Jurassic Reservoirs of the Barents Sea Shelf

Jurassic reservoirs of the Barents Sea shelf. Environments of sedimentation

A.A. Suslova, A.V. Stoupakova, Y.K. Burlin, N.M. Kirykhina, P.O. Golinchik.

The Barents Sea shelf is located in the north Norway and adjacent part of Russia. The area represents the one of the major undeveloped petroleum province of the world. Huge petroleum resources have been proved in the Barents Sea: the giant gas field – Shtokmanovskoye, large gas fields Ludlovskoe and Ledovoye in the Russian sector and Snøhvit gas and Goliath oil fields in the Norwegian sector.

The main discoveries have been made in Jurassic reservoirs. A geological framework of the Jurassic on the Barents Sea shelf is presented in this work. The set of seismic profiles and logs were interpreted and thickness maps for the Jurassic succession have been compiled. There are 5 large sedimentological cycles in the Jurassic succession. Maximum flooding surfaces separate these cycles.

The main target of this study is to trace the distribution of the Jurassic section and to understand the evolution of the basin throughout Jurassic period. We aimed also to determine the main sediment source areas for that time and to understand their relative contribution.

Compilation of literature combined with rock and core materials, seismic interpretation and well-logs analysis have been done in order to describe the focused interval.

The Barents Sea was a part of a large epicontinental seaway in the Mesozoic. Jurassic rocks are widely distributed in the eastern part of the Barents Sea. In the western Barents they are located in the separate depressions. In the north-western and north-eastern parts of the Barents they were eroded during the regional uplift in the Cenozoic. The warm and humid climate promoted increased weathering and erosion of the older sediments and basement rocks on the land. Large volumes of gravel, sand and mud were transported out into the shelf basins.

The traces of distribution of the Jurassic strata can be followed on seismic by series of clinoforms. For example, the progradation of the Middle Jurassic clinoforms has been mapped by seismic from the Finnmark platform into the Hammerfest basin. In the eastern part of the Barents Sea the clinoforms progradate from the Frants Joseph Land and Novaya Zemlya archipelago into the South and North Barents depressions. According to this data the probable sediment source areas were Finmark platform, Frantz Joseph Land and the Novaya Zemlya archipelago. The Svalbard archipelago could be also the source of material.

Early Jurassic marine basins were shallow and rarely more than 100 meters deep. However, continued subsidence across the Permian-Triassic basins resulted in sediment thickness of several hundred meters up to 1000 meters in the depressions. The maximum thickness of the Jurassic strata according to well data is in the eastern Barents Sea and reaches 1400 meters in the South Barents depression. A set of thickness maps for each epoch of the Jurassic period is included with superposed Late Palaeozoic tectonic elements to discuss the potential tectonic control on deposition spatially and through time.

Eastern and Western part of Barents have been developed simultaneously within the one basin. Thereby that allowed us to mark out five transgressive-regressive regional cycles within the Jurassic section, using Lower and Upper Jurassic sections of the different localities of the Barents sea. These cycles of sediments accumulation are caused by lateral zoning and eustatic periodicity of sea level change. During Late Jurassic and Tithonian, the sea level reached its maximum, and an extensive marine shelf covered most of the Barents Sea.