伊拉克M油田白垩系Mishrif组沉积特征及控储机理

为明确伊拉克M油田白垩系Mishrif组碳酸盐岩储层成因，基于岩芯观察、铸体薄片、物性分析及测井资料，通过沉积微相分析确定研究区沉积环境，系统分析不同沉积相储层特征。结果表明:M油田Mishrif组为带障壁的缓坡环境，包括潟湖边缘坪、潟湖、台内滩、滩后、潮道、浅滩、滩前及开阔浅海。中、高渗储层主要发育于浅滩和滩前等高能沉积环境，储集层以粒间孔和粒间溶孔为主，发育大孔喉，生屑滩储集层和滩前储集层物性分布区间较大。潟湖边缘坪、潟湖、台内滩及滩后等低能沉积环境以低渗和特低渗储集层为主，孔隙度跨度大，孔隙类型主要为基质微孔、颗粒微孔、铸模孔和粒间孔，以微喉和中喉为主，喉道分选较好。综合分析认为:沉积相通过控制沉积物的结构组分控制了岩石的成岩演化。高能沉积型储集层以溶蚀作用和胶结作用为主，储集层物性是胶结物对孔隙和喉道充填封堵程度的函数；低能沉积型储层是生物多样性和差异成岩作用的结果，选择性溶蚀作用、与生物扰动相伴生的白云化作用、泥晶化作用、胶结作用、非选择性溶蚀作用和混合白云化作用形成的复杂孔隙控制了储集层物性。

Sedimentary Characteristics and Control in Reservoirs in the Cretaceous Mishrif Formation,M Oilfield,Iraq

To clarify the genesis of the Cretaceous Mishrif Formation carbonate reservoirs in the M oilfield， Iraq， analyses were carried out based on core samples， casting thin sections， experimental data and logging. Systematic microfacies analysis was used to determine the depositional environment， in particular the differences between facies in the reservoir rock. This showed that the Mishrif Formation in M oilfield was a ramp with barrier shoal， in which a lagoon margin flat， lagoon， point shoal， back shoal， tidal channel， barrier shoal， the front shoal and the open shallow shelf were identified. The medium? and high?permeability reservoirs were mainly developed in high?energy environments such as the barrier shoal and the front shoal， in which the bioclastic reservoirs and the front shoal reservoirs exhibit a broad range of physical properties. The pores in the high?energy reservoirs are mainly intergranular and dissolved?pore types， with large pore throats developed. The low?energy reservoirs in the lagoon margin flat， lagoon， point shoal and back shoal possess a wide porosity range， and are mainly of low? or ultra?low permeability. The pore types were mainly matrix?host micropores， granular?host micropores， moldic pores and intercrystalline pores. The throats are mainly micro?throat size， and the sorting is better. From this it was concluded that the facies controlled the diagenesis via their components. The diagenesis in the high?energy environment was mainly dominated by dissolution and cementation. The physical properties of the reservoirs were a function of the pore and throat cementation The strong heterogeneity of the low?energy environment reservoirs is the result of differential diagenesis. Complex pores developed by selective dissolution， and dolomitization associated with bioturbation， mud crystallization， cementation， non? selective dissolution and Dorag dolomitization influenced the reservoir property.