Environmentally Focused Crosslinked-Gel System Results in High Retained Proppant-Pack Conductivity

Abstract

Abstract This paper presents the retained conductivity results of a new environmentally focused fracturing fluid whose components are sourced from the food industry, as described in the US Code of Federal Regulations Title 21 (CFR 21) or the Generally Recognized as Safe (GRAS) affirmation process. The fluid is comprised of the following components: a low-residue polysaccharide gelling agent, a metal crosslinker, a surfactant, and a suite of breakers. The suite of breakers provides consistent fluid cleanup in retained conductivity testing in temperatures ranging from 120 to 200°F. Fracture conductivity testing was performed using a wet-gas cleanup protocol used in modeling hydraulically fractured wells. Hydraulic fracturing and the environmental effects of the chemicals involved in the fracturing process have become the subjects of public discussion. This discussion has encouraged the petroleum industry to address public concern regarding the potential environmental impact of chemicals used in fracturing. Service companies have responded by improving their current chemical portfolio and developing new environmentally focused chemical technologies. This paper describes an environmentally focused metal-crosslinked polysaccharide fluid that not only is more environmentally acceptable under the criteria described in this work, but also has little or no proppant-pack conductivity impairment, as measured by fracture conductivity testing. Wet-gas retained conductivity of 1-lbm/ft2 20/40-mesh Ottawa sand was performed with humidified nitrogen gas flow. Retained conductivity of 84 to 100% was obtained after wet-gas cleanup for temperatures ranging from 120 to 200°F under a 2,000-psi closure stress. All conductivity tests were performed between Ohio sandstone wafers with filter-cake buildup from dynamic fluid-loss testing. Wet-gas retained conductivity was verified by a third-party laboratory. These results indicate that a fracturing fluid can be designed using defined environmental criteria based on food grade materials to provide similar performance and excellent retained conductivity.