Ormen Lange—a Giant on the Fast Track

Guargena, Claudia G.¹, Ron Den Ouden², Helge Hamre¹, Sigbjorn Kalvenes¹ (1) A/S Norske Shell, Stavanger, Norway (2) Hydro ASA, Sandvika, Norway

The Ormen Lange gas field was discovered in 1997 by Hydro in 1000 m water depth and covers an area of ca. 350 km2. It was further appraised by 3 wells prior to development approval in April 2004 by the Norwegian authorities. The partnership of Hydro (development operator), Norske Shell (production operator), Petoro, Statoil, ExxonMobil and Dong are currently preparing the first 8 production wells, with a planned production-start in October 2007. The development of the Ormen Lange Field is characterized by a number of extraor­dinary challenges, like rough seabed topography, subzero temperatures at sea bottom, metocean conditions and a handover process preceding the change of operatorship at pro­duction start-up.

The turbidite reservoir is intensely faulted. These polygonally distributed faults are not expected to be sealing; developed close to seabed, rules out cataclasis and cataclasis­enhanced cementation. The common gas gradient and the absence of measurable depletion during well tests support non-sealing faults and vertical connectivity. However, the dynam­ic fault seal uncertainties have necessitated the risking of the relatively simple ”tank” sce­nario and a more cautious, stepwise approach for the development concept chosen. Earliest indications of the size of the connected gas accumulation will be derived from production versus pressure decline relations. Results of time-lapse seismic modelling have been stud­ied, but remain inconclusive as to detecting possibly bypassed gas compartments and early water movements.

The continuous improvement of the seismic data quality by reprocessing has culminat­ed in better definition of the fault pattern and connectivity models. These models have been constructed in a 3D visualization environment where optimal integration of a multitude of seismic data cubes, derived attributes and geological model concepts has been achieved.