Hydrocarbon Reversed Accumulation Model of Big Depression Syncline Area——A Case of the Fuyang Reservoir in the Sanzhao Depression
LIU Zongbao,FU Xiaofei,Lü Yanfang,FU Guang,PANG Lei Geoscience College of Daqing Petroleum Institute,Daqing,Heilongjiang,163318
The Fuyang reservoir of the Sanzhao depression in the Songliao Basin is a typical large-depression reserved-migration accumulation.300 seismic sections,log curves of 825 wells,11 well-cores and exploratory well testing data were applied to do some composite study on the features and moving periods of faults,hydrocarbon down-migration depth,reservoir depositional characteristics and so on, the main factors controlling hydrocarbon accumulation. They are concluded that: (1) T2 faults are controlled by basement fault,lower craters,difference between the amount of oblique tension and extension,having the association characteristics of concentrated into ribbons in plane,"flower-like" combination in section. And the oil sources faults that are active at the hydrocarbon accumulation period are mainly boundary faults of concentrated ribbons. (2) Theoretical calculations of down-migration depth driven by overpressure and the statistics on the practical oil pan envelope suggest that the thickness bearing oil in the Fuyang reservoir is 200m. (3) Heavy mineral analysis that the Fuyang reservoir are mainly affected by the northern Baiquan—Qinggang source and the southwest Baokang source.And the two source meet in the region of Xujiaweizi then flow to the east. (4) Sedimentary microfacies reveal that the Fuyang reservoir grow gradually retrogradation shallow delta depositional system.The top is delta front facies,and the middle and bottom is delta distributary plain facies. The development period of FⅠ7—FⅡ1 is the largest period of region water regression,which are the main enrichment horizon. At the end of the Mingshui Group,the Qingshankou source rocks reach oil generation peak,hydrocarbon migration episodic pass down to along open boundary faults of concentrated ribbons,and crossrange migration for short distance along distributary river sand on uplifted side of the both side.That is,horst and fault horst that located with both sides of the fault concentrated ribbons are hydrocarbon concentrate region,the concentrated ribbons are always combinative graben which is not good for accumulation.At the guidance of the accumulation model,47 hydrocarbon-riched target area were depicted,which gave a clear direction in the exploration and development for the Fuyang in the Songliao basin.