Cost Reduction of Subsea Boosting Systems by Use of Innovative Technologies
Authors: Carpenter Chris 
Published: August 2017

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 27639, “Significant Cost Reduction of Subsea Boosting Systems by Innovative Technologies,” by J. Davalath and D. Wiles, TechnipFMC, prepared for the 2017 Offshore Technology Conference, Houston, 1–4 May. The paper has not been peer reviewed. Copyright 2017 Offshore Technology Conference. Reproduced by permission.

One of the more promising opportunities for brownfield investment is low-cost subsea boosting systems. These projects do not require the drilling of new wells or significant infrastructure investments in new subsea equipment or new topside facilities. Incremental investments in low-cost boosting systems result in substantial increases in revenues and, therefore, high rates of return. The costs of subsea boosting systems have been reduced by adopting three primary strategies: simplifying the system design to reduce weight and cost, simplifying the installation and intervention, and reducing complexity and risk.

Introduction

Analyses of well and reservoir conditions suggest that there are hundreds of wells worldwide that have the economic potential for low-cost subsea boosting. The return on investment (ROI) in these cases ranges from 250% to greater than 500%. Subsea boosting systems are a robust and mature technology; worldwide, more than 65 mudline units and more than 50 submersible pumps have been installed. Consequently, 19 operators have addressed production challenges with subsea boosting technology.

Key applications have used subsea pumps as part of a subsea-processing station. For example, subsea pumps were installed to boost liquids separated subsea in three-phase separation systems, for the purposes of debottlenecking topside facilities, in the Petrobras Marlim project and the Statoil Tordis project, the former with horizontal pipe separator technology and the latter with conventional horizontal three-phase separator technology.

Subsea pumps have also been installed downstream of gas/liquid separators in Angola’s Block 17 in the Pazflor Field. This application enabled a higher-pressure boost than could be achieved by multiphase pumps available at that time. The separation of the gas from the liquid enabled the use of a hybrid pump, with centrifugal stages in addition to the helicoaxial stages typical of a multiphase pump, to provide a higher differential pressure.

Improvements in multiphase-pump technology have occurred such that higher differential pressures can be generated as a result of high-speed-motor technology, rapid-control technology, and monitoring systems.  Therefore, subsea boosting stations have become less-expensive and more-reliable solutions for increased oil recovery (IOR).

Market Potential

The need to reduce the backpressure on producing wellheads, and increase the recovery factor from oil and gas reservoirs, is omnipresent in subsea fields. The decision to install subsea boosting on the mudline is made in the context of the incremental improvement in recovery achievable with a subsea pump