Quantifying methane emissions from the Tampen area (Norwegian North Sea)

The Norwegian Continental Shelf (NCS) hosts tens of thousands of active and extinct natural occurring methane seeps (NOMS), which support unique ecosystems. As a mature area for oil and gas exploration and production, the NCS contains ~8,000 wells, including ~2,000 that have been plugged and abandoned and over 2,000 slated for decommissioning. When these gas emissions occur at or near wells, they are known as well-associated methane seeps (WAMS). Here we present the first integrated quantification of methane flux from both NOMS and WAMS over a vast area of the NCS.

Our multidisciplinary survey was conducted on the Tampen area west of the Norwegian Channel. We combined 1) a large 800 km² multibeam and water column survey to locate, identify and classify each individual gas flare in the area and determine its intensity; 2) in situ ROV sea floor observations and gas flux measurements conducted at different seepage intensity sites; 3) gas sampling and individual geochemical analyses to fingerprint the fluids origin.

Nearly 2,000 flares have been mapped, identifying Tampen as potentially the region with the highest flares concentrations in the Norwegian part of the North Sea; 175 of these flares are associated with plugged and abandoned wells. Geochemical analyses show that methane is the main seeping gas with a distinct microbial signature. This suggests a shallow origin of the seeping gas likely trapped in the glaciogenic wedge along the western edge of the Norwegian Channel. The identified flares were categorized into six classes based on height, width, and intensity from the multibeam echosounder water column data. Applying class-averaged flux estimates, we derive a first-order, internally consistent assessment of methane release across the survey area.

These findings provide an unprecedented opportunity to evaluate the environmental consequences of gas emissions from NOMS and WAMS. Until now, it has been difficult to quantify the emissions reaching the atmosphere and their impact on ocean acidification. These new datasets also provide essential insights for mitigation measures and for implementing the design of future CO₂ and hydrogen storage projects in depleted reservoirs on the NCS. Ensuring long-term stability and safety of these systems will support sustainable resource management and compliance with environmental regulations.