Abstract
Core analyses are carried out on the selected rock samples with the aim of establishing the basis of the building a data base to provide direct and quantitative measurements and interpretations about the reservoir characteristics. During a careful sample selection process, besides available conventional data such as porosity and permeability it is also important to understand the degree of heterogeneity that exists within the core samples. Computerized Tomography (CT) scanning technique, in this respect, has efficiently been used due to its non-destructive cross sectional imaging capability. CT scanning images obtained by medical type CT scanners are reconstructed on a 512×512 grid of pixels, with a typical resolution of 50 to 300μm depending on the sample size. Since the CT numbers are based on the density within rock samples, the heterogeneity analysis based on the CT numbers reflects the lithology of the samples being examined. Therefore, understanding the statistics of the CT images can significantly contribute towards an accurate classification and improved sample selection of the rock samples into different level of heterogeneities/homogeneities, which in turn significantly contributes towards the success of specialized studies, e.g. SCAL tests, Enhanced Oil Recovery and Acid Treatment. To examine the level of heterogeneity of rock samples on the basis of CT numbers, this study focuses on the application of statistical parameters, including Coefficient of Variation (CV) and Heterogeneity Index (HI) as well as histogram. The results indicated that only visual examination of CT images are not adequate but more thorough examination, such as statistical methods are required and have been proven to be an effective approach.
