Comparison of formation and fluid-column logs in a heterogeneous basalt aquifer

Groundwater
By: , and 

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Abstract

Deep observation boreholes in the vicinity of active production wells in Honolulu, Hawaii, exhibit the anomalous condition that fluid-column electrical conductivity logs and apparent profiles of pore-water electrical conductivity derived from induction conductivity logs are nearly identical if a formation factor of 12.5 is assumed. This condition is documented in three boreholes where fluid-column logs clearly indicate the presence of strong borehole flow induced by withdrawal from partially penetrating water-supply wells. This result appears to contradict the basic principles of conductivity-log interpretation. Flow conditions in one of these boreholes was investigated in detail by obtaining flow profiles under two water production conditions using the electromagnetic flowmeter. The flow-log interpretation demonstrates that the fluid-column log resembles the induction log because the amount of inflow to the borehole increases systematically upward through the transition zone between deeper salt water and shallower fresh water. This condition allows the properties of the fluid column to approximate the properties of water entering the borehole as soon as the upflow stream encounters that producing zone. Because this condition occurs in all three boreholes investigated, the similarity of induction and fluid-column logs is probably not a coincidence, and may relate to aquifer response under the influence of pumping from production wells.

Publication type Article
Publication Subtype Journal Article
Title Comparison of formation and fluid-column logs in a heterogeneous basalt aquifer
Series title Groundwater
DOI 10.1111/j.1745-6584.2002.tb02544.x
Volume 40
Issue 6
Year Published 2002
Language English
Publisher Wiley
Contributing office(s) Toxic Substances Hydrology Program
Description 9 p.
First page 577
Last page 585
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