Main controlling factors of hydrocarbon accumulation in Baiyun Sag at northern continental margin of South China Sea

Abstract

To examine the distribution pattern and controlling factors of oil and gas accumulation in Baiyun Sag systematically, this study analyzes the key factors controlling hydrocarbon accumulation using a large amount of seismic, drilling and geologic data. It is concluded that the oil and gas accumulation is controlled by the following factors: (1) Massive source rock is the physical basis of the formation of medium and large oil and gas fields. (2) Orderly distribution and accumulation of hydrocarbon is regulated by the differential generation of hydrocarbon and differential hydrocarbon accumulation: spacial differential leads to “inner gas, outer oil” pattern, differential accumulation of hydrocarbon controlled the pattern of “inner gas, outer oil” in the east subsag of Baiyun; the timing differential leads to the “upper gas, lower oil” pattern. (3) Late fault activity, diapirs and inherited structural ridges controlled the favorable migration in the Neogene: the activity of faults and diapirs regulated the trap formation and vertical migration of hydrocarbon; inherited structural ridges controlled the Neogene hydrocarbon accumulation. The result effectively guides the exploration in the Baiyun Sag and surrounding area, and provides experience and evidence for the exploration in deepwater area of Pearl River Mouth Basin and other similar basins. Key words: continental margin of northern South China Sea, Baiyun Sag, massive source rock, differential hydrocarbon generation, differential hydrocarbon accumulation, late faults/diapirs, structural ridge