Translation. Region: Russian Federation –
Source: Novosibirsk State University –
An important disclaimer is at the bottom of this article.
Researchers Advanced Engineering School of Novosibirsk State University (AES NSU) Developed mathematical models and monitoring tools that allow assessing the safety of carbon dioxide (CO₂) disposal in geological formations. The work was conducted under a three-year grant from the Russian Ministry of Science and Higher Education, in collaboration with colleagues from Tongji University (Shanghai, China).
We're talking about CO₂ capture and storage technology, which is considered a promising way to reduce the negative effects of greenhouse gas emissions. The approach involves injecting carbon dioxide into well-sealed geological structures, including depleted hydrocarbon deposits, and reliably sequestering it there for decades or even hundreds of years. The key objective is to eliminate the risk of gas leaks to the surface.
As Alexander Valov, a research fellow at the NSU School of Physical Analysis, explained, the project focused on the most vulnerable elements of such systems.
"We studied the wellbore and near-wellbore zone stability—that is, scenarios in which its integrity could be compromised and the injected CO₂ would begin to leak out, damaging the space behind the well casing. Our task is to model such risks in advance and propose ways to prevent them," he explained.
Scientists have developed several mathematical models describing possible mechanisms of well failure due to man-made causes. Particular attention was paid to the cement casing, which seals the well and is considered the weakest link in the structure. The models take into account the mechanical and thermal effects that occur during gas injection, as well as scenarios of cement delamination leading to leakage.
At the same time, the team developed monitoring systems to detect leaks at an early stage. Acoustic methods and distributed temperature sensing (DTS)—sensors that detect characteristic noises and temperature changes in the well—were used. The developed approaches were tested on a special experimental rig, which simulated the CO₂ injection process on a scale.
"Experiments have shown that some sensors perform well, while others require higher sensitivity. Based on the results of these experiments and comparisons with the mathematical models we developed, we have developed specific technological recommendations," noted Alexander Valov.
The work was conducted in collaboration with China's Tongji University. The partners focused on the conditions characteristic of basaltic shelves near Shanghai, while the Novosibirsk scientists focused on the geological features of sedimentary rocks common in Russia. This allowed them to cover a wide range of possible CO₂ storage conditions.
A Russian oil and gas company, which views mature wells as potential carbon dioxide storage facilities, has expressed practical interest in the project's results. Tools have been developed for this company to model injection scenarios for specific field parameters and select the safest modes.
"The model is needed precisely to 'play out' various scenarios in advance and understand which ones minimize risks. Specific parameters always depend on the geology and well design," emphasized Alexander Valov.
According to the scientists, the competencies gained during the project can also be used to assess the risk of cement casing failure in cased boreholes and other technological operations that involve intensive wellbore impacts. The developed approaches not only allow for assessing the safety of CO₂ disposal but also for mitigating environmental risks during the development of oil and gas production technologies.
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