Perez, Christopher R (2022-04). Numerical Modeling of Pumping Responses in Shallow Aquifer Systems Containing an Abandoned Borehole. Master's Thesis.
Thesis
With the number of abandoned wells increasing each year and a previously estimated three million abandoned oil and gas wells in the United States, the impact of these wells on shallow groundwater aquifers is a growing concern. Many works have been conducted to evaluate the potential hazards of these wells when an injection and unplugged/partially plugged well are in close proximity. However, few studies have been conducted on the effect of a pumping well that is pumped near an abandoned well. Using Visual MODFLOW as a platform, a sequence of simulations for various possible scenarios are conducted to evaluate drawdown and fluid leakage rates in a three-layer system that consists of a top and a bottom aquifer separated by an aquitard, a pumping well screened in either the top or bottom aquifer, and an abandoned well. Six different scenarios were created. The first two scenarios evaluated the effects of pumping at a constant rate with the pumping well screened in either the top or bottom aquifer; for the third and fourth scenarios, the pumping rate was gradually increased by 250 m3/day every 250 days until t=1000 days, and the fifth and sixth scenarios evaluated the effects of tripling the thickness of the confining layer. The results of the study showed that both distance between the two wells and drawdown was inversely related to the fluid leakage rate flowing through the abandoned well. It also showed that when pumping from the bottom aquifer, the fluid was more likely to leak at a higher rate through the abandoned well compared to the scenarios when the pumping well was set in the upper aquifer. This research provides a better understanding of the effects that abandoned wells have on shallow aquifer systems, which is useful for assessing the potential risk and hazards, more specifically the cross-formational flow from one aquifer into another, associated with abandoned wells in the field.
ETD Chair
Zhan, Hongbin Holder of Endowed Dudley J. Hughes '51 Chair in Geology and Geophysics
