Method of sonic logging while drilling a borehole traversing an earth formation
US5796677A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 29, 1994 |
| Grant date | Aug 18, 1998 |
| Priority date | — |
| Expiry date | Apr 29, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V1/52
- 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 traversed by 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 enhance the natural stop band. The transmitter is mounted transverse 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. Received acoustic energy waveforms are electronically processed to reliably detect, in the presence of drilling noise, those acoustic signals which are produced by the …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.