Hydrologic detection of abandoned wells near proposed injection wells for hazardous waste disposal

Abstract

Deep saline aquifers are being used for disposal of hazardous liquid wastes. A thorough knowledge of the competency of such aquifers and their confining geologic beds in permanently isolating the hazardous substances is the key to successful disposal operations. Characterization of such systems, and in particular the detection of any conduit that may permit hydraulic communication between the host aquifer and nearby freshwater aquifers, must be carried out prior to the initiation of disposal projects. In deep, multi‐aquifer systems, leaky faults, abandonded wells, highly conductive fractures, or shear zones may all provide leakage paths. If not initially detected, such conduits may show no apparent effect until contaminants in the freshwater aquifer reach detectable levels at the discharge point. By then, of course, detection is generally too late. This paper is an attempt to address the problem of initial detection of improperly plugged or open abandoned wells. A new analytic solution has been derived to calculate the amount of leakage from an abandoned well and the corresponding drawdown at monitoring wells. A method is proposed that can be used to detect such deep abandoned wells in the area of influence of a proposed deep injection well in a multiple‐aquifer system.