Three-layer Tectonic Framework and Deep Oil Reservoir Prospecting in the Songliao Basin

Songliao Basin is a structure belt controlled by the Siberian plate,North China plate and Pacific plate,which belongs to the mosaic micro-massif active orogenic belt in the Jiameng block.It is an extension and variant superimposed basin formed by Mesozoic-Cenozoic continental oil-bearing basin superimposing on the late Paleozoic marine basin.Mesozoic-Paleozoic strata in the basin show the dual structure of water and fire.Volcanic-magmatic activity in the area is frequent with the features of multi-period,multi-cycle and multi-intrusive-eruptive center,and it aslo has the superimposed oil reservoir with features of organic and inorganic,continental facies and marine facies.The opening and closing tectonic activity is the appearance of collapse rift.Based on the study of three-layer structure pattern of the surface(continental basin),crustal(marine late-Paleozoic residual basin) and lithosphere,it appears to be NNE-NE and EW overpass structural pattern.In short,Songliao basin has the features of broken basin(fracture developed,volcanic-magmatic activity destructed),mine basin(basin rich in oil and gas reservoirs with wide distribution of polymetallic mineral on the edge of the basin),hot basin(geothermal gradient appear to be higher),magmatic basin(large amount of volcanic rocks and igneous rocks distributed within and outside the basin),crooked basin(depression and fracture on both sides of the central uplift are not symmetrical),and water basin(produced from the Paleozoic to Mesozoic and Cenozoic sedimentary rocks).In view of the reservoir forming effects of superimposed basin,and since deep marine carbonate rock type or volcanic rock type gas reservoir can be taken as the main direction of reservoir prospecting,a strategic guideline of regional prospecting and major breakthrough as well as concrete proposals of deep reservoir prospecting were also put forward.By the research and forecasting,it is preliminarily considered that the deep part has favorable reservoir prospecting potential,so it is aslo proved that the grand plan of centennial Daqing will be achieved in the future.