四川盆地东部多重滑脱构造变形系统及其控油气作用

East Sichuan Basin is one of the large gas province in the extensive intra-continental deformation setting, and boasts for its series of discoveries both the conventional gas and shale-gas in the recent years. To disclose the characteristics of large hydrocarbon accumulation in a relatively stable area under complex tectonic zone is not only an important reference to petroleum exploration in China, and but also a key basis for addressing the deformation mechanism of South China continent. Guided by the new advances of continental dynamics and rheology, the proposal is based upon the large quantities of exploratory wells, geophysical data and geological surveys, makes systematic rock mechanic tests and seismic interpretation, utilizes the methods of analogue modeling and mathematical modeling, firstly to explore the distribution of detachment zone and its deformation mechanism, and chiefly to study the formation and evolution of the multi-level detachment structural deformation system (MDS), and successively to analyze its controls upon the geological conditions for the oil and gas, and to explore the rules for the multi-layer and poly-type hydrocarbon accumulations. To establish a series of structural cross sections covering the whole East Sichuan Basin, the proposal constructs the geometrical and kinematic models, and discusses the mechanics of the deformation. It is also to reconstruct the temperature field, the fluid pressure field, and the stress field during the geological history, analyze the fluid migration, especially of the migration crossing the detachment-zone boundaries, locate the oil and gas preserving units, and explore the accumulation mechanisms in the different stratigraphic layers in the MDSs.

四川盆地东部是强烈陆内变形环境中的一个大型含气区，近年来，常规气与页岩气勘探都取得重要进展，揭示这一“复杂构造区相对稳定单元的大型化油气聚集”特征对于我国油气勘探有重要借鉴意义，对探讨华南大陆变形机制将提供重要依据。本项申请立足该区大量的钻井、地球物理与地质调查资料，以系统的岩石力学测试和地震资料解释为基础，应用构造物理模拟与数值模拟方法，以大陆动力学、流变学的新进展为指导，以研究滑脱层的分布与变形机制为出发点，以多重滑脱构造变形系统的形成演化研究为核心，剖析其控油气作用，探讨多层系、多类型油气聚集与分布规律。本项研究将建立覆盖川东地区的系列构造地质大剖面，开展构造几何学与运动学建模，揭示构造变形的力学机制；重建地质历史时期的“温度场、压力场与应力场”，探讨多重滑脱系统的流体运移尤其是跨层运移特点；剖析油气保存单元及其分层聚集机制。

四川盆地东部是强烈陆内变形环境中的一个大型含气区，近年来，常规气与页岩气勘探都取得重要进展，揭示这一“复杂构造区相对稳定单元的大型化油气聚集”特征对于我国油气勘探有重要借鉴意义，对探讨华南大陆变形机制将提供重要依据。本研究立足该区大量的钻井、地球物理与地质调查资料，以系统的地震资料解释为基础，应用构造物理模拟与数值模拟方法，以研究滑脱层的分布与变形机制为出发点，以多重滑脱构造变形系统的形成演化研究为核心，建立了覆盖川东地区的系列构造地质大剖面，开展了构造几何学与运动学建模，剖析油气保存单元及其分层聚集机制。取得的主要认识为：.①川东-湘鄂西地区中生代以来构造变形具有穿时递进扩展特征，从湘鄂西地区向川东地区具有整体逐渐变年轻的趋势。印支末期（~201Ma）湘鄂西褶皱带南东边缘具构造雏形，晚侏罗世至早白垩世（201Ma -145Ma）为桑植-石门构造带、南北镇构造带和宣恩构造带依次形成时期；早白垩世至晚白垩世（145Ma-100Ma）恩施构造带、利川构造带与川东隔档式背斜开始隆起；晚白垩世（100Ma-75Ma）之后川东-湘鄂西地区快速隆升，构造样式基本定型的时期。.②川东-湘鄂西地区构造在平面上具有明显的分带性，由南东向北西发育隔槽式褶皱带、槽档过渡带与隔档式褶皱带，卷入变形地层逐渐变新，变形强度依次减弱；在垂向上呈分层变形特征，被寒武系膏盐层、志留系泥岩、二叠系煤系地层与三叠系膏盐层等4套区域性分布的滑脱层垂向分隔，形成基底、深部、中部、浅部4套构造变形层，湘鄂西隔槽式褶皱带构造变形受控于基底变形层中的大型基底逆冲断层，川东隔档式褶皱带变形受浅部三叠系膏盐层活动影响更强。.③川东-湘鄂西地区的变形符合临界楔形角理论，且基底滑脱层相互联结并逐步抬升是研究区构造变形与褶皱叠加的主要形成机制。.④提出多重滑脱构造体系下相对稳定保存单元作为可能的油气聚集带，中、深部滑脱体系为有利勘探区带。