Multiphase Pump
A multiphase pump is a mechanical device designed to simultaneously compress and transport mixed streams of gas, liquid crude oil, produced water, and suspended solids without upstream phase separation, using pump geometries tolerant of high gas volume fractions (GVF) to boost wellstream pressure at the wellhead or on the seabed and transport the commingled production over long tiebacks to a central processing facility.
Key Takeaways
- Twin-screw multiphase pumps are the most widely deployed technology, tolerating GVF up to 97 percent and handling slug flow, because the intermeshing helical screws seal the fluid in progressive cavities that compress and move it axially regardless of phase composition.
- Subsea multiphase boosting (seabed pump stations) extends the economic tieback distance of deepwater fields by 20 to 50 kilometers or more compared to passive flowline design, unlocking reserves in satellite accumulations too small to justify standalone infrastructure.
- Helico-axial (Poseidon-type) multiphase pumps use contra-rotating impellers to handle GVF up to approximately 97 percent and are preferred for high-flow-rate applications, while progressive cavity pumps handle high-viscosity, sand-laden heavy oil streams at lower GVF.
- Subsea multiphase pumps are rated for water depths up to 3,000 metres and are installed with dual electric motor drives for redundancy; power is supplied via an umbilical from a topside power system with variable-frequency drives for flow control.
- Multiphase pumping economics are assessed by comparing the cost of a seabed or wellhead pump station and power infrastructure against the value of the additional reserves recovered and the capital cost saving from deferring or eliminating a new platform or FPSO.
Fast Facts
GVF tolerance: twin-screw up to 97%; helico-axial up to 97%; progressive cavity typically up to 50%. Typical differential pressure delivered: 50 to 200 bar. Flow rate range: 100 to 20,000 boe/d liquid equivalent. Operating temperature: minus 10 to 120 degrees C. Maximum water depth deployed (subsea): approximately 3,000 metres (Perdido, Asgard, Ormen Lange). Major suppliers: SLB (OneSubsea), Sulzer, Leistritz, Bornemann, TechnipFMC. Power requirement: 0.5 to 5 MW typical for subsea units.
Tip: When sizing a multiphase pump for a new tieback, use a multiphase flow simulator (OLGA, LedaFlow) to model the full range of GVF and slug sizes expected over the production life, not just plateau conditions; pump performance at end-of-field-life when GVF can exceed 90 percent is often the binding constraint on impeller speed and differential pressure that determines which pump technology is appropriate.
What Is a Multiphase Pump
Conventional oil and gas production systems separate gas from liquid at the wellhead or manifold before pumping the liquid and compressing the gas independently. This requires separation vessels, dedicated pumps, and dedicated compressors at every production point. A multiphase pump eliminates the need for upstream separation by handling the wellstream as it arrives: a mixture of gas bubbles, crude oil droplets, formation water, and sometimes sand or scale particles, all at variable proportions that change over the life of the field as the reservoir depletes and GVF rises.
The economic value of multiphase pumping is greatest in two scenarios. In deepwater tiebacks, the pump station sits on the seabed near a satellite wellhead cluster and boosts the combined wellstream through a long-distance multiphase flowline to a host platform or FPSO, avoiding the cost of a new host facility. In onshore or shallow-water applications, wellhead multiphase pumps can maintain production at lower reservoir pressures than passive flow would allow, extending the economic life of a field and deferring the transition to artificial lift.
How Multiphase Pumps Work
Twin-screw pumps contain two intermeshing helical rotors turning in opposite directions inside a close-tolerance casing. The screw geometry divides the mixed fluid into sealed progressive chambers that advance axially from suction to discharge as the screws rotate. Because the chambers are mechanically sealed rather than relying on centrifugal force, the pump maintains differential pressure across the full GVF range from pure liquid to near-pure gas. Gas is compressed as the chamber volume decreases toward discharge; liquid fills the spaces between screw flights and acts as a sealing medium. Internal recirculation of a small liquid fraction from discharge to suction (the recirculation line) maintains lubrication and sealing at high GVF.
Helico-axial (Poseidon) pumps use contra-rotating impeller stages, each consisting of a rotor and a diffuser. The impellers impart kinetic energy to the fluid mixture and convert it to pressure in the diffusers. This design handles high flow rates efficiently but requires more stages at high GVF because centrifugal efficiency degrades with increasing gas content. Poseidon-type machines have been deployed extensively in the North Sea by SLB's OneSubsea division.
Subsea multiphase pump systems include the pump module, a direct-drive or gearbox-coupled wet or dry motor, a motor controller and variable-frequency drive in the umbilical termination assembly, and a condition monitoring system that reports vibration, temperature, flow, and differential pressure to the topside control room. Subsea systems are designed for multi-year intervention-free operation with all critical components retrievable by ROV or wireline without pulling the flowline.
