Method of and apparatus for sonic logging while drilling a borehole traversing an earth formation
US5852587A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 20, 1992 |
| Grant date | Dec 22, 1998 |
| Priority date | — |
| Expiry date | Feb 20, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V1/46
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The present invention is directed to sonic logging while drilling. A transmitter and at least one receiver are mounted on a drill collar for performing sonic investigations of the formation traversing a borehole. It has been discovered that a drill collar has a natural stop band or notch where acoustic energy propagating in this frequency range is severely attenuated. Thus, to reduce drill collar acoustic coupling, the transmitter is operated within this natural stop band of the drill collar. An imperforate stop band filter is also included between the transmitter and receiver to amplify the natural stop band. The transmitter is mounted transvere to the longitudinal axis of the drill collar, and is preferably mounted within means that reduce drill collar acoustic coupling. The transmitter preferably includes a material whose acoustic response is more favorable along its longitudinal axis relative to its radial axis, thereby directing the acoustic energy into the formation rather than the surrounding drill collar.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.