Factors affecting water blocking and gas flow from hydraulically fractured gas wells

This study presents results which were generated and analyzed over a 2-yr period. Several hundred computer runs were made during this project and an extensive amount of rock property data was reviewed to insure that these data were representative of tight gas reservoirs. The following conclusions reflect the combined information which was generated during the study. The reservoir properties, such as capillary pressure, change of capillary pressure in damaged zones, and relative permeability (in low permeability gas reservoirs) are primary factors in determining the behavior of a fractured well during cleanup. If the reservoir rock permeability is not damaged by frac fluid invasion, no serious water blockage to gas flow will occur when (1) the pressure drawdown is much greater than the capillary pressure in the formation, or (2) the capillary pressure and water mobility are large enough to rapidly imbibe the frac water into the formation. If the reservoir rock permeability is not damaged by frac fluid invasion, a complete water block to gas flow cannot occur; however, gas production can be severely curtailed if the pressure drawdown does not exceed the formation capillary pressure and the water mobility is so low that the frac water remains immobile nextmore » to the fracture face.« less