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The benzene method for finding oil pools uses a combination of two technologies: A. The application of benzene analysis of formational brines in dry wells for the discovery of oil reservoirs hydraulically upstream; and B. The application of geochemical soil gas surveys to find an oil reservoir in the direction and distance indicated by the benzene analysis and the flow direction of the underlying formational brines.
Extensive reservoir fluid compositional studies and research have shown that soluble aromatic hydrocarbons, such as, benzene, ethyl benzene, toluene and xylenes make up a large proportion of the dissolved hydrocarbons found in brines associated with oil reservoirs. BTEX aromatic hydrocarbons are the primary volatile liquid hydrocarbons dissolved in the brines due to their high solubility in water. Empirical studies indicate that the benzene content of brines from typical oil reservoirs range from about 5 to 20 ppm depending on oil composition and source.
Benzene and related aromatic constituents of oils in reservoir partitions into the brines at the oil-water interface and form a plume of decreasing magnitude with increased distance from the reservoir edge. Analyses of benzene concentrations in brine samples from non-productive exploration wells can therefore be used to predict the distance to a nearby petroleum accumulation with a reasonable level of confidence. The distance to an oil reservoir is directly proportional to the log of the benzene concentration of the adjacent brines. This relationship is due to solubility and diffusion factors.
With tests from the same formation, in two or more nearby wells, results can often be used to provide a much more accurate prediction of the distance and direction, to potential undiscovered reservoirs within the stratigraphic horizon tested. As a data base of local wells is developed, the benzene magnitude to distance relationship can be further refined for a specific basin or formation of interest, improving the quality of the distance predictions.
Now that benzene (BTEX) analysis of formational brines in one or more dry wells has indicated the distance and direction of a nearby reservoir, it is now the role of geochemical soil gas surveys to find and delineate the new pool. This is accomplished by a geochemical soil gas transect in the upflow direction of the underlying brines.The benzene method depends on the accuracy of the sampling and analysis of benzene as well as the directional flow of formational brines underlying the reservoir. Geochemical surveys can mitigate any of these inaccuracies by several transects if necessary.
To start a project a company would provide to Petro-Find the location of the dry wells, benzene (or BTEX) analysis of the formational brines encountered in the drilling and the direction of hydraulic flow for the Basin. Petro-find would then calculate the approximate distance from the dry holes to the petroleum reservoir. Because of the possible inaccuracies of benzene sampling and analysis and direction of formational brine flows, a geochemical soil gas survey is employed to find the reservoir in the indicated direction. This can be accomplished by a single transect of a geochemical soil gas survey. Once the edge of the reservoir is found a geochemical soil gas survey is conducted to find the areal extent and configuration of the oil reservoir. Seismic may confirm if the anomaly represents a structural trap; the lack of correlation indicates a stratigraphic trap invisible to seismic. A combination of benzene analysis and Petro-Find geochemical soil gas surveys would provide a scientific basis for drilling a successful well.For further information on methdology refer to the following Link... Also refer to a paper entitled "Cost-Effective Helium/Hydrogen/Neon Soil Gas Surveys in Uranium Exploration" Link...
PETRO-FIND GEOCHEM LTD
215 Mallin Crescent
Saskatoon, Saskatchewan, Canada S7K 7X3
Contact: Paul Lafleur, President
Phone: (306)931-3156 Fax: (306)931-9773
E-Mail: plafleur@sasktel.net