Seismic sedimentology research on fault-depressed lacustrine basin gravity flow channels of Oligocene Es1 in Qi’nan area, Qikou Sag
Liu Huaqing1,2, Hong Zhong1,2, Zhang Jing1,2, Niu Haiqing1,2, Su Mingjun1,2, Li Shuangwen1,2
1. Northwest Branch, Research Institute of Exploration and Development, Petro China, Lanzhou, Gansu 730020, China;
2. Key Laboratory of Reservoir Characterization, CNPC, Lanzhou, Gansu 730020, China
Abstract：Based on the first Member of Shahejie Formation (Es1) in Qi'nan area, Qikou Sag, we conducted seismic sedimentology analysis, including sedimentary textures, well logging characteristics, seismic facies models, and channel distribution of a faulted-lacustrine basin gravity flow depositional system dominated by channel sandy debris flow. The following observations have been obtained: 1There are at least three types of gravity-flow deposits developed in the Oligocene fault-depressed lacustrine basin: sandy debris flow, slump, and turbidite, in which the sandy debris flow with considerable suspension content is the main depositional type. 2Seismic facies models of fault-depressed lacustrine basin gravity-flow channels can be divided into U-shaped (or V-shaped), saucer-like, worm-like, and spindle-shaped (lenticular-like) facies, which are probably related to the changes from strong fluid energy to weak fluid energy. 3When tectonic movement was active, the lacustrine basin was steep, and gravity-flow channels developed along valleys were narrow and straight with obvious erosion to underlain strata; when the tectonic movement was inactive, the lacustrine basin was flat, and channels were much wider with less erosion to underlain strata.
