The Research & Development Path of the Multiphase Pump Technology

Dipl.-Ing. Gerhard Rohlfing
Joh. Heinr. Bornemann GmbH, Germany

Abstract
The multiphase pump technology is considered to be a “Young Technology”. However it is already mentioned in the Oil & Gas literature in 1957. After these initial steps with frequent pump-failures due to “unsolvable tasks” Bornemann gave up and the vision of handling liquid- and gas-mixtures disappeared in the companies strategy for nearly 30 years.

The restart of the multiphase boosting technology finally leading to technical success and implementation of this technology in the E&P industry was initiated in the late 80-ies of the last century with the important Poseidon Project conducted by Statoil and Total. Several national and international research projects followed. This paper summarizes the Bornemann R&D path achieved during in these research projects during the last two decades.

1. Poseidon Project

The starting point of the commercial development of multiphase boosting certainly was the Poseidon project in 1985. One of the main reasons for this development was the huge investment involved in offshore structures. If it would be possible to boost the total well production right from the subsea wellhead to distant, possibly dry processing installations, enormous cost savings would set the off-shore activities into a much better economic situation. Bornemann entered the Poseidon project in 1986 and delivered the first multiphase pump in 1990 for the start of the Poseidon field test campaign in Tunisia until 1992.

Fig. 1a: Multiphase Pump in Poseidon test field in Tunisia

Fig. 1b: Multiphase Pump in Poseidon test field in Tunisia

In the course of the field test campaign two major unexpected phenomena could be
observed:
Prolonged gas phases

Even at moderate average gas volume fractions below 90 %, prolonged 100 % gas phases as dry running occurred frequently (several times a day), leading to excessive heat generation, temperature shut down, or even blocked the rotating pump internals.

Thermal load on mechanical seals

The mechanical seals of this first generation multiphase pump were located in the inlet chamber of the multiphase pump directly exposed to an inhomogeneous multiphase flow. Permanent temperature variations (shocks) of the seal faces led to temporary seal leak-ages or even seal failures.

2. MTT Project

In the year 1987 the German Ministry for Research and Technology asked GKSS-Research Institute, located in Northern Germany, to summarize the activities of several German companies and institutes working on multiphase technology and to suggest a joint research and development project. The target was to define the aim of such a develop-ment and to work out the market potential of the new multiphase technology. The avail-able data regarding energy consumption, oil & gas demands, hydrocarbon reserves and resources were considered together with a forecast until the year 2020.

In the course of MTT-Project Bornemann developed a similar multiphase pump like for the Poseidon project which was subject to intensive scientific tests in a test campaign from 1990 until 1992.

Fig. 2a and b: Multiphase Pump in GKSS test field in Geesthacht/Germany

In the GKSS test facilities, using water-nitrogen mixtures, the capability of a twin-screw multiphase pump to handle gas fractions up to 90 % was proven, the pressure build up along the feed screws was examined, and the capacity increase during pumping of liquid/ gas mixtures was verified.

Fig. 3a and b: Test result GKSS, pressure profile along screw and flow versus differential pressure

During the MTT Project the test campaign also included liquid slug simulation and extended gas cap simulation. As a result of these observations Bornemann applied for their base multiphase patent in 1993.

3. PROCAP 2000 Project

The Procap 2000 Project and the directly following research projects of the Brazilian state-oil-company Petrobras are considered to be one of the most important milestones for multiphase technologies worldwide. Bornemann entered the Procap 2000 Project in 1993 and delivered a multiphase pump type MW7T-28 in 2004 for scientific examinations at Atalaia test field close to the city of Aracaju in Northern Brazil.

The Atalaia test field was the first full scale multiphase test loop using “real” products (crude oil and natural gas) for scientific examination of multiphase pumps. The results were presented at the Offshore Technology Conference in 1997 (OTC 8448).

Fig. 4: Atalaia test field

Fig. 5: Atalaia test field, process flow diagram

Fig. 6: Atalaia test field, flow rate curves for oil and gas

Another important result was gained at Atalaia test field. The inlet piping arrangement was long enough (approx. 200 m) for perfect generation of slug flow entering the multiphase pump. The test field was equipped with two different choke devices for generating the
differential pressure across the multiphase pump. One directly located at the discharge and two located at the top & bottom of the separator downstream of the pump (for separately choking of liquid & gas stream). Using the choke valve directly located a the discharge in slug flow conditions pulsation of differential pres-sure higher than 20 bar could be observed leading to not uniform, rough running behavior of the multiphase pump.

