Addition to hydrocarbon reserves (HC) from the Bazhenov Formation in Western Siberia is evident and confirmed by commercial oil inflows.
Presently, a number of projects aimed at the study of oil and gas potential of Bazhenov Formation (Bzh. fm.) at the regional, zonal, and local levels is developing in Gazpromneft Company.
In 2012, as a part of the regional assessment of the Bzh. fm. deposits, the area was ranked according to the petroleum potential. Later on 2015, as a continuation of the project, a 3D basin model of Bzh. fm. system (unique by its size and quantity of input data) was built to establish the criteria for a comprehensive assessment of petroleum potential of the area. The geochemical parametres was used for the 3D model calibration.
Despite the significant potential and the oil inflows from the Bzh. fm. deposits, any detailed prospectivity assessment of the total area has not been done.
A large complex of actual data and studies including 10 wells core pluggings, full set of geochemical studies involving pyrolitic (1,200 samples), chromatographic (60 samples) (GC), and gas chromatography-spectrometry analysis (60 samples) (GC-MS), bitumen and oils group composition (180 samples) was integrated to the project.
The results of the work allowed understanding of geochemical processes in-situ (primary cracking, secondary cracking, HC adsorption) and the regional scale of HC system developing.
The potential and the in-place reserves of the Bzh. fm. were evaluated of up to 1 trillion tons of HC and 173 billion tons of oil, respectively.
One of the main results was the quantification of the HC adsorption on the kerogen surface. The Rock-Eval analysis of the organic matter (OM) showed that the most of the HC (S1 and S2 peak) are in the adsorbed form. For the Bzh. fm. deposits the amount of adsorbed HC does not exceed 20–25 mg of HCs per g/rock. The results obtained allowed to adjust the resource evaluation of the HC potential and to estimate the in-place reserves, and to rank the adsorbed HC as non-recoverable.
Taking into account the results of the geochemical analysis, and using the basin modeling technology, maps for different types of HC distribution within the Bzh. fm. were built for the entire area.
Thermal history of the basin was reconstructed based on published data (Kurchikov et al., 1987) corrected in respect of mesuared BHT data. Integration of the geochemical data and the 3D basin modeling tool allowed for Bzh. fm potential the additional evaluating parameter to be invented. This parameter is based on physical and chemical HC fluid composition.