Range of application of the Brooks-Corey model for approximation of capillary curves in reservoirs of Western Siberia

摘要

This paper considers issues in approximation of capillary curves under conditions of producing reservoirs of Western Siberia. Brooks-Corey model was selected as the main function for the approximation. For each experimental capillary measurements curve, values of parameters characterizing steepness and initial capillary pressure were obtained by statistical treatment. It has been revealed, that the values of capillary curve parameters are largely determined by such properties of reservoirs as absolute permeability and residual water saturation. By analysis of laboratory capillary curves for samples from a deposit in Western Siberia, application area of Brooks-Corey formula was determined: this model allows approximating capillary curves with accuracy sufficient for practical use only in reservoirs with average or high permeability (K_p>0.1 micron~2). This is due to the model under consideration describing only plateau-like section of the capillary curve when the parameters values are unchanged. If the rock has a large number of microcapillaries, the curve approaches the vertical asymptote gradually on a long interval of current water saturation values and ends only at comparatively high values of capillary pressure. Thus, in low-permeability collectors, the accuracy of approximation dips down, requiring application of other, more complex models.