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

Abstract

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.

Rigorous review of electrical submersible pump failure mechanisms and their mitigation measures

“…Unlike electrical or mechanical failures, operational failures are tied to conditions of the wellbore fluids and thermodynamics that may result in mechanical or electrical failures. These failures can be a resultant of severe downhole temperature, sudden change in pressure gradients, introduction of gaseous phase due to reservoir pressure decline, and deposition of scale, asphaltene, or wax on the downhole ESP components (Rodrigues et al 2015;Morrison et al 2014;Nallipogu et al 2012). In many ESP cases worldwide, operational failures resulted in the shortening of the ESP mean time between failure significantly and impact the operational costs greatly.…”