Method for validating a downhole connate water sample
US6729400B2 · kind B2 · utility
Assignees
Inventors
Key dates
| Filing date | Nov 27, 2002 |
| Grant date | May 4, 2004 |
| Priority date | — |
| Expiry date | Nov 27, 2022 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B49/0875
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A downhole connate water sample drawn from the formation surrounding a well is validated when mud filtrate concentration is acceptably low. A preferred method includes drilling the well with a water-based drilling fluid, or more generally a water-based mud (WBM), containing a water-soluble dye. The dye acts as a tracer to distinguish connate water from WBM filtrate in a downhole sample of formation fluid contaminated by mud filtrate from the water-based mud. Preferably, an optical analyzer in a sampling tool measures light transmitted through the downhole sample to produce optical density data indicative of dye concentration. Preferably, optical density is measured at a first wavelength to obtain a first optical density, and at a second wavelength, close in wavelength to the first wavelength, to obtain a second optical density. First and second optical density data are transmitted to the surface. At the surface, in a data processor, the second optical density is subtracted from the first optical density to produce a third optical density that is substantially free of scattering error. The data processor validates each sample that has an acceptably low third optical density. The inv…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.