The pictures went around the world. In April 2010, huge amounts of methane gas escaped from a well below the Deepwater Horizon platform in the Gulf of Mexico. This "blow-out" caused an explosion, in which eleven people died. For several weeks, oil spilled from the damaged well into the ocean. Fortunately, such catastrophic "blow-outs" are rather rare. Continuous discharges of smaller amounts of gas from active or old and abandoned wells occur more frequently.
The pictures went around the world. In April 2010, huge amounts of methane gas escaped from a well below the Deepwater Horizon platform in the Gulf of Mexico. This "blow-out" caused an explosion, in which eleven people died. For several weeks, oil spilled from the damaged well into the ocean. Fortunately, such catastrophic "blow-outs" are rather rare. Continuous discharges of smaller amounts of gas from active or old and abandoned wells occur more frequently.
Scientists from GEOMAR Helmholtz Centre for Ocean Research Kiel and the University of Basel now published new data in the international journal Environmental Science & Technology, indicating that gas migration along the outside of wells could be a much bigger problem than previously assumed. This type of leakage is currently neither considered by operators nor regulators, but could be just as important as fugitive emissions through damaged wells, which are usually recognized and quickly repaired. "We estimate that gas leakage around boreholes could constitute one of the main sources of methane in the North Sea", says Dr. Lisa Vielstädte from GEOMAR, the first author of the study.
During expeditions to oil and gas fields in the central North Sea in 2012 and 2013, the scientists discovered a number of methane seeps around abandoned wells. Interestingly, the gas originates from shallow gas pockets buried less than 1,000 meters below the seabed. They are simply penetrated when drilling into the underlying, economically interesting hydrocarbon reservoirs. "These gas pockets usually do not pose a risk to the drilling operation itself. But apparently disturbing the sediment around the well enables the gas to rise to the seafloor," explains Dr. Matthias Haeckel from GEOMAR, who initiated the study.
Continue reading at Helmholtz Centre For Ocean Research Kiel (GEOMAR)
Photo: Methane gas leakage near a well. Credit: ROV KIEL6000, GEOMAR
