中国东、西部火山岩油气藏运聚成藏机理

目前对火山岩油气藏储层形成的控制因素、油气运聚机理认识不清,现有油气勘探理论不能有效指导火山岩油气藏勘探,导致其勘探潜力被严重低估。为此,通过剖析中国东、西部典型火山岩油气藏的成盆背景、储层形成与分布、油气运聚规律等,明确了中国东、西部火山岩油气藏不同的形成机制,首次提出了"相—面控储、断—壳控运、复式聚集"的火山岩油气藏运聚成藏机理,即岩性岩相界面、不整合面或火山旋回界面、期次界面控制了优质储层的发育;油源断层控制油气垂向运移,风化壳则控制油气侧向运移(火山岩油气运聚成藏过程的数值模拟实验结果表明,断裂与裂缝控制了天然气的输导通道,裂缝改善了低孔隙度、低渗透率火山岩的孔渗特征,提高了油气运移效率);火山多期次喷发,各期喷发界面(喷发间断界面、岩性岩相界面)顶部发育风化淋滤作用形成的有效孑L隙,纵向可形成多层有效储层,从而使得同一成藏背景下发育多层系、多类型火山岩油气藏。该创新性研究成果拓展了火山岩油气勘探层系和领域,丰富和完善了油气藏勘探理论。

Hydrocarbon migration and accumulation mechanism of volcanic reservoirs in eastern and western China

Currently, we still have such a poor understanding of the controlling factors for migration and accumulation mechanism of volcanic oil and gas reservoirs that the existing oil and gas exploration theories fail to effectively guide the oil and gas exploration in volcanic reservoirs. Consequently, the potentials of volcanic reservoirs are seriously underestimated. In this paper, basin-forming background, reservoir formation and distribution, and hydrocarbon migration and accumulation law of typical volcanic reservoirs in eastern and western China were analyzed to highlight different formation mechanisms of such reservoirs. And for the first time, the hydrocarbon migration and accumulation mechanism of volcanic reservoirs characterized by "rock facies & interfaces controlling reservoir, fracture & weathered crusts controlling migration, and multiple accumulation" was proposed. Specifically, lithologic and lithofacies interfaces, unconformities interfaces or volcanic cycle interfaces, and stage of such interfaces control the development of high-quality reservoirs. Oil source faults control the vertical migration of hydrocarbons, while weathered crusts control the lateral migration of hydrocarbons. Numerical simulation results for the hydrocarbon migration and accumulation of volcanic reservoirs show that faults and fractures control the transmission channels of natural gas, and fractures enhance porosity and permeability features of low-porosity and low-permeability volcanic reservoirs, and consequently improve the migration efficiency of hydrocarbons. Multistage volcanic eruption form eruption interfaces (discontinuous interfaces of eruption, lithologic and lithofacies interfaces); at the top of eruption interfaces, effective pores exist as a result of weathering and leaching, contributing to multiple effective reservoirs vertically, which result in the development of multilayer and multi-type volcanic oil and gas reservoirs under the same background. This innovative research results may effectively expand the exploration layers and fields of volcanic reservoirs and perfect the theories in reservoir exploration.