EVALUATION ON DALONG FORMATION SOURCE ROCK IN THE NORTH SICHUAN BASIN

The argillaceous and siliceous rocks in the Dalong Formation of Upper Permian in the north Sichuan Basin are excellent marine source rocks with high organic matter abundance and good organic matter type. The maturity of Dalong Formation changes greatly,which reach over-mature stage in Well Heba1 section while still in low-middle mature satge in Guangyuan and Wanyan areas localed in edge of the basin. The hydrocarbon-generation intensity of Dalong Formation source rocks is mainly lower than 20×10⁸ m³/km². There is a good time-space matching relationship between the source rock in Dalong Formation and the excellent reef and shoal facies reservoirs in Changxing-Feixianuan Formations,which result in the oil and gas origined form Dalong Formation accumulated in the excellent reservior more efficiently and make great contribution to the large and medium-sized gas fields such as Puguang. Related to the marine source rocks in other geological periods, main hydrocarbon-generation periods of Dalong Formation source rocks is later and that is beneficial to the preservation of gas reservoir. Is there any residual oil pool in Guangyuan and Wanyuan areas where Dalong Formation is still in low-middle maturity, which is worth of particular attention.