How to optimize offshore pump performance and reliability
Asset reliability and performance are the two most important factors for the oil and gas sector but as processes change and equipment ages, optimizing uptime can become a greater challenge.
Changes to pump performance may be required for a number of reasons. For instance, refineries looking to increase production will examine the assets involved and identify any bottlenecks. In some cases, flowrates will need to be increased beyond the existing capabilities of the equipment; a drilling well may need to increase water injection rates, or the reliability of certain assets may need to be improved to meet the new targets.
New for old
The first, and most straightforward, solution is to replace the existing pumps with new equipment that has been specified for the new production rates. This has many advantages in terms of reliability, performance and efficiency; using the latest materials and design technology will ensure a long-lasting and effective solution.
There are, however, some drawbacks – the time to complete the project, the lost production while the work is completed and the overall capital expenditure. Together, these will nearly always rule this option out.
Adapt and survive
A more favorable option is to modify the existing assets to enable them to deliver the new targets. There are many challenges that can be resolved to some degree by implementing a retrofit project. Reliability issues can be improved through a change in materials to resolve erosion or corrosion; performance can be enhanced by altering the hydraulic design of the pump.
Retrofit projects are a very cost-effective alternative to replacing large assets when a production site requires a change in performance or an improvement in reliability. By minimizing the number of components being modified, both the time and the cost involved in the project are kept to a minimum.
For example, in Norway, the government offers support to the oil and gas industry to reduce its carbon footprint. One of the biggest gains can be achieved by reducing the energy consumption of pumping assets. Using a retrofit project to optimize pump performance to each application, operators have made significant savings in running costs, which help to meet national carbon targets.
One of the major areas of pump operation is water injection systems, which are used to maximize the productivity of the oil wells. As the oil field matures, there is a need to increase the water injection rates to maximize oil production. This requires the capacity of the injection pumps to be increased without affecting the layout of the plant or the existing pipework.
In this case, the flowrate needs to increase while maintaining the head, which means that the power demand will rise and the pump design will need to be altered. By working closely with the platform engineers and establishing the limits of the motor or turbine, pump designers can draw up a modified hydraulic proposal that will improve both performance and efficiency.
In an alternative scenario, the system pressure may need to be reduced, while maintaining the original flowrate. Reducing the pressure generated by a pump can be achieved by removing a number of stages from the pump rotor, which will significantly decrease the energy requirement of the pump. In some cases, the rerate solution may include a variable speed drive, which can deliver more flexibility in the output from the pump.
Rerating a pump’s hydraulic conditions to the new duty point, a combination of flow and head, will enable the system to operate more efficiently. Based on the downstream requirements, the pump characteristics can be redesigned so that it delivers the necessary flow and pressure while operating at or close to its best efficiency point (BEP).
Ongoing support for production facilities
Oil and gas production facilities are driven by performance and equipment reliability, which can be enhanced by engineering expertise and design experience. Rerate projects offer an opportunity to increase uptime, reliability and therefore productivity. In some applications it is possible to improve efficiency, which reduces energy costs as well as the carbon footprint of the business. Whatever the goal, when it comes to pump performance, the retrofit project should always be considered as one of the prime options.