Petrobras tests new technologies for CO2 capture, storage

Two other projects were negotiated: technologies to determine contamination in bottom hole fluid samples and well production behavior simulations in the laboratory.

Additionally, 12 other projects are still under negotiation. The agreement will be in effect for three years and can be renewed for an equal term. Petrobras foresees it will invest some $15 million in these projects.

The agreement will lead to the deployment of the Halliburton Brazil Technologies and Solutions Center in Rio de Janeiro in 2011.

For Estrella, the partnership between Petrobras and Halliburton “will help the company to overcome the challenges it will be up against in the next few years, not only in the pre-salt, but in several other projects as well.”

Petrobras CCS projects analyzed by expert

In an exclusive interview, Alberto Sampaio de Almeida, Ph.D, Petrobras E&P technical advisor to the pre-salt executive manager Jose Formigli (who also represented Petrobras at the Halliburton signing ceremony) speaks about some latest developments undertaken by the company concerning CCS.

Offshore: Please describe the technologies being developed by Petrobras to separate the CO₂, the natural gas from petroleum, and to compress and transport this gas.

Almeida: Twenty four years ago, the company sought to apply a CO₂ injection technique at high pressures in the Araçás field, in the Recôncavo basin, Bahia state. In 1991, in the same basin, it deployed in the Buracica field, a low-pressure CO₂ injection project. This project was very successful, resulting in the maintenance of the field’s oil production for about 20 years.

Petrobras researches technological solutions to make the capturing, transporting, and the geological storage of CO₂ feasible. The CO₂ can be captured from exhaust gases (resulting from combustion processes) from industrial units or from natural gas itself. At the platforms, for example, CO₂ can be separated from the gaseous current, transported, and then stored in underground geological formations, such as deep saline aquifers (salt water accumulations in rock reservoirs), and oil and gas reservoirs.

The development of capture-related technologies involves, mainly, reducing the gas pre-treatment and separation costs. With regard to CO₂ separation in the pre-salt environment, the main technological bottlenecks are related to the size, weight, and efficiency of the separation process to be installed in floating units. In that sense, the strategy has been to map, through contacts with suppliers, partners, and others operators, the available solutions, to identify the most suitable technologies to apply.

In parallel, efforts are being made to develop, together with providers and research institutions, new options more appropriate to the pre-salt scenario.

The following carbon geological sequestration stage is transportation. The gas must be pressurized and transported to the place where it will be injected. The CO₂ transportation technologies are already known.

In the storage phase, the main technological challenge is to understand the interactions among the rocks, fluids, and CO₂. The usual alternatives for geological storage are saline aquifers (salt water accumulations in rock reservoirs), general oil and gas fields, salt caves, and layers of coal. Petrobras’ current studies for the pre-salt environment are concentrated on saline aquifers and the oil reservoirs.

Offshore: Please speak about storage, the effects of corrosion, acids, and other undesirable characteristics of CO₂.

Almeida: The storage of the CO₂ expected to be produced with the hydrocarbon streams in Santos basin pre-salt cluster was studied under a “holistic” perspective. That is, not any possibility or disposal technology was disregarded in advance.

The pre-salt is a corrosive environment with significant amounts of carbon dioxide in associated gas (8% to 18%) and hydrogen sulfide (H2S). This places a high demand on special cement and metallurgy throughout the process.

The following options were technically and economically evaluated: enhanced oil recovery (EOR) in the Tupi area; CO₂ storage in saline aquifers; EOR in heavy oil fields, in the Santos basin; CO₂ storage in depleted gas fields; and CO₂ storage in salt caverns, to be constructed in the cluster area.

Although all five alternatives were equally appraised, some of them showed more promising for the Santos basin pre-salt cluster scenario. The ones that Petrobras are concentrating its efforts are reinjection of the CO₂ in the oil reservoirs (EOR) and in saline aquifers.

CO₂-EOR is a proven technology widely used in the US and other countries, which allows the recovery of an additional 10-15% of the original stock, according to an IEA study.

Offshore: What technologies are being developed for Tupi, Guará, and Iracema pre-salt fields? What are the differences in these technologies for pre-salt, deep waters (Campos basin), and onshore?

Almeida: There are still no conclusive studies about the CO₂ concentration in the region. A few wells have shown to have concentrations above those found in the Campos basin in Brazil, while others concentrations are nearing zero. Nonetheless, Petrobras proactively commits to not release the CO₂ associated to the natural gas produced in the pre-salt layer to the atmosphere.

The Tupi region, in the Santos basin, is the starting point to get to know the pre-salt better. The Tupi Extended Well Test (EWT) was kicked-off in May 2009. The results obtained with the EWT will be important to define the area’s development approach and the pre-salt exploration and production model.

Offshore: What are the advantages and disadvantages of EOR for CCS?

