A New Capillary Pressure Model from Fractal Characterization of Porous Medium: A Case Study from Malaysia

Capillary pressure is an essential input in reservoir modeling and simulation. Laboratorymeasurements of capillary pressure are costly and time-consuming; hence, a limited number of core plugsare tested, and capillary pressure models were required to fill this gap. Several capillary pressure modelswere presented in the literature to match the measured laboratory data, e.g., Brooks and Corey’s model.However, matching capillary pressure remains a challenge for reservoir engineers and petrophysicists. Onthe other hand, various publications demonstrated the fractal characteristics of porous media and employedthe fractal theory to develop capillary pressure models for drainage and imbibition processes. This studydeveloped a new capillary pressure model by representing the pore structure as bundles of capillaries withequilateral triangular cross-sections whose inscribed radii follow a fractal distribution. Using triangulartubes reflects the angularity of the actual pores; therefore, providing a better representation of the porestructure. The genetic algorithm, GA, is then utilized to match the measured capillary pressure anddetermine the parameters of the developed model. Capillary pressure data for five core samples from anoffshore well in Malaysia were used to validate the developed model. The error analysis indicated that thefractal model matches the experimental data with reasonable accuracy. Moreover, compared with Brooksand Corey’s model, the newly developed fractal model provides a better match to the experimental data,especially for low permeability rock samples.