APPLICATION OF DIGITAL AND CONVENTIONAL TECHNIQUES TO STUDY THE EFFECTS OF HETEROGENEITY ON PERMEABILITY ANISOTROPY IN A COMPLEX MIDDLE EAST CARBONATE RESERVOIR

摘要

Most carbonate reservoirs are commonly characterized by multiple-porosity systems that impart petrophysical heterogeneity to the gross of reservoir interval. This heterogeneity complicates the task of reservoir description and thus necessitates the establishment of accurate and detailed understanding of the geological heterogeneities and their impact on petrophysics and reservoir engineering.One of the fundamental input parameters into reservoir geological models is the permeability anisotropy in the reservoir, where permeability tends to vary as a function of spatial locations both in vertical and areal directions (i.e Kv/Kh). The impact of rock heterogeneity on permeability becomes more pronounced when permeability is measured at various scales ranging from small one-inch diameter core plugs to full diameter whole core samples. The challenge would be to select appropriate samples that can represent reservoir heterogeneity and acquire accurate Kv/Kh data to assist in the update of geological static models and help improve the physical and geological understanding behind this heterogeneity.In a previous work thousands of plug permeability measurements were performed in a conventional laboratory to acquire Kv/Kh ratios across a large carbonate field in the Middle East. The results were largely influenced by reservoir heterogeneity and yielded large ratios of Kv/Kh, greater than unity.In this work, a high resolution Dual Energy CT Scanning Study was initiated on one-inch plugs and full diameter four-inch whole core samples to provide accurate 3D visualization of the geometric fabric of the rocks. Detailed thin-section descriptions and MICP were extended to the plug scale to understand the geological variations in 3D. CT-derived porosity and mineralogy were quantified along sample lengths by the dual energy CT technique. An improved geological interpretation of the diagenetically altered carbonate rocks was explained based on the high resolution CT images and conventional geological descriptions. Directional permeability was computed by the Lattice Boltzmann methodology and upscaled to the plug and whole core levels. These analyses offered an improved understanding of the heterogeneity in the reservoir and the impact on multi-scale permeability measurements.