中东M油田白垩系Mishrif组碳酸盐岩储层特征及主控因素

Reservoir characteristics of carbonate rock of Mishrif Formation in Cretaceous,M Oilfield in the Middle East

基于岩心观察、铸体薄片、物性分析、压汞实验及测井资料,对中东M油田白垩系Mishrif组厚层碳酸盐岩储层特征进行研究,并明确其主控因素。结果表明:M油田Mishrif组不同沉积环境的储层物性差异显著,相同沉积环境中储层物性级差较大;储层孔隙类型多样、孔喉结构复杂,喉道分布曲线具有单模态、双模态和多模态特征;岩石结构包括颗粒结构、泥粒结构、粒泥结构、泥晶结构和细晶结构,结构组分以多样的生物介壳为主;储层内部“贼层”隐蔽性较高,地球物理方法难以有效识别;隔夹层成因多样,发育深水环境沉积型、潟湖环境沉积型、暴露风化胶结型、浅滩淋滤胶结型和潟湖暴露炭化型5类隔夹层;Mishrif组发育6期四级层序旋回,海平面升降控制沉积环境演化,并对早成岩环境具有重要影响,沉积环境不但决定岩石的结构组分和原始物性,还控制成岩演化路线;高能沉积颗粒组分含量高,原生粒间孔发育,成岩作用以溶蚀作用和胶结作用为主;低能沉积泥质组分含量高,生物扰动现象普遍,成岩作用以白云石化作用和选择性溶蚀为主。

Based on core,cast thin section,physical property data,mercury intrusion experiment and well logging,the characteristics of carbonate reservoirs of the Mishrif Formation in the Cretaceous,M Oilfield in the Middle East and its controlling factors were studied.The results show that reservoirs in different environments of the Mishrif Formation in M Oilfield have different physical properties.In the same sedimentary environment,there are large differences in the physical properties of the reservoirs,the pore throat structure was complicated,and the distribution curve had three types which are single-mode,dual-mode,and multi-modal.The structures of the reservoirs include grainstone,packstone,wackestone,mudstone and finely crystalline structures.The component is diverse bioclastic.The thief zone in the reservoir is highly concealed,which is difficult to identify by geophysical methods.There are five types of interlayers in the Mishrif Formation which developed in deep water,lagoon,exposed environment with weathering and cementation,exposed environment with leaching and cementation,and exposed lagoon with carbonization.It is concluded that the Mishrif Formation was developed in six phase sequence cycles.The sea level cycle controlled the sedimentary evolution and had an important impact on the early diagenetic environment.The sedimentation controlled not only the rock component and original physical property,but also the digenesis route.Rocks in high-energy environment usually have high grain fraction with larger amount of intergranular pores,and diagenesis were dominated by dissolution and cementation.Rocks in low-energy environment usually had have argillaceous.The primary pores were mainly matrix-hosted micropores and the bioturbation were widely developed.Diagenesis was mainly dominated by dolomitization and selective dissolution.