Near-surface thermo-atmo-geochemical structural mapping for oil and gas exploration in Ukraine

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Bagriy, Igor; Gozhik, Petro; Bagriy, Olga
Holding Date 10 September 2008

The technique of thermo-atmo-geochemical structural mapping (TAGSM) as non-traditional and cost-effective exploration technology is originally developed at Institute of Geological Sciences. It consists of phased geo-structural researches and analysis of fault tectonics, morphological analysis and neotectonic interpretation of space images, thermal and atmo-geochemical surveying, lab measurements and processing of the data acquired to build thematic map using GIS technologies. Field data acquisition stage includes thermometric, emanation and gas surveying (Rn/Tn, He, CO2, H2, free hydrocarbons) in petroleum-prone onshore areas and bottom sediments (up to 2 m below the surface) thermometry, Rn-metering and measurements of gas content in the near-bottom layer offshore.
To conduct the surveying there was developed a special instrument with some modifications designed to work onshore and offshore respectively. This technology is tested in different regions of Ukraine over known oil and gas fields. Upon interpretation of TAGSM reading there was elaborated the set of most characteristic features indicating presence of subsurface hydrocarbon pools :
- the pools related to geodynamically passive and low-permeable micro-blocks favorable for hydrocarbon trapping are revealed by near-surface atmo-geochemical halos with background concentrations of Rn, CO2, H2, and He rimmed by their local maxima featuring zones of increased geodynamic activity and fluid permeability;
- presence of diffusive halos of methane and ethane above hydrocarbon pools surrounded along their periphery with local maxima of concentration of higher methane homologues;
- slightly increased temperature in sub-soil/sub-bottom layer. TAGSM results have proved the potential productivity and readjusted contours of prospective leads for most of structures with commercial reserves in the Dnieper-Donets basin, Ukrainian Carpathians and Azov-Black Sea region. The analysis and generalization of data acquired testifies that complex neotectonic network of subseismic faults (detected via interpretation of space images and atmo-geochemical anomalies) stipulates distribution of the near-bottom temperatures and gas fluxes.
The technique is targeted onto improvement of the fault detection for prospective plays and mapping of fluid fluxes linked to neotectonically active faults governing near-surface discharge of hydrocarbons as indicators of their deep pools. This approach provides an optimal data set (upon its information content balanced with time and cost) favorable for better understanding of structural model of exploration prospects, their potential productivity and probable contours of the hydrocarbon pools.
The technique of thermo-atmo-geochemical structural mapping is applied for reconnaissance and exploration stages (combined with detail seismic mapping) of the hydrocarbon prospects and further development of oil and gas fields to choose optimal locations of production wells.