Estimating molecular size distributions in formation fluid samples using a downhole NMR fluid analyzer
US9645277B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 12, 2013 |
| Grant date | May 9, 2017 |
| Priority date | — |
| Expiry date | Mar 12, 2036 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R33/20
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method for estimating a property of subsurface material includes extracting a sample of the material using a downhole formation tester and performing a plurality of nuclear magnetic resonance (NMR) measurements on a sensitive volume in the sample where each measurement in the plurality is performed in a static homogeneous magnetic field with a pulsed magnetic field gradient that is different in magnitude from other NMR measurements to provide a waveform signal. The method further includes transforming each received waveform signal from a time domain into a frequency domain and comparing the frequency domain signal to a reference to provide proton chemical-shift information related to a chemical property of one or more molecules in the sample and transforming the frequency domain signals into a complex number domain that quantifies waveform signal amplitude changes to provide one or more diffusion rates with each diffusion rate being associated with a corresponding frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.