Abstract:

Based on the modern hydrocarbon accumulation theories, through analyzing causes for hydrocarbon accumulation and
distribution characteristics, this paper analyzes factors that influence differential hydrocarbon distribution in the Majiazui area of
Gaoyou Sag, Subei Basin. The results indicate that fault-lithologic reservoir is the main reservoir type which contains two kinds
of hydrocarbons originatied from the E1f4 source rock in Shaobo sub-sag and hydrocarbon charging occurred in the middle-late
stage of the Eocene. The zonal distribution of different hydrocarbons was caused by different migration pathways, not by different
sources or different migration periods; Zhen② and Hanliu faults serve as the dominant migration pathways; Zhen② fault shows
relatively stronger ability for hydrocarbon migration, thus hydrocarbon that occurred along Zhen② fault shows lower maturity than
that along Hanliu fault. Under the influence of sedimentary microfacies on reservoir properties, reservoirs of middle-terminal fan
far from faults show higher oil-bearing properties than those of root-fan near faults; the degree to which fault-lithologic traps are
filled is determined by matching fault orientations, sand beds pinching-out directions, and strike of strata.

Key words: faults, hydrocarbon migration, migration pathway, accumulation period, fault-lithologic reservoirs, Gaoyou Sag