Analysis of sedimentary facies characteristics and source reservoir allocation of fault depressed Lake Basin—Taking Xu-Xi area of Songliao Basin as an example

Abstract

At present, Xu-Xi area is in the primary stage of exploration, and its sedimentary characteristics and distribution law are not clear. In this study, based on the analysis of regional structural background, through core observation and description, grain size analysis, well logging and seismic and other technical means, the sedimentary facies types and spatial distribution characteristics of Shahezi Formation in Xu-Xi area are studied. It is believed that there are three types of sedimentary systems in Shahezi Formation in the study area: Fan Delta, braided river delta and lake. The fan delta is mainly developed in the steep slope belt in the west of Xu-Xi area, while the braided river delta is mainly developed in the gentle slope belt in the East and the axial belt in the north, and the lake facies is developed in the depression belt between them. On the whole, the sedimentary pattern shows the obvious characteristics of “North-South block, east-west belt”. From the West steep slope to the East gentle slope, the sedimentary facies type transits from fan delta to deep lake semi deep lake and then to Braided River Delta. Combined with the study of reservoir forming conditions, it is found that the sand bodies of fan delta front and braided river delta front have good reservoir physical properties and are often adjacent to large-scale high-quality source rocks in the upper and lower or lateral directions. The reservoir forming conditions are superior and are favorable for oil and gas accumulation facies belt.