Model based inversion of acoustic impedance of annulus behind casing
US9829597B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 20, 2015 |
| Grant date | Nov 28, 2017 |
| Priority date | — |
| Expiry date | May 17, 2036 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B47/005
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Techniques involve obtaining acoustic data from an acoustic logging tool, where the acoustic data includes waves reflected from the casing, the annular fill material, the formation, and/or interfaces between any of the casing, the annular fill material, and the formation. A crude casing thickness, tool position (e.g., eccentering), mud sound velocity may be estimated using the acoustic data. A specular reflection signal may also be estimated based on the acoustic data. A modeled waveform may be generated using the estimated specular reflection signal and one or more model parameters, such as an estimated crude casing thickness, an estimated tool position, an estimated sound velocity of mud between the acoustic logging tool and the casing, an estimated impedance of the annular fill material, and an estimated impedance of the mud. The modeled waveform may be calibrated in some embodiments. Furthermore, a casing thickness may be estimated by matching the modeled waveform with the corresponding measured acoustic data. The techniques may output one or more of a thickness of the casing, an apparent impedance of the annular fill material, and the impedance of mud.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.