黄骅坳陷南区古生界天然气聚集的构造约束条件

黄骅坳陷南区古生界天然气主要源于同期的海相―海陆交互相煤系地层。该区古生界天然气经历了复杂的运移和充注过程,这些过程贯穿在整个中生代和新生代构造演化史中。气藏的聚集过程和充注机制以及重组期间的迁移路径不可避免地受到印支、燕山和喜山旋回构造的约束。印支―早燕山阶段古生界逆掩和走滑构造是研究区煤系烃源岩排烃和中生代、新生代早期油气藏分布的关键约束条件――为天然气聚集提供着必要的驱动应力和充注通道。而第三纪断块翘倾和构造反转活动则约束着天然气的再充注形式和控制着早期油气藏的改造与重组。黄骅坳陷南区天然气藏的最终分布、聚集特点及分布形式受古生界复杂断裂体系和储层非均质性的影响,并表现出了隐蔽油气藏的某些特点,但与第三纪晚期定型的构造圈闭无关。

LIMITED TECTONIC CONDITIONS FOR NATURAL GAS ACCUMULATION IN PALEOZOIC GROUP IN SOUTHERN HUANGHUA DEPRESSION

Natural gases gathered in Paleozoic group in southern Huanghua depression, which sourced from contemporaneous coal-bearing series in marine or limnic sequences, experienced complicated migration and charging history along with tectonic evolution through Mesozoic-Cenozoic era. The accumulation process, filling mechanics and alteration of remigration pathway for reconstructing of gas pool are inevitably controlled by structural deformation during Indosinian, Yanshanian and Himalayan cycle. The thrust and strike-slip event during Indosinian and early Yanshanian are boundary conditions of hydrocarbon discharging from coal-bearing sources, and of distributing of early gas pools which formed late Mesozoic and early Cenozoic, by providing essential dynamic stress and drainage channels. Meanwhile, the fault-block rotation and reversing tectonic movement during Cenozoic era limited gas recharging style, dominated reconstruction of early gas pool. In this paper we argue that the final accumulation tapes and distribution styles of gas pools in southern Huanghua depression showed some characteristics of subtle ones, due to complex fault system and heterrosphere of reservoir in Paleozoic horizon, and most probably irrelevant to structural traps formed in later Cenozoic.