Geological Characteristics and Main Controlling Factors of Tight Sandstone Oil in G3 and G4 Oil Layers of Qijia Area in Northern Songliao Basin

Abstract

AbstractThere are great differences in sedimentary conditions, geological characteristics and main controlling factors between China's continental basin and foreign marine tight oil reservoirs, which lead to different favorable target selection and exploration direction. In order to deepen the understanding of tight sandstone oil in G3–G4 oil layers of Qingshankou Formation in Songliao Basin, based on the test data of porosity and permeability, CT scanning, cast thin section, inclusions, nuclear magnetic resonance and mercury injection, the geological characteristics of tight sandstone oil in G3–G4 oil layers in Qijia area were systematically analyzed, and the distribution law and enrichment controlling factors of tight sandstone oil in delta front subfacies in continental basin were summarized. The results show that G3–G4 tight reservoirs has fine grain size, poor sorting, low compositional maturity and structural maturity. Under strong compaction and cementation, the primary pores are decreased by 10–30%, and the pores are mainly micro pores with throat radius of 30–500 nm. In the tight reservoir development area, the reservoir mainly includes pure oil, and the oil distribution is controlled by sand body and reservoir physical property.Under the drive of hydrocarbon generation pressurization and buoyancy,the present reservoir is characterized by continuous strip distribution in horizontal direction and large area distribution in plane. The enrichment of tight oil is mainly controlled by the matching of mature source rock, favorable structural parts and favorable sedimentary facies belts in the second member of Qingshankou Formation. The microfacies sandbodies of mouth bar and distal bar are the most favorable enrichment parts of tight oil. The research results enrich the exploration theory of tight sandstone oil in continental basin, and provide theoretical basis for the optimization of favorable enrichment area and well location deployment of tight oil in northern Songliao Basin.KeywordsContinental basinDepressionSource rockTight sandstone oilGeological characteristicsMain controlling factors