Characteristics and Potential Analysis of Source Rocks of Weizhou Formation in Haizhong Sag

Based on the drilling data and experimental results of source rocks, combined with the TSM basin modeling technology, this paper studies the characteristics and potential of source rocks of Weizhou Formation in Haizhong Sag. In Oligocene, the lake basin of Haizhong Sag developed successively, source rocks in Weizhou Formation were deposited. The dark mudstone of Weizhou Formation has medium abundance of organic matter, and the organic matter type is mainly humic type (II₂). Source rocks of the fourth member of Weizhou Formation in the sag belt reached the mature thermal evolution stage after the Middle Miocene, and began to generate a large amount of hydrocarbons, which is the main source rock for Weizhou Formation in Haizhong Sag. As a relatively complete source rock series revealed by drilling in Haizhong Sag, the geological resource of Weizhou Formation is 81.49×10⁶ t oil equivalent. The effective source rocks are mainly distributed in the sag belt, and the hydrocarbon generation center is located in the downthrown block of Fault 3. In the SINOPEC chemical exploration area, the downthrown block of Fault 3 is close to the hydrocarbon generation center, which is the most favorable area for the source rock conditions of Weizhou Formation, which should be the preferred breakthrough area for the next exploration work.