Gas-condensate relative permeabilities in propped-fracture porous media: Coupling vs. inertia

Hydraulic fracturing is one of the most common well stimulation techniques for gas/condensate reservoirs. In recent years, considerable effort has been directed toward the understanding of flow around hydraulically fractured wells, especially for tight gas reservoirs. However, there has been no report of a study of flow behavior within propped-fractured porous media for the low interfacial tension (IFT) gas/condensate fluid systems. It is now a well established finding both experimentally and theoretically that the flow of gas/condensate fluid systems in porous media is affected by both coupling (the increase of relative permeability kr as velocity increases or IFT decreases) and inertial (i.e., the reduction of k_r as velocity increases) effects. However, the interaction of capillary, viscous, and inertial forces within highly conductive propped fractures is not yet understood. In this work, different series of steady-state gas/condensate k_r values for a proppant-filled and a sand-packed fracture with permeability of 146 darcy and 15 darcy, respectively, are reported. These experimentally measured sets of k _r data cover IFT and velocity values ranging between 0.85 and 0.15 mNm^-1 and 250 to 3000 md^-1, respectively. The results indicate that inertia is quite dominant at all the tested conditions albeit to a greater extent at lower IFT and higher gas fractional flow rates. In the case of the fracture with the higher permeability, some k_r values measured at the higher IFT are also reported, which are higher than the corresponding values at a lower IFT. These k_r measurements are also compared with the corresponding predicted k_r values using the generalized k _r correlation reported recently by Jamiolahmady et al. (2009). The correlation expresses the combined effect of coupling and inertia with universal parameters. The unique contribution of inertial forces, as observed in the experiments and predicted by the correlation, is mainly attributed to the velocity, petrophysical properties of the fracture, and fluid properties of the flowing phases. Copyright © 2010 Society of Petroleum Engineers.