赵县背斜油藏成藏机理及油气分布规律探析

赵县背斜位于冀中坳陷晋县凹陷，是富集油气的底辟构造，为多种原油性质、多种类型油气藏的复式油气藏集合体。该背斜形成的物质基础是存在早第三纪早期发育的比较稳定的膏岩和膏泥岩塑性地层，其形成机制是塑性地层底辟拱升和区域性右旋拉张构造应力场作用下发生的滑脱拉张。该背斜核部及北翼以中部生油洼槽为烃源区，因主要油源层为盐湖相沉积，成烃机理为沥青热降解，所以成为重质稠油聚集区；背斜南翼以南部生油洼槽为油源区，其主要油源岩属于淡水—微咸化湖沉积，成烃机理为干酪根热降解，因此成为中—轻质稀油聚集区；东翼以自生自储油气源为主，因其油源岩发育于两种沉积环境的过渡区，两种成烃机理均可形成原油，故成为中质常规油聚集区。在分析成藏机理和油气分布规律的基础上，提出下步勘探的３个重点方向：①尚未钻探的背斜北翼地堑构造，主要寻找Ｅｓ３—Ｅｋ１的构造油藏；②背斜南翼构造低部位，主要寻找Ｅｓ３、Ｅｓ４—Ｅｋ１的岩性油藏、地层超覆油藏等非背斜油藏；③背斜东翼构造高部位，主要寻找Ｅｓ４—Ｅｋ１中下部的构造油藏和非背斜油藏。图４参３（梁大新摘）

A discussion on the forming mechanism of Zhaoxian anticlinal oil pool and the distribution of its oil and gas.

Zhaoxian anticline is a oil and gascontaining diapir structure located in Jinxian sag, Jizhong depression. It is a collection of composite oil and gas traps with multiple oil properties and multiple types of oil and gas reservoirs. The material base forming this anticline is the rather stable gypsalyte or gypsomuddy plastic formation developed in Early Tertiary. Its forming mechanism is sliding tension caused by an arching movement combined with dextrostructural stress. The oil source region for the core and north wing of the anticline is the central oil source trough, because the main source beds are saltlake phases and the mechanism of oil generation is the thermal degradation of bitumens, heavy oil accumulation region was resulted in. The oil source region fEk1. Zhaoxian anticline or the south wing is the south source region, its main source formations are fresh waterbrackish lake phases, and the mechanism of oil generation is the thermal degradation of kerogen; and therefore mediumlight oil accumulations formed. In the east wing, major oil came from the source rocks which are also the reservoirs there, source rocks developed in a transitional region of 2 depositional environments, both 2 mechanism of hydrocarbon generation existed and therefore medium conventional oil accumulations were resulted in. Based on an analysis of forming mechanism of pool and the distribution regularity of oil and gas, 3 important targets in next exploration are suggested: grabens in north wing which have not been drilled, mainly to find out structural pools in Es3 Ek1; low part in the south wing, mainly to find out nonanticlinal oil pools like lithological and stratigraphic overlap traps etc. in Es3, Es4 Ek1; in structurally high part of the east wing, mainly to find out the anticlinal as well as non anticlinal pools in middle lower part of Es4