Capture probability and well vulnerability to contamination: A framework for evaluating potential impacts of unconventional oil & gas development on groundwater resources
Abstract
Surface spills of drilling fluids, frac fluids, and produced water have been documented to cause groundwater well contamination in areas of active unconventional oil and gas development (UD). One traditional approach to investigate the fate of spilled contaminants has been to simulate forward transport from known source locations, assuming the composition, volume, and temporal input history related to the spill are also known. However, in the context of UD, these details are often highly uncertain as spills may include complex mixtures of undisclosed chemicals, and existing regulatory requirements may preclude detailed reporting of spill volumes and histories. We aim to address these limitations by focusing attention on receptors, particularly, groundwater wells. In our current study, the transport problem is formulated in the reverse or upgradient flow direction to quantify capture probability, which is the probability that a parcel of water at any given location will be captured by a groundwater well within a specified time period. Capture probability is calculated for each reported spill location; groundwater well vulnerability to contamination is then defined as the union of these capture probabilities. The approach is demonstrated through case studies in northeast Pennsylvania, where many household groundwater wells are located within 1-5 kilometers of UD well pads, and cases of contamination resulting from spills associated with UD have occurred. Comparisons with geochemical data, as well as implications of alternative model conceptualizations, are also explored.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H51L1643S
- Keywords:
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- 1822 Geomechanics;
- HYDROLOGY;
- 1847 Modeling;
- HYDROLOGY;
- 1869 Stochastic hydrology;
- HYDROLOGY;
- 1873 Uncertainty assessment;
- HYDROLOGY