Hydrocarbon habitat of the Dniepr-Donets Depression

Abstract

Basin inversion, depending on its intensity, can enhance the trapping potential of a basin or causes destruction of major hydrocarbon resources. Post-inversion subsidence, depending on its magnitude and the amount of syn-inversion erosion, can induce a second phase of hydrocarbon generation and the charging of inversion structures. However, this mechanism, which contributed, for instance, to the hydrocarbon habitat of inverted basins in the Southern North Sea, was not effective in the Dniepr-Donets Basin. The Dniepr-Donets Depression forms part of the Pripyat-Dniepr-Donets-Donbass-Karpinsky aulacogen that evolved as a Devonian rift. The post-rift subsidence of this basin was interrupted during the late Early Permian when its southeastern parts were partly inverted. Further inversion pulses straddle the Jurassic-Cretaceous and the Cretaceous-Tertiary boundaries. The Dniepr-Donets Depression hosts the most important hydrocarbon province of the Ukraine. At the beginning of 1994, ultimate recoverable reserves in established accumulations (past production and remaining reserves) amounted to about 170 × 10 6 t of oil and gas-condensate and 980 × 10 9 m 3 gas. The bulk of oil and gas accumulations is contained in Carboniferous to Early Permian postrift series. Source-rocks occur in Devonian syn-rift and Carboniferous post-rift series; these attained maturity prior to basin inversion. Hydrocarbon accumulations are characterized by multiple reservoir-seal pairs. The mature syn-rift Devonian and the immature post-inversion series contain only minor hydrocarbon accumulations. Oil and gas accumulations are mainly trapped in syn-rift, salt-induced and inversion-related structures. The latter received their hydrocarbon charge mainly due to inversion-induced destruction of pre-existing accumulations and ensuing re-migration of hydrocarbons.