OIL AND GAS COMPOSITION PERSPECTIVES FOR DEEPLY BURIED SEDIMENTS IN EASTERN GEORGIA
Despite a long history of oil extraction in Georgia and numerous studies carried out, current economic outcomes for the industry are not impressive. However there were certain periods of progress in the development of industrial extraction. For example, in the 1970s and 80s annual oil extraction in Georgia exceeded 3 million tons (see G. Khmaladze, N. Khmaladze, Georgia’s oil industry during the transition period; TSU Publishing House, 2002, p.14).
Based on targeted studies, scientists in Georgia distinguish five existing oil and gas districts and two potential ones. Officially, 15 oil fields (mostly small-debit), one gas-and-oil and one gas only have been registered. Presently, TSU scientists believe it is expedient to focus on one of the potential reserves to increase oil extraction in Georgia, specifically in the deeply buried Meso-Cenozoic sediments.
With financial support from the Shota Rustaveli National Science Foundation, from 2013 till 2016 the Alexander Tvalchrelidze Caucasian Institute of Mineral Resources began implementing a project in 2013 – Assessment of Oil and Gas Composition Perspectives of Deeply Buried Meso-Cenozoic Sediments in Eastern Georgia—which will terminate in 2016.
The project was initiated by Nani Aslanikashvili, Chairperson of the Scientific Council at the Caucasian Institute of Mineral Resources; Head of the Department of Energy Resources at the same Institute; and Doctor of Geological and Mineralogical Sciences. Unfortunately Dr. Aslanikashvili passed away before she could see the end of the project.
Today scientists carrying out the program include Professor Mirian Topchishvili, Doctor of Geological-Mineralogical Sciences, a corresponding member of the Georgian National Academy of Sciences; Vakhtang Iorashvili, Research Fellow at the Department of Energy Resources of the Caucasian Institute of Mineral Resources; Aslan Suladze, Doctor of Geological-Mineralogical Sciences, Head of the Department of Informatics and New Technology at the same Institute; Zurab Kilasonia, Research Fellow at the Caucasian Institute of Mineral Resources; and Maia Chichinadze, Research Fellow at the Simon Janashia Museum of Georgia.
In order to ensure the conversion of bio-organic compounds diffused in rocks into oil, sediments must pass through a long stage of sedimentogenesis (sedimentation), then diagenesis (change of sediments into a sedimentary rock) and finally catagenesis (secondary conversion of bio-organic compounds existing in already-formed rock).
The scientists have studied and described the peculiarities of sedimentary and volcanic-sedimentary rocks, conducted genomic typification and analyzed lithological and geochemical criteria of rocks. They carried out paleo-geographic and paleo-volcanic reconstructions and focused on determining the role of deep processes in the formation of oil and gas basins and in the mobilization of hydrocarbons. Modern and paleo-geothermal conditions of the basins were reconstructed and the vitrinite reflectance of disseminated humus organic matter was measured (humus – a dark-brown or black organic substance made up of decayed plant or animal matter). Based on this, the quality of organic matter and rock catagenesis was determined In addition, a complex stadial analysis was conducted to assess the quality of conversion of sedimentary and volcanic-sedimentary rocks.
Statistical data on the distribution of oil and gas deposits showed that gas fields are mainly located deeper (>4.5 km) and their reservoirs (so-called collectors) are connected to secondary induration zones. Moreover, their distribution according to depth is unequal. This could largely be determined by specific regimes in the depths for which identification has both theoretical and practical importance. Special attention is being paid to the quality of initial types and catagenesis of organic compounds according to the composition and color of dispersed organic matter. Organic compounds change their color according to the composition of organic matter and microfossils (spores, stamens and micro plankton). In addition to the fact that palynological research would further enrich the results already achieved by the Institute, this would be an innovative approach and yield important results in the field of oil and gas composition research in Georgia.
The oil and gas district of eastern Georgia is a western endpoint of a mega-depression of southern part of the Caspian Sea (downstream of the Mtkvari (Kura) River, in Azerbaijan). Thus, studies conducted will be interesting for Azerbaijani specialists too. The national oil and gas company Saknavtobi has carried out exploratory assessments of the oil and gas composition of deeply buried Meso-Cenozoic sediments inside the Caspian depression, by drilling medium and deep (3700 m) wells. According to the data, some have potential for producing important oil resources.
Previous studies show that factors that largely determine the hydrocarbon potential of sediments were not fully taken into consideration when assessing the oil and gas composition potential of deeply buried sediments. This has created difficulties in forecasting deposits and exploitation.
One of the novelties of the project is to determine the apparently consistent patterns between oil and gas composition and endogenous regimes (processes caused by forces from within the earth), including volcanic processes. For this purpose the researchers will study the formation conditions of the Meso-Cenozoic sedimentary basins to determine lithological and geochemical characteristics of the rock. (Lithology is the science of sedimentary rocks and sedimentary deposits, present-day sediments, their composition, structure, genesis and distribution.)
The importance of various geological processes for the formation of filtration characteristics of rocks will be assessed before the project is over. The stages and zones of catagenesis will be determined on the basis of the complex stadial analysis and vitrinite reflectance data. The vertical gradient of catagenesis will be determined by extrapolation, through which it will be possible to assess thermobaric regimes in deep horizons. The same data can also be used in adjacent areas where no drilling data are available so far.
The team pointed out that on the basis of analysis and generalizations that can be made about materials studied the hydrocarbon potential of deeply buried sediments can be forecast. The project’s success will have practical results as well, as it will enable interested oil-extraction companies to save significant financial resources.