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Title: Method and apparatus for determining vertical heat flux of geothermal field

Abstract

A method and apparatus for determining vertical heat flux of a geothermal field, and mapping the entire field, is based upon an elongated heat-flux transducer (10) comprised of a length of tubing (12) of relatively low thermal conductivity with a thermopile (20) inside for measuring the thermal gradient between the ends of the transducer after it has been positioned in a borehole for a period sufficient for the tube to reach thermal equilibrium. The transducer is thermally coupled to the surrounding earth by a fluid annulus, preferably water or mud. A second transducer comprised of a length of tubing of relatively high thermal conductivity is used for a second thermal gradient measurement. The ratio of the first measurement to the second is then used to determine the earth's thermal conductivity, k.sub..infin., from a precalculated graph, and using the value of thermal conductivity thus determined, then determining the vertical earth temperature gradient, b, from predetermined steady state heat balance equations which relate the undisturbed vertical earth temperature distributions at some distance from the borehole and earth thermal conductivity to the temperature gradients in the transducers and their thermal conductivity. The product of the earth's thermal conductivity, k.sub..infin., and the earth's undisturbedmore » vertical temperature gradient, b, then determines the earth's vertical heat flux. The process can be repeated many times for boreholes of a geothermal field to map vertical heat flux.« less

Inventors:
 [1]
  1. LaJolla, CA
Publication Date:
OSTI Identifier:
864118
Patent Number(s):
US 4313342
Assignee:
United States of America as represented by United States (Washington, DC)
DOE Contract Number:  
E(04-3)-1318
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
method; apparatus; determining; vertical; heat; flux; geothermal; field; mapping; entire; based; elongated; heat-flux; transducer; 10; comprised; length; tubing; 12; relatively; thermal; conductivity; thermopile; 20; inside; measuring; gradient; positioned; borehole; period; sufficient; tube; reach; equilibrium; thermally; coupled; surrounding; earth; fluid; annulus; preferably; water; mud; measurement; ratio; determine; infin; precalculated; graph; value; determined; temperature; predetermined; steady; balance; equations; relate; undisturbed; distributions; distance; gradients; transducers; product; determines; process; repeated; times; boreholes; map; vertical heat; thermal gradient; surrounding earth; period sufficient; heat flux; temperature gradient; thermal conductivity; temperature gradients; temperature distribution; thermally coupled; thermal equilibrium; vertical temperature; preferably water; heat balance; geothermal field; determining vertical; /374/73/

Citation Formats

Poppendiek, Heinz F. Method and apparatus for determining vertical heat flux of geothermal field. United States: N. p., 1982. Web.
Poppendiek, Heinz F. Method and apparatus for determining vertical heat flux of geothermal field. United States.
Poppendiek, Heinz F. Fri . "Method and apparatus for determining vertical heat flux of geothermal field". United States. https://www.osti.gov/servlets/purl/864118.
@article{osti_864118,
title = {Method and apparatus for determining vertical heat flux of geothermal field},
author = {Poppendiek, Heinz F},
abstractNote = {A method and apparatus for determining vertical heat flux of a geothermal field, and mapping the entire field, is based upon an elongated heat-flux transducer (10) comprised of a length of tubing (12) of relatively low thermal conductivity with a thermopile (20) inside for measuring the thermal gradient between the ends of the transducer after it has been positioned in a borehole for a period sufficient for the tube to reach thermal equilibrium. The transducer is thermally coupled to the surrounding earth by a fluid annulus, preferably water or mud. A second transducer comprised of a length of tubing of relatively high thermal conductivity is used for a second thermal gradient measurement. The ratio of the first measurement to the second is then used to determine the earth's thermal conductivity, k.sub..infin., from a precalculated graph, and using the value of thermal conductivity thus determined, then determining the vertical earth temperature gradient, b, from predetermined steady state heat balance equations which relate the undisturbed vertical earth temperature distributions at some distance from the borehole and earth thermal conductivity to the temperature gradients in the transducers and their thermal conductivity. The product of the earth's thermal conductivity, k.sub..infin., and the earth's undisturbed vertical temperature gradient, b, then determines the earth's vertical heat flux. The process can be repeated many times for boreholes of a geothermal field to map vertical heat flux.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1982},
month = {1}
}

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