Researchers have uncovered the vital role of mysterious Lithocodium–Bacinella algae in shaping the reservoir quality of the Early Cretaceous Yamama Formation in southern Iraq. This discovery sheds new light on the complex interplay between microfacies and diagenetic processes that determine the heterogeneity of this important hydrocarbon-bearing carbonate reservoir.
Uncovering the Complexity of the Yamama Reservoir
The Yamama Formation in southern Iraq is a significant carbonate reservoir that has long captivated the attention of geologists. Researchers from the University of Miskolc in Hungary have conducted a comprehensive study, combining well log analysis and detailed petrographic examination, to unravel the complex factors influencing the reservoir heterogeneity of this formation.
The Pivotal Role of Lithocodium-Bacinella Algae
One of the key findings of this study is the pivotal role played by the enigmatic Lithocodium-Bacinella algae in shaping the reservoir quality of the Yamama Formation. These calcareous organisms, which thrived in shallow, warm marine environments during the Cretaceous period, formed extensive buildups and patches within the formation, significantly impacting its porosity and permeability.
The researchers identified seven distinct microfacies within the Yamama Formation, with the Lithocodium-Bacinella float/boundstone and reefal bioclastic rudstone facies (MF2 and MF4) accounting for a remarkable 45% of the studied intervals. These facies, characterized by their encrusting growth habit and sediment-trapping capabilities, exhibited excellent reservoir properties, including high porosity and permeability.
Deciphering the Diagenetic History
The study also delved into the complex diagenetic history of the Yamama Formation, which played a crucial role in enhancing or diminishing the reservoir quality. Early dissolution processes created secondary porosity in the form of vugs and channels, while subsequent cementation, compaction, and pyritization led to the occlusion of pore spaces in certain intervals.
Interestingly, the early formation of isopachous cement around the Lithocodium-Bacinella grains helped protect the porosity from the effects of compaction, contributing to the overall preservation of the reservoir quality in these facies.
Implications for Hydrocarbon Exploration and Production
The findings of this study have significant implications for the exploration and development of the Yamama Formation’s hydrocarbon resources. By identifying the critical role of Lithocodium-Bacinella buildups in defining the best reservoir units, the researchers suggest that targeting these features, particularly in the northeastern part of the Ah’Dimah Oilfield, could be a promising strategy for future field development.
Moreover, the detailed understanding of the depositional environments and diagenetic processes shaping the Yamama Formation’s heterogeneity can aid in optimizing hydrocarbon exploration and production strategies, enabling more efficient recovery of the trapped hydrocarbons.
Author credit: This article is based on research by Abbas Mohammed, Felicitász Velledits.
For More Related Articles Click Here
