25th International Meeting on Organic Geochemistry IMOG 2011

P-093
Organic geochemistry, petroleum systems, history of oil and gas
generation and accumulation in northern part of West Siberian
basin
Alexey Kontorovich, Lev Burshtein, Sergey Ershov, Valery Kazanenkov, Natalya Kim,
Vladimir Kontorovich, Vasiliy Melenevsky, Pavel Safronov, Alexander Fomin, Elena
Fursenko, Georgiy Shemin
Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russian Federation
(corresponding author:burshteinlm@ipgg.nsc.ru)
The present study is considered regional in scope,
aiming to refine on the conceptualization of
hydrocarbon accumulation processes in the area of
northern, the deepest part of West Siberian basin
including the Kara Sea off-shore area.
The main processes of hydrocarbon generation in the
basin took place in Later Cretaceous and Cenozoic.
Three distinctly different stages have become
apparent over its geological history, each of them
being equally important for the evolution of oil and gas
generation and accumulation in the north of the West
Siberian basin; however, the nature of processes
occurred during those stages proved crucially distinct.
The separation of the stages was driven by global
geodynamic and climatic changes.
During the Palaeogene time, which is comprised in
the first stage, likewise in Mesozoic, the West
Siberian geocyneclise continued downwarping. There
accumulated thick strata of Paleocene, Eocene and
Oligocene sediments, with the temperature of rocks
in the Jurassic and Cretaceous complex continuing to
grow, and the processes of katagenetic
transformations of organic matter occurring actively,
accompanied by the intense generation of liquid and
gaseous hydrocarbons.
The second stage began late in Late Oligocene and
continued throughout all the Neogene. At this stage,
in close connection with the history of the Arctic
Ocean evolution, proceeded the uplift of the northern
portion of the geosyneclise and the intense erosion of
the previously accumulated sediments. The
temperatures rising during the uplift ceased to
increase in the sedimentary cover. As a result, the
generation of hydrocarbons either slowed, or ceased.
The third stage began in Late Pliocene and comprised
the entire Pleistocene. It is associated with the drastic
cooling of climate in the northern hemisphere,
followed by the permafrost and thick ice sheets build
up, which radically changed the thermodynamic
conditions of the sedimentary cover and also had a
significant impact on the formation of hydrocarbon
accumulations.
Geological model of the study area, reflecting its
modern state, contains a set of regional structural
maps for Jurassic, Cretaceous, and Cenozoic
reference horizons, actual thicknesses maps for some
separate stratigraphical complexes with established
lithological varieties, as well present-day
temperatures and heat-flow maps; thickness maps for
rocks eroded in Cenomanian –Cenozoic, and glacier
and permafrost thickness maps. The model includes a
series of paleo-geographic maps for various time
intervals.
The work defines the main source-rock complexes
and the type of OM predominant in them, as well as
its modern and initial concentrations. Some special
geochemical studies done resulted in building
schematic maps for katagenetic transformation of
OM and Corg content, complemented by geochemical
characteristics of OM of oil-and-gas –source rocks,
and oils, gases and condensates derived from them.
In addition, the evaluation of kerogenes‘ kinetic
parameters was carried out for basic types of oil and
gas source-rocks. Assessed were both the dynamics
and scales of hydrocarbons generation therewith, and
the phase composition of the products generated.
Analyzed the relations of timing of seals formation
(lithification), timing of traps formation and the phases
of HC generation by various types of source-beds. A
special attention was called to early katagenetic
hydrocarbons generation.
In the study to follow the mentioned geological and
geochemical modeling, there were built variouslyscaled
4D (3D+T) models of oil and gas generation,
migration and accumulation simulations both for all
the study area and with the focus on some local
zones within its borders.
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