| For a long time, the focus of the hydrocarbon source rocks in the Qiangtang Basin has mostly been on the Mesozoic strata. However, in recent years, a large number of oil and gas discoveries have been found in the Upper Permian sequences in the Qiangtang Basin, indicating a good oil and gas potential. To further identify the source rock conditions of the Upper Permian, dark mudstone samples from 6 profiles and 1 drilling well in the Upper Permian Nayixiong Formation were analyzed by organic geochemical methods. The results show that the organic matter abundance in studied samples is relatively high, with the majority reaching the standards of source rocks and containing a considerable amount of high-quality source rocks (TOC>2%). The organic matter types are mainly II2 and III, and contain a small amount of type II1. Its parent material exhibits a mixed source characteristic, with greater contributions of aquatic plankton and algae and a certain input of terrestrial plants. These source rocks mostly deposited in a reducing environment, and some of them formed in an anoxic condition with hypersaline waters. The degree of thermal evolution of organic matter has reached the mature stage, and mainly falls into the high maturity to over maturity period, which prone to the generation of condensate oil and moisture. It is concluded that the Upper Permian Nayixiong Formation has good hydrocarbon generation ability, and the quality of the bioclastic limestone reservoir above it is good. Both of the source rocks and the reservoir form a favorable oil and gas system and have good oil and gas exploration potential. |