Petroleum exploration potential and targets in fault depressions, southern Songliao Basin

The Songnan fault depressions locate in the south of the Songliao Basin. According to the development ages and late reforming characteristics of the fault depressions, with the Xar Moron River fault as the northern boundary and the Chifeng-Kaiyuan fault as the southern boundary, the Songnan fault depressions can be divided into three belts from north to south:the Changtu-Manghan fault depression belt (the north), the Zhangwu-Dongsheng fault depression belt (the middle) and the Heishan Jurassic residual basin (the south). The Zhangwu-Dongsheng fault depression belt has good structure and is rich in oil all over the belt; hence explorations should be focused on the source rocks with continuous layered reflection, and the structural and subtle reservoirs should be targeted. In the Changtu-Manghan fault depression belt, the source rocks of the Jiufotang Formation has the characteristics of big thickness and fine geochemical index, so explorations should be carried out close to or in the source faults, and oil and gas mainly distribute in traps in the fault or close to it.