Impact of fracture cleanup on the productivity of gas condensate systems

The performance of fracturing treatments has been an issue for over fifty years and considerable effort has been devoted to improve its prediction performance. However, the effect of cleanup in tight gas-condensate reservoirs where fracturing considered as the most common well stimulation technique, has not been fully investigated for these low IFT systems. The performance of cleanup operation heavily depends on the mobility, i.e., viscosity and relative permeability (k_r), of fracturing fluid compared to those of gas and condensate. This determines the extent of invaded zone near the wellbore region and the ease with which fracturing fluid is removed during the back-flow operation. In this work, measured values of permeability, single-phase inertial factor and k_r of a propped fracture and those of a tight reservoir rock have been used to evaluate the performance of fracturing treatments. ECLIPSE 300 compositional reservoir simulator, which includes our in-house k_r correlations accounting for coupling (i.e., the increase of k _r as velocity increases and/or IFT decreases) and inertial (i.e., the reduction of k_r as velocity increases) effects, was used to develop realistic fractured flow systems. A sensitivity analysis on the impact of different hydraulic fracturing fluid, fracture characteristics and reservoir fluids on the productivity of a single-well model were conducted resulting in some practical guidelines. The results indicated that the performance of 300 cp high viscosity fracture fluid is better than that of 10 cp low viscosity fluid, due to a lower penetration depth. When k_r of oil based fracturing fluid is improved, compared to that of water based, the back flow of fracturing fluid is facilitated especially for the 10 cp low viscosity fluid. Presnece of condensate facilitate the backflow of fluid, hence, cleanup efficiency is better for richer fluid systems. Copyright 2007, Society of Petroleum Engineers.