The utilization of integrated geophysical profiles to reveal the basement geology and geophysical characteristics of the Songliao Basin: A case study of the profile of Well SK-2

Songliao Basin is a Meso-Cenozoic continental sedimentary basin in Northeast China. Based on a detailed analysis of the Paleozoic stratigraphic characteristics, sedimentary environment and tectonic evolution in Northeast China, the authors conducted the interpretation of the comprehensive geophysical data across Well SK-2 to investigate the properties and geophysical characteristics of the basement in this paper. On the SN profile, the authors have found some phenomena:the Bouguer gravity anomaly in Well SK-2 is high in the middle and low on both sides; the magnetic anomaly shows a negative correlation with gravity anomaly; magnetotelluric properties are characterized by partial layers and high-low resistance crossover in the shallow part and partial regions in the deep part. On the EW profile, the gravity anomaly curve has the trend high in the west and low in the east; the magnetic anomaly curve is "bowl-shaped"; there exists a high resistance structure compared with features of the SN-trending profile. Combining geophysical characteristics with lithofacies palaeogeography, the authors have reached the following conclusions:1. From the Late Carboniferous to Late Permian in the Upper Paleozoic, there were many sedimentary environments such as shallow marine facies, continental facies, rivers and lakes. The corresponding lithologic combinations had different physical characteristics; 2. The geomagnetic characteristics of the gravity, magnetic method and magnetotelluric sounding's results reveal that the basement of the study area is mainly composed of mudstone, marble and intrusive rocks, and the burial depth of the roof of the basement is about 7km. The base of the study area is formed by the Upper Paleozoic and intrusive rocks. 3. The location and orientation of the Binzhou fault zone, the Sunwu-Shuangliao fault zone, the Helen-Renmin fault zone and the deep fault system are identified. The fault structures are mainly dominated by SN and EW trending structures. They are important components of the Paleozoic structural skeleton and control the migration and storage of deep oil and gas.