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Snow White is Dead!


While idly clicking through LinkedIn this weekend, as you do when you have some time to kill, I came across a repost of a SPE article on carbon dioxide (CO2) plumes:



This is an intriguing title and promised to provide a pleasant read where my preconceived notions would be confirmed. For the most part the author, Stephen Rassenfoss, indeed delivered on this promise. Predictably, an expert is quoted saying that a layer-cake reservoir model with homogenous properties is a red flag. This expert is Amanda Livers-Douglas, assistant director for integrated subsurface projects at the Energy & Environmental Research Center (EERC) at the University of North Dakota. With a title like that, citing the statement takes more space than the statement itself. The article continues with more comfortably reassuring statements about how to build a reservoir model.


All seems well as I am approaching the end of the text, but then suddenly another example is introduced and attributed to another expert. Philip Ringrose, adjunct professor at the Norwegian University of Science and Technology (NTNU more familiarly to most of us), is said to have presented a paper on the unexpected growth of the CO2 plume in the Snøhvit Field, offshore Norway, and the subsequent shut down of operations. Now that is alarming! Billions of dollars are being spent on CO2 sequestration projects, so any real-life example where the sequestration went so badly that the project was shut down is a nightmare come true. Unfortunately, Rassenfoss leaves his reader with this bombshell and a final quote from Ringrose: “expect surprises when you start injection”.


Well, now that my pleasant read turned into a disturbing revelation of new information, I could not move on to my regular Sunday dilemma of walking the dogs before or after my second cup of coffee. I had to get some details about what evil queen poisoned Snow White! My first stop was at Wikipedia which shows that Snøhvit is an Equinor-operated gas field in the Barents Sea. Development was controversial in 2002 because the LNG plant was going to increase Norway’s CO2 emissions by 2%. Protesters were arrested after blocking the construction site, but I am getting distracted. From Wikipedia I get to the Equinor website. Here it seems that rumors of Snøhvit’s death have been greatly exaggerated. Equinor writes that on December 20th, 2022, Equinor submitted a NOK 13.2 billion plan for development and operation (PDO) of Snøhvit Future on behalf of the Snøhvit partnership to the Minister of Petroleum and Energy. Equinor also gives details on the production: A total of 16 wells have been drilled on the Snøhvit field, 14 producers and two wells for reinjecting carbon dioxide. The plant on Melkøya captures CO2 from the well stream, before returning it to the field far below the seabed. Evidently, the CO2 is mixed in with the gas and is prudently separated out and reinjected.


From the Equinor site, I am linked to the Norwegian Petroleum site and then on to the Norwegian Petroleum Directorate’s website, the regulator in Norway. The most recent update on the NPD website is from December 13th, 2022, and shows Snøhvit’s status as: Snøhvit production is in its plateau phase. Since production started, additional production wells have been drilled in different structures. Work is ongoing to evaluate future compression solutions, as well as measures for reducing CO2 emissions from the onshore facility at Melkøya. The Snøhvit production was shut-in after a fire at the LNG plant at Melkøya in 2020, but was resumed in June 2022 when the plant was fully operational again. I seem to have come to a dead-end here.


My next attempt to find out if Snow White is dead or alive bring me to Philip Ringrose, the source of Rassenfoss’ alarming news. Ringrose conveniently has an accessible employee website courtesy of his employer NTNU. As expected in academia, he has a comprehensive list of publications, going all the way back to 1987. Control-F helps out to find the one publication that mentions Snøhvit in the title; it’s from 2011. The paper is a bit challenging to find, but persistence is rewarded. Not surprisingly, all is well with our princess in 2011. Scrolling though Ringrose’s publications brings me to a 2018 paper that promises ‘some insights from 22 years of saline aquifer storage’. Perhaps he will mention Snøhvit? I am not disappointed and find out about an interesting hiccup in the CO2 injection plan: By the end of 2017, almost 5 Mt CO2 had been injected into the subsurface. Initially, the CO2 was injected into the Tubåen Formation, a saline aquifer below the gas-bearing Stø Formation. However, during the first three years of injection, a gradual rise in pressure was observed, mainly due geological barriers which limited the access to the available pore space. This led to the decision to perform a well intervention in 2011, leading to a modified injection plan for the CO2 injected into the aquifer of the Stø Formation. Injection has continued since then with a stable pressure trend. Crucial to this evaluation was the use of seismic 4D data, downhole gauges, and reservoir modelling which allowed optimization of the CO2 injection plan. Could this 2011 event be the rumored death of Snow White? I have asked Rassenfoss and Ringrose to comment on LinkedIn, but have so far not received a reply.

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Here is a link to the segment of the video where Phillip Ringrose gives an explanation as to why they re-completed the Snøhvit CO2 injection well in the shallower Stø formation. It also details the success of the intervention.


https://www.youtube.com/live/ETALqgtagaE?feature=share&t=1194

いいね!
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