Reservoir Characteristics And Favorable Zone Prediction Of Xujiahe Formation In Wolong River - Ssangyong Structure

Based on lots of relevant literature research, outcrop and laboratory analysis, macro and micro observation, qualitative and quantitative comparative analysis, a systematic research has been carried out in the aspects of the characteristics of sedimentary, reservoir and fracture development on the Upper Triassic Xujiahe formation of Wolonghe and Shuanglong area.Through core observation and sedimentology analysis, combined with the feature of log facies, we found that the study area mainly developed delta-lake sedimentary system. Furthermore, there were two kinds of facies types and a variety of microfacies can be recognized. Xujiahe depositional system was controlled by source and eustatic lake level. Xu-1member mainly developed shallow lake sedimentary, with shallow lacustrine sandbar developed. The Xu-2,4,6members are of delta front deposit with the characteristics of "full of sand", and the distributary channel sand body developed. The Xu-3,5members are of delta front and front delta deposit, with distributary bay between marsh developed; the most beneficial belt to reservoir formation and evolution of sedimentary facies is the delta front distributary channel sand body, which developed in Xu-2,4,6members.The reservoirs characteristics of the Xujiahe Formation in Wolonghe and Shuanglong areas have been deeply studied. The result shows that the physical properties are classified as low-porosity and low-permeability, but there were relatively higher porosity in local depths and horizons. The second member of Xujiahe Formation reservoir is mainly controlled by porous type. Some areas are concentrated fractured-porous reservoirs. The Xu-4member has the characteristics of crack-porosity reservoir type, and the reservoir porosity is dominated by fine-microporous with micro throat. The distributary channel of reservoir performance is obviously better than subprime distributary channel.Through the analysis of characteristics of reservoir fracture development, the result shows that the high quality reservoir of Xujiahe Formation tend to have the fracture-pore characteristics, and the plane distribution of fracture performance was characterized by the following features. Cracks developed most in the steep structures as well as near the fault zone, followed by the surrounding area, and the part of the construction-relief is relatively poor.Based on the above research, with the relevant research achievements of predecessors, drilling and logging datum, we put forward the favorable reservoir distribution zones of Wolonghe, Shuanglong areas, and point out the direction of the oil and gas exploration in the study area.