The Material and Energy Effects of Neotectonics/Late-stage Tectonics and Petroleum Accumulation

HAO Fang~ 1,2) , ZOU Huayao~ 1) , GONG Zaisheng~ 3) , FANG Yong~ 1) 1) Key Lab for Hydrocarbon Accumulation Mechanism in the Ministry of Education, China University of Petroleum, Beijing, 102249; 2) Department of Petroleum Geology, Faculty of Earth Resources, China University of Geosciences, Wuhan, 430074; 3) China National Offshore Oil Corporation, Beijing, 100027  

Neotectonics is defined as tectonic motions since the Late Miocene (about 5.2 Ma) in Cenozoic basins, and late-stage tectonics is defined as tectonic motions since the beginning of the Tertiary in superimposed basins in this paper. Neotectonics/late-stage tectonics behaves differently in different basins due to different plate-tectonic settings and different deep-crustal processes. Neotectonics/late-stage tectonics may considerably affect the hydrocarbon-generation potentials of source rocks, reservoir-seal assemblages, fluid conduit frameworks and the nature of traps, producing important material effects. Neotectonics/late-stage tectonics may also considerably affect thermal fields, pressure and stress regimes, producing strong energy effects. The roles that neotectonics/late-stage tectonics may play in petroleum accumulation depend on the stages of hydrocarbon generation and expulsion of the source rocks, the dynamic nature of neotectonics/late-stage tectonics, the velocity and amount of sedimentation or erosion during the neotectonics/late-stage tectonics, and the activity of the faults. During the construction stage, neotectonics/late-stage tectonics, combined with overpressure, may result in non-steady, cross-formation petroleum migration and rapid petroleum accumulation, leading to the enrichment of petroleum in shallow (young) reservoirs and in tectonically active belts or stress-relief structural zones. During the reform stage, neotectonics/late-stage tectonics with strong fault activity may lead to abrupt cross-formation re-migration of accumulated petroleum, forming secondary petroleum reservoirs. Neotectonics/late-stage tectonics with no fault reactivation may lead to intra-reservoir re-migration (adjustment) of accumulated petroleum, forming a series of genetically-related petroleum layers with complicated oil/water or gas/water contacts, complicated relationship between oil/gas saturation and porosity and permeability of reservoir rocks. Neotectonics/late-stage tectonics may play constructive, adjusting or even destructive role in petroleum accumulation, depending on the stage of the basin evolution and the nature of the neotectonics/late-stage tectonics.

【Fund】： 国家“973”重点基础研究发展规划项目(编号G1999043309);; 国家自然科学基金重点项目(编号40238059)资助的成果
【CateGory Index】： P546;P618.13

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