Repair and optimisation of water injection pumps
Oil and gas continue to form the building blocks of our essential everyday items. As these resources become more difficult to reach, oil producers need to optimise the efficiency of their processes.
The Scandinavian oil platform has operated two BB5 water injection pumps for over ten years, but they have suffered from rapid wear and high vibration. The original equipment manufacturer had delivered several upgrades, but there was little improvement in either performance or reliability. There were also long periods when there was no water injection capacity, which severely impacted oil recovery rates. To help resolve this, the operators decided to approach Sulzer for a solution.
RETROFIT OF EXISTING PUMPS
Initial discussions led to an offer to investigate the spare pump cartridge, which had also exhibited the same symptoms of vibration. Sulzer took the cartridge to its Stavanger Service Center and dismantled it. The engineers discovered that the main shaft had rotodynamic issues, which caused the vibrations, and that this fault had been an issue from new.
To restore the water injection capability of the platform with minimal delay, Sulzer suggested, in the short term, that the cartridge should be replaced with a hybrid component. This would fit precisely into the existing barrel of the pump on the platform and enable the first pump to operate.
Sulzer did not manufacture the pump in question, but this would pose no problems for the project because it can apply its expertise to equipment from any manufacturer. Over the next six months, the new hybrid cartridge was manufactured. Together with the onsite maintenance provider, Sulzer engineers installed and commissioned the water injection pump and returned the platform to normal operations.
NEW PUMPING ASSETS
In the meantime, Equinor had decided to replace both of the original water injection pumps with new assets designed and manufactured by Sulzer. Sulzer began manufacturing the new injection pumps, which would be installed during separate, planned maintenance windows. The projects were carefully coordinated to ensure the pumps were delivered on time, together with other auxiliary components, to meet the installation program set out by Equinor.
Oddvar Holta, Project Manager for Sulzer, said: “The greatest challenge has been the very short delivery time on the hybrid cartridge, which would normally have taken ten months. We have managed to streamline this process and meet the objectives of our customer, getting the water injection pump up and running on time.”
ADDITIONAL ENERGY SAVINGS
However, the story continues; having manufactured the new pumps to match the specifications of the original components, and after the first one had been installed, a change in site conditions prompted the decision to reduce the operational head of the new pumps to reduce energy consumption and CO2 emissions. This required the pumps to be de-staged, removing four of the original eight impellers in cartridge A and two impellers in cartridge B.
The design engineers in Leeds created the necessary drawings for the transition tubes, which were manufactured at the same site. Once complete, engineers from Sulzer travelled to the platform, removed the impellers that were no longer required, and installed the new components.
Pump A achieved a power saving of 2MW, which equates to 5,536 tonnes of CO2 per year. Similarly, Pump B’s power consumption was reduced by 1MW, saving 2,768 tonnes of CO2 every year.