Relationship between Rock Typing and Petrography - A Case Study on the Fahliyan Formation in the Persian Gulf

The Lower Cretaceous Fahliyan Formation in the Persian Gulf was the subject of this study. The main target of the study is investigation of relationship between different rock types and sedimentology study. In order to define rock types based on porosity-permeability data, hydraulic flow units were investigated based on Flow Zone Indicators (FZI). As a result, six hydraulic flow units were recognized in the Fahliyan Formation of the studied area. Moreover, productive intervals of the reservoir were identified using Normalized Cumulative Reservoir Quality Index (NCRQI).

Assessment of porosity and permeability data indicates that microfacies pertaining to shoal and channel facies belts with grain-supported texture have the best reservoir quality. This is due to abundance of interparticle porosity. These facies belts correspond with HFU-4, 5, and 6. According to Winland plot, the mentioned HFUs are comparable with macroport and megaport classes. Microfacies of tidal flat facies belt also have good reservoir quality due to fenestra porosity. Microporosity is dominant in most facies of the studied samples. The samples with microporosity pore type (such as most of the microfacies belong to shallow open marine and lagoon facies belts) do not have enough permeability to make a good reservoir zone.