Research On Areas Of Profitability Of Oil In The Chang8Layer In Yanchang Formation Of The Upper Triassic In WP Area

WP area, the study area of this thesis, is located in the Ordos Basin. At present, we have found several oil-bearing series in Yanchang Formation of Triassic and Yanan Formation of Jurassic. Although certain results have been obtained through these years’exploration and exploitation, difficulties and risks of exploration and exploitation are increasing constantly, some main reservoirs, such as the Chang2, the Chang4+5and the Chang6are in the later stages of exploitation. In order to ensure high and stable yield of this area, we need to find alternative layers. The purpose layer of this study is one of the most important oil-bearing series—the Chang8layer in Yanchang Formation. Beacuse the time of exploration and exploitation in this region of the Chang8layer is relatively late, the study on some basic geological problems is not so deep, such as the distribution of sand body, reservoir characteristics, identification of favorable zones are insufficient. Those problems restrict the work of exploration and exploitation. The study is designed to solve these problems, providing technical support for the Chang8layer as the alternative layer.On the basis of analyzing regional geological background and sedimentary evolution of the Ordos Basin, collecting the related geological data and combining with the results of previous studies, we apply with theories of petroleum geology, sedimentology and so on to do our study. We extract corresponding marker bed of Yanchang Formation in this block to do accurate stratigraphic division and coenocorrelation by the materials of drilling, logging and so on; Then we analyze and evaluate the sedimentary facies(single well facies and well tie facies), sedimentary microfacies and sand body plane distribution of the Chang8reservoir groups; we study the physical characteristics, heterogeneity, diagenesis of this reservoir by core, thin slice and scanning electron microscope, thus to investigate the control factors of the reservoir. We summary oil and gas accumulation by the foregoing study, find out the controlling factors of favorable area distribution through combining with the oil testing data, thus to do comprehensive evaluation and optimize several favorable target areas.Through this research, we divide the Chang8oil formation into four layers, the Chang8period mainly developes underwater distributary channel, interdistributary bay and mouth bar of delta front microfacies sediment. The sand body’s distribution roughly follows the North to the South. Layer heterogeneity, which is controlled by sedimentary microfacies, dominates the distribution of the reservoir, the characteristics of layer heterogeneity are the uneven distribution of porosity and permeability. Underwater distributary channel and mouth bar are the important oil and gas reservoirs, providing favorable conditions and places to the accumulation of hydrocarbon. Extensively developed mud shale of the Chang7and mudstone of interdistributary bay in the updip direction as block jointly form good sealing gland conditions and possible oil source. Finally, we integrate structure, reservoir and other factors, optimize favorable exploration areas on the Chang811layer and the Chang821layer, thus to provide basis to the next step of exploration and exploitation in this area.