A note on drillhole depths required for reliable heat flow determinations

Chapman, David S.; Howell, Jack; Sass, J.H.

doi:10.1016/0040-1951(84)90070-2

Cited by 16 publications

(5 citation statements)

References 8 publications

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“…Only few deep boreholes are available for comparison with KTB results, as most of the boreholes used for geothermal research in the past decades do not exceed I km in depth (Chapman et al, 1984]. For those that penetrate into the deep crystalline basement, heat production rate varies in a similar way with depth as in the KTB: in both the 6.7 km deep Gravberg-I well [Bailing et al, 1990], located in the Siljan impact structure (Sweden) and in the 12.2 km deep SG-3 borehole [Arshavskaya et al, 1987] on the Kola peninsula (Russia), heat production rate is strongly correlated with lithology and does not decrease exponentially.…”

Section: Processes Near the Surfacementioning

confidence: 99%

The thermal regime of the crystalline continental crust: Implications from the KTB

Clauser¹,

Giese²,

Huenges³

et al. 1997

J. Geophys. Res.

140

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Abstract. An extensive geothermal research program within the German Continental Deep Drilling Program (KTB) covered an almost complete spectrum of experimental and theoretical aspects. The main results and conclusions are as follows: (1) Equilibrium temperature is 118.6øC at 4000 m in the KTB pilot borehole (KTB-VB) and will be around 260øC at 9100 m in the KTB main borehole (KTB-HB). Time required for thermal equilibration of the KTB-HB to within 1% of the initial perturbation will be about 13-16 years. for large rock volumes, but simple numerical models indicate that the associated temperature regimes are imcompatible with KTB borehole data. (6) Heat production rate shows no systematic variation with depth and is related to lithology at the KTB as in other deep boreholes in crystalline rock. Numerical models, using heat production rate derived from seismic velocities, yield temperatures compatible with KTB borehole data.

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Section: Processes Near the Surfacementioning

confidence: 99%

The thermal regime of the crystalline continental crust: Implications from the KTB

Clauser¹,

Giese²,

Huenges³

et al. 1997

J. Geophys. Res.

140

View full text Add to dashboard Cite

show abstract

“…Quite often temperature gradients demonstrate nonlinear characteristics incompatible with thermal conductivity changes that would result in a constant heat flux with depth. Perturbations to the conductive geothermal gradient are generally more profound at shallow depth (excluding the near-surface 20-m depth where noticeable yearly temperature cycles occur), and relatively deep depths may be required to measure representative conductive gradients (e.g., REITER and MANSURE, 1983;CHAPMAN et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

Possible Ambiguities in Subsurface Temperature Logs: Consideration of Ground-water Flow and Ground Surface Temperature Change

Reiter

2005

Pure appl. geophys.

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Subsurface temperature regimes can commonly be influenced by both ground-water flow in the saturated zone and ground surface temperature change. Both phenomena are widespread and one or the other may be unnoticed and/or unanticipated in various temperature logs. As a consequence, it is often difficult to determine the relative impact of the two phenomena on the temperature-depth data at a site. A number of models for ground-water flow, ground surface temperature change, and a combination of the two processes, are fitted to two example temperature logs showing characteristic nonlinearity. Examples of the possible impact of one phenomenon on the parameters calculated for the other phenomenon demonstrate the potential interactive influence. The analysis can be used to estimate potential uncertainties in calculations of ground-water flow and ground surface temperature change from subsurface temperature data, and therefore how interpretations of ground-water flow and ground surface warming might be affected. From the analysis presented the relative importance of the two phenomena may be further considered at different locations.

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“…Workers in geothermal studies have long recognized that heat flow estimates often varied with depth and attributed such variations to the disturbing effects of climate changes and groundwater movement [e.g., Bullard, 1939]. Data below depths of hundreds and even thousands of meters are often required to avoid detectable groundwater flow and the associated temperature effects in order to acquire conduction temperature gradients representative of thermal conditions in the Earth's deep crust and upper mantle [Reiter and Mansure, 1983;Chapman et al, 1984]. In the past two decades a number of workers have related the curvature observed in temperature logs to depths of a hundred meters or more as indicative of surface temperature warming, the effects being more prominent in northern latitudes [e.g., see Pollack and Chapman, 1993].…”

Section: Introduction and Theorymentioning

confidence: 99%

Using precision temperature logs to estimate horizontal and vertical groundwater flow components

Reiter¹

2001

Water Resources Research

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A new method of estimating the horizontal and vertical specific discharge components of groundwater flow from precision subsurface temperature measurements is presented. Plotting the vertical temperature gradient as a function of both Z and T and then fitting a plane to the data can provide coefficients from which the vertical and horizontal groundwater specific discharge components may be estimated. Alternatively, by considering the vertical component of groundwater to be zero, it is shown that quadric or cubic fits to temperature data provide coefficients from which horizontal groundwater flow may be estimated. These expressions along with expressions previously derived to estimate only vertical, only horizontal, or both vertical and horizontal flow components are fitted to observational data from four sites and five flow zones. It is learned for these examples (using an available fitting program) that although many of the expressions fit the observational data very well statistically, those expressions which incorporate both the vertical and horizontal flow components of specific discharge must generally be constrained so that resulting parameters will provide flow estimates consistent in direction and heat transfer with available piezometer data and/or the fundamental curvature of the temperature log. Expressions incorporating only νX or only νZ can sometimes yield estimates quite different from the estimates obtained from the expressions incorporating both νX and νZ. It is concluded that an estimate of the horizontal and vertical flow components requires both consideration of the flow calculations along with available piezometric data and the fundamental curvature of the temperature log.

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A note on drillhole depths required for reliable heat flow determinations

Cited by 16 publications

References 8 publications

The thermal regime of the crystalline continental crust: Implications from the KTB

The thermal regime of the crystalline continental crust: Implications from the KTB

Possible Ambiguities in Subsurface Temperature Logs: Consideration of Ground-water Flow and Ground Surface Temperature Change

Using precision temperature logs to estimate horizontal and vertical groundwater flow components

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