A New Boosting Concept: Pumps Installed Inside Production Risers in FPSOs

In oilfield exploitation, pumping is one of the most productive artificial lift methods. The use of downhole pumps, where applicable, allows increasing production. However, service life of this type of systems may be short, around 2.5 years for electrical submersible pumps - ESPs, one of the most widely used types. Furthermore, failures in wet completion subsea wells require tubing removal, a heavy workover operation, demanding high costs offshore rigs. Besides, due to production halt, revenues are impacted. As a tendency for subsea wells, whenever allowed by production conditions, pumps are installed on the seabed, outside the production well. Depending upon the free gas fraction at pump intake, ESPs (with or without previous gas separation) or multiphase pumps may be used. Examples of ESP usage outside the producing wells are the pumping module (MOBO) and the Skid-ESP. In such cases, ESPs strings are installed on the seabed. In cases of failure, ESP replacement is simpler and faster, executed by rigs or special vessels, avoiding the costly intervention in the production well. But, even saving resources due to the operation simplification, the costs of required naval resources and the time spent awaiting for their availability and mobilization are still high. Several days may pass from system failure until the intervention is finally performed. At Perdido and Nansen Spar platforms, operated by Shell and Anadarko respectively, ESP were deployed and installed in the production risers. Recent developments of compact and high speed ESP may contribute for their placement inside production risers for other production unit types, FPSO, for instance. This paper proposes a new boosting concept based pumps, ESP or Hydraulic Submersible Pumps - HSP, installed inside production risers in FPSO, comparing their advantages and disadvantages of the proposed concept to seabed ESP systems, multiphase pumps and gas-liquid separation systems.