Abstract
Controlling fluid matrix leakoff into the formation is of critical importance during fracture stimulation treatments to ensure objectives are met. Decreasing the amount of fluid leakoff increases the volume that is available to maintain and propagate a hydraulic fracture. The need to minimize fluid leakoff is even more significant during acid fracturing since maintaining the fracture is difficult because of the ability of acid to spend quickly as it enters the formation. Traditional approaches utilize solids-laden viscous gels to reduce the volume of fluid leakoff as a fracture is propagated; however, it has been amply documented that the solids typically used are capable of damaging the formation if not properly removed after the treatment. Moreover, removal of treatment gels, which is required to minimize formation damage, is contingent on selection and design of breakers or other compounds, which are often chosen based on a number of uncertain reservoir parameters.
This paper will present both laboratory and field application results from a new solids-free fluid loss (SFFL) system designed to reduce matrix permeability to aqueous fluids, thereby resulting in longer fracture propagation caused by a significantly lower fluid-leakoff rate. This fluid loss system does not require the use of breakers, which eliminates the potential negative impact on post-stimulation well productivity. Laboratory test data will show the ability of the material to control fluid leakoff and its ability to achieve high levels of regained permeability to hydrocarbon.
Field results from the application of the new system during acid fracturing treatments in high condensate gas producers in Saudi Arabia, in which achieving long half-length fractures with acid is very difficult due to excessive fluid leakoff, are also discussed. Post-treatment analysis showed that utilization of the new system resulted in significant reduction of fluid leakoff, thereby allowing treating pressure to remain above closure pressure throughout the treatment and achieve a longer fracture extension. A post treatment performance comparison between gas producers treated with the new system and those stimulated using conventional fluids will show that using the new system consistently exhibited better productionperformance (normalized for reservoir characteristics).
