Method and system for skin effect correction in a multiple transmit frequency induction logging system
US5698982A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 18, 1996 |
| Grant date | Dec 16, 1997 |
| Priority date | — |
| Expiry date | Mar 18, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/28
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An induction logging tool is disclosed for utilization in conjunction with surface electronic equipment for measuring a characteristic of subsurface formations. A transmit signal which is comprised of a repetitive sequential series of at least three transmit frequencies is generated by coupling an oscillator to a transmitter coil and a plurality of selectable tuning capacitors. A signal characteristic of the response of the formation to this transmit signal is detected at a receiver coil array and two phase sensitive detectors are then utilized to generate output signals indicative of the magnitude of the X and R components of the formation signal which is in phase with a reference phase signal. The output signal of each phase sensitive detector is then utilized to accurately determine the X and R component of the receiver coil signal for each frequency by nulling the output of the phase sensitive detector utilizing a closed loop conversion circuit which eliminates errors due to phase and gain variations. The X and R signals from two or more frequencies are then utilized to correct for skin effect in both magnitude and spatial response.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.