Shallow shale gas enrichment model of Taiyang-Haiba in Zhaotong demonstration area

Key words:  Zhaotong demonstration area  Taiyang-Haiba area  shallow shale gas  enrichment patter

Abstract:

The Taiyang-Haiba block in Zhaotong shale gas demonstration area is the first shallow shale gas field in China, butthe research on the enrichment and preservation model of shallow shale gas is relatively weak, which hinders efficient exploration of shallow gas in complex structural areas in South China. By analyzing and testing data of shale gas components and alkane carbon isotopes, shale fracture fillers and carbon and oxygen isotopes, fluid inclusions and apatite low temperature geochronology of typical wells in different structural positions,this study systematically discusses the enrichment and preservation model of shallow shale gas field in Taiyang-Haiba. The results indicate that the target layer of Wufeng-Longmaxi Formation is in contact with the tight top-bottom partition, and is confined by the compressive-torsional fault with good lateral sealing, forming a "three-dimensional storage box". Fluid geochemical characteristics reveal that the reservoir-forming environment of Wufeng-Longmaxi Formationis closed.The total gas content, gas composition and free gas proportion of shale gas indicate that the conditions of "three-dimensional storage box" are different, and the conditions of deep Yunshanba syncline are better than those of shallow Taiyang-Haiba anticline. The Taiyang-Haiba anticline is characterized by late uplift, strong shale self-sealing ability, and short-distance migration of free gas from the deep syncline to the shallow anticline.