Pumping Liquid CO2

Sulzer designs pumps for enhanced oil recovery project in Qatar

The oil and gas industry is using innovative solutions to reduce its carbon emissions and this is exemplified by the current pilot project being undertaken by Qatargas. The new system will use Sulzer pumps to improve the recovery of oil and gas by using liquid carbon dioxide (CO2) instead of water to pressurize the well.

Every industry is being encouraged to reduce the amount of greenhouse gasses it is responsible for to help meet global targets. One measure that the oil and gas sector is supporting is carbon capture and storage (CCS), which uses depleted oil fields to store liquid CO2.

Dense phase or supercritical CO2, held at sufficient temperature and pressure to keep it in the liquid phase, also has some advantages over water when it is used to purge oil and gas from a well. In a supercritical state, the CO2 can be pumped like a liquid but has the effusiveness of a gas. This means that as it sweeps through the reservoir to push the oil to the riser, it is more effective than water, making for a more efficient process.

Taking the next step
In Qatar, there is a major program of investment in the capture and sequestration of CO2, some of which will be used for enhanced oil recovery (EOR). As part of this, Sulzer has been involved in the development of a recovery system using liquid CO2 for Qatargas. To this point, similar projects have mainly used either reciprocating or rotary compressors, but more recently a growing number of pumps have been adopted. An initial feasibility study was conducted with the Sulzer’s engineering teams and confirmed that a pump would be the best solution in this application.

Designing a pump for such a project, requires considerable experience as well as expertise and Sulzer has been involved in this specialist area for almost 40 years. Based on its experience and excellent working relationship in Qatar, Sulzer was awarded the contract to supply an API 610 type BB5, multi-stage, opposed impeller pump with a design pressure around 240 barg, driven by high voltage electric motor and associated variable frequency drive.

Along with the relatively high suction pressures, the lightness and effusiveness of the supercritical CO2 needed to be managed well. A detailed rotor-dynamic assessment and clearance review was conducted based on Sulzer’s time-served methodologies; along with a thorough investigation into the material selections, both metallic and elastomeric components along with the casing tightness calculations to ensure leak free operation under all extreme operating conditions.

Martin Uere - Head Global Technology for Sulzer Pumps explains: “High suction pressures and lightness of CO2 have a significant effect on the design of the pump and this is one of the reasons why other manufacturers have steered clear of this application in the past. Sulzer, on the other hand, has spent nearly four decades fine-tuning designs and providing increased efficiency. As a result, the operator of this pilot scheme decided that Sulzer was well-placed to support the project, from feasibility through to installation and commissioning.”