Sequence stratigraphy, facies, and sea level change of the Hauterivian productive complex, Priobskoe oil field (West Siberia)

The productive complex of the Priobskoe field formed during the Hauterivian in the central part of the West Siberian basin as part of the Neocomian (E arly Cretaceous) progradational complex. Its depositional setting was a she lf-break margin with well-developed clinoform units and a 1-2 degrees slope gradient. Two depositional sequences have been identified and consist of d istinct systems tracts. The low-stand systems tract of the lower sequence ( AC12.2-4) formed as a result of rapid high-amplitude relative sea level fal l, and is clearly differentiated into low-stand fan and lowstand prograding wedge deposits. Sea level fall of lower amplitude (and rate) led to deposi tion of a lowstand systems tract in the upper sequence (AC10.1-2) in which no lowstand fan unit was deposited. A thin transgressive systems tract of t he lower sequence (AC11.0) formed during a short-term sea level rise. In co ntrast, prolonged high-amplitude sea level rise led to deposition of a thic k transgressive deposit in the upper sequence (AC10.0-AC8). Deposition of t he sandiest units is related to shelf (shoal-water) deltas and shelf-edge d eltas on the shelf, and to submarine fans in basinal portions. Deposition o f shelf-edge deltas was accompanied by abundant gravity-driven processes an d formation of shingled turbidites, during which the basin margin significa ntly prograded and infilled accommodation space. In many cases, sediment su pply into the deep-marine systems of Priobskoe was provided from multiple f eeder entry points that led to coalescence of individual submarine fans int o thick submarine ramps. Because it is based on copious drilling and seismi c data, the sequence stratigraphic framework developed for the Priobskoe he ld may serve as a useful analog model for exploration and prospect generati on in Hauterivian clinoforms, as well as in the entire West Siberian Neocom ian. There is good correspondence between the relative sea level change interpre ted for Priobskoe to the quantified eustatic curve (QEC) generated from Rus sian platform stratigraphy. This implies that eustasy played an important r ole in controlling sedimentation ia the Priobskoe field. In addition, it su pports the validity for the Hauterivian interval of the QEC.