渤海海域浅层原油物性分布规律与主控因素

Physical property distribution law and main controlling factors of shallow crude oil in Bohai Sea

明化镇组下段和馆陶组(本研究称浅层)是渤海海域主力含油层系,其原油物性平面变化较快,但区域上原油物性平面分布规律缺乏系统研究,制约了浅层油气分布规律认识。本次研究结合区域地质认识,利用丰富的钻井、原油分析大数据资料,从浅层原油物性特征分析出发,探讨其分布规律的主控因素。研究认为:①渤海海域浅层原油物性参数在凸起区、凹陷区差异明显,凹陷区原油普遍具有“四低一高”的特征,即密度低、黏度低、胶质+沥青质低、含硫量低、含蜡量高,而凸起区原油表现为相反的“四高一低”;②油藏埋深、保存条件、运移距离控制了浅层原油物性的差异分布,埋深大、保存好且运移距离短时,原油降解作用和色层效应弱,利于形成原油物性较好的油藏;③烃源岩条件主要影响渤海东部盆缘凹陷的浅层原油物性,烃源岩热演化程度较高、水体环境偏淡时,利于形成原油密度小、黏度小、含硫量低的优质油藏。研究成果总结了渤海海域明下段和馆陶组原油物性平面分布规律及控制因素,为寻找浅层优质油藏潜力区带具有指导意义。

The lower member of the Minghuazhen Formation and the Guantao Formation(shallow formations)are the primary oil-bearing formations in the Bohai Sea.The physical properties of these formations exhibit rapid planar variations.However,there is a shortage of systematic research on the regional planar distribution law of physical properties of crude oil,which impedes the understanding of the distribution law of shallow oil and gas.Regional geological insights and extensive drilling and crude oil analysis data were used to analyze the physical property characteristics of shallow crude oil and investigate the main controlling factors of its distribution law.The research gave some suggestions:①The physical properties of shallow crude oil in the Bohai Sea are markedly different between the uplifted and the depressed areas.The crude oil in the depressed areas is characterized by low density,low viscosity,low content of resins and asphaltene,low sulfur content,and high wax content.Conversely,the crude oil in the uplifted areas exhibits the opposite traits of high density,high viscosity,high content of resins and asphaltene,high sulfur content,and low wax content.②The burial depth,preservation conditions,and migration distance govern the variable distribution of physical properties of the shallow crude oil.Large burial depth,good preservation,and short migration distance weaken the degradation and chromatographic effects on crude oil,which is beneficial for the formation of oil reservoirs with superior physical properties of crude oil.③The conditions of the hydrocarbon source rock significantly affect the physical properties of the shallow crude oil in the marginal depressions of the eastern Bohai Bay Basin.When the hydrocarbon source rock has undergone a high degree of thermal maturation,and the aquatic environment is less saline,it favors the formation of high-quality oil reservoirs characterized by low crude oil density,low viscosity,and low sulfur content.The research results summarize the planar distribution law and controlling factors of physical properties of crude oil in the lower member of the Minghuazhen Formation and the Guantao Formation in the Bohai Sea,which has guiding significance for finding potential zones of shallow high-quality oil reservoirs.