EVALUATION OF FRACTAL MODELS TO DESCRIBE RESERVOIR HETEROGENEITY AND PERFORMANCE

Our work uses fractals to characterize the spatial correlation structu res of porosity and permeability of vertical and horizontal logs in a braided-fluvial sandstone reservoir. The data comprise cores and logs of adjacent vertical wells and logs of horizontal wells. Small-scale r ealizations of interwell heterogeneity were generated with successive random additions (SRA) technique for new observed fractal models, A de terministic description is also developed. Effects of fractal and dete rministic reservoir heterogeneity on reservoir performance were studie d for waterflood and water-alternating-gas (WAG) injection processes. The effects of scale up on spatial correlation of porosity was investi gated. The fractal model of fractional Brownian motion (FBM) in the ho rizontal direction, having same intermittency exponent as for fraction al Gaussian noise (FGN) in the vertical direction, is not supported by log observations in horizontal wells. Fractal character of core and l og data of vertical wells is similar. The incremental WAG recovery res ponse compared to waterflooding response is more sensitive to reservoi r heterogeneity. Scale-up experiments indicate that spatial correlatio n structure of reservoir properties may be different at different scal es. Results of this paper will be useful for evaluation of infill dril ling, and design, selection, and optimization of an EOR process. The p roposed techniques also provide a framework to quantify uncertainty in reservoir performance.