富油凹陷压力结构成因机制与油气运聚关系

Pressure structure refers to the superimposed relationships, the morphological characteristics and the transition relationships between different vertical overpressure systems, which is the external comprehensive performance of multiple mechanisms, such as overpressure formation and fluid released. Therefore, it is significant for hydrocarbon geology and exploration to analyze pressure structure formation mechanism. In this application, taking Zhanhua Depression in Bohai Bay Basin as research area, pressure structure and morphology types are divided based on accurate prediction of strata pressure. Combined with geological statistics, basin simulation and laboratory simulation technology, overpressure evolution pattern and pressure structure evolution model controlled by disequilibrium compaction and hydrocarbon generation during the burial process is established. Thus, the influence of overpressure formation mechanism on pressure structure can be illustrated. In addition, according to the observation and test of fluid inclusion, scanning electron microscopy, geochemical tests and other technologies, pressure structure evolution under different fluid releasing media can be studied, such as sealing beds, faults (fractures), beddings and sand body. Subsequently, the opening dynamic conditions under different fluid media can be recovered as well. Consequently, pressure structure formation mechanisms and its hydrocarbon geology significance can be revealed, and hydrocarbon migration-accumulation model controlled by the pressure structure can be established combined with hydrocarbon migration tracer technique. This research favors to probe the differentiation of pressure structures characteristics under different fluid release mechanisms and overpressure origin, which provides important references for hydrocarbon distribution prediction in overpressure basin.

压力结构是指垂向上超压系统的叠置关系、形态特征以及压力系统间的过渡关系，是超压成因、流体释放等多种机制的外在综合表现，剖析压力结构成因有利于揭示其油气地质意义，指导油气勘探。本申请拟以渤海湾盆地沾化凹陷为例，在地层压力精细预测的基础上，划分压力结构类型和压力曲线形态样式。结合地质统计、盆地模拟和实验室模拟，建立基于埋深过程中欠压实作用和生烃作用的超压演化模式与压力结构演化模型，明确超压成因机制对压力结构的影响；通过包裹体观察与测试、扫描电镜、地化测试等技术，分析封闭层、断裂（裂缝）、层理以及砂体等不同流体释放介质下压力结构的演化，恢复各类流动介质的开启动力条件。综合研究，揭示压力结构的成因机制及其油气地质意义，结合油气运移示踪，建立压力结构指示下的油气运聚模式。通过本项研究，有利于探索超压成因与流体释放机制下压力结构的特征差异，为超压盆地油气分布预测提供重要借鉴。

含油气盆地超压发育，生烃演化和流体释放的差异造成发育复杂的压力结构，影响着油气的聚集和分布。基于含油气盆地超压特征分析，明确了富油气盆地压力结构发育特征，利用测井响应、地质统计、盆地模拟和理论分析，厘定了富油气盆地超压成因，建立了不同超压成因下压力结构演化模型，结合油气分布，明确了不同压力结构下油气分布样式，综合油气来源分析、封闭层裂缝、活动断层发育特征、地化示踪等，揭示了压力结构对油气运聚的控制作用，建立了压力结构控制下的油气运聚模式。.结果表明，渤海湾盆地垂向发育多个压力系统，与烃源岩具有良好的对应关系。平面上发育常压型、单超压型、底部强双超压型和顶部强双超压型凹陷，微观上存在漏斗形、复杂漏斗形、钟形、丘状、箱形和箱-钟复合型单超压体，空间分布存在差异。生烃增压是富油气盆地超压的主要成因，有机质丰度和演化程度控制了生烃增压强度。不同压力结构下流体释放介质存在差异，漏斗形压力结构顶部泥岩封闭层封闭性强，有利于封堵油气，油气在底边界聚集；钟形压力结构顶部封闭层高角度裂缝发育，油气易向上运移在封闭层内聚集；丘状压力结构油气运移动力强，封闭层内发育相互连通的高角度裂缝，油气分布于超压体上方；复杂漏斗形压力结构受膏盐封闭层封堵，封闭性强，油气难以突破封闭层向上运移，在超压体内聚集；箱形压力结构泥岩厚度较大且连续发育，油气多在超压体下部聚集；箱-钟复合压力结构指示断层垂向封闭性强，油气垂向集中在超压体底边界。该研究成果阐明了微观压力结构样式及其成因机制，揭示了压力结构与油气运聚的本质联系，丰富了超压盆地油气成藏理论，为超压盆地油气分布预测提供了理论依据。