STUDY ON THE SEDIMENTARY CHARACTERISTICS OF THE OIL-BEARING LAYERS C-8 AND C-9 OF YANCHANG FORMATION IN PINGBEI AREA, ORDOS BASIN

Good oil and gas shows are discovered in the exploration of oil-bearing layers C-8 and C-9 in Yanchang Formation, Pingbei area. Combining the data of well logging, geological logging, drill core and chemical analysis, a comprehensive study is conducted on the petrological, paleontological and geophysical characteristics of C-8 and C-9. The results show that the lacustrine-delta depositional systems, mainly delta front facies and shore-shallow lacustrine or prodelta sedimentary facies, are developed in the Pingbei area during the sedimentary period of C-8 and C-9, which can be subdivided into underwater distributary channel, underwater distributary interchannel, distant sandbar, shore-shallow lacustrine mudstone and prodelta mudstone microfacies. Among the facies above, the sand body of underwater distributary channel is relatively developed, serving as the main oil-gas accumulation place.