Year: 2026
Type: article
Abstract: Mishrif Formation, deposited during the Middle Cretaceous (Middle Cenomanian to Early Turonian), represents a major carbonate reservoir in southern Iraq. This study aims to characterize its microfacies and diagenetic evolution based on petrographic analysis of 221 thin sections obtained from wells RT-2 and RT-6 in the Ratawi Oilfield. Six principal microfacies were identified: lime mudstone, wackestone, packstone, grainstone, rudstone, and floatstone. In addition, sixteen submicrofacies were distinguished, including unfossiliferous lime mudstone, bioclastic wackestone, algal wackestone, benthic foraminiferal packstone, and peloidal grainstone. These facies reflect deposition within a range of environments, from deep marine to shallow open marine, shoal, restricted lagoon, and rudist biostrome settings. Vertical and lateral facies transitions suggest dynamic environmental shifts influenced by relative sea-level changes and synsedimentary tectonics during the formation’s development. Diagenetic processes—including dissolution, dolomitization, cementation, micritization, compaction, neomorphism, and mechanical fragmentation—played a critical role in modifying reservoir properties. Multiple porosity types were identified, such as moldic, vuggy, fracture, and channel porosity, each contributing distinctly to the pore system and overall reservoir quality. Moreover, Mishrif Formation exhibits six depositional sequences, each initiated by transgressive and highstand systems tracts. These sequences reflect recurring sea-level fluctuations, with facies stacking patterns that transition from deep to shallow marine environments. The observed progradational trend suggests a relative sea-level fall or increased sediment supply, both of which controlled sediment distribution and facies development across the studied wells.
Source: Iraqi Geological Journal
Authors: Saja A. Abdulkariem, Hamid A. Alsultan
Institution: University of Babylon
Subfield: Earth-Surface Processes
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $175
OpenAlex ID: W7126423774