History Matching for Determination of Fracture Permeability and Capillary Pressure

For naturally fractured reservoirs, it is very difficult to quantify future prediction without proper fracture properties, including such factors as fracture permeability, fracture orientation, and fracture length, and capillary pressure. Capillary pressure and fracture permeability can interact in a way that can produce nonunique results. Evaluation of core data may provide us with some information about imbibition capillary pressure curves; however, quantification of fracture permeability is determined largely by matching production data. This paper presents an integrated approach to history matching naturally fractured reservoirs by adjusting the fracture permeability of individual fractures and water/oil capillary pressure curves. This paper is focused mainly on history-matching procedure and not on geological-model construction. By minimizing an objective function to history matching production data, we generate estimates of fracture permeability of individual fractures and water/oil capillary pressure curves. All implementations were incorporated into a commercial simulator and iterated in the automatic-historymatching scheme. The adjoint method and an efficient direct solver were used to reduce CPU time for calculating the sensitivity-coefficient matrix. A 2D synthetic case was used, with the fracture distribution from a Middle East reservoir, to validate this method.