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Peculiarities of migration of hydrocarbons in geological conditions of the South Caspian basin

Abstract

Based on results of theoretical and experimental worldwide studies, analyses of lithofacial characteristics, macro- and micro-features of texture of the Oligocene-Miocene source rocks, thermo-dynamic conditions of their occurrence, main forms, phases, directions and distance of migration of hydrocarbons in geological conditions of the SCB were examined. These were allowed to draw the following basic conclusions:

  • The transport of oil in the form of molecular solution in connate waters cannot be considered in the SCB as a potential mechanism of primary migration of oil because bulk of these waters was discarded up to the depth of 3–4 km, but oil window is situated at depths interval 5–9 km.
  • Occurring of overpressures in the Baku archipelago is one of the evident signatures of hindered expulsion of hydrocarbons generated in the source rocks. Possibly, this can explain the low efficiency of prospecting of commercial accumulations of hydrocarbons in this area. In this conditions primary oil migration unlike the classic concept will probably has pulse/explosive character.
  • In massive source rock sequences hydrocarbons moved mainly laterally upwards up to highly permeable vertical fractures, faults, conduit of mud volcanoes and then due sub vertical migration along this pathways to carrier rocks/reservoir.
  • Presence in main Low Pliocene reservoir of SCB of the fault systems, feeding structures by hydrocarbons from underlying sediments was established.
  • Discovering in a several fields the commercial petroleum accumulations in the Quaternary and Upper Pliocene suites is an indicator of re-formation of underlying hydrocarbon accumulations in main reservoir.
  • The process of destruction of hydrocarbon accumulations is expressed by multiple large-scale hydrocarbon macro seepages, related with deep faults and mud volcanoes. The tertiary micro flows of hydrocarbons are manifested by formation of epigenetic gas anomalies above commercial petroleum accumulations.
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