伊宁凹陷中二叠统含膏岩层的形成及其对油气勘探的意义

Formation of middle Permian gypsum bearing strata in Yining sag and its significance for oil and gas exploration

通过岩石组合、古生物特征等对伊宁凹陷古气候进行分析,结合微量元素特征推断古环境,证实了伊宁凹陷中二叠世为炎热干燥的咸水沉积环境,具备形成含膏岩层的地质条件,并在野外露头和钻井资料中发现了一套厚约50 m的含膏岩层,对伊宁凹陷的油气成藏形成良好的保存条件。含膏岩层下伏地层发育一套以浮游生物和藻类来源为主的较好烃源岩,具备大量生烃的地质条件;同时,含膏岩层对油气具有良好的封盖作用。综合分析认为,含膏岩层下伏地层是油气生成、运聚、成藏的有利层系,也是伊宁凹陷二叠系油气勘探的重点层系。

The paleoclimate of Yining depression is analyzed by rock assemblage and paleontological characteristics.In combination with the analysis of the paleoclimate of Yining sag and the trace element characteristics,it is confirmed that the middle Permian in Yining sag is a hot and dry saline water sedimentary environment,which has the geological conditions for the formation of gypsum bearing strata.A set of gypsum bearing strata with a thickness of about 50 m is found in the field outcrop and drilling data,which is of good preservation conditions for hydrocarbon accumulation in Yining sag.A set of high abundance and high-quality source rocks,mainly from plankton and algae,are developed in the underlying strata of the gypsum bearing strata,with a large number of geological conditions for hydrocarbon generation.Meantime,the gypsum bearing strata have a good sealing effect on oil and gas.Comprehensive analysis shows that the underlying strata of the gypsum bearing strata are the favorable strata for oil and gas production,migration and accumulation,and accumulation,and also the key strata for oil and gas exploration of Permian in Yining sag.