Comparison of Approaches to Characterize Flow Conditions in Bedrock Wells

Evaluating vertical flow in bedrock wells is important for understanding aquifer hydraulic parameters, and borehole flowmeter methods are critical for analyzing flow in fractured-rock aquifers. Single borehole logging is used to identify active hydraulic zones under ambient and pumping conditions, and crosshole flowmeter logging is used to identify hydraulic connections between boreholes. To identify potential zones of interest for flowmeter logging in fractured rock, first a series of conventional borehole logs are collected. Then, locations for flowmeter logging are selected and data are collected under ambient and stressed conditions to distinguish fracture flow zones. Because flowmeters are limited by their resolution and operational range, tool selection is critical and should be matched to site conditions and project goals. In this study, data were collected in three boreholes in a fractured rock setting in Storrs, Connecticut, to compare three flow logging methods. Prior to flow logging, acoustic- and optical-televiewer, fluid temperature, and conductivity logs were collected in the wells. Flow measurement data were collected under ambient and pumping conditions using spinner, heat-pulse, and electromagnetic flowmeters. Factors for comparing the flow data include the spatial resolution of flow zones, maximum and minimal flow detection rates, and rapidity and ease of data collection and analysis. Fracture transmissivity results of the flow logs were also compared to results from a dissolved oxygen alteration method and a newly designed packer method