济阳坳陷断裂活动和CO_2气藏的关系研究

A STUDY ON RELATIONSHIP BETWEEN FAULT ACTIVITY AND CO_2 POOLS IN THE JIYANG DEPRESSION

济阳坳陷在惠民凹陷和东营凹陷的地壳中各存在1个低速体，位于惠民凹陷上地壳底部的低速体是坳陷内已经发现火成岩的岩浆房以及CO2的气体库。凹陷的边界断层在10～12km±的深度其倾角变得平缓，并以韧性剪切方式沿拆离带向下延伸。拆离带内岩石多为糜棱岩，在岩石圈上部巨大的压力作用下，呈现韧性状态的拆离带是良好的封盖层。由于拆离带的作用，沿岩石圈下部裂缝上升的岩浆和气体等在拆离带下部聚集而形成低速体。在地壳相对较稳定期，拆离带也处于较稳定阶段并起分隔作用；如果地壳发生拉分作用，则低速体也会随之发生暂时性破裂，从而导致低速体内的岩浆和气体运移、聚集和成藏。郯庐断裂是间接的成气断裂，埕南断裂及惠民凹陷内地幔隆起区上地幔及下地壳张性断裂是直接的成气断裂；高青-平南断层以及商店-平方王断层等为输气断裂；临邑-商河断层、林樊家断层和齐河-广饶断层等是有利的输气断裂。

Two low-speed bodies existed in the crust of the Huimin Sag and the Dongying Sag, Jiyang Depression, among which the upper layer of the Huimin low-speed body was source areas of the igneous rocks and the CO2 gas. Boundary faults of the two sags became stretch gently dip below the depth of 10 - 12 km and stretched by a mode of ductile shearing along the detachment belt, and along which mylonite was dominant rock. The detachment belt, under a situation of ductility since a giant pressure of upper lithosphere, should be a good seal-cap rock. As a result of magma and gas going up along fissures or faults in lower part of lithosphere, they congregated and created the low-speed body in lower part of the detachment belt. During the stable period of crustal movement, the detachment was relatively stable and acted as a seal. If the crust extended and broke up, the magma and gas in the lower-speed body would migrate, concentrate and accumulate. The Tan-Lu fault zone was an indirect gas-source fault for the CO2 gas in the studied area, while the Chengnan fault and the extensional faults in upper mantle and lower crust of mantle upheaval area of the Huimin Sag were direct gas-sourcing ones. The GaoqingPingnan and Shangdian-Pingfangwang faults were gas-supply faults, and the Baiqiao, Linyi- Shanghe, Linfanjia, Qihe-Guangrao and Shicun faults might be prospective gas-supply faults.