Reservoir Characterization of Carbonate Reservoir by Heterogeneity Analysis Using High-Definition Borehole Image & Petrophysical Data of Upper Shuaiba Formation Daleel Field, Oman

Abstract The study's main objective was to conduct a heterogeneity analysis to understand the nature of the complex carbonate reservoirs by integrating geological, and petrophysical parameters to comprehend the different types of facies and their effect on reservoir characteristics. The approach utilizes borehole electrical images to measure the extent and type of the vuggy fraction, porosity dissemination, and its impact on reservoir quality. The heterogeneity analysis of reservoirs from borehole images is carried out using proprietary software that examines the resistivity spectrum to extract information on porosity, layering and other heterogeneities to quantify, characterize and provide a distribution of these relevant heterogeneities. Several iterations are needed to optimize parameters. Each iteration is validated by comparing core data, and density-neutron x-plots with a visual examination of the images to see whether all heterogeneities are identified. Single-depth histograms were generated from the derived porosity spectrum to show the distribution of primary and secondary porosity. The Upper Shuaiba Member (USH) is the main pay zone in the Daleel field in northern Oman and is subdivided into 5 layers comprising of A, B, C, D, and E of which layers D and layer E are the most productive. These layers consist of thinly bedded bioclastic packstones and wackestones. The exploration development of the Daleel field requires knowledge of the composition and collocation of these various layers in the sedimentary system. Our method consists of several steps that combine a probabilistic image analysis with petrophysical properties to derive electrical facies based on the texture, heterogeneity, resistivity spectrum, fracture identification, and petrophysical properties. These facies are translated into curves, codes and colors that represent the porosity distribution as volume fractions. Primary and secondary porosities (vuggy porosity) are common in this field. We are able to provide color coded distributions showing the more connected vugs, partially connected vugs and isolated or tight vugs. These are separated from connected fractures. This information is critical to developing a geological model to aid field development. Borehole imagers are important to determine petrophysical parameters in highly heterogeneous carbonate reservoirs. They provide information on a wide variety of pore types including vuggy, fracture and matrix. This study shows that the USH formation contains bimodal and trimodal pores resulting from vugs. All vuggy intervals are classified as connected and unconnected vugs. The results go into a geological model to provide a deeper understanding of the facies extension across the field to optimize exploration.