Study on“source-facies-potential”coupling relationship during oil and gas accumulation in Paleogene red beds,Boxing subsag-a case study of the section Jin26-Binxie703
Aiming at oil and gas accumulation in the Paleogene red beds in Boxing subsag,Dongying sag,a north-south strike section Jin26-Binxie703 was chosen as main research object. A quantitative relationship between the probability of hydrocarbon accumulation in the study area and the distance from hydrocarbon reservoir to hydrocarbon kitchen was set up by using a statistical method,the reservoir paleo-physical properties were researched using the corresponding present reservoir physical properties charts and the dynamic evolution history of hydrocarbon reservoir during key hydrocarbon accumulation was restored through basin modeling constrained with procedure. The results show that the distribution of red beds hydrocarbon reservoirs is correlated better with the distances from the reservoirs to the center source or to the source boundary in Boxing subsag,which is characterized by Gauss normal distribution,so as to establish the quantitative model of oilgas accumulation probability that is controlled by source rock. Reservoir physical properties that can reflect“facies”change significantly during the key hydrocarbon accumulation period,and the residual fluid pressure of formation that can reflec“t potential”mainly comes from abnormal pressure of formation in Boxing subsag. The relationship between“facies”and “potential”can be characterized quantitatively finally by using the corresponding formula to calculate the“source-faciespotential”coupling index which can be used to predict favorable reservoir zones based on the relationship between these indexes and the reservoirs that has been found in the red beds. In the section Jin26-Binxie703,all the hydrocarbon reservoirs found at the lower sub-segment of the 4th member of Shahejie Formation and Kongdian Formation locate in the zone with“source-facies-potential”coupling indexes above 0.5. During the hydrocarbon accumulation period,coupling indexes of the zones on the north of Well Fan141 are comparatively high,all above 0.55,which can be favorable exploration areas for further exploration.