A new flow skin factor formulation for hydraulically fractured wells in gas condensate reservoirs

Fracturing is one of the most common well stimulation techniques especially for tight gas-condensate reservoirs. Gas condensate flow around hydraulically fractured wells (HFWs) is different from conventional gas oil systems. This is mainly due to phase change, condensate drop out and coupling (i.e., the increase of relative permeability as velocity increases and/or interfacial tension decreases) and inertial (i.e., the reduction of relative permeability as velocity increases) effects. Description of HFWs in gas condensate reservoirs using the existing reservoir simulators requires the use of very fine grids to capture the significant changes of flow and rock properties occurring in and around the fracture. This tasks it very cumbersome, time consuming and impractical. In this work a two dimensional mathematical simulator has been developed, which is based on finite-difference methods and accounts for the combined effects of coupling and inertia using our recently developed generalized correlation. This single-well model, which simulates the steady-state flow of gas and condensate around HFWs, also allows for phase change in these low interfacial tension systems. A series of sensitivity studies were carried out using this simulator. The results were used to develop a general method for estimation of flow skin factor based on the definition of dimensionless effective fracture conductivity. In the proposed method the skin factor expressing the impact of pertinent parameters are then converted to an effective well bore radius, which can be used by a reservoir engineer to conduct a realistic open-hole simulation of flow around HFWs. Copyright 2008, Society of Petroleum Engineers.