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Stratigraphic Partitioning of Lower Permian Carbonate Reservoir Facies from Yuzhno Khilchuyu (Yk) Field, Timan Pechora Basin, Russia - Integrating Sequence Stratigraphic, Biostratigraphic, Geochemical, and Seismic Inversion Data for Improved Reservoir Prediction

Morgan, William A.1; Mitchell, Raymond W.2; Snow, John H.3; Kuvaev, Igor A.4; Swirydczuk, Krystyna 5
1 ConocoPhillips, Upstream Technology, Houston, TX.
2 ConocoPhillips, Upstream Technology, Bartlesville, OK.
3 Naryanmarneftegaz, Moscow, Russia.
4 ConocoPhillips, Moscow, Russia.
5 Consultant, Las Cruces, NM.

Description of nearly continuous cores from 5 new wells and 2 wells cored in the early 1990’s, acquisition of biostratigraphy and geochemical data, and the creation of a 3-D seismic inversion volume afford an opportunity to revisit stratigraphic correlations and facies characterization of the reservoir succession at Yuzhno Khilchuyu (YK) field, building on considerable geoscience work of current and past workers.

The reservoir succession at Yuzhno Khilchuyu field has a net thickness of approximately 100 m and comprises a lower Assellian carbonate aggradational succession and an upper Assellian-Sakmarian carbonate progradational succession, spanning some 6 million years total duration. The petrophysical characteristics and reservoir geometries of these successions differ. Based on core interpretation, sedimentary cycles of the lower succession typically consist of transgressive to highstand deposits of argillaceous, fine-grained, skeletal wackestones and packstones, overlain by late highstand boundstones, with the dominant reef builders being phylloid algae, Tubiphytes, and probable microbial organisms. Cycle tops do not commonly exhibit evidence of subaerial exposure. Some of the buildups are porous, others not, and porosity and permeability tend to be lower than reservoirs in the upper succession. The transgressive and highstand fine-grained wackestones and packstones will likely function as widespread barriers to vertical flow.

Cycles of the upper succession are grainstone-dominated, with abundant forams, Palaeoaplysina, and bryozoan fragments. Microcodium, a paleosol alteration product, typically defines cycle tops, indicating that subaerial exposure was common. Boundstone fabrics are rare and transgressive deposits are thinner and have less or no argillaceous component, suggesting that widespread seals are less likely to be present in the upper grainstone-dominated succession.

Well-tests, seismic inversion data, and geochemical typing of oils confirm that the porous buildups of the lower succession are less connected both laterally and vertically than grainstones of the upper succession, which have good connectivity.

Integration of YK data into the updating of a stratigraphic and depositional framework that feeds into a geocellular model is an important ongoing process that yields insights into reservoir characterization and field development of an important asset in the Timan Pechora Basin.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009