Hydraulic fracturing fluids and their environmental impact: then, today, and tomorrow

Abstract

Beginning in the 1860s, fracturing was used to stimulate or rather shoot rock formations for oil production. To increase both initial flow and ultimate extraction, liquid and solidified nitroglycerin was used in these years. The concept of (hydraulic) fracturing with pressure instead of explosives grew in the 1930s. Beginning in 1953, water-based fluids were developed using different types of gelling agents. Nowadays, aqueous fluids such as acid, water, brines, and water-based foams are used in most fracturing treatments. The breakdown of the fluids to decrease viscosity is mostly carried out by use of oxidizing agents. Thereby, the technology is facing concerns regarding microseismicity, air emissions, water consumption, and the endangerment of groundwater due to the risk of perforating protective layers and the ooze of chemicals through the surface. Furthermore, particularly both cross-linking and breaking agents pose serious risks for humans respectively are environmentally hazardous in terms of eco-toxicity—while the degradation effect of common oxidizing agents is relatively low in cases of high-temperature fracturing treatments. According to our comparative viscosity tests, the viscosity of both common hydrogels with and without oxidizing agents can be reduced to the same level when heated to 130 °C or above. Furthermore, in both cases no non-Newtonian behavior could be observed after the temperature treatment (anymore). Therefore, we developed a hydrogel that allows for optimized cross-linking without toxic linkers and that can be dissolved without environmentally hazardous chemicals. Furthermore, it avoids the clogging of pores by hydrogel residues and improves oil and gas exploitation.