In November, Petrobras will start injecting high-pressure CO2 into the Miranga onshore field, in the municipality of Pojuca, state of Bahia, to test technologies that might contribute to future development projects for the Santos Basin's Pre-Salt cluster. The carbon dioxide produced at the future pre-salt fields will be reinjected into the reservoirs themselves to boost the recovery factor.
The Miranga field project foresees the geological sequestration and removal of 370 tons of CO2 from the atmosphere per day. In addition to the excellent environmental gains it affords for, the technology to be applied will considerably increase the recovery percentage of the oil nestled in that field's reservoir.
This project will serve as a proving ground for new technologies that might be applied in other fields to be developed in Brazil, particularly in new pre-salt discoveries, since the reservoirs there have shown the presence of natural CO2 associated to the oil.
Other alternatives, such as storage in caves or saline reservoirs, are also under analysis. The Miranga field was ed for the tests on account of its geological characteristics and because of the logistics that are already available at the site.
The technique to be used in Miranga is based on injecting CO2 under high pressures. In this case, the CO2 works like a type of solvent that changes the properties of the oil and allows it to flow better through the reservoir-roc'’s porous system.
Attaining supplementary oil recovery by injecting CO2 is nothing new to the Company in Brazil. The procedure was first used 28 years ago, in Bahia. When it started experimenting with the concept, Petrobras applied a high-pressure CO2 injection technique at the Araçás field, in the Recôncavo Basin. In 1991, it deployed a low-pressure CO2 injection project in the Buracica field, in the same basin. The project was highly successful and resulted in the partial maintenance of the field's oil production for nearly 20 years. Additionally, this technique allowed 600,000 tons of CO2 to be removed from the atmosphere through the geological sequestration approach.
The Miranga field project is the outcome of the knowledge that was acquired in the previous experiments. Project implementation will require investments in the order of R$250 million. The deployment work was kicked-off in mid-2006, and oil production is slated to begin next December, a month after the CO2 injection procedure begins. The project includes the laying of nearly 70 km of injection lines for saltwater, which will come from the reservoir itself, of some 30 km of CO2 injection lines, and of 18 km of a 6-inch pipeline to transport the CO2.
Project production is expected to peak in mid-2012 at 1,500 barrels of oil per day. A total of 5 million additional barrels of oil are expected to be recovered from the field. To make the project feasible, Petrobras invested in the creation of labs specialized in CO2 and in research and development at universities in the state of Bahia.
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