川西北中二叠统栖霞组白云岩储层特征及控制因素

The dolostone reservoirs from the Middle Permian Qixia Formation in northwestern Sichuan Basin: Characteristics and controlling factors

关键词:  四川盆地西北部  中二叠统  栖霞组  白云岩储层  控制因素

Key words:  northwestern Sichuan Basin  Middle Permian  Qixia Formation  dolostone reservoirs  controlling factor

摘要:

本文以四川盆地西北部钻井岩心及露头剖面样品的镜下岩石学特征为基础,以微区多参数实验分析数据为依据,对四川盆地西北部中二叠统栖霞组白云岩储层进行了研究。认为栖霞组白云岩储层类型主要为结晶型白云岩及残余颗粒型白云岩。储集空间主要为晶间孔、晶间溶孔、粒间孔、溶蚀孔洞以及裂缝。白云岩储层的发育主要受到沉积微相、早期白云石化作用、晚期白云石化作用、溶蚀作用以及构造作用等因素控制。其中浅滩沉积微相是储层形成的环境基础;早期白云石化作用是储层保存的重要条件;溶蚀作用及构造裂缝是储层改善的关键因素;而晚期白云石的生成则对储集空间有一定的破坏作用。

Abstract:

The dolostone reservoirs in the Middle Permian Qixia Formation are dealt with in the light of petrographic and laboratory analysis of the core samples and outcrop samples collected from northwestern Sichuan Basin. The dolostone reservoirs in the Formation are composed of crystalline dolostones and residual grainy dolostones. The reservoir spaces include intercrystal pores, intercrystal solution openings, intergranular solution openings, solution pores and solution fissures. The development of the dolostone reservoirs are dominantly constrained by sedimentary microfacies, early dolomitization, late dolomitization, dissolution and tectonism. The shoal microfacies is believed to facilitate the formation of the dolostone reservoirs. The early dolomitization may be favourable for the preservation of the dolostone reservoirs. The dissolution and structural fissures may have exerted key influence on the improvement of the reservoir quality. However, the generation of late dolomites may be destructive to the reservoir spaces.