| abstract |
The present invention provides a downhole method and apparatus to determine the percentage of oil based mud or water based mud filtrate contamination in a formation fluid sample. The present invention determines the percentage of filtrate contamination in a sample comprised of a mixture of crude oil and an oil based mud filtrate or of formation brine and a water based mud filtrate. The filtrate contamination percentage is determined from a relationship between the densities of uncontaminated formation fluid and filtrate. Filtrate may oil based or water based mud. The density of formation fluid is determined from a series of high precision pressure measurements of formation fluid at a plurality of depths in a hydrocarbon producing well. The density of filtrate is provided by downhole measurements with a flexural mechanical resonator or by measurements made downhole or at the surface. |