阿姆河盆地查尔朱阶地及邻区盐相关断裂特征与油气地质意义

Salt-related fault characteristics and their petroleum geological significance in Zarzhu terrace and its adjacent areas,the Amu Darya Basin

阿姆河盆地查尔朱阶地及其邻区在上侏罗统发育一套盐膏岩,使断裂性质与组合类型复杂多样,对油气勘探具有重要意义。通过钻井资料和地震资料的构造解释,研究了盐相关断裂发育特征及其对油气聚集成藏的控制作用。结果表明,研究区发育有盐上层和盐下层两套断裂系统,形成了盐上逆冲-盐下逆冲、盐上走滑-盐下逆冲和盐上走滑-基底卷入3种断裂组合样式。盐相关断裂受构造应力场、基底先存断裂和盐膏岩厚度控制,在盐膏岩厚度大、挤压应力强的东部地区发育有盐上走滑-盐下逆冲和盐上逆冲-盐下逆冲断裂组合样式,断裂提供了圈闭条件,未破坏盐膏岩盖层的封盖性能,对油气聚集有利;在盐膏岩厚度薄、挤压应力较弱的地区,发育了盐上走滑-基底卷入断裂组合样式,断裂发育受早期基底断裂控制,对盐下油气聚集不利。

A set of salt-gypsum rocks occur in the Upper Jurassic in Zarzhu terrace and its adjacent areas in the Amu Darya Basin, making fault and their combination types complicated, thus being of great significance for petroleum explora- tion. Through the analysis of the drilling data and seismic data, we studied the development characteristics of salt-related faults and their control on hydrocarbon accumulation. The results show that there are two fault systems in the pre-sah lay- er and above-salt layer in the study area respectively. They appear in 3 combination styles, i. e. thrust fault in above-salt layer-thrust fault in pre-salt layer, strike-slip in above-salt layer-thrust fault in pre-salt layer, and strike-slip-basement in- volvement in above-salt layer. The salt-related faults are controlled by tectonic stress field, pre-existing basement faults and thickness of salt-gypsum rocks. In the east part of the study area, where the salt-gypsum rock is thick, there develops two fault combination styles, i. e. strike-slip in above-salt layer-thrust fault in pre-salt layer, and thrust fault in above-salt layer-thrust fault in pre-salt layer. The faults provide trap conditions for hydrocarbon accumulation and do not destroy the sealing integrity of the salt-gypsum rock. While in the west part of the study area, where the salt-gypsum rock is thin and the compress is weak, there develops strike-slip-basement involvement in above-salt layer. The development of faults were controlled by the basement fault, and is destructive to the accumulation of oil and gas in pre-salt layers.