波斯湾盆地中白垩统Mishrif组碳酸盐岩储层特征及其发育模式

Mishrif组碳酸盐岩储层是波斯湾盆地最主要的储集层之一,储层岩石类型主要为礁滩相生物礁灰岩、生屑灰岩和含生屑泥灰岩,储集空间主要为粒间(溶)孔、晶间(溶)孔、铸模孔、表生期组构选择性溶蚀孔洞和基质微孔。储层多呈层状展布,横向上连续,边界受沉积相带约束; 纵向上发育多套致密隔夹层,呈强非均质性。储层发育与保存主要受沉积作用、成岩作用和构造作用影响。碳酸盐岩缓坡背景下发育的生物礁和生屑滩空间分布受盆地基底古构造格局控制,是优质储层分布相带。相对海平面升降旋回控制相带迁移和成岩作用差异,导致优质孔渗层与致密隔夹层交互发育。构造圈闭发育与油气充注时间的耦合有效抑制压实作用和胶结作用对储层的破坏,是储层得以保存的有利因素。

Reservoir characteristics and development model of Middle Cretaceous Mishrif Formation, Persian Gulf Basin

Mishrif Formation is one of the principal carbonate reservoirs in Persian Gulf Basin.The best reservoir conditions occur in rudist-bearing facies,such as rudstone and rudistid packstone/grainstones; other carbonate facies,such as pelagic mudstone/wackestone,bioclastic wackestone and peloidal packstones,are less significant as reservoir rocks.The reservoir spaces are mainly interparticle porosity, intercrystalline, moldic, solution-enhanced porous,fabric selectivity denudation vugs and microporosity.The reservoir is stratified and continuous in lateral,and distribution is controlled by depositional facies boundaries.Tight limestone as flow baffles and barriers distributed within the sequence is the main cause for extremely vertical heterogeneity of the reservoir.Primary deposition,later diagenesis and structural deformation control the porosity development and preservation.The main reservoir facies,such as patch-reefs and rudist shoals,are deposited in carbonate ramp,which distribute directly related to palaeogeomorphology.The cyclicity of the relative sea-level changes controls the migration of reef-shoal facies and diagenetic evolution,which further determine the development of porous layers and tight layers and the feature of significant heterogeneity.The formation of trap well matches the injection of hydrocarbon,which restrains the damages of compaction and cementation to reservoir effectively.