Reservoir Characteristies And Sedimentary Faeies Of Chang8and Chang6Formation In Zhouwan-Changcheng Area Of Wuqi County On Ordos Basin

We select Chang6&Chang8oil groups in Yanchang formation of Triassic in Zhouwan-Changcheng area of Wuqi country Ordos basin as our study area in this paper. We put the results of previous research results as a basis, and also the combined regional geological setting of the study area. Meanwhile, we’ve made structural geology, sedimentary petrology, reservoir sedimentology, logging geology and other disciplines as our theoretical basis. According to the above methods, we’ve made a in-depth research for the stratigraphic characteristics, the sedimentary facies and the reservoir characteristics of Chang8and Chang6oil group, which provides a theoretical basis for further exploration and development of oil and gas in the study area.After we’ve fully understood the regional tectonic and sedimentary evolution of the characteristic features of the Zhouwan-Changcheng area, we refer to the Changqing Oilfield recognized stratigraphic division mark layer (K0-K9) as well as their own classification scheme Yanchang Formation. Meanwhile, Chang8&Chang6oil group of the Yanchang Formation have been divided by the characteristics which include stratum lithology, logging curve sedimentary cycles Characteristics and other characteristics. According to the above researches by the following sequence, we subdivided the Chang8&Chang6Formations into Chang82, Chang81and Chang63, Chang62, Chang63.We make a comprehensive analysis by the characteristics of facies markers, and other analytical data from Zhouwan-Changcheng area, where the sedimentary system of chang8&Chang6formation is a lake-delta system at the Zhouwan-Changcheng area. At the same time, our research reveals that Chang8is delta front facies, which has three main microfacies, including distributary channel, mouth bar and interdistributary bay. Chang7is a semi-deep lake-deep lake facies, and the "Zhangjiatan" Oil shale is a little thicker in the southwest region of the study area. The results also show that the deposition system of Chang6and Chang8are similar, but also is the delta front facies, including three sedimentary microfacies: distributary channel, mouth bar and interdistributary bay.The reservoir characteristics of the Chang8&Chang6oil group Yanchang Formation in Zhouwan-Changcheng area are studyed and evalued respectively by the characteristics which include the reservoir rock characteristics, pore structure characteristics, diagenesis and reservoir characteristics et al. The results show that: the reservoir sandstone type group of the Chang8&Chang6oil group Yanchang Formation mainly consists of feldspathic sandstone, lithic feldspathic sandstone slightly less, but the Chang8oil group also contains small amounts of feldspar lithic sandstone. Reservoir space group of the Chang8&Chang6oil group has intergranular pore, based micropores; dissolution holes intergranular porosity and micro-cracks and micro-structural cracks. In addition, there are two types of factors that control the reservoir properties of the Chang8&Chang6oil group, which are sedimentation and diagenesis. According to the reservoir space characteristics and reservoir performance characteristics, and oilfield reservoir classification and evaluation criteria, the reservoir of Chang8&Chang6oil group is low porosity and low permeability-especially extra low porosity and extra low permeability reservoir, but the reservoir of Chang6performance was better than that of Chang8.