The example of background determination and mathematical processing of data from surface geochemical survey for the purposes of petroleum exploration

The paper reports on the methods of mathematical processing of the results of surface geochemical survey applied to petroleum exploration. The results include concentrations of methane analyzed in 1251 soil gas samples collected from the area over the Wierzchowice gas field (SW Poland). The methods were presented of determining the geochemical background, the anomalous threshold as well as of data normalization and filtration. The advantages were presented of iterative method for determination of background values proposed by the authors. In the authorsʹ opinion, selection of the background should be preceded by statistical analysis of each set received during the iteration process. The method presented relies on the assumption of normal distribution of this dataset. The spatial distributions were compared of raw (measured) concentrations and mathematically process values. The applied mathematical data processing enables the researcher to eliminate the “noise” and to select objectively the anomalous values. Thus, such an attempt facilitates the comprehensive interpretation of geochemical data referred to geological model of a field. Results of the studies have demonstrated that the distribution of surface anomalies of methane over the Wierzchowice gas field has been disturbed by long-lasting exploitation. The anomalies appear mainly over dislocation zones, and in the SE part of the area they take the “halo” form around exploited portions of the field due to unexploited areas off the field.