TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractPolymeric damage is due to inconsistent breaks of stimulation fluids as well as to dynamically formed filter cakes. Fluid viscosity reduction is commonly used to gauge polymer degradation, and, although viscosity reduction indicates polymer degradation, reduced viscosity does not necessarily equate to improved fracture conductivity or retained formation permeability. Polymer fragments which contribute to fluid viscosity are not a measure of residual polymer damage.Historically, several methods have been employed to remove polymeric damage and increase well productivity. Prior treatments to remove polymeric damage include bleach (sodium hypochlorite) and acids. In cases of horizontal wells with slotted liners or screens, bleach or acids are not preferred. Additional expensive trips have become mandatory, when coiled tubing or drill-pipe are utilized for spotting the treatment. Additionally, some formations are acid sensitive.Laboratory evaluations of the effects of various gel breakers on linear and crosslinked, guar-based fracturing fluids from room temperature to 210°F, based on the size distribution of generated polymeric fragments, have been previously discussed. Additional studies have demonstrated that a correlation exists between formation rock permeability and the degree of damage resulting from residual polymer fragment deposition -the greater the formation rock permeability, the greater the degree of damage to the formation.The development of a treatment which could effectively reduce polymeric damage in fracture stimulated wells has been a subject of recent research. Core flow and regained conductivity testing have shown that multi-fold improvements can be achieved, even at elevated temperatures exceeding 250°F, and over a wide pH range.Results of extensive core flow and fracture conductivity testing, performed in an effort to correlate cleanup effectiveness to original rock permeability using near neutral and high pH cross-linked frac fluids, have been conducted. In general, a greater percentage of regained permeability was noted for more severely damaged (i.e. permeable) rocks. Rocks tested in this study exhibited permeabilities from 3 md to 2 darcies. Conductivity proppant pack baseline ranges were 250 to 500 darcies. Detailed analyses of the data are provided. Several field case histories of wells which were suffering from polymeric damage are presented.
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