Methods for Upscaling Diverse Rock Permeability Data for Reservoir Characterization and Modeling

摘要

The primary sources of rock permeability data are cores and logs. Core-based permeability data are sampled from the reservoir at different scale from log-based permeability data. Consequently, porosity-permeability cross-plots from core plugs and logs are sensitive to the methods used in averaging the permeability data. For instance, arithmetic averaged core permeability data translated to log scale can be an order of magnitude greater than the core plug data at a given porosity. Using Dykstra-Parsons coefficient as a measure of reservoir heterogeneity, arithmetic averaging of permeability data is not suitable as the rock becomes more heterogeneous. Other methods such as geometric or harmonic averaging may be more appropriate. Core heterogeneity below the vertical resolution of log NMR measurements has an impact on the methods used to calibrate NMR permeability data using core data. A method presented in this paper compares core permeability data with the NMR permeability data to account for sample volume differences utilizing high-density mini permeameter or high-density RCAL permeability data with different averaging techniques to simulate the vertical resolution of the NMR log. This paper demonstrates the impact of averaging methods on upscaling permeability from core to log scale. Several unique methods for scaling up permeability data of heterogeneous rocks for reservoir characterization are recommended. These methods will generate more realistic characterization of reservoir models in terms of distributions of permeability property in the models. The paper compared kh (permeability-thickness product) calculated from mini-DST tests to those calculated from core and profile (mini-permeameter) permeability data. The results of the comparisons are inconclusive. The kh from the mini-DST tests are not correlateable to those calculated from profile permeability data. The differences in kh values are traceable to uncertainty associated with depth shifts and the difficult task of ensuring that we are actually comparing data from the same depths or formation intervals.