塔里木盆地寒武系膏盐岩对盐下白云岩储层的影响

塔里木盆地寒武系盐下白云岩作为重要的战略接替区已成为近年来的研究热点.前人主要集中对寒武系白云岩的形成机制和膏盐岩的封盖作用进行了研究,而关于膏盐岩对白云岩储层的影响则少有涉及.本文总结了塔里木盆地寒武系白云岩储层特征,同时探讨了膏盐岩对白云岩储层的影响机制,以期为寒武系盐下白云岩勘探提供指导.塔里木盆地寒武系白云岩主...

The impact of gypsum salt rock on Cambrian subsalt dolomite reservoir in Tarim Basin

The Cambrian dolomite in Tarim Basin has become focus in recent years as the significant strategic area. Previous studies have mainly focused on the dolomitization mechanism and the capping effect of salt rock. However, studies of the impact of salt rock on the dolomitization and reservoir formation are very rare. In this study, the authors summarized the dolomite reservoir characteristics of Cambrian Tarim basin and discussed the impact of salt rock on the subsalt dolomite. The Cambrian dolomite in Tarim basin can be classified into two major types, i.e. crystalline dolomite and microbial dolomite. The crystalline dolomite can further be divided into dolomicrite, crystal dolomite and granular dolomite. The microbial dolomite can be divided into thrombolites dolomite, stromatolite dolomite and foamite dolomite. Influenced by salt rock, the dolomite reservoir can be classified into anhydrite dissolved pores type reservoir, intercrystalline pores type reservoir and intercrystalline dissolved pores type reservoir. The salt rock mainly exerted impact on the dolomitization process and the formation of reservoir pores. The precipitation of gypsum and anhydrite in evaporated flat settings increased the Mg²⁺/Ca²⁺ ratio in the formation fluid, which was favorable for the dolomitization. Besides, the reduction of SO₄^2- influenced by microbial action promoted the precipitation of dolomite. In the aspect of impact on reservoir, the anhydrite dissolved pores were normally good reservoir space, the relative high thermal conductivity was favorable for the retrograde solution of dolomite, the dissolution of sulfate in near-surface condition was favorable for the precipitation of dolomite, and thermochemical sulfate reduction produced sour gas to form dissolved pores.