Estimation of Depth Occurrence of the Oil and Gas Sources in the South Caspian Basin

Akper A. Feyzullayev
Petroleum Geology and Geochemistry, Geology Institute, Baku, Azerbaijan

Taking into account the great importance of the estimation of maturity of oil and gas for understanding of the mechanism of formation of their pools, the goal of this presentation is the generalization of all researches carried out for the South Caspian basin (SCB) up to now with the purpose of creation of summary model of vertical zonality of oil and gas formation in this basin. This paper is dedicated to the estimation of maturity of hydrocarbon (HC) fluids and creating of the summary model of vertical zonality of their formation in sedimentary complex of SCB. The methods of a direct estimation of maturity of oil and gas were carried out by using of appropriate isotope-geochemical parameters. The estimation of maturity of gas is based on the experimentally revealed dependence between isotope composition of carbon (ICC) of HC gases and vitrinite reflectance
According to created model the interval of generation of oil occurs on 5-9 km (peak on 7-8 km) and gas - on 7-15 km (peak on 11-12 km). It is important to note, that the revealed vertical zonality of oil and gas formation do not reflect zonality of their accumulation in reservoirs, which is caused by the processes of intensive subvertical migration of HC fluids, having presumably injection character The distance of subvertical migration of the most oils is, presumably, about 4 km and gases’ is 8 km and more.

It is interesting that the maturity of oil seepages related to mud volcanoes coincides with the maturity of Miocene-low Pliocene reservoir oils. This fact allows concluding that oils of the mud volcanoes are a product of destroying of oil accumulations in the mentioned reservoirs.

On the basis of geological structure of SCB, the regularities of change of maturity of oil and gas in space and stratigraphic control of their sources location were established.

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