Study On Tight Oil Accumulation Conditions In Qijia Area Of Songliao Basin

Tight oil is an important supplement to conventional oil and gas resources,and its accumulation mechanism and main control factors are different from conventional oils.Through the observation and description of 38 coring wells in Qijia tight oil zone of Songliao Basin,combining with the organic geochemical experimental data of nearly 1500 rock samples from 197 wells,the source rocks are divided into two types according to their lithology and geochemical characteristics.The Qing1 formation is composed of I type source rocks and conforms to the“mudstone is above the sandstone” and “near the source rock ”contact relation.The Qing23 formation is composed of II type source rock,vertically from the Mudstone surrounds the sandstone to sandstone is wrapped in mudstone,“the inter layer contact relationship” gradually transition.The hydrocarbon source allocation of Qijia Qingshankou formation was determined by using hydrocarbon potential analysis and chemical dynamics.Based on the basin simulation technique,the temporal and spatial matching relationship between source rock accumulation and reservoir compaction is determined,and three types of hydrocarbon migration and accumulation models for different source reservoir combinations are proposed.Combined with previous research results,the oil and gas migration regularity in Qijia tight oil field is summarized.Tight oil in Qijia Qing23 formation is mainly from inner source rock or underlying Qing1 formation.Oil and gas from Qing1 formation will migration across active faults to Qing23 formation.On this basis,combined with the analysis results of physical,lithofacies,formation overpressure,fracture fractal index and other factors,the favorable accumulation area of tight oil is defined.