Standoff compensation for nuclear logging while drilling systems
US5486695A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 29, 1994 |
| Grant date | Jan 23, 1996 |
| Priority date | — |
| Expiry date | Mar 29, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V5/08
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A standoff compensation system is disclosed for use in an LWD system implementing gamma density and/or neutron porosity measurements. An acoustic transducer is provided to measure the standoff distance between the logging tool and the borehole wall. The present invention includes a downhole processor for determining a weighting factor for the density and/or porosity measurements based upon the measured standoff distance. The weighting factor can either be calculated by the downhole processor according to a predetermined weighting function, or can be retrieved from a pre-calculated look-up table in ROM. The processor then multiplies the weighting factor by the count data from the sensor to determine a weighted count value. The weighted count values are accumulated during an averaging period and normalized, so that a single normalized count value can be generated and either stored in downhole memory, used immediately, or transmitted by telemetry to the surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.