Study On Petroleum Generation Kinetics Of Source Rocks And Gas Pool Formation In The Yanan Depression Of The Qingdongnan Basin

The Yanan Depression is an important gas source area in the Qingdongnan Basin.Much work has been done recently on the conditions of petroleum pool formation. However, there are still some problems on the gas source area and gas pool formation in this area. In this paper, methane generation kinetics and carbon isotopic fractionation kinetics were applied to investigate some typical source rock. The kinetics parameters from two samples from the Yacheng formation including a dark mudstone and a coal were obtained. With combination of the burial and paleogeothermal history of the Yanan Depression, the geological models of both gas generation and methane isotopic fractionation were established. These models are quite different from the models directly based on thermal simulation test. On the basis of this, the kinetics models were combined with fluid inclusion to investigate the effective source area and gas migration and accumulation efficiency of the Ya13-1 gas pool. The results indicate that the gas source ofthe gas pool is a set of coal measure in the Yacheng Formation from the Yanan Depression and the gas pool was formed after 2 Ma, and the effective gas source rock area is located in the slope area of the Yanan Depression, with a present burial depth of 4000-5500 m. On this basis, a model showing the gas generation, migration and accumulation for the Ya13-1 gas pool is suggested. This model indicates that the gas from the slope area is much important to present gas pool and that the earlier-formed trap structures would be more suitable to gas pool formation. It is believed that the methods and the models developed in this study are important guides to further research and exploration for natural gases in the Qingdongnan Basin.