Using the 2 choke valves at the separator in the same slug flow conditions pulsation of differential pressure did not occur and the running behavior of the multiphase pump was uniform and smooth. Herewith the worldwide first practical prove for perfect slug handling
capabilities of twin-screw multiphase pump technology was demonstrated.

Furthermore this test field layout in Atalaia had important impact on other test fields world-wide (especially on the actual Bornemann test field).

4. MPA Project

In the year 1997, 10 years after the start of the first German multiphase technology project MTT, the German Ministry for Research and Education decided to support the next re-search project for this technology: The MPA Project. In a group of scientific partners from the universities of Hannover, Bochum, Hamburg and Munich, and the industrial partners Burgmann/ Seals, GISMA/ Connectors, Helmke/ Electric Motors and Bornemann as pro-ject leader, a Multiphase Pump Aggregate was manufactured and installed in a dry loca-tion with capabilities to simulate subsea conditions of 1000 meter water depth by means of a pressure vessel.

Fig. 7: MPA test location

The MPA Test Aggregate is installed and operated in a Wintershall sour gas field in Northwest Germany since 2004. Besides the simulation of a subsea environment the MPA Project achieved the following targets:

• Extrapolation for power requirements up to 7 MW (10 000 HP),
  Verification of mechanical seal reliability in multiphase pumps,
• Management of component wear in the presence of aggressive fluids and solids,
  Continuous operation, control and observation for 24000 working hours in order to im-prove reliability figures of all major components, and
• General further development of multiphase boosting technology in regard to design,
  monitoring and control.

Fig. 8: Extrapolation for power requirements up to 7 MW (10000 HP)

Within the MPA Project Bornemann applied for two important patents for multiphase boosting technology:

• The Smart Seal System for special demands in multiphase pumping service,
• And the manufacturing process for feed screws allowing digressive screws, i.e. screws
  with a decreasing pitch.

Fig. 9a to d: Digressive Screws, theory and practice

5. DEMO 2000 Project
In 1998 AkerKvaerner and Bornemann entered in a cooperation agreement for subsea multiphase boosting equipment. In the course of this agreement AkerKvaerner was participating in the DEMO 2000 project supported by the Norwegian government. Bornemann delivered the pump internals (type SMPC 335) for AkerKvaerner’s Subsea MultiBooster.

Fig. 10a and b: Pump internals for DEMO 2000

This module was subject to several scientific test campaigns at AkerKvaerner’s internal test facilities as well as Statoil’s K-Lab. Finally the DEMO 2000 module was installed in CNRI’s Lyell Field in the North Sea, as the first twinscrew multiphase pump under real field sub sea conditions and is in operation since February 2006.

Fig. 11a and b: DEMO 2000 subsea pump module and field installation at Lyell in the UKNS

6. MPT Project

In the frame work of a Russian / German Agreement for scientific and technical coopera-tion from the year 2005 the German Ministry of Education and Research decided to sup-port the MPT Association with the research project for sustained utilization of hydrocarbon reserves by implementing multiphase boosting technology. This project covers the whole process chain, from the reservoir until hydrocarbon utilization.

In the course of this project the Russian industrial partner and Bornemann manufactured a test multiphase pump system especially designed for the demands of single well multi-phase boosting.

This test aggregate was officially presented in Russia on March 12, 2008 and will be in-stalled for field testing in an oilfield in Western Siberia in summer 2008.

Fig. 13: Single well boosting

7. Acknowledgements

The actual state of the art of the Bornemann multiphase boosting technology is a result of numerous national and international research projects.

The presented scientific work has been developed within the MTT/MPT joint research pro-jects supported by the Federal Ministry for Education and Research in close cooperation with the involved industrial companies Burgmann, Helmke, Gisma and Wintershall. We would like to thank the partners there intensive cooperation and broad support. Special thanks to the Governments of Brazil, France, Norway, and Russia, as well as to the oil companies Statoil, Total, PDVSA, Petrobras, CNRI, LUKoil and Wintershall for the support of these projects by operating multiphase pumps in their oil & gas fields.

Finally very special thanks to Professor Heinrich Günter Schafstall for the coordination of all German scientific activities in multiphase boosting technology for more than 20 years.

8. References

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