Publication History: This article is based on "Crain's Petrophysical Pocket Pal" by E. R. (Ross) Crain, P.Eng., first published in 1987, and updated annually until 2016. This webpage version is the copyrighted intellectual property of the author.

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In bitumen bearing oil sands or heavy oil, you can add the deep resistivity method for calculating shale volume. The purpose is to eliminate small Vsh anomalies caused by feldspar or uranium salts in the reservoir. The method works best with Phasor or Array Induction and High Res Laterologs, but may also be helpful in SAGD projects with olde logs.

1: Vshr = (log(RESD) - log(RMAX)) / (log(RSH) - log(RMAX))

  RESD = deep resistivity log reading (ohm-m)
  RMAX = deep resistivity reading in clean oil sand (ohm-m) 
  RSH = deep resistivity log reading in shale (ohm-m) 
  Vshr = shale volume from deep resistivity (fractional)



DOES NOT work in water zones so combine this methhod with any other feasible model to handle the water zones.



Bitumen sand example using Vsh calculated from minimum of Vshr and Vshgr. Final Fsh is light gray in lithology track at far right.


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