Method of predicting mechanical failure in formation utilizing stress derivatives which measure formation nonlinearity
US5619475A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 9, 1995 |
| Grant date | Apr 8, 1997 |
| Priority date | — |
| Expiry date | Nov 9, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2291/0422
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method for determining whether a formation is subject to incipient failure are disclosed. The method comprises determining in situ a nonlinear parameter of a formation, and determining whether the nonlinear parameter and/or a derivative of that nonlinear parameter as a function of stress has a relatively large negative value in order to determine whether the formation is subject to incipient failure. In a preferred embodiment, the nonlinear parameter of the formation is a derivative of the square of the shear or compressional velocity with respect to formation stress. The nonlinear parameter of the derivative of the square of the shear velocity with respect to stress is considered to have a large negative value when it is .ltoreq.-0.1 (km/sec).sup.2/ MPa, while the nonlinear parameter of the derivative of the square of the compressional velocity with respect to stress is considered to have a large negative value when it is .ltoreq.-0.2 (km/sec).sup.2 /MPa. The derivative of the derivative of the square of the shear or compressional velocity with respect to stress is considered to have a large negative value when the derivative is .ltoreq.-0.06 (km/sec).sup.2 /(MPa).sup.2. Typical…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.