shelf deposits. High quality shale mainly occurs in the transgressive systems tracts (TST) of a sequence. Facies analysis is then made, as a most important mean for sequence stratiigraphic study and prediction of sweet spots. Geophysics is the most efficient tool for identification and prediction of sweet spots under the framework of sequence stratigraphy. In addition, it has advantages in determination of organic carbon content (TOC), cracks, brittleness and stress field, etc. and may provide powerful technical support to the fracturing during the stage of horizontal well drilling.