The Sedimentary Microfacies Studies Of Chang8-9Oil Reservoir Group Of Yancahng Formation In Yanding Area

On the basis of predecessors’researches and on the guiding of sedimentology, oil geology, sequence and logging geology theories as, and using experimental data such as thin section identification, drilling core observation, testing and so on, the strata, material sources, sedimentary facies and sedimentary microfacies of yanchang formation in yanding area are studied. The results show that the thickness of major reservoirs chang8-9in the area is stable; The material sources are from the Archeozoic granulite and gneiss of ALaShan ancient land in the northwestern margin basin; The sedimentary face of chang8-9of yanding area is mainly braid river deltas, divided into delta plain and delta front subfacies, in which the latter distributes widely. There are mainly four sedimentary microfacies which are distributary channel, underwater distributary channel, interchannel and distributary interchannel. According to the sedimentary facies profile and plane distribution of chang8-9, the chang9sand body thickness is thicker than that of chang8; the chang9sectors-connecting degree and river extension length are better than that of chang8. This may be relevant with the continuous downwarped and braided river diverted. According to sedimentary microfacies, sand body thickness, the distance from hydrocarbon-generating depression, reservoir physical properties and test and so on, it is predicted that there has29favorable containing oil region of chang8-9strta in studied area. There are10Ⅰ class advantageous area,4class Ⅱ advantageous area and15Ⅲ class advantageous area.