Coalification, Gas Generation and Migration in Donets Basin (Se Ukraine): 2D and 3D Modelling Study

D. Alsaab¹, M. Elie¹, R.F. Sachsenhofer², A. Izart¹, V.A. Privalov³, and L. Martinez^1
1UMR CNRS G2r/7566 – Géologie et Gestion des Ressources minérales et Energétiques. Faculté des sciences. Université Henri Poincaré, Nancy 1. BP-239, Boulevard des Aiguilletes, 54506 Vandoeuvres-lès-Nancy-France
²Institut für Geowissenschaften, Montanuniversität Leoben, Peter-Tunner-Strasse 5, A-8700 Leoben, Austria
³Donetsk State Technical University, Artem str., UA-84000 Donetsk, Ukraine

The goal of this work is to study the thermal history of the Donets Basin, to estimate the amount of Hcs generated from coals and to model the gas migration in order to improve the gas exploitation in Donets Basin. Several points are particularly under the scope of this study: the evolution of heat flow in this area during the evolution of the basin (taking into account a new geodynamic model proposed), the possible effect of magmatic intrusions on coalification trends and the role of tectonic structures in gas migration and trapping.
The Donets Basin is located in the south-eastern part of Ukraine is one of the major late Paleozoic coal basins in the world. This Basin contains more than 60 Gt of coal; the average of methane content is about 14 m³/ton of coal. Total coal thickness in carboniferous formations is ~ 60 m.
By using PetroMod 9.0 software developed by Integrated Exploration Systems (IES GmbH, Germany), 2D & 3D models were performed by using date from more than 30 wells, located on 6 sections in 3 areas of the Donets Basin: Donetsk, Krasnoarmeisk and Krasnodon. Burial history modelling provides the physical framework for thermal and hydrocarbon generation simulation. Calibration of the burial and heat flow histories was performed by using %Rr values and present-day recent formation temperatures. The models were calibrated by modifying the heat flow and the thickness of eroded rock until a satisfactory fit between measured and simulated thermal indicators (%Rr and formation temperatures) was observed. In some wells %Rr values are > 4.69%, thus an extended model of Easy%Ro algorithm is integrated in PetroMod Software by using data published by Everlien (1996) to do the calibration.
Therefore, numeric models (2D & 3D) reveal that many factors control coalification in Donets Basin: i)- Depth Carboniferous rocks during max Permian burial, ii)- Permian uplift, iii)- Lateral HF variation during max burial and iiii)- A late Permian Triassic heating event, probably caused by magmatic activity. Finally, a grand amount of Hcs gases generated during coalification phase in this Basin have been loosening during Permian uplift and erosion phases (Mesozoic and Cenozoic). We suggest that, due to the migration in Donets Basin the favourable sites for gas exploitation are not the better generative zones of methane.

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands