Porosity Type Quantification and Rock Typing of Ediacaran Complex Carbonate Reservoir (Khufai) Using Advanced Bore Hole Image Analysis

Abstract Carbonate reservoirs are famous of being notorious and complex, and challenging for modeling. The Ediacaran Khufai formation is one of the oldest commercially proven petroleum plays in the world located in sultanate of Oman. It Imposes challenges in sub surface characterization due to its post depositional diagenetic and structural overprints. A holistic approach is necessary to capture different scales of the heterogeneities and complement the traditional Petrophysical evaluation in a feedback loop to modeling. A Methodology developed on two key pillars; The first one lies in identification and quantification of different rock fabrics, which specifies the porosity type: matrix, fractures and vugs that are not easily quantified using conventional open hole logs without a full core. Secondly, linking each of these rock fabrics to a specific petrophysical workflow for the fundamental reservoir petrophysical properties, water saturation and permeability. The high-resolution borehole images complement the conventional petrophysical evaluation. It provides high vertical and azimuthal resolution Images for geological features like natural fractures and textural information with its spatial arrangement in the borehole wall. The high-resolution images’ quantitative heterogeneity mapping and partitioning of matrix and vugs/fractures showed a good match with core analysis allowing an integration of conventional petrophysical logs. It was applied on a data set of number wells resulting in a detailed differentiation of pore types at different scales for rock typing. The new rock types scheme including the vuggy and fractures were used for petrophysical evaluation. It re-defined reservoir/non-reservoir intervals which impacted the final product of petrophysical model. Furthermore, it supported with surveillance and production logs and facilitates for optimization of well planning and completion. This workflow fills the gap of the impact of heterogeneities such as m variable due to fractures or vugs and its impact on saturation computation and permeability. It also demonstrates their influence not only the storage but also transmissibility in the form of fractures and or the characters of vugs into modeling workflows and well centric performance. The ultimate goal is to utilize newly developed petrophysical rock types as inputs for static and dynamic models construction pursuing more accurate reserves estimation and a good match with actual well and reservoir performance