Integrating Geological Processes and Petrophysics in Carbonate Reservoir Rock Typing

Abstract

Porosity distribution in carbonate petroleum reservoirs is commonly controlled by a combination of factors, including depositional texture, geochemical and mechanical processes. Without a clear knowledge of these parameters, the prediction of reservoir properties is speculative. Reservoir models often require the implementation of permeability-modifying coefficients to match the actual reservoir behaviour during production. The discrepancy between predicted and actual reservoir behaviour is usually poorly understood, arguably in large part because a strong, geological process-driven model is missing.

This study provides an innovative methodology to understand what has spatially and temporally controlled the distribution of porosity by back-stripping pore evolution and defining diagenetically-controlled pore fabrics. Importantly, the methodology relies on a sedimentological and structural framework which should be in place prior to such study. First, pore types and cement types should be quantified and the relationship between these parameters, lithofacies and reservoir quality should be analysed. Second, a pore fabric scheme, which considers the depositional texture, pore types and shapes and the impact of pore-filling cements should be established in order to combine these parameters in a practical manner. Third, mapping the distribution of open and cemented porosity at several key stages of the burial history and the final distribution of pore fabrics should provide the framework in which the diagenetic reconstruction can be implemented. Finally, by combining the diagenetic model and the mapped pore-fabric distribution, petrophysical rock types can be defined that honour those geological process that led to the formation of the final pore network. The methodology is introduced here using a virtual database but was previously tested on a multiscale, multimodal pore network (Lower Cretaceous oil reservoir, Middle East).

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018