Report of Leakage Assessment

Pedersen, Rolf B.; Baumberger, Tamara; Berndt, Christian; Blomberg, Ann E.A.; Bünz, Stefan; Chadwick, Andy; Class, Holger; Darcis, M.; Flemisch, Bernd; Holloway, S.; Karstens, Jens; Landschulze, Karin; Tasianas, Alexandros; Thorseth, Ingunn H.; White, James C.

doi:10.3289/eco2_d1.1

Cited by 1 publication

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“…Our estimate for CH 4 leakage along hydrocarbon wells in the North Sea is based on the lower two measured leakage rates 20 and the assumption that wells poking through shallow gas pockets will leak, which is corroborated by observed ebullition of biogenic gas at wells 15/9-13 and 16/7-2, 20 as well as 15/9-11 and 15/9-16. 43 However, Vielstadte et al 20 also found leakage at well 16/4-2, where no shallow gas pockets could be imaged in the seismic data (Figure 2b, note that the spatial resolution of the seismic data is ∼10 m) but seismic turbidity may suggest the presence of gas in the vicinity of the well (see Figure 2b, 0.1−0.4 s two-way travel time (TWT)).…”

Section: ■ Results and Discussionmentioning

confidence: 97%

Shallow Gas Migration along Hydrocarbon Wells–An Unconsidered, Anthropogenic Source of Biogenic Methane in the North Sea

Vielstädte

Haeckel

Karstens

et al. 2017

Environ. Sci. Technol.

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Shallow gas migration along hydrocarbon wells constitutes a potential methane emission pathway that currently is not recognized in any regulatory framework or greenhouse gas inventory. Recently, the first methane emission measurements at three abandoned offshore wells in the Central North Sea (CNS) were conducted showing that considerable amounts of biogenic methane originating from shallow gas accumulations in the overburden of deep reservoirs were released by the boreholes. Here, we identify numerous wells poking through shallow gas pockets in 3-D seismic data of the CNS indicating that about one-third of the wells may leak, potentially releasing a total of 3-17 kt of methane per year into the North Sea. This poses a significant contribution to the North Sea methane budget. A large fraction of this gas (∼42%) may reach the atmosphere via direct bubble transport (0-2 kt yr) and via diffusive exchange of methane dissolving in the surface mixed layer (1-5 kt yr), as indicated by numerical modeling. In the North Sea and in other hydrocarbon-prolific provinces of the world shallow gas pockets are frequently observed in the sedimentary overburden and aggregate leakages along the numerous wells drilled in those areas may be significant.

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