System and method for EM ranging in oil-based mud
US8844648B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 26, 2011 |
| Grant date | Sep 30, 2014 |
| Priority date | — |
| Expiry date | Dec 12, 2032 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B47/022
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
Nearby conductors such as pipes, well casing, etc., are detectable from within a borehole filled with an oil-based fluid. At least some method embodiments provide a current flow between axially-spaced conductive bridges on a drillstring. The current flow disperses into the surrounding formation and causes a secondary current flow in the nearby conductor. The magnetic field from the secondary current flow can be detected using one or more azimuthally-sensitive antennas. Direction and distance estimates are obtainable from the azimuthally-sensitive measurements, and can be used as the basis for steering the drillstring relative to the distant conductor. Possible techniques for providing current flow in the drillstring include imposing a voltage across an insulated gap or using a toroid around the drillstring to induce the current flow.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.