Restoring burial history, correlating maturities and biomarkers of gas-condensate source rocks, measuring fluid inclusions, and stable carbon isotope data show that two petroleum systems charge the YA13-1 gas field in Yinggehai and Qiongdongnan basins in the South China Sea. The first source came from the Yanan depression in Qiongdongnan basin, at a depth of 4450 m, with the critical moment of 5.8 Ma. The second source came from the Yinggehai basin, at a depth of 4700 m, with the critical moment of 2.0 Ma. The YA13-1 drape anticline trap formed at 10.5 Ma, which was earlier than gas migration and accumulation. The Meishan Formation, with 7-10 MPa (1015-1450 psi) expelling pressure and 49-66 MPa (7105-9570 psi) overpressure combined, effectively seals YA13-1 gases. The reservoir of Lingshui Formation sands has average values of 14.9% porosity and 213X10 (super -3) micrometers 2 permeability because the weathering of the feldspathic sands at the end of the Oligocene, the preserving of K-feldspar and quartz overgrowths, and dissolution of carbonate cements by organic acid enhanced the reservoir quality. Consequently, trap formation coincided with gas generation, migration, and accumulation.

You do not currently have access to this article.