Method for correcting an electrical log for the presence of shale in a formation
AssigneeShell Oil Company
InventorsHarold J. Vinegar, Monroe H. Waxman
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Abstract
An apparatus is disclosed for borehole measurements of the induced polarization of earth formations. The apparatus consists of an induced polarization logger capable of measuring both in-phase and quadrature conductivities in the frequency domain. A method is described which uses these measurements to determine cation exchange capacity per unit pore volume, Q.sub.v, brine conductivity, C.sub.w, and oil and water saturations, S.sub.o and S.sub.w, in shaly sands.
Claims7
A method for providing a corrected electrical log of shaly sand formations penetrated by a wellbore using measurements made in-situ in the wellbore, said method comprising:
- inducing an electrical current in the formation;
- measuring both the in-phase C.sub.I and quadrature conductivity C.sub.Q of the formation in response to said induced current;
- determining the conductivity of C* of the formation from the relation ##EQU14## and recording the values of C* with respect to depth to provide an electrical log corrected for the presence of shale in said formations penetrated by the borehole.
Dependencies are inferred from the claim text.