Characteristic of faults and its control on hydrocarbon accumulation in Laoyemiao structural belt, Nanpu Depression
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摘要: 【研究目的】断陷盆地多期断裂叠合发育对油气运移和富集差异至关重要。【研究方法】以渤海湾盆地南堡凹陷老爷庙构造带为例，基于地质分析和物理模拟实验，对多期断裂组合样式、成因及其与油气成藏关系进行了研究。【研究结果】结果表明，老爷庙构造带发育阶梯状、复合”y”型、复合反”y”型等断裂组合，其形成过程与凹陷边界断层的活动性密切相关，其中沙河街期-东营早期受北西-南东、近南北向应力场作用，形成阶梯状断裂组合，东营晚期-明化镇期叠加晚期断裂，形成复合”y”型、复合反”y”型等断裂组合。分期异向伸展的离散元数值模拟结果证实，老爷庙构造带东营组内部大套塑性泥岩层的存在是导致深层与浅层变形差异及断裂垂向叠置的关键物质因素。【结论】多期断裂叠合对油气成藏具有重要控制作用，其中早期断裂控制凹陷和构造带的形成，晚期断裂控制圈闭发育和油气运移，断裂组合样式的差异决定了油气富集层系差异。Abstract: [Objective] The superimposed development of multistage faults is very important to the difference of hydrocarbon migration and accumulation in faulted basins. [Methods] Taking Laoyemiao structural belt in Nanpu Depression, Bohai Bay Basin as an example, the fault assemblage style and its origin, the relationship between fault system and oil and gas reservoir formation were studied based on geological analysis and physical simulation experiment. [Results] The results show that Laoyemiao structural belt developed fault combinations of "ladder" type, "domino" type, compound "y" type, compound anti "y" type. The formation of fault combinations is closely related to the boundary of the fault activity, in which "ladder" type and "domino" type fault combinations formed by the northwest-southeast and nearly north-south direction stress fields in Paleogene, while compound "y" type and anti "y" type fault combinations formed because of late superposition of fracture in Minghuazhen period. The discrete element numerical simulation results show that the existence of large plastic mudstone layers in Dongying Formation is the key material factor leading to the difference of deep and shallow deformation and vertical superposition. [Conclusions] Multistage fault superimposition plays an important role in controlling hydrocarbon accumulation:early faults control depressions and structural belts, late faults control traps and hydrocarbon accumulation, and fault assemblages affect hydrocarbon enrichment strata.
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