The Research On Sedimentary Microfacies And Forcasting Perspective Of Chang 6 Reservoir In Wangyao And Pingqiao Areas, Ansai Oilfield

This paper studies the Chang 62 and Chang 63 of Chang 6 oil reservoir beds of Yanchang formation in Wangyao, Houshi, Xinghe and Pingqiao aears in Ansai oilfield. Taking sedimentology,geological logging and reservoir geology as guidance, many modern analysis are used to systematically research stratigraphic sequence and source analyses of the bed of interest based on the study of geological background and divisions of substratums. The types of sedimentary microfacies are divided on the basis of lithological characteristics, fossils and logging facies. The paper predicts the character and trend of the distribution of the skeletal sand body, and discusses the relationship between microfacies and reservoir,oil and gas distribution. Finally, six favourable areas of oil and gas are presented.It is concluded that that Chang 6 oil-bearing formation in the studied area is interpreted to be a river-dominated delta deposited in lacustrine environment, consisting of underwater distributary channel, interdistributary bay, front santsheet and natural levee. The underwater distributary channel sand bodies constitute the dominated reservoir. By the influence of river course, underwater distributary channel distributes alternating with interdistributary bay which forms the principal source-reservoir-seal assemblage mode. The sedimentation forms the foundation of sandstone reservoir, decides its clastic constituents, texture, and controls the distribution of sand body. The reservoir sand body of Chang 62 is well developed to Chang 63; the pore texture type is influenced by diagenesis which mainly forms plenty of secondary pores. The underwater distributary channel sand bodies which should be the main destinations of exploration of this area in the near future is not merely good physical property, it is also favourable places for hydrocarbon accumulation.