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Oilfield Glossary
Oilfield Glossary
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buoyancy method

1. n. [Formation Evaluation]
A technique for measuring the bulk volume of a core sample by submerging it in a bath of mercury and observing the increase in weight of the bath, following Archimedes principle. The bulk volume is calculated from the increase in weight divided by the density of mercury at the temperature of the bath. The sample must not touch the side of the bath and be only a few millimeters below the surface. Mercury is used because it is so strongly nonwetting and therefore does not enter the pore space. Other, less toxic, liquids may be used in the bath, such as brine, refined oil or toluene. In this case, the sample must be fully saturated with the liquid before immersion. In an alternative method, the saturated sample is weighed in air and then again once immersed. The bulk volume is then the difference in weight divided by the density of the liquid used.