Date of Award

2011

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

Andrew Reeve

Second Committee Member

Amanda Olsen

Third Committee Member

Shaleen Jain

Abstract

A computer model has been developed to simulate borehole flow in heterogeneous aquifers where the vertical distribution of permeability may vary significantly. In crystalline fractured aquifers, flow into or out of a borehole occurs at discrete locations of fracture intersection. Under these circumstances, flow simulations are defined by independent variables of transmissivity and far-field heads for each flow contributing fracture intersecting the borehole. The computer program, ADUCK (A Downhole Underwater Computational Kit), was developed to automatically calibrate model simulations to collected flowmeter data, providing an inverse solution to fracture transmissivity and far-field head. ADUCK was scripted using the Python (www.python.org) computer language and has been coupled with NLOPT (Johnson, 2010) optimization algorithms to optimize the calibration process. The computer program has been created using open-source software to make the ADUCK model widely available to anyone who could benefit from its utility. The ADUCK computer program has been evaluated using multiple borehole flow data sets collected in heterogeneous aquifers. These data sets range from fairly simplistic flow scenarios to more complex ones. The ADUCK model converges to reasonable solutions for each one of the data sets used. To further evaluate the ADUCK computer program solutions, they have been compared with the recently released USGS FLASH (Flow Log Analysis of Single Holes) model (Day-Lewis et al, 2011). The FLASH model simulates flowmeter data using the same independent variables of fracture transmissivity and far-field head, but uses different computational methods. The ADUCK and FLASH models provide similar solutions to flowmeter data inversion for more simplistic borehole flow scenarios. In more complex situations the two models provide significantly different solutions. The second chapter presents the findings of additional hydrogeologic field tests performed in boreholes W119 and W123 in Jonesboro, ME. Groundwater in these boreholes has elevated concentrations of dissolved chloride, suspected to originate from de-icing salts stored at a nearby MEDOT facility. The data collected included single well borehole geophysics, cross borehole flow testing, and water level data recorded over a two month period.

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