Relationship of Polymeric Fragments In Broken Gel To Formation Permeability Reduction

Although fluid viscosity reduction is commonly used to gauge polymer degradation and viscosity reduction does indicate that polymer degradation has occurred, it is misleading to conclude that reduced viscosity equates to improved fracture conductivity or retained formation permeability. Polymer fragments which result from the normal breaking of gelled, cross-linked fracturing fluids no longer contribute significantly to fluid viscosity but do contribute to proppant pack and/or formation permeability damage. Laboratory evaluations and procedures to characterize the efficiency of gel breakers, based upon the size distribution of the generated polymeric fragments, have been presented in previous studies. Results of core flow evaluations are presented in this study, and demonstrate the relationship of typical molecular weight distributions produced by degraded typical cross-linked fracturing fluids to permeability and production reduction within the rock matrix. Several ranges of core permeability were evaluated. Data yield a quantitative profile of the extent of formation permeability damage that can be expected based upon polymer fragment distributions and the original rock permeability. Detailed analysis of the data are provided.