A Sensitivity Analysis of Geostatistical Parameters on Oil Recovery Predictions

Abstract

The effect of different spatial covariance parameters; range, covariance model, anisotropy direction and ratio on important reservoir engineering parameters such as breakthrough time, fractional flow of oil and oil recovery as a function of pore volumes injected is examined. The study is conducted for situations where the range of spatial continuity of permeability is smaller than the well spacing, meaning it cannot be detected through the calculation of an experimental variogram. This is a relatively common occurrence for even well developed oil reservoirs. The impact of the different parameters on the flow behavior is analyzed using a hybrid finite-difference/streamtube approach for the fluid displacement simulations. The permeability and porosity grids are generated using both Gaussian based conditional simulation techniques and non-parametric methods such as indicators. Some of the results indicate that Gaussian simulation techniques are not suitable for fluid flow predictions while the choice of the variogram type (exponential, Gaussian or spherical) is unimportant.