Direct measurement of subsurface hydrocarbon true thickness and volume

A method to directly measure subsurface hydrocarbon true thickness and specific volume was developed under the laboratory conditions of vertical equilibrium and no-flow boundaries. The method utilizes a neutron moisture probe and was based on the premise that the neutron probe can detect hydrogen density differences between water and hydrocarbon. The hydrocarbon to be detected must be sufficiently deficient in hydrogen for the difference to be noticeable. The hydrocarbon used in this research was the wood preservative fluid mixture of 95% diesel and 5% pentachlorophenol found at the Montana Pole Plant, Butte, Montana. This hydrocarbon mixture displayed a difference from the groundwater at this site of approximately 11%. The minimum resolution was 0.5 foot of true product thickness with an accuracy of 93%. Specific volume estimates were nearly as good with 91% accuracy for predictions on a product specific volume of 1.2 gal/ft2 or greater