伊拉克鲁迈拉油田Mishrif组碳酸盐岩储层特征及成因

Mishrif组碳酸盐岩岩石类型主要有泥晶灰岩、生屑泥晶灰岩、泥晶生屑灰岩、生屑灰岩和白云质灰岩。储集空间为粒间(溶)孔、铸模孔、晶间孔、微孔、溶蚀缝和压溶缝。沉积环境属于碳酸盐缓坡,发育潟湖、滩后、生屑滩、生物礁、滩前和浅水陆棚6种沉积亚相。储层层间和层内非均质性严重。成岩作用主要有泥晶化作用、 准同生期胶结作用、重结晶作用、溶蚀作用、埋藏期胶结作用、压实压溶作用和白云石化作用。三级相对海平面变化影响下的相带迁移是造成层间非均质性的主要因素,五级和六级相对海平面变化影响下的差异溶蚀和差异胶结作用是控制层内非均质性的主要原因,微裂缝的存在改善了局部储层的物性。

Characteristics and genesis of carbonate reservoir of the Mishrif Formation in the Rumaila oil field,Iraq

The carbonate reservoir rocks of the Mishrif Formation in the Rumaila oil field, are mainly composed of cryptite, bioclastic wackstone, bioclastic grainstone, bioclastic limestone and dolomitic limestone with various cavities, such as intergranular (dissolved) pores, mould pores, intercrystal pores, micropores, dissolution fractures and pressure-solution fractures, The Mishrif Formation develops mainly in a carbonate ramp sedimentary environment and its main subfacies include lagoon, back-shoal, bioclastc shoal, bioherm, fore-shoal and shallow shelf. There exist severe heterogeneities in interlayers and inner layers of the reservoir. The main diagenesis types in the Mishrif Formation include micritization, penecontemporaneous cementation, recrystallization, dissolution, buried cementation, compaction-pressolution and dolomitization. The interlayer heterogeneity is mainly controlled by facies migration affected by the third-order relative sea-level change. While the main factors controlling the innerlayer heterogeneity are the differential dissolution and cementation influenced by the fifth-or sixth-order relative sea-level change. Micro-fractures dominated by tectonism can increase local porosity and permeability.