Developing Facies Models of Jurassic Deposits and Lower Cretaceous Clinoform Deposits for Forecasting Reservoir Rocks, Western Siberia
M.D. Belonin1, Vladimir Shimansky1, I.M. Kos2, and Sergey Hafizov3
1 All-Russia Petroleum Research Exploration Institute (VNIGRI), St.Petersburg, Russia
2 Surgutneftegas, Surgut, Russia
3 TNC-BP, Moscow, Russia
At present the prospects of discovering oil and gas pools in Western Siberia are bound up with the non-structural traps in the Jurassic and Lower Cretaceous producing complexes. However, the sharp lateral and vertical variation of reservoir properties make the forecast of hydrocarbon pools difficult. The reconstructions of sedimentation environments have been used for recognizing the regularities in reservoir rocks distribution. The data of petrographic, paleontological, granulometric, textural, paleostructural, chemical analysis, seismic survey and logging data have been used for such reconstructions.
It was established that the Jurassic deposits had been formed in a wide range of environments: from continental to shallow-water ones. The sedimentation criteria of forming and distributing these reservoir rocks have been established. The reservoir rocks in Lower and Middle-Jurassic deposits are confined to buried paleoriver-beds and proluvium deposits. The lithological reservoirs of the Upper Jurassic deposits are confined to the sea continuation of delta and to the accumulative sandy-silty bodies of a near-shore zone. About 50 zones prospective for oil have been established on the territory of Surgutsky, Krasnoleninsky swells and Uvatsky district.
The Lower Cretaceous clinoform complex of Western Siberia is formed by turbidite deposits. The best reservoir rocks are confined to incurrent canals, the central parts of fans of grain flows, and the zones of reworking the deposits of ancient fans by contour currents. Lithological traps occurred mainly on the flanks of structures or in depressions on the way of clastic material transportation. More than 70 prospective objects are established in clinoforms.