| US 7,457,707 B2 | ||
| Method for determining an effective formation conductivity for induction log borehole correction | ||
| Andrei I. Davydychev, Sugar Land, Tex. (US); and Gerald N. Minerbo, Missouri City, Tex. (US) | ||
| Assigned to Schlumberger Technology Corporation, Sugar Land, Tex. (US) | ||
| Filed on Nov. 30, 2006, as Appl. No. 11/606,631. | ||
| Prior Publication US 2008/0133138 A1, Jun. 05, 2008 | ||
| Int. Cl. G06F 19/00 (2006.01) | ||
| U.S. Cl. 702—7 [324/339] | 12 Claims |
| 1. A method for correcting induction conductivity well log measurements for conductivity of a wellbore and a formation proximate
the wellbore, comprising: estimating an effective formation conductivity for the formation proximate the wellbore from measurements
made by an induction receiver proximate an induction transmitter; wherein the estimating effective formation conductivity
comprises selecting an initial value of the effective formation conductivity and iteratively calculating estimates of the
effective formation conductivity using an output of each iterative calculation as input to successive iterative calculations
thereof, using the effective formation conductivity to correct apparent conductivity measurements made by at least one induction
receiver on the instrument
wherein the iteration is performed according to the expression:
 σt is the effective formation conductivity,
J is an iteration step index,
σt(J) is the J-th approximation of σt,
σt(0) is the initial value of effective formation conductivity,
σR is the real part of the apparent conductivity determined from the proximate receiver measurements,
rb is a wellbore radius,
d is an amount of displacement of a well logging instrument from a center of the wellbore,
σm is conductivity of a fluid in the wellbore,
γ(σt) the skin-effect magnitude for the effective formation conductivity, and
gR(rb,d,σm,σt) is a pseudo-geometrical borehole correction factor.
|