Method for cementation evaluation using acoustical coupling and attenuation
US4896303A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 17, 1988 |
| Grant date | Jan 23, 1990 |
| Priority date | — |
| Expiry date | Nov 17, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V1/50
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Acoustical coupling is proposed as a means of determining the presence and acoustical impedance of materials behind casing in cementation evaluation. Expressions for computing coupling and attenuation in multi-receiver/transmitter logging systems are analyzed in an exponential model for the spatial decay of elastic wave energy propagating axially along the casing. Amplitude change between transmitter(s) and receiver(s) is separated into a change dependent on coupling into and out of the casing wave, as well as a change related to attenuation along the casing. Coupling which is dependent on geometrical factors such as casing size and thickness, and on distribution and mechanical properties of the material outside the casing, shows principally the mechanical impedance of the material outside. Significantly, the bonding of this material to the casing is not a dominant factor for the coupling. Thus an estimation of cement strength may be made even in the presence of microannulus.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.