Method and apparatus for producing a more accurate resistivity log from data recorded by an induction sonde in a borehole
US5210691A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 9, 1991 |
| Grant date | May 11, 1993 |
| Priority date | — |
| Expiry date | May 9, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/28
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A maximum entropy method (MEM) determines a more accurate formation parameter profile, such as conductivity profile, of a formation. The MEM method employs an iterative procedure for determining the formation parameter profile. At each interation, theoretical logs are computed and compared with the measured log data. One iterative step is the calculation of a forward model to predict the response of the tool in a given assumed formation. Another iterative step is the solution of a set of linear equations to update the assumed formation parameter in the formation to produce closer agreement to the measured data. In a solution iterative step, the input is the measured values of the voltages denoted by V.sub.k.sup.j and the calculated values V.sub.k.sup.j, the output is an improved formation parameter profile .sigma..sub.l.sup.(n+1). In the solution step, a set of linear equations is solved for intermediate quantities q.sub.l.sup.(n), related to .sigma..sub.l.sup.(n) by the formula EQU .sigma..sub.l.sup.(n) =.pi.exp(q.sub.l.sup.(n)), where .pi. is a constant. Upon completion of the solution step, the updated formation parameter profile .sigma..sub.l.sup.(n+1) is stored and the followi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.