冲断构造与油气聚集

Thrust tectonics and hydrocarbon accumulation

逆冲断层叠加组合形成的冲断构造带或褶皱冲断带是地壳中一种常见的构造单元,按构造环境的不同,可分为6 种基本类型。近年来对褶皱冲断带的研究取得重要进展,表现在:①成因机制,地表作用过程与褶皱冲断带演化之间的动态作用;②褶皱冲断带中的基底卷入构造与先存张性断层挤压复活(反转)的影响,基底卷入变形与盖层薄皮滑脱变形的耦合作用;③断层相关褶皱作用机制以及可以反映褶皱作用时间与机制的生长地层的结构特点;④冲断活动对油气成藏关键事件的影响和对油气藏分布的制约作用。大多数褶皱冲断带由于先存张性断层的复活表现为薄皮冲断作用与基底卷入冲断作用的联合,很多的断层相关褶皱具有复合成因,且变形机制与运动学过程随时间而变化。关于滑脱褶皱、翼旋转褶皱机制以及生长地层几何学等方面的研究成果极大地提高了对冲断带断层相关褶皱的认识。冲断作用加速了烃源岩的热演化,改善了储集岩的储集性能,提高了排烃效率,增大了运聚概率,形成了大量构造圈闭,导致油气成藏条件在空间与时间上有效匹配,形成了一系列大油气田。由于冲断构造样式与运动学特点的差异,不同的褶皱冲断带有利的油气聚集部位变化较大,油气田分布规律各异。

Reverse or thrust faulting is one of the main deformation styles. Remarkable progresses on fold-and-thrust belts have been made in recent years as follows: (1) formation mechanism of the fold-and-thrust belts, and the dynamic interaction between surface processes and fold-thrust belt evolution; (2) role of basement involvement and the contractional reactivation (inversion) of preexisting extensional faults in many thrust belts, the coupling between basement involved deformation and the sediment cover thin-skinned deformation; (3) mechanisms of fault-related folding and growth strata architectures as indicators of timing and mechanisms of folding; and (4) role of thrusting in the key factors of oil and gas pool formation, and the control of thrusting upon the distribution of oil and gas pools or fields. Many thrust-and-fold belts are combinations of both thin-skinned thrusting and basement-involved thrusting as a result of reactivation of preexisting extensional faults. Many fault-related folds appear to be hybrid structures involving changes in their deformation mechanisms through time and changes in their kinematic evolution. Recognition of the importance of detachment folding, limb rotation, and growth-strata geometries advances the understanding of thrust-belt folds. It resulted in the much more favorable association of pool formation factors in space, and much more important the best timing of the processes of pool formation, which give rise to lots of oil and gas fields in a large size. The different structural style and kinematics in the fold-and-thrust belts has primarily led to the change in the hydrocarbon fairways and enrichment of large oil and gas fields.