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Nonaqueous Phase Hydrocarbon in a Fine‐Grained Sandstone: 1. Comparison Between Measured and Predicted Saturations and Mobility
Author(s) -
Huntley David,
Hawk Robert N.,
Corley Helen P.
Publication year - 1994
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1994.tb00898.x
Subject(s) - hydrocarbon , capillary pressure , saturation (graph theory) , borehole , geology , petroleum , permeability (electromagnetism) , capillary action , mineralogy , petroleum engineering , geotechnical engineering , chemistry , porosity , porous medium , materials science , composite material , paleontology , biochemistry , mathematics , organic chemistry , combinatorics , membrane
The distribution and mobility of light, nonaqueous phase hydrocarbons in the subsurface is poorly understood, particularly in relation to observations of hydrocarbons in monitoring wells. Recent work by Lenhard and Parker (1990) and Farr et al. (1990) resulted in an equilibrium model in which the degree of hydrocarbon saturation was shown to be a function of the apparent thickness of hydrocarbon in a monitoring well, the height above the oil/water interface, and the capillary pressure/saturation characteristics of the soil. The current investigation compared measured hydrocarbon saturations, hydrocarbon volumes, and hydrocarbon mobility to those predicted by the capillary characteristic model of Farr et al. (1990) and Lenhard and Parker (1990). Five monitoring wells were completed in boreholes drilled in a hydrocarbon‐contaminated area of downtown San Diego, where apparent hydrocarbon thickness varied from zero to over 1.5 meters. Up to 2.5 meters of continuous core was obtained from each of the boreholes and split into 3 cm intervals. Alternating 3 cm samples were analyzed for total petroleum hydrocarbon, and the remaining samples were used for grain‐size analysis and measurement of capillary characteristic curves. Slug‐withdrawal tests were conducted on the hydrocarbon intervals, and constant‐rate discharge tests were conducted on the water‐saturated intervals of the monitoring wells. The results show typical hydrocarbon saturations of 5% to 20%, with one borehole showing a limited zone of up to 50% saturation. Hydrocarbon mobility (relative permeability) is greatly reduced due to the low saturations, as predicted by capillary theory. These observations are consistent with both the capillary model of hydrocarbon distribution and with the very low recoveries achieved using hydrocarbon skimming systems.