Abstract
Wells drilled in tight sand and shale gas reservoirs require hydraulic fracturing treatments to become economically profitable. The primary objectives for these treatments are twofold: (1) create high-conductivity paths from the wellbore to deep penetration; (2) and/or connect natural microfractures within the reservoirs.
Current fracturing fluid systems generate formation damage and/or fracture damage due to fluid leakoff into natural fractures and matrix or polymer residues. This makes tight gas reservoir stimulation much less effective than expected.
This paper will briefly evaluate the damage mechanisms of current fluid systems and introduce an advanced surfactant micelle fluid technology for tight gas reservoir stimulation. Surfactant micelle fluids structured from very low-molecular-weight surfactants into elongated micelles have been used as stimulation fluids in an attempt to remove the drawback of polymer fluids. The viscoelastic behavior of these surfactant micelle fluids is believed to be rooted in the overlap and entanglement of elongated micelles. This yields both the viscous and elastic characteristics to the fluid.
High fluid leakoff and difficult cleanup associated with traditional surfactant micelle fluids have, however, limited their use in tight gas stimulation applications. Recent work has shown that adding carefully selected inorganic nano-crystals—less than 100 nm in size—to a surfactant micelle fluid formulation can overcome damage limitations. This can be done without negatively affecting the internal breaking mechanisms. Recent results highlight the mechanism of fluid loss control and easy cleanup of this nanoparticle reinforced surfactant micelle fluid system for tight gas stimulation applications.
