The Well Log Interpretation Research Of Low Resistivity Gas Zone In The Sulige Eastern Area

Ordos Basin is the second largest sedimentary basin in China, and also be one of the largest and earliest discovered, explored and developed hydrocarbon-bearing basins in China. The Upper Paleozoic in Ordos Basin consists of fluvial-deltaic facies, the natural gas reservoirs are dominated by clastic rocks. Porosity of main reservoirs is less than 10% and the permeability less than 1.0×10^-3μm²,belonging to the low-permeability and extremely low-permeability one in general. In the past few years, great breakthroughs have been made in petroleum exploration in this basin, due to the progress on the low-permeability petroleum geology and the development of petroleum exploration and exploitation techniques. As a result, the oil and gas reserves and output are keeping a rapid increase, showing great potential of low-permeability petroleum exploration and development in Ordos Basin.In the case of low resistivity gas layer, how to find pay zone where high quality. reservoirs develop and how to improve individual well producing rate through scientific exploration technology become the key to the oil and gas exploration and development. Through long-term practice of oil and gas exploration and development and reservoir research, people have gradually realized that sedimentary facies zone where sandston bodies develop and diagenetic facies zone where secondary pores are developed are crucial to the distribution of high quality reservoirs. That making clear the genetic mechanism of low-resistivity gas zone, setting up the model of reservoir parameter calculating, and determining logging interpretation method are the ways of improving interpreting coincidence rate. That obviously is of great significance in petroleum exploration in Ordos Basin.This dissertation studies Upper Paleozoic 8 section low-resistivity gas layer in Sulige eastern area, Based on the outcrop investigation and core information. According to the former research achievements and the sedimentary background of region, define the facies types of the sedimentation belong to Plain Deltaic Deposit. Analysis of Core facies and electrofacies reveals the distribution of sedimentary and the evolution pattern of the distribution and the evolution of reservoir within isochronous stratigraphic frameworks. So according to the testing result and statistics of core geologic parameter, from the relation study of four characteristics, through the research causative mechanisms of low-resistance gas layer, combined with secondary interpretation to log information that established model in this area, improved logging interpretation chart, established an attributes crossplot model for log and lithology. On this foundation, we did an integrated interpretation test of more than 50 wells in our territory. The result is satisfactory practically; provide reliable information for making adjust ments to future projects, improving the efficiency of opening new wells, enhancing the awareness of wells.It is showed that the east of Sulige low-resistance is affected by fine lithology, cementation, formation water salinity, high extent of porosity, irreducible water saturation, pore configuration drilling fluid invasion and many other factors. Consequently, it is needed to apply all kinds of identify ways to well log interpretation, which is analyzed and valued comprehensively, for the sake of decreasing the multi solution problem in the course of interpretation, with the qualitative estimation integrating the quantitative interpretation, multi-methods processing interpretation integrating the crossplots and oil and gas shows integrating the log response .