The accurate quantification of the secondary porosity portion and the characterization of the macro-porous features seem achievable only through extensive logging services and lengthy coring campaigns. Traditional logging measurements have limitations when trying to characterize the nature of the dual-porosity system of carbonate reservoirs. In a complex carbonate reservoir, such as in the Middle East case analyzed in this study, the processing of borehole images has enabled location, characterization, and quantification of the secondary porosity portion. The use of high-resolution electrical images provides the additional information necessary to obtain a continuous, detailed core-like view of the reservoir.
This paper presents the results of a pilot study performed over four key wells located in an onshore Field, 210km SW of Abu Dhabi City, UAE. The zone of interest is the Lower Arab D Member, which is part of the Upper Jurassic Arab Formation.
The novel approach presented in this paper integrates high-resolution electrical images with conventional reservoir characterization logs. This combination provides detailed full mapping and quantification of the dual-porosity system in wells logged with water-based mud. Additionally, the high-quality logging-while-drilling (LWD) and wireline images have been further exploited to obtain a continuous high-resolution permeability curve along the full length of the drain. A subsequent calibration of the results with available core data determined key paramenters that could be applied to uncored wells. Similar coefficients were used on wells with similar log signatures, structural position and image electro-facies to cored wells to obtain accurate and continuous high-resolution permeability readings.
Accurate identification of the unit with the best secondary porosity attributes will support further field development plans of the Lower Arab D Member. With the help of high-resolution full-bore electrical images, this paper aims to investigate the relationship between secondary porosity and the presence of dissolution features and natural fractures.