Study On Development Geology Of Chang-6Reservoir In Zhengzhuang District,Qilicun Oilfield

By the use of the theories and methods including sedimentology, logging geology, reservoir geology, petroleum geology, this article systematically analyzed the sedimentary facies, reservoir characteristics, calculated the petroleum reserve of the Chang-6oil-bearing formation in Zhengzhuang district, Qilicun oilfield.Zhengzhuang district, Qilicun oilfield is located in the southest of Ordos basin. The Chang-6oil-bearing formation is the major oil-producing layer. According to the lithologic features, electrical property, sedimentary rhythm, and the distribution of regional marked beds, the Chang-6oil-bearing formation can be divided into4oil-bearing sublayers, i.e. Chang61, Chang62, Chang63, and Chang64. Based on the sub-level sedimentary rhythm, the Chang61can be further divided into6zones, the Chang62into4zones, and the Chang63into3zones.According to a series of facies symbols, including rock types and their association, sedimentary rhythm, grainsize distribution of sandstone, primary sedimentary structures, fossils and sandbody shape, combined with regional depositional background and logging curve shapes, the author discussed the types of sedimentary facies, microfacies and their characteristics of the Chang6oil-bearing formation in the studied area. It is considered that the Chang-6formation in Zhengzhuang district is a set of lacustrine delta deposition, in which the Chang61sublayer belongs to delta plain subfacies including distributary channel, inter-channel bay, levee and crevasse-splay microfacies. The Chang62to Chang63sublayers belong to prodelta subfacies developing subaqueous distributary channel, subaqueous levee, subaqueous crevasse-splay, inter-distributary bay and channel-mouth bar microfacies. The distributary channel, subaqueous distributary channel and channel-mouth bar deposition are main reservoir sandbodies.Based on core observation and a lot of samples analysis datum, the reservoir sandstone of the Chang-6formation is mainly made up of fine arkose. The reservoir’s physical properties are low porosity and low permeability with some relative higher porosity and higher permeability area. The types of pore are mainly intergranular pore and intergranular dissolution pore. The types of pore structure are mainly medium pore-fine throat, little pore-...