(1) Geo-Microbial Technologies, Inc, Ochelata, OK
ABSTRACT: The Dynamic Nature of Hydrocarbon Microseepage: An Overview
Hydrocarbon microseepage rates and near-surface hydrocarbon concentrations can vary significantly over time. Surface hydrocarbon seeps and soil geochemical anomalies have been shown to appear and disappear in relatively short times, weeks to months to years. Published reports document (1) the disappearance in less than 20 years of a soil hydrocarbon anomaly from above Hastings field in Brazoria County, Texas, (2) the increased strength of a surface geochemical anomaly over Hibig field in Bastrop County, Texas, during repressurization for secondary recovery studies, (3) leakage of gas from 1000-meter deep gas storage reservoirs into shallow water wells within a one year period, (4) response of soil gas hydrocarbon concentrations above gas storage reservoirs within 2-4 days to pressure changes in the reservoir, and (5) significant changes in microseepage intensity and distribution over existing fields and waterfloods in time intervals as short as one year.
These studies clearly demonstrate rapid variations in gas flux associated with pressure changes in gas storage caverns and conventional oil and gas reservoirs. Based on these and other reports, the rate of hydrocarbon migration and microseepage appears to vary from less than one meter per day to tens of meters per day.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.