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The analysis of the soil gases on the chosen example of oil mine.

Zbigniew Fąfara, Igor Ilkiv, Joanna Przybyłowicz

Vol. 32, no. 2 (2015), s. 443-454, [1]

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In the autumn of 2014 were performed the geochemical research of the soil gases composition in the area of selected oil mine in southern Poland. For a total were carried out of 75 individual analysis at 55 measuring points. The average depth of the measuring point was about 84.4 cm. The grid selection of the measurement points was made ad hoc, taking into account arrangement the existing mine installation and the location of the abandon wells. Finally, geochemical studies were performed in the vicinity of 6 exploitation wells (1 liquidated, one flowing well and 4 pumped periodically), on the route of transmission pipelines and in the area of group centers. The free choice of the measurement point location was limited by buildings and agricultural crops. In the area of the analyzed deposit were drilled more than 100 wells, most of which were liquidated and usually did not stay after them no trace on the surface. Based on the results of the geochemical research of the soil gases composition there was determined the spatial distribution of the methane concentration in the soil in the nodes of a regular grid by geostatistical methods using kriging. On this bases there were developed the maps of the methane concentration. Generally, on the oil deposit site there were detected two areas with the increased methane concentration in the ground. The distribution of the methane concentration in soil on the first one shows the installation leak in the vicinity of several wells. In the second much smaller area it may suspect that the pipeline transporting crude oil to the group centre is leaky. In the research area are vast cultivated fields of high oxygenation and small wet ground. There are no permanently wetlands areas. This means that in soil occur at most aerobic rot and decay processes, resulting in the production of carbon dioxide but not methane. There is no reason to assume that occur also the natural anaerobic putrefaction processes. Therefore, the detected abnormally high methane concentration in the ground is not of biological origin. To confirm formulated hypothesis should also be do the chromatographic research of C14 carbon isotope content in the taken methane samples from the soil to determine his age and confront it with the age of methane produced from the deposit. In general, the results analysis of the geochemical research of the soil gases composition leads to the conclusion that the rock mass is hermetic from the geological point of view, but there are occasional leaks in the production system of several wells and transmission pipeline, that can remove.