Stimulation-Fluid Systems for Naturally Fractured Tight Gas Sandstones: A General Case Study

Extensive production testing and core analyses show that production from the low-permeability sandstones in the Mesaverde formation at the U.S. DOE Multiwell Experiment (MWX) field laboratory is dominated by natural fractures. Stimulation data strongly suggest that damage to the narrow natural fractures significantly affects poststimulation production. This paper summarizes the field data that show evidence for production from natural fractures and for damage to those narrow natural fractures by stimulation fluids resulting in decreased gas production. The nature of these interactions was clarified through laboratory studies on the degradation of stimulation fluids and the permeability damage to artificially fractured core exposed to the fluids. Evidence confirms that stimulation-fluid damage to the narrow natural fractures restricted the production of gas in early MWX stimulations, consistent with the partial reversibility of fluid damage to natural fractures following a long-term shut-in. A controlled breaker system was designed for use with temperature-stable biopolymer foam. Use of this fluid system in a later MWX stimulation substantially increased gas production and reduced the evidence of damage.