Invasion Profiling With The Phasor Induction Tool

The Phasor induction tool is the first new low-frequency tool to result from the intensive modeling efforts undertaken to better understand the induction log. In addition to the usual deep induction (ID), medium induction (lM), and spherically-focused (SFL) measurements, the Phasor tool makes additional measurements which aid in real-time environmental correction. These additional measurements are the induction quadrature, or X-signals, which are an integral part of the Phasor shoulder-effect correction algorithm. By combining these internal measurements with borehole geometry measurements in the same tool string, both shoulder effect and borehole effect can be corrected. With the environmental effects removed, a real-time inversion of the induction and SFL data into a three-parameter invasion model (Rxo, Rt, and di) can be done at the wellsite. The linear vertical response of the Phasor logs allows accurate response matching to eliminate bed-boundary effects on the invasion profiling algorithm. In higher resistivity environments, frequently Rxo is less than Rt. The Phasor log can be inverted in this regime and will show an interpretation similar to that of the Dual Laterolog. The Rxo interpretation is consistent with measurements with Rxo devices. Wellsite determination of the invasion profile can be related to other formation parameters such as permeability and "moved oil." The values of Rxo and Rt, along with knowledge of Rmf, are useful as a one-tool SW "quicklook" computation.