库车坳陷白垩系含油气系统与高压气藏的形成

CRETACEOUS PETROLEUM SYSTEM AND HIGH PRESSURE GAS RESERVOIR FORMAT ION IN KUCHE DEPRESSION

库车坳陷形成于中新生代 ,具有克拉通边缘和造山带前缘双重结构。结构上貌似通用的前陆盆地 ,但二者具有本质的区别 ,称之为坳陷可能更加科学并符合实际。目前它仍是塔里木盆地的组成部分。库车坳陷具备大气田形成的基本条件 ,白垩系砂岩和第三系膏盐岩构成的油气系统是库车坳陷主要富气系统。储层、盖层分布范围 ,成熟烃源岩展布范围以及油气运移边界共同限定了油气系统的展布范围。根据其成藏特征 ,将该系统北部的逆冲推覆带划为白垩系异常高压区 ,油气以垂向运移为特征 ;南部的前缘隆起带划分为白垩系正常压力区 ,油气以侧向运移为主。克拉 2气藏为典型的异常高压干气藏 ,高压的成因与气藏的抬升和构造挤压有关 ,干气是烃源岩高成熟演化阶段的产物。

Kuche Depression was formed in Mesozoic-Cenozoic, being of dual-structure which is composed of cratonic margin and front orogenic belt. It seems to be a common fore land basin structurally, however there is an essential distinction between both of them. It may be more scientific and more corn formable to reality to call it depression. Now, it is still a part being comprised in Talimu Basin. The Kuche Depression is of the basic conditions of forming giant gas fields and the petroleum system which is composed of the Cretaceous sandstones an Tertiary evaporites if the major rich-in-gas system in the depression. The petroleum system is limited to the area controlled b the ranges of the reservoir beds, caprocks and matured hydrocarbon source rocks and by the oil and gas migration boundary. According to the characteristics of reservoir formation, the thrust nappe structural belt in the north part of the system is classified as the Cretaceous abnormal high pressure area with the character of vertical oil and gas migration and the front uplift belt i its south part as the Cretaceous normal pressure area with the character of lateral oil and gas migration. Kela-2 gas reservoir a typical abnormal high pressure dry gas reservoir, the high pressure being related to the structural rising and tectonic corn pression, and the dry gas being the products generated at the high maturity step of hydrocarbon source rock evolution.