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The increased use of hydraulic fracturing for oil and gas production has raised concerns regarding potential effects on humans and the environment. Gradient's multi-disciplinary team of experts brings unparalleled technical power to addressing such issues, whether they relate to fracturing and faulting of rock, potential chemical migration through water or air, or potential risks to humans and the environment. Our staff members have advanced hydraulic fracturing understanding and science through significant peer-reviewed publications and scientific input to regulatory agencies, and we advise clients on the hazards of chemical additives and potential risks associated with hypothetical leaks or spills.
Verslycke, T; Reid, K; Bowers, T; Thakali, S; Lewis, A; Sanders, J; Tuck, D. 2014. "The Chemistry Scoring Index (CSI): A hazard-based scoring and ranking tool for chemicals and products used in the oil and gas industry." Sustainability 6:3993-4009.
Flewelling, SA; Sharma, M. 2014. "Constraints on upward migration of hydraulic fracturing fluid and brine." Groundwater 52(1):9-19.
Flewelling, SA; Tymchak, MP; Warpinski, NW. 2013. "Hydraulic fracture height limits and fault interactions in tight oil and gas formations." Geophysical Res. Lett. 40:3602-3606.
Hydraulic Fracturing National Risk AssessmentFull Description
Gradient assessed potential human health risks associated with possible drinking water exposure for chemical additives in fluids used in hydraulic fracturing (HF) operations in tight oil and gas plays throughout the contiguous United States. We modeled HF fluid constituents in both groundwater and surface drinking water supplies for hypothetical surface spills of HF and flowback fluids and evaluated potential HF chemical migration from the deep oil- and gas-bearing formations to overlying potable aquifers.
Limits to Hydraulic Fracture Height GrowthFull Description
Gradient developed a physics-based limit to how tall hydraulic fractures could grow upward from oil- and gas-bearing formations targeted for HF and compared this limit to over 12,000 HF stages monitored with microseismic sensors. The analysis demonstrated that the maximum possible hydraulic fracture height is limited by the volume of HF fluid pumped, regardless of whether the fluid interacted with pre-existing faults in the rock.
Constraints on Potential Upward Migration of Hydraulic Fracturing FluidFull Description
Gradient synthesized existing literature on groundwater hydraulics, geology, and HF operations to evaluate the constraints on potential upward migration of HF fluid and brine from oil- and gas-bearing formations to shallower potable groundwater. We analyzed the extent of hydraulic fracture growth above the targeted formation, under what circumstances there might be a driving force for upward fluid migration, and the inherent capacity of rocks to transmit fluid.
Potential Impact of Hydraulic Fracturing on Groundwater Quality in WyomingFull Description
Gradient submitted comments to US EPA on its investigation of potential impacts of HF on drinking water quality in Pavillion, WY. We analyzed groundwater hydraulics, aquifer geochemical reactions, HF fluid chemistry, chemical forensics for natural hydrocarbons in the area, and data quality. We evaluated the design and implementation of the study for its impact on study results.
Review of a Comprehensive Ranking System for Chemicals and ProductsFull Description
Gradient evaluated a comprehensive hazard evaluation system developed by an energy services company for scoring and ranking its products. We reviewed the underlying components of the hazard evaluation system, conducted a sensitivity analysis of the ranking "variables" to evaluate the system's robustness, and compared it with other existing chemical hazard evaluation and product scoring/ranking systems.
Potential Exposure and Health Risks Related to Hydraulic Fracturing in the Marcellus ShaleFull Description
Gradient provided a critical review of potential exposure and health risks related to natural gas development using hydraulic fracturing in the Marcellus Shale Region, including air emissions, accidental spills at the surface, and fluid migration upward from the hydraulically fractured formation. We also assessed the potential for induced seismic events related to hydraulic fracturing and wastewater disposal.
Potential Groundwater Impacts of Natural Gas Development in Southwestern PAFull Description
Gradient evaluated whether hydraulic fracturing fluid or methane could potentially migrate upward from black shales in Southwestern Pennsylvania to drinking water wells. We synthesized the current state of knowledge regarding potential upward fluid migration through overlying rocks with site specific information on geology, microseismic monitoring of fracture growth, and groundwater geochemistry.
Hydraulic Fracturing Chemical Registration in the European UnionFull Description
Gradient reviewed the existing regulatory framework under REACH and associated technical tools for chemical registration in the European Union (EU). Gradient's evaluation included an assessment of whether the current technical tools used under REACH (e.g., exposure scenarios and models) were adequate for characterizing and screening the extent to which humans and ecological receptors could possibly be exposed to chemicals used in hydraulic fracturing. The analysis considered potential exposures related to handling chemicals at the well pad, accidental spills, and the overall plausibility of fluids migrating upward from deep hydraulically fractured formations.