RIO DE JANEIRO—As Brazil’s output grows, mainly due to the success of its presalt fields, concerns about CO2 emissions caused by increased E&P activity have grown.
The country is among those that are aiming to limit greenhouse gas emissions, having signed the Paris climate agreement.
Researchers at the Research Centre for Gas Innovation (RCGI), which was created by a partnership between the University of São Paulo (USP), Royal Dutch Shell and the State of São Paulo Research Foundation, are looking for a method to significantly reduce the amount of CO2 emitted from southeastern Brazil.
The research encompasses two regions where there are rocks that could store the gas: the Paraná Sedimentary Basin and the Santos Basin. Oil is extracted from both of the basins’ presalt and post-salt layers.
The carbon capture and sequestration (CCS) project aims to verify types of rock capable of storing CO2. CCS, in its integrated form, involves capturing CO2, purifying, compressing and transporting CO2 to a sequestration site and injecting it into a geological reservoir or in the ocean.
For Royal Dutch Shell Brazil Sustainable Gas Lead Camila Brandão, the RCGI is an extension of the company’s team that works toward CO2 abatement. “This platform supports Shell in terms of looking at this issue [CO2 abatement] concerning international agreements such as the Paris agreement, and the University of São Paulo is seen as a key partner in this process,” she said.
One of the reasons behind the company’s support of the CO2 storage project is its push toward a cleaner energy mix. CCS minimizes the environmental impact of emissions generated by fossil fuels, allowing for the production of resources in a sustainable way, she said.
The idea of storing gas within rocks came from CCS technologies used by the oil and gas industry, said geologist Colombo Celso Gaeta Tassinari, director of the Institute of Energy and the Environment and a professor for the Institute of Geosciences of USP.
Tassinari, who is leading the team of researchers, said the studies involve researching the size of the area needed to retain CO2 and the existing clay mineral that helps the storing process. According to the professor, the CCS project aims to store CO2 in rocks for roughly 1,000 years.
“We are in the process of selecting methods used around the world for assessing the capacity for storing CO2 in geological reservoirs in order to validate those methods for the Brazilian sedimentary basins studied,” Tassinari said.
The CCS team is in the initial phase. Researchers are collecting samples and observing geological conditions of fields. Investment in the application of CCS research should be seen as environmentally sound because it is a sustainable way to reduce greenhouse gas emissions, according to Tassinari.
High CO2 Levels
Due to its geological conditions, the presalt layer has high amounts of CO2, which poses technical and economic challenges. Conventional CO2 separation technology is difficult to be implemented in reservoirs with a high gas-oil ratio (GOR) and CO2 contamination. The Libra presalt field, for example, has a gas-oil ratio of 410 to 450 cu. m/cu. m with produced gas having a CO2 content of about 45%.
“Oil extracted from the presalt has naturally a greater amount of CO2, and the practice of reinjecting more CO2 into these rocks will worsen the quality of the oil more and more,” Tassinari explained. “It is not advisable to do this.”
The turbidites of the Santos Basin are sedimentary rocks of variable granulometry that contain intercalated layers of clay. “We will study analogous samples, from another place, that are similar to those of the Santos Basin in our labs. We will make the assessment based on geological information that we have at hand in the literature,” Tassinari said.
For Tassinari, the CO2 storage project not only has environmental benefits—as it helps to reduce CO2 emissions—but the project also presents cost-saving benefits. With this technique, the CO2 captured will be stored in other dry rocks, avoiding the wasting of the reservoir.
Located in Brazil’s southern region, the Paraná Basin could hold an estimated 226 trillion cubic feet of recoverable shale gas resources. Although Brazil has not started shale gas E&P activities, Tassinari said the research team will study the Paraná Basin’s black shale rock, a clayey sedimentary rock rich in organic material that could store CO2.
Tassinari emphasized that the CCS project can also be used to store CO2 emitted from thermoelectric plants in Brazil. Thermoelectric plants are responsible for more CO2 emissions than E&P sites.
“It would be possible to think of a closed system: place the thermoelectric plant over a shale gas deposit, remove the gas from the shale rock for the plant and inject the CO2 emitted, where it would be a sustainable process,” he said.
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