Other Electrode and Toroid Devices

  • Darwin V. Ellis
  • Julian M. Singer

Electrode devices have been put to many other uses than those described in Chapter 5, the earliest of these being the measurement of the resistivity of the invaded or flushed zone Rxo. Historically, the first use of the invaded-zone resistivity was, in the absence of any other measurement, to make an estimate of the formation porosity. Since then Rxo has found many applications. In earlier chapters we saw that Rxo, when compared with Rt, gives a visual indication of permeable zones and evidence ofmoved hydrocarbons. In Chapter 5 we saw the need for Rxo in obtaining a better estimate of the deep-resistivity Rt. Rxo can be combined with other information to determine the water saturation of the invaded zone, Sxo, and thereby estimate the efficiency of hydrocarbon recovery. Sxo can also be a useful indicator of hydrocarbons on its own.


Drill String Borehole Wall Guard Electrode Toroid Device Core Photograph 
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Supplementary material

978-1-4020-4602-5_6_MOESM6_ESM.pdf (1.4 mb)
Supplementry material (PDF 2565 kb)

Copyright information

© Springer Science+Business Media B.V 2007

Authors and Affiliations

  • Darwin V. Ellis
    • 1
  • Julian M. Singer
    • 2
  1. 1.Schlumberger-Doll ResearchRidgefieldUSA
  2. 2.RichmondUK

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