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Seismic and Core Based Reservoir Characterization, the Giant Priobskoye Field, West Siberia, Russia


The Priobskoye Field is one of the largest stratigraphic traps in the world, covering over 5,400 km2 and with a recoverable resource of 5.86 BBO and 1.17 TCF of gas. The trap is a complex series of fine-grained, highly heterogeneous reservoirs varying from basin floor fans to slope channels and shallow water deltas. The traps are within an overall progradational ‘clinoform’ complex with regional seals created where shore face ravinement of the delta top sets has removed the reservoir facies landward and placed marine shales over pro-delta shales and siltstones. Additional pure stratigraphic traps occur within a multitude of turbidite fans and slope channels in the ‘Achimov’ Formation. Hydraulic fracturing is generally needed to obtain commercial flow rates. Most reservoirs are dominantly meso and micro-porous, with the best reservoirs in hummocky cross-stratified deltaic shore face and delta front sandstones. Locally, ‘massive’ deep water sandstones and bioturbated shore face sandstones form effective reservoirs. Most of the other facies are micro-porous and have a high content of bound-water and high water saturations. 3D seismic facies analysis clearly delineates many of these productive trends and can be used to high-grade ‘sweet’ spots of better reservoir quality rock in the complex. Recognition of these better reservoir fairways can be used to enhance production with additional infill drilling and perhaps even horizontal well placement. The Priobskoye Field is a superb analog for similar combination and stratigraphically trapped reservoirs in deltaic successions.