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Abstract: Improvements in Field and Analytical Methods for Measuring Surface and Near-Surface Hydrocarbons in Various Onshore Surface Environments

John V. Fontana, Robert D. Edmondson

Methods used to detect seepage of the lighter hydrocarbon gases (C1-C6) include collection of interstitial Previous HitsoilNext Hit gases, static Previous HitsoilNext Hit head-space analysis of dissolved/adhered gases, and acid extraction of occluded/adsorbed gases. The methods have advantages and disadvantages that are tied to the Previous HitsoilNext Hit environments. Previous HitSoilNext Hit extraction methods have higher yields per unit of Previous HitsoilNext Hit volume, but are more affected by Previous HitsoilNext Hit composition differences. Interstitial Previous HitsoilNext Hit-gas methods yield lower concentrations, but reflect active seepage and are less affected by Previous HitsoilNext Hit composition changes.

Recent developments in Previous HitsoilNext Hit-probing equipment and tool design have significantly improved the quality of Previous HitsoilNext Hit and Previous HitsoilNext Hit-gas sample collection for these methods. Careful pre-survey study of the Previous HitsoilNext Hit environment can significantly improve a survey's results by identifying potential problems with certain methods. A common example is residual source rocks in the Previous HitsoilNext Hit releasing "relic" hydrocarbons. A two-stage interstitial Previous HitsoilNext Hit-gas sampling method eliminates this problem by using Previous HitsoilNext Hit-gas monitoring implants set at depths of 10-25^prime.

Fluorescence techniques are shown to be very effective at detecting heavier hydrocarbons in the near surface. Properly scanned, the spectra can reveal at least six peak groups of aromatic hydrocarbons. The relative fluorescence intensities of these groups are associated with gravity of the oil, for biodegraded oils. The spectra are unique to a given oil. This allows correlations, or fingerprinting, of produced oils with Previous HitsoilTop extracts.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994