Impact of Surfactants on Fracture Fluid Recovery

Abstract

Abstract One of the many challenges of unconventional reservoirs is maximizing the recovery of fracturing fluid following hydraulic fracturing treatments. Effective fracturing fluid recovery reduces water saturation of the fractured network and fluid invasion into the formation, enabling better hydrocarbon production from the reservoir. Each chemical component present in complex fracturing fluid systems should first be carefully formulated to achieve the stimulation design requirements for the well and second to help ensure complete or maximum recovery of the broken fracturing fluid. To help achieve maximum fracturing fluid recovery, it is necessary to understand the complex, multistep processes that occur during the fracturing fluid breaking chemistry (gel degradation) and to incorporate this understanding into the fracturing fluid design. Considerable attention has been given to insoluble residue, breaker concentration, break time, and broken fluid viscosity, all which are crucial for fluid recovery, but these do not address the tendency of insoluble materials contained within the fluid or formed during the polymer degradation process to aggregate, which can result in a significant loss of proppant pack permeability. Polysaccharide-based polymers are typically degraded by breakers composed of enzymes, oxidizers, or acids. These breakers are designed to reduce viscosity of the fluid to enable easy flowback, but they generally do not degrade the polymer completely to the monosaccharide state; rather they leave fairly long chained oligomers. These broken polymer fragments tend to aggregate, forming malleable flocs. The nature of these oligomeric fragment aggregates, such as type, size, and strength of the association, affect the efficiency of fluid debris recovery following a fracture stimulation treatment. Surfactants added to the fracturing fluids, if properly chosen, can also act as inhibitors to the formation of the oligomeric aggregates and prevent flocculation, thus helping to avoid a significant loss of proppant bed permeability. This paper demonstrates the importance of surfactants in preventing permeability damage resulting from oligomeric polysaccharide aggregation. Selection of the proper surfactant helps prevent flocculation and enhances the recovery of broken fluids from proppant packs. Fracture design engineers can use these strategies to maximize both the rate and efficiency of fracturing fluid recovery following the fracture stimulation of a well. This can lead to improved hydrocarbon recovery and is particularly important for the stimulation of extremely low permeability, unconventional reservoirs.