Oil based mud imaging tool with common mode voltage compensation
US8212568B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 12, 2010 |
| Grant date | Jul 3, 2012 |
| Priority date | — |
| Expiry date | Apr 12, 2030 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/24
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus and method for minimizing the effects of a common mode voltage signal in downhole logging tools utilized to determine the resistivity of an adjacent portion of a borehole wall. Two current electrodes are energized by an excitation source to create an oscillatory electric field in a borehole wall. A voltage drop across a segment of the borehole wall is measured by two voltage electrodes, and the differential voltage is used in combination with a measured current flow to determine a resistivity value for the borehole wall. A common mode voltage in front of the two voltage electrodes is measured and minimized by controlling the excitation source, thereby reducing the resistivity measurement error.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.