Prediction Of Basement Lithology In The Central Uplift Belt Of Songliao Basin

The Songliao Basin is a terrestrial hydrocarbon basin in northeastern China,and the central paleo-uplift zone within it is a new area of exploration and development for the Daqing Oilfield.However,the basement geology of the central uplift zone is complex,and the structure and tectonic features of the inner curtain are poorly understood,leading to disagreement on the composition of the basement rocks.In this paper,the latest seismic profiles,drill cores and remagnetisation data are used to predict the basement lithology of the central uplift zone in the Songliao Basin through a combined remagnetisation and seismic study.The following insights were obtained:(1)The central uplift zone in the Songliao Basin has low gravity values in the north and south,high gravity values in the east and central part of the zone,and the macroscopic orientation of gravity anomalies is north-south;the eastern part of the central uplift zone has high magnetic values and the western part has low magnetic values.The gravity and magnetic anomalies are different due to the difference in density and magnetisation of the basement lithologies in the central uplift zone.(2)Two types of rock bodies are found at the base of the central uplift zone of the Songliao Basin through the heavy magnetic fitting profiles.The density value of one type of rock body is about 2.58 g/cm3 and the magnetization rate is 4.7×10-5SI,while the density value of the other type is 2.65 g/cm3 and the magnetization rate is 59×10-5SI.Andesite.(3)The basement intrusions in the study area are granites.The simulated seismic orthogonal profiles of the central uplift zone of the Songliao Basin are in good agreement with the actual seismic profiles,and the simulated homogeneous axis energy matches the strength of the homogeneous axis energy of the actual seismic profiles.(4)The Permian medium-basic magmatic rocks(andesites)are more developed in the eastern part of the Songliao Basin Central Uplift Zone,and deep channels may exist locally;acidic magmatic rocks(granites)are more developed in the south and north,and deep channels may exist in the acidic magmatic rocks(granites)in the south,and mixed rocks(granites and andesites)exist in the central and northwestern parts.