Almeida: The option of EOR with a CO₂ rich gas stream, probably in association with sea water injection, was the top priority for economical and technical reasons. The studies performed up to now point to a significant additional oil recovery over water flooding base case. The relatively low reservoir temperatures and high original reservoir pressure may promote an efficient miscible displacement process of the oil by the CO₂ rich stream.

Safe CO₂ storage conditions are achieved due to very thick salt rock seal (in geological time extremely high pore pressure was kept intact in this reservoir).

From the hydrocarbon production point of view, there are still some issues to be further evaluated concerning CO₂ injection. One of them is related to the possibility of asphaltene deposition. As any non-polar solvent, CO₂ can flocculate colloidal heavy asphaltene components present in the oil, impairing flow assurance conditions.

Wax and hydrate formation can also be affected by CO₂. Depressurization of high gas flow rates can cause a decrease in temperature (mainly in the production riser) due to the Joule-Thompson effect, increasing the risk for wax deposition; a similar process may occur for hydrates.

Another important concern is the risk of corrosion in the well casing and tubing, caused by the association of CO₂ and produced/injected water. The problem is being “engineered” through extensive use of special alloys, plastic covered pipes, and proper chemical injection. The possibility of CO₂ permeation across the polymer in the flow lines and risers is another issue which is being addressed with providers.

Offshore: Kindly evaluate the pilot project in Miranga, one of the largest CO₂ projects in the world.

Almeida: The CO₂ reinjection technique will be used on a larger scale by Petrobras in the Miranga field, Bahia, where the company foresees that some 370 tons of CO₂ will be injected per day. Although the main focus of the process is to increase the reservoir oil recovery, it also focuses on the prevention of CO₂ emissions. In the Miranga case, the CO₂ performs as a type of solvent, which changes the properties of the oil, reduces its viscosity, and facilities its flow.

Partnership with oil companies and universities

One of Petrobras’ next collaboration agreements will be with the French services company Geogreen to develop an R&D activity related to “Risk Assessment for CO₂ Reinjection and Storage in Pre-Salt - Santos Basin,” considering the four envisaged disposal solutions: re-injection and EOR in the same reservoir; storage in shallow aquifers (post-salt); storage in deep saline aquifers (below salt); and buffer storage in salt caverns.

The project will start in the first quarter of 2010. The objectives of the project are to provide a risk-assessment study for the different storage solutions and to make the necessary recommendations in terms of site characterization, monitoring, and remediation.

Some oil companies involved with Petrobras in CO₂ transport and carbon capture storage of CO₂ include: Statoil, BP, Royal/Dutch Shell, Vattenfall, Chevron, ConocoPhillips, Eni, Suncor, Gassnova, Gassco, Schlumberger, Cabon Services, and IEA.

The CO₂ issue is also a subject in the Universities Thematic Networks, a technical cooperation and financial support initiative of Petrobras for science and technology entities throughout Brazil. The Carbon Sequestration and Climate Change Thematic Network was created in 2008, and is currently composed of 13 universities with investments of some $30 million.

Congressional climate change commission hearing

Beatriz Espinosa represented Petrobras in a public hearing held by the Mixed Commission for Climate Change in Brazil’s Congress last November. Espinosa said Petrobras has already defined as a guideline to not allow emissions of the CO₂ associated to natural gas that will be produced in the pre-salt layer. The solution includes CCS. “We expect to store it in deep saline aquifers, in depleted fields, or in salt caves,” she said. “The climate change issue is included in the company’s (Petrobras) strategic plan.” The actions and programs the company has developed are expected to avoid the emissions of 2.3 million tons of CO₂ in 2009, and 4.5 million in 2013.

Sources at the Mines and Energy Ministry said the extended well tests in the Tupi and Jubarte fields have indicated a CO₂ content ranging from 8 to 12% in the first, and 0 to 3.5% in the second, proving there are heterogeneous layers in the pre-salt.

Climate law approved, oil industry protected

Brazil’s President, Luiz Inácio Lula da Silva, approved in late December the National Policy on Climate Change, transforming in law the country’s voluntary commitment in reducing their greenhouse gases emissions by 36.1% to 38.9% by 2020. However, Lula has imposed three vetoes to the bill approved by the National Congress which will protect the oil industry and the large scale hydroelectric generation companies. Lula has accepted three of the 10 vetoes suggested by ministries. One of them removes the word “abandonment” of an article which proposed the “gradual abandonment” of fossil energy sources.

Under pressure from the Ministry of Mines and Energy, Lula decided to remove the expression from the bill because it would prevent Brazil from using oil and natural gas in energy production in the future. The Brazilian government wanted to avoid having to go back over the climate policy with the pre-salt discovery in the future. The second veto allows blocking the resources used for gas emission reduction measures.