Reservoirs types,characteristics and main controlling factors of Cenomanian-Early Turonian in the South-eastern Iraq
Based on the data of drilling core,casting thin sections,mercury injection capillary pressure,physical property,scanning electron microscope and wireline loggings,the reservoir types of Cenoma-nian-Early Turonian in Southeastern Iraq were classified based on geological origin and petrophysical characteristics,and reservoirs characteristics and the main controlling factors were clarified.The results show that the reservoirs in Cenomanian-Early Turonian are divided into sedimentary type,diagenetic,sedimentary-diagenetic and composite types.Sedimentary type is developed in high-energy environ-ments,with abundant primary interparticle pores,and its physical properties are high-porosity and high-permeability,which is the first choice of the target for the development.Diagenetic type is deposited in a low-energy environment,with a large number of secondary pores formed by penecontemporaneous dis-solution and physical properties are medium-high porosity and medium-low permeability.It is an impor-tant replacement resource for long-term stable production.The depositional energy of sedimentary-diage-netic type is moderate,developing a small amount of primary intergranular pores,and penecontempora-neous dissolution forms secondary pores,with medium-high porosity and medium-permeability,and which is an important support resource to increase the production.The pores of composite types are un-der the comprehensive control of tectonics,sedimentation and diagenesis,and the physical properties are medium-high porosity and medium-permeability,which is an important perforation target in the early stage of development.During Cenomanian-Early Turonian,Southeastern Iraq is a wide and shallow car-bonate ramp,the sedimentary facies is significantly differentiated,and the penecontemporaneous dia-genesis is sufficient;during the sequence cycle,the sedimentary facies evolves rapidly,and the climate and exposure span control the type and intensity of diagenesis.Tectonism forms faults locally,and pro-motes burial dissolution.The results provide a geological basis for the evaluation and development of the thick bioclastic limestone reservoir.
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