Consideration of Micrite Texture and its Relationship with Microporosity Development and Reservoir Quality, Dariyan Formation, Central Persian Gulf

The focus of this study is on the facies, sedimentary environments, diagenetic processes and microporosity of Dariyan Formation in three wells of one field in central Persian Gulf. The results showed that the Dariyan Formation is made from six microfacies and has been deposited in six sub-environments. Regarding the sub-environments of the microfacies, lack of widespread carbonate shoals, gradational change of facies into one another, lack of talus sediments and slumping structures, these facies have been deposited in a carbonate ramp environment. Consideration of the diagenetic processes in this formation showed that sediments experienced marine, meteoric and burial diagenesis. Regarding the mud-dominated nature of the most samples, marine diagenesis has no considerable effect on them while meteoric effect is significant. The meteoric diagenesis caused dissolution of grains and increased roundness of micrites. The resulted empty voids have been cemented with calcite in burial diagenetic environment. No considerable porosity is visible in petrographical studies while routine core porosity measurements show high empty spaces. This proves the role of microporosity as the main pore type in these samples. Study of mud-dominated samples with scanning electron microscope showed that the micrites are rounded with punctic contacts and this caused creation and remaining of high porosity amount in the samples. Consideration the relationship between facies, sedimentary environments and microporosity in this formation shows that this type of porosity exists in all mud-dominated facies and increase with increasing depth of deposition and resulted increasing micrite content.