Tight Oil Reservoir Forming-dynamic Of Gaotaizi Oil Layer In Qijia Area, The Songliao Basin

Fuyu oil layer and Gaotaizi oil layer are the two sets of tight oil reservoir in Qijia area,the Songliao Basin. Based on the comprehensive analysis of geological data(history of tectonic evolution, the history of tight sandstone reservoir and accumulation), the study of log response characteristics, hydrodynamic, tectonic force and buoyancy are not reservoir forming-dynamic of tight oil reservoir, can only push oil to tight sandstone reservoir is overpressure.Inclusion testing results showed that Gaotaizi oil layer had two stage charging accumulation, in the end of Nenjiang Formation and MingShui Formation deposition, and the later one is obvious abnormal high pressure, further confirmed that the oil is driven by the overpressure into tight sandstone reservoir.Mudstone undercompaction and hydrocarbon generation are the main kinds of the formation mechanism of overpressure, which cause the preservation of overpressure period before the reservoir tight, it is not the main driver of tight oil accumulation, only overpressure caused by hydrocarbon generation was able to push the oil into the tight sandstone reservoir.In order to measure the overpressure caused by hydrocarbon generation, puts forward the concept of accumulated maximum overpressure, refers to the assumes that the source rocks in the process of a continuous period of hydrocarbon generation in a fully closed environment, no hydrocarbon discharge, the generated hydrocarbon saving in the porosity of the source rocks, achieved the accumulated overpressure.The accumulated maximum overpressure of source rock,Qingshankou Formation,was calculated by the improved source pressure calculation model combining with the basin simulation technique, the results showed that the overpressure caused by hydrocarbon generation in the late MingShui Formation deposition can reach more than 50 MPa, greater than the fracture pressure of hydrocarbon source rock and the expulsion pressure of tight sandstone, can be forming dynamic of tight oil reservoir.In the end of the accumulation of the Nenjiang formation deposition, oil discharged source rocks by the overpressure caused by undercompaction and hydrocarbon generation, then formed a reservoir.