Application of surface organic geochemistry to petroleum exploration and environmental pollution
Abstract
A database of analyses of C$\sb1$ to C$\sb7$ hydrocarbons from an oil and gas producing region in Mexico was examined. Samples were collected at depths of 3, 15 and 30 meters from surficial holes drilled in traverses over producing and barren structures. The surface consisted of subtropical swamps; depth to structures was 3500 to 5800 meters. This study changes the general concept of geochemical exploration proving that: (1) the traditional 3 m depth of sampling is not the ideal depth to differentiate producing from barren structures; (2) comparison of data at a 30 m depth of sampling is necessary to differentiate producing from barren structures; (3) halos when present at 3 m disappear at 30 m; (4) differentiation of producing from barren areas can be 80% successful by integrating geology, geophysics and geochemistry. Hydrocarbon analyses from six structures were subjected to multiple discriminant function analysis to produce a retrospective statistical test of the ability of geochemical prospecting to distinguish producing from non-producing structures. The hydrocarbon spectra from 3 meters depth yielded ambiguous results: those from 30 meters produced clear distinction between barren and producing structures. Further, the discriminant functions established a base of geochemical characteristics founded on known areas (retrospective), to which additional unknown areas (prospective) may be compared for classification. A transfer of this petroleum exploration geochemical technology to environmental pollution problems caused by hydrocarbons was conducted. The application of this methodology improves the soil gas method currently used to detect and delineate hydrocarbon contaminated areas by: (1) Introducing the concept of differentiating biogenic from petroleum related gases, a crucial idea in the evaluation of hydrocarbon polluted areas. (2) Introducing a statistical method capable of differentiating anthropogenic pollution from natural background levels of contaminants. (3) Introducing a rapid technique to delineate areas contaminated with hydrocarbons by the analysis of aromatic hydrocarbons present in near-surface soils and sediments overlying subsurface polluted areas.
Subject Area
Geochemistry
Recommended Citation
Saenz De Herrera, Ma Guadalupe, "Application of surface organic geochemistry to petroleum exploration and environmental pollution" (1990). ETD Collection for University of Texas, El Paso. AAI9104093.
https://scholarworks.utep.edu/dissertations/AAI9104093