稠油油藏油气运移路径刻画与成藏过程分析——以渤海海域辽东湾坳陷LD16含油气构造为例

Characterization of migration pathway and analysis of oil accumulation process of heavy oil reservoirs:a case study of LD16 oil-bearing structure in Liaodong Bay Depression in Bohai Sea area

稠油油藏在油品性质、油水关系、保存机制等方面与常规油藏存在较大差异,成藏过程也极为复杂。以渤海海域辽东湾坳陷LD16含油气构造为例,运用测井、岩心描述、地震、地球化学分析等资料,总结了其主要的油藏特征,并在储层物性非均质性刻画、断层立体分析的基础上,创新提出运用基于充注段与储层非均质性的定量运移模拟技术对油气运移路径进行精细刻画,进而对稠油的成藏过程进行研究。研究结果表明:断层的活动速率与曲率形态决定了断层带油气有效运移区段;储层物性与构造形态共同决定了稠油在储层中的优势运移通道,充注量与高孔渗带共同决定了稠油的不规则分布;稠油油藏是新构造运动时期东营组古油藏中遭受过初次降解的原油沿断层向浅层运移调整形成的,稳定盖层的存在与原油受温压下降造成的黏度突然增大,是油气在馆陶组砂砾岩中聚集成藏的关键。

The heavy oil reservoir varies greatly from conventional oil reservoir in terms of oil properties,oil-water contact and preservation mechanism,and its oil accumulation process is extremely complicated.Taking the LD16 oil-bearing structure in Liaodong Bay Depression in Bohai Sea area as an example,the main characteristics of heavy oil reservoir is summarized in this study by using logging,core description,seismic and geochemical analysis data.Based on the characterization of reservoir heterogeneity and stereoscopic fault analysis,a quantitative migration simulation technique combining the charging section and reservoir heterogeneity is proposed to fi nely describe the hydrocarbon migration pathway,and further to study the heavy oil accumulation process.The results show that:(1)The active rate and curvature shape of faults determine the effective hydrocarbon migration section in fault zone;(2)The reservoir physical property and structural morphology jointly determine the dominant migration pathway of heavy oil,and the amount of oil charging and high porosity/permeability zone result in the irregular distribution of heavy oil;(3)The heavy oil reservoir is formed by the migration and adjustment of crude oil along the fault that was primarily degraded of Dongying Formation paleo oil reservoir during the neotectonic movement.The stable caprock and the abrupt increase of oil viscosity due to the decrease of temperature and pressure are the key factors for hydrocarbon accumulation in glutenite reservoir of Guantao Formation.