Charging dynamic, resistance and accumulation process of tight sandstone oil of the paleogene Es3 member in linnan sag, jiyang depression

Abstract

The study of the coupling relationship between the dynamic and resistance of oil charging is the key to revealing the process of tight oil accumulation. The Paleogene Es3 member of Linnan sag, Jiyang Depression was taken as an example, basin simulation, fluid inclusion analysis, and porosity inversion were comprehensively utilized to recovery the residual fluid pressure and charging resistance during the critical oil accumulation periods. Combined with the physical modeling of tight oil charging, the charging process and characteristics of tight oil under dynamic and resistance coupling were reproduced and the effects of dynamic and resistance on the oiliness of tight reservoirs were analyzed. The comprehensive analysis indicates that there were early and late periods of oil accumulation in early Dongying period and late Guantao-Quaternary period. The reservoirs had not been densified during the early oil accumulation period. The residual pressure of the formation was between 1.0–4.4 MPa and the reservoir charging resistance was generally small, so that the dynamic was generally greater than the resistance. But the oil saturation of the reservoirs was low due to the small amount of hydrocarbon generation. During the late oil accumulation period, the source rocks entered the peak period of hydrocarbon generation and expulsion and the residual pressure of the formation was between 4.2–12.1 MPa. The reservoirs had been close to or completely densified. The dynamic, resistance and dynamic and resistance difference all increased significantly. Under the stronger dynamic, the oil saturation of reservoirs rapidly increased, ultimately achieving tight oil enrichment. The results of this study provide insights into the dynamic process of tight oil accumulation and the distribution of oil in tight reservoirs.