Signs of Natural Renewal of Oil and Gas Reserves in Fields of the South Caspian Basin

Abstract

A.A. Feyzullayev, I. Lerche, I.M. Mamedova, A.A. Gojayev

Results are given of oil and gas production in the long-lived fields Bibieybat and Garadag of the Absheron Peninsula, South Caspian Basin (SCB). The analysis for the Bibieybat oil field covered the period from 1935 to 2018, and for the Garadag gas condensate field from 1955 to 1979. The development is the Productive Series (lower Pliocene) - main reservoir of the SCB. The intensive development of these fields leads to the disturbance of the natural dynamic equilibrium established in the reservoir over geological time. A sharp drop of formation pressure (significantly lower than hydrostatic) during field development contributes to the natural inflow of hydrocarbon fluids to the reservoir. The rate of natural oil replenishment calculated for 29 operating facilities of the Bibieybat field varies per well within 0.32-1.4 ton/day (averaging 0.76 ton/day) or about 277 ton/year. The rate of natural gas inflow at the Garadag gas condensate field is different for its various blocks, averaging 5.2 thousand m3/day per well. Stable oil and gas production and the equivalent rate of natural recharge are determined by the influence of a complex of factors, of which reservoir pressure, temperature and permeability of the reservoir rocks are dominant.

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