断弯褶皱和断展褶皱中的油气运移聚集行为

断弯褶皱和断展褶皱是前陆冲断带中的两种典型构造形式.运用有关断层中流体运移和封堵理论及方法,结合塔里木盆地库车前陆冲断带的油气勘探实例,对断弯褶皱和断展褶皱中油气运移和聚集行为进行分析讨论.初步认为断展褶皱中的油气运移与聚集能力优于断弯褶皱。具体特征表现在断弯褶皱中是:1)台阶状逆断层具有较强的封堵能力,使得其上、下盘构造被隔离为两个不同的油气运移与聚集体系;2)上盘背斜圈闭中的油气主要来自于褶皱后翼的向斜凹陷;3)背斜圈闭中的储层有可能被轴面变形条带分隔为3个隔离油气舱;在断展褶皱中其特征是1)断层端点的扩展作用过程,就是在断层阀机制作用下,油气沿断层带从下部地层向上部背斜核部运移输送的过程.2)断层上、下盘及背斜两翼可以构成一个统一的油气运移聚集体系.3)背斜储层中的油气往往处于异常流体压力状态.

Hydrocarbon Migration and Accumulation Behaviour in Fault-Bend Folds and Fault-Propagation Folds

Fault-bend folds and fault-propagation folds are typical structural styles in the foreland thrust belts. Based on theories and methods of fluid migration/sealing in fault zones, the hydrocarbon migration and accumulation behavior in fault-bend folds and fault-propagation folds is discussed, taking example by Kuqa foreland thrust belt of Tarim basin in this paper. We recognize preliminarily that hydrocarbon migration/ accumulation potential of fault-propagation fold is better than that of fault-bend fold. In fault-bend fold, its features are as follows: (1) because the step-thrusts possess very capable sealing, hanging-wall and footwall parts are divided into two different hydrocarbon migration/accumulation systems; (2) Oil and gas in the hanging-wall anticline trap come largely from the syncline depression behind the anticline; (3) The reservoir trap in the anticline can be separated into three isolated hydrocarbon compartments. In fault-propagation fold, its features are as follows: (1) the propagating process at tip of fault gives rise to that oil and gas migrate from lower strata to upper anticline under the fault-valve mechanism; (2) Hanging-wall/footwall parts and two limbs of anticlinemake up an united oil-gas migration/accumulation systems; (3) Oil/gas in the anticline often has abnormal fluid pressure.