Reef control factors and new seismic prediction techniques of Changxing Formation, east of Kaijiang-Liangping trough, Sichuan Basin

The sedimentary characteristics, main controlling factors and reef reservoir facies of the Upper Permian Changxing Formation reef on the eastern side of the Kaijiang-Liangping trough in the northeastern Sichuan Basin were studied using comprehensive seismic prediction technology.Through the study of single well sedimentary facies, it is found that there are two stages of longitudinal development of the reefs in this area. The paleogeomorphology of the Changxing Formation has a controlling effect on the development and migration of the reefs:the larger the slope, the thicker the reefs.Early paleo-geomorphology controlled the development of reefs. In the northern steep slope zone, early reef strips developed, while in the southern gentle slope zone, late reef blocks developed. Late paleotopography controlled the migration of reefs to the platform, resulting in the second row of reefs.Targeted prediction techniques were used to account for differences in sedimentary environments in different regions. In the central transitional belt, the amplitude property on the top of Changxing Formation on the platform margin was optimized to predict reef thickness. In the southern gentle slope sedimentary zone, the bioreef is predicted by the seismic-based interpretation technique. The predicted results have been confirmed by actual drilling, and many wells have obtained high-yield gas flow.