System and method for lithology-independent gas detection using multifrequency gradient NMR logging
US6242912A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 19, 1997 |
| Grant date | Jun 5, 2001 |
| Priority date | — |
| Expiry date | Mar 19, 2017 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02A90/30
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A well logging system and method are disclosed for detecting the presence and estimating the quantity of gaseous and liquid hydrocarbons in the near wellbore zone. The system uses a gradient-based, multiple-frequency NMR logging tool to extract signal components characteristic for each type of hydrocarbons. To this end, a new data acquisition method is proposed in which measurements at different frequencies are interleaved to obtain, in a single logging pass, multiple data streams corresponding to different recovery times and/or diffusivity for the same spot in the formation. The resultant data streams are processed to determine mineralogy-independent water and hydrocarbon saturations and porosity estimates. Gas and oil saturations are used to obtain accurate estimates of the water content, permeability and other parameters of interest.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.