Understanding Heterogeneities in Turbidite Reservoirs Using Sedimentology and Production Data and the Implications for Hydrocarbon Recovery: Sleipner Field, Norwegian North Sea

Satur, Nicholas¹, Helga Hansen¹ (1) Statoil ASA, Stavanger, Norway

Sleipner consists of four gas-condensate fields and is located in the Southern Viking Graben, Norwegian North Sea and has been in production since 1993. The Tertiary-aged Ty Formation comprises one of the fields and is made up of deep-water turbidite sandstones and associated mudstones. This reservoir has a net to gross of 91% with high porosity (0.27%) and permeability (700mD) values.

The drainage strategy of the Ty Field has been to recycle surplus dry gas to increase the condensate production. Different chemical gas-tracers have been injected into the reservoir to map out the 3-dimentional pathways of the injected dry gas, and thereby identify unswept areas. Initially the pressure was identical in all areas of the reservoir, and during the production the wells show similar pressure development. This indicates very good pressure communication within the entire reservoir. A large aquifer is giving pressure support and biannual 4D seismic and RST-C logging give valuable information of the water movements in the reservoir.

However, hemipelagic and turbiditic mudstone layers up to 5m thick and laterally extensive across most of the field are present and play an important role in fluid flow within the reservoir. Sedimentological models can be made to help predict mudstone distribution, with these models refined using production data. Understanding these heterogeneities in the reservoir are important for planning new wells and well interventions, like additional perforations to target poorly swept areas of the reservoir.