TEDESCO, STEVEN A.
Atoka Geochemical Services Corp., Englewood, CO

Abstract: Surface Geochemical Expression Through Time Over Producing Fields and A Natural Gas Storage Facility

The basis of surface geochemistry in petroleum exploration is the detection of leaking hydrocarbons and associated by-products in the soil. Early work suggested vertically, migrating hydrocarbons took years to reach the surface. The dynamic nature of soil would preclude a slow rate of vertical migration, as these processes would quickly remove the hydrocarbons and any evidence of their existence without rapid recharge. Over the past fourteen years, approximately 30 petroleum productive fields and one underground natural gas storage facility have been sampled through time. The sampling over these petroleum reservoirs began prior to discovery and in some cases continued for up to ten years after production was established. The methods of detecting the hydrocarbon leakage utilized soil gas, iodine, magnetic susceptibility, Eh, pH and conductivity. The reservoirs vary in depth form 400 to 10,000 feet; produce form both clastic and carbonate reservoirs; and are located in several different geologic basins. The underground natural gas storage facility was sampled over a one year period utilizing iodine and soil gas methods. The petroleum reservoirs demonstrated a similar pattern of rapid loss of anomaly by the second or third year of full production. The surface geochemical anomaly appeared and disappeared over the underground natural gas storage in a delayed but direct response to the injection and withdrawal of gas. The results of this study demonstrated the relative real-time nature of vertical migration.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas