Explaining Spatial Variability in Wellbore Impairment Risk for Pennsylvania Oil and Gas Wells, 2000-2014

Abstract:

Previous modeling (ingraffea et al. PNAS, 2014) indicated roughly two-times higher cumulative risk
for wellbore impairment in unconventional wells, relative to
conventional wells, and large spatial variation in risk for oil and
gas wells drilled in the state of Pennsylvania. Impairment risk for
wells in the northeast portion of the state were found to be 8.5-times
greater than that of wells drilled in the rest of the state. Here, we
set out to explain this apparent regional variability through Boosted
Regression Tree (BRT) analysis of geographic, developmental, and
general well attributes. We find that regional variability is largely driven by the
nature of the development, i.e. whether conventional or unconventional
development is dominant. Oil and natural gas market prices and total
well depths present as major influences in wellbore impairment, with
moderate influences from well densities and geologic factors. The figure depicts influence paths for predictors of impairments for the state (top left), SW region (top right), unconventional/NE region (bottom left) and conventional/NW region (bottom right) models. Influences are scaled to reflect percent contributions in explaining variability in the model.