Evaluating Domestic Well Vulnerability to Contamination From Unconventional Oil and Gas Development Sites

Abstract

The rapid expansion of unconventional oil and gas development (UD), made possible by horizontal drilling and hydraulic fracturing, has triggered concerns over groundwater contamination and public health risks. To improve our understanding of the risks posed by UD, we develop a physically based, spatially explicit framework for evaluating groundwater well vulnerability to aqueous phase contaminants released from surface spills and leaks at UD well pad locations. The proposed framework utilizes the concept of capture probability and incorporates decision-relevant planning horizons and acceptable risks to support goal-oriented modeling for groundwater protection. We illustrate the approach in northeastern Pennsylvania, where a high intensity of UD activity overlaps with local dependence on domestic groundwater wells. Using two alternative models of the bedrock aquifer and a precautionary paradigm to integrate their results, we found that most domestic wells in the domain had low vulnerability as the extent of their modeled probabilistic capture zones were smaller than distances to the nearest existing UD well pad. We also found that simulated capture probability and vulnerability were most sensitive to the model parameters of matrix hydraulic conductivity, porosity, pumping rate, and the ratio of fracture to matrix conductivity. Our analysis demonstrated the potential inadequacy of current state-mandated setback distances that allow UD within the boundaries of delineated capture zones. The proposed framework, while limited to aqueous phase contamination, emphasizes the need to incorporate information on flow paths and transport timescales into policies aiming to protect groundwater from contamination by UD.

Groundwaters in Northeastern Pennsylvania near intense hydraulic fracturing activities exhibit few organic chemical impacts

“…(2) geospatially-specic transport zones that account for subsurface transport heterogeneities (Fig. 5B and C, see also Soriano et al 2020 38,55 ). Over the 10 year time horizon, the transport distance of the phthalate was always shorter than the distance between gas wells and drinking water wells (Fig.…”

Assessment of groundwater well vulnerability to contamination through physics-informed machine learning

“…Metamodels were trained on a PB, high resolution, three-dimensional model of groundwater flow and solute transport in a 190 sq km domain in southeastern Bradford county (dashed box in figure 1) [27]. The PB model used was Hydrogeosphere, a finite element hydrologic simulator [60].…”

“…The PB model used was Hydrogeosphere, a finite element hydrologic simulator [60]. The calibrated model successfully replicated observations of hydraulic head determined from USGS monitoring wells and drillers' well logs and estimates of groundwater discharge from regression equations [27]. The PB model utilizes the concept of capture probability to operationalize vulnerability.…”

“…The objective of this research is to test the appropriateness of the metamodeling approach for groundwater vulnerability assessment. In particular, we employ a novel combination of a source-pathwayreceptor PB model [27] and ML to evaluate the vulnerability of drinking water wells to contamination from unconventional oil and gas development (UD). We trained metamodels to classify the vulnerability of receptors using spatial metrics readily computable in a geographic information system.…”

Invited Perspective: Oil and Gas Development and Adverse Birth Outcomes: What More Do We Need to Know?

“…Increasing the accuracy and specificity of current commonly used exposure models and metrics could have the power to illuminate causal mechanisms, reduce exposure misclassification, direct new monitoring efforts, and inform exposure mitigation strategies. Advancements have been made toward developing more specific metrics, including models to capture the practice of flaring (Franklin et al 2019), radioactivity (Li et al 2020), drinking water vulnerability (Soriano et al 2020), and oil and gas infrastructure other than well pads (Koehler et al 2018); more such research is needed.…”