Multiphase Pumps Across International Jurisdictions
In Canada, multiphase pumping is applied primarily in Cold Lake and Lloydminster heavy oil fields where progressive cavity pumps (PCPs) handle high-viscosity, sand-laden bitumen-water emulsions from SAGD and CSS wells. Canadian Natural Resources, MEG Energy, and Cenovus have deployed large-diameter PCP systems in ESP strings for SAGD production wells. Offshore Canada, multiphase boosting has been studied for potential Flemish Pass deepwater developments (Bay du Nord), where subsea tiebacks of 200 kilometres or more would require seabed boosting. The Canada-Newfoundland and Labrador Offshore Petroleum Board (C-NLOPB) oversees offshore production system approvals.
In the United States, deepwater Gulf of Mexico fields were early adopters of subsea multiphase pumping. Shell's Perdido development uses seabed boosting at approximately 2,450 metres water depth to produce from three subsea fields through a single host spar. BP, Chevron, and TotalEnergies have used multiphase boosting in Mars, Tubular Bells, and Jack/St. Malo fields respectively. The BOEM regulates subsea production system design under the Outer Continental Shelf Lands Act, with technical requirements in 30 CFR Part 250 covering subsea production system approvals and safety systems. Onshore, wellhead multiphase pumps are used in Permian Basin gathering systems to reduce back-pressure on low-rate wells.
In Norway, the NCS has been the global testbed for subsea multiphase boosting technology since the early 1990s. Equinor's Asgard field uses large-scale seabed compression and multiphase boosting to extend plateau production from the Mikkel and Midgard reservoirs. Ormen Lange's seabed compression project, delivered in 2021, is the world's first large-scale seabed gas compression system with multiphase boosting capability. Sodir oversees production system approvals; Norwegian regulations (Petroleum Activities Act, Facilities Regulations) require detailed safety assessments for novel subsea technology before deployment.
In the Middle East, multiphase pumping has been applied primarily in onshore applications in Saudi Arabia and Kuwait, where pump stations on surface gathering lines handle high-GVF wellstreams from mature fields with declining reservoir pressure. Saudi Aramco has evaluated subsea multiphase boosting for potential Red Sea deepwater developments. ADNOC's Abu Dhabi offshore fields have studied multiphase boosting for satellite tie-ins to existing platform hubs in the Lower Zakum and Umm Shaif fields. The technology's adoption in the Middle East has been more gradual than in the North Sea due to the shallow water depths and existing infrastructure density of the Arabian Gulf.
Synonyms and Related Terminology
Multiphase pumps are also called wellstream pumps or multiphase boosting systems. Subsea installations are referred to as seabed boosting or subsea boosting. Related pump types include the twin-screw pump, progressive cavity pump (PCP), and helico-axial pump. Key performance parameters include gas volume fraction (GVF) and differential pressure. Related flow assurance concepts include slug flow, multiphase flow, and subsea tieback. The alternative to multiphase pumping for deepwater tie-backs is conventional subsea separation with dedicated liquid pumps and gas compressors.
Frequently Asked Questions
What is the maximum tieback distance that subsea multiphase pumping enables?
Without boosting, passive multiphase tiebacks are typically limited to 10 to 30 kilometres depending on water depth, fluid properties, and reservoir pressure. With seabed multiphase pump stations providing 50 to 200 bar of differential pressure, tieback distances of 50 to over 100 kilometres have been achieved. The Ormen Lange seabed compression project in Norway effectively ties back reservoirs at 850 metres water depth over approximately 120 kilometres to an onshore processing terminal at Nyhamna.
How are multiphase pumps monitored and maintained subsea?
Subsea multiphase pumps are equipped with comprehensive condition monitoring: vibration accelerometers, bearing temperature sensors, differential pressure transmitters, and flow meters on suction and discharge. Data is transmitted to the topside control room via the umbilical in real time. Variable-frequency drive control allows speed adjustment for flow optimization. Maintenance typically follows a run-to-fatigue or planned-intervention strategy using either a crane-deployed replacement module swapped by an ROV, or a pull-and-replace retrieval to a maintenance vessel. Major suppliers design pump modules for multi-year run-to-maintenance intervals of 3 to 5 years.
Why Multiphase Pumps Matter
As the world's easily accessible oil and gas fields mature, the industry is moving into deeper water, more remote locations, and longer tiebacks where conventional surface-separation-plus-pump infrastructure is technically impractical or economically prohibitive. Multiphase pumping is one of the enabling technologies that makes these frontier developments viable. By eliminating the phase separation step and allowing commingled wellstreams to be boosted over long distances, multiphase pump systems reduce capital expenditure on processing infrastructure, extend field economic life by maintaining production at lower reservoir pressures, and unlock stranded satellite reserves that would otherwise be abandoned. The technology is central to the industry's deepwater growth strategy in the Gulf of Mexico, Brazil pre-salt, and the Norwegian Barents Sea.