Bootstrap Calibration and Uncertainty Estimation of Downhole NMR Hydraulic Conductivity Estimates in an Unconsolidated Aquifer. Issue 1 (12th February 2014)

• Record Type: Journal Article
• Authors: Parsekian, A.D.; Dlubac, K.; Grunewald, E.; Butler, J.J.; Knight, R.; Walsh, D.O.
• Is Part Of: Ground water. Volume 53:Issue 1(2015:Jan./Feb.)
• Page Start: 111
• Page End: 121
• Publication Date: 2014-02-12
• Subjects: Groundwater -- Periodicals; Wells -- Periodicals; Eau souterraine -- Périodiques; Puits -- Périodiques; Grondwater; Eau souterraine; Puits; Electronic journals; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 551.49
• DOI: 10.1111/gwat.12165
• Languages: English
• ISSNs: 0017-467X

Abstract

<abstract abstract-type="main" id="gwat12165-abs-0001"> <title>Abstract</title> <p id="gwat12165-para-0001">Characterization of hydraulic conductivity (<italic>K</italic>) in aquifers is critical for evaluation, management, and remediation of groundwater resources. While estimates of <italic>K</italic> have been traditionally obtained using hydraulic tests over discrete intervals in wells, geophysical measurements are emerging as an alternative way to estimate this parameter. Nuclear magnetic resonance (NMR) logging, a technology once largely applied to characterization of deep consolidated rock petroleum reservoirs, is beginning to see use in near‐surface unconsolidated aquifers. Using a well‐known rock physics relationship—the Schlumberger Doll Research (SDR) equation—<italic>K</italic> and porosity can be estimated from NMR water content and relaxation time. Calibration of SDR parameters is necessary for this transformation because NMR relaxation properties are, in part, a function of magnetic mineralization and pore space geometry, which are locally variable quantities. Here, we present a statistically based method for calibrating SDR parameters that establishes a range for the estimated parameters and simultaneously estimates the uncertainty of the resulting <italic>K</italic> values. We used co‐located logging NMR and direct <italic>K</italic> measurements in an unconsolidated fluvial aquifer in Lawrence, Kansas, USA to demonstrate that <italic>K</italic> can be estimated using logging NMR to a similar level of uncertainty as with traditional direct hydraulic measurements in unconsolidated sediments under field conditions. Results of this study provide a benchmark for future calibrations of NMR to obtain <italic>K</italic> in unconsolidated sediments and suggest a method for evaluating uncertainty in both <italic>K</italic> and SDR parameter values.</p> </abstract>