BERGEN, Norway – Octio Gravitude will conduct gravimetry measurements this summer over the deepwater Ormen Lange gas field in the Norwegian Sea.
The four-week campaign will involve measurements of water depth and the gravitational field at the seabed above the gas reservoir.
Since 2012, seabed gravimetry and subsidence measurements have been acquired over the field every second year.
According to Octio Gravitude, gravimetry measurements detect mass changes in the subsurface and reveal how fluids are moving in the reservoir.
Seabed subsidence measurements indicate how reservoir rocks respond to the pressure decrease caused by hydrocarbon production. Combining these two sets of measurements is said to assist reservoir management and production efficiency.
For this survey, the company will deploy its new gWatch technology from Siem Offshore’s survey vessel Siem Pride on 120 subsea measurement locations, via an ROV supplied by IKM Subsea. gWatch is said to provide more efficient operation, at lower cost and with improved sensitivity compared with traditional gravimetry instrumentation.
At Ormen Lange, gravimetry works in parallel with 4D seismic to broaden the understanding of the reservoir.
However, gravimetry and subsidence surveys are less costly than 4D seismic, hence the strategy of combining two-yearly monitoring at the field with gWatch with less frequent 4D seismic acquisitions.
Ormen Lange operator Norske Shell is working on installing a subsea compression system to further enhance recovery, and the data acquired this summer should provide insight into reservoir monitoring with compression added.