SUBSIDENCE HISTORY AND HYDROCARBON MIGRATION MODELING IN SOUTH CASPIAN BASIN

We study the mechanisms of migration and spacial distribution of hydrocarbon deposits along a regional 1000 km long SW - NE seismic cross section of the South Caspian Basin. A retrospective 2D geological simulation of basin subsidence and sediment filling history is performed taking into account accompanying processes of thermal and catagenetic transformations of organic matter, and subsequent migration and accumulation of hydrocarbons. The start of the basin opening with accumulation of considerable sedimentary mass can be dated as middle Mesozoic (Triassic or Jurassic), and hydrocarbon prone horizons can now be located at depths of 12 km. The hydrocarbon saturation of the Pliocene Productive Series is of epigenetic (allochtonous) nature, which is also confirmed in literature by geochemical data from mud volcanoes and by other facts. Geochemical age, depth of provenance and reworking degree of hydrocarbons point at generation sources in Mesozoic (gas) and Paleogene-Miocene formations (oil) with only subordinate participation of the lower "Productive Series" Pliocene suites. The dominant migration pattern of fluids is interformational (interstratal) intermittent injective subvertical flow along disjunctive planes, zones of increased fracturing and loose rocks, diapir intrusion contacts, eruptives of mud volcanoes, lithofacial unconformities and other structures, breaking the rocks continuity. This implies the possibility of commercial-scale accumulations of hydrocarbons at ultra high depths, if trap structures of sufficiently large sizes are available, comparable with already discovered giant oil and gas fields (Shah-Deniz, Azeri-Chirag-Gyuneshli etc).

Seismic stratigraphy of the late Quaternary sedimentary infill of Lac d'Armor (Kerguelen archipelago): a record of glacier retreat, sedimentary mass wasting and southern Westerly intensification

Lac d'Armor (49°27′S, 69°42′E) is a medium-sized, fjord-type lake located on the ‘Grande Terre’ island of the Kerguelen archipelago. A dense grid of high-resolution reflection seismic profiles was collected from this lake basin. The seismic stratigraphic facies reveal a last deglaciation to Holocene infill comparable to the seismic facies found in other glacigenic lakes all over the world. Remarkable features in the seismic stratigraphy are mounded structures found at the southern edge of both sub-basins. The sediment mounds can be interpreted as sediment drifts created by wind-induced bottom currents. The onset of the build-up of these drifts initiated at some point in the Holocene and indicates a strengthening of the southern Westerlies, which are currently the dominant winds on this island.