Integrated the Core Analysis Data, Image logs, and Conventional Logs to Understand the Reservoir Rock Type of the Mauddud Formation

Abstract

Inner ramp carbonates with dolomitic limestone make up the Late Albian Mauddud reservoir in Arabian plate. The age of the Mauddud Formation is Albian–Early Cenomanian, and it overlies the Nahr-Umr Formation and the Ahmadi Formation. The depositional environments range from subtidal to lagoon and shoal environments. The main goal of this study is to integrate all the available information to recognize different rock types within Mauddud reservoir. Due to the limited core available in Mauddud reservoir, the rock types have been identified mainly based on the Full-bore formation micro imager tool. The formation micro imager readings were compared and calibrated by available core data and conventional well logs (Density Neutron).
This study concludes that there are three rock types were recognized within Mauddud reservoir: The first rock type is grainstone, which is characterized by having relatively higher porosity and permeability than rock types one and two (porosity is more than 15 pu and permeability is more than 1 mD). The second rock type is wackestone to packstone with a porosity value of between 10% and 15% and a permeability range of 0.1–1 mD. This rock type image reflection generally shows mixed laminated and fine mottled size image facies that is shown in the lagoon environment. Finally, the third one is Cemented Wackestone and Packstone which is characterized by having low porosity and permeability (Φ<10%, perm<0.1 md). The image reflection of cemented wackestone and packstone is almost like a massive image reflection. This rock type usually reflects the intertidal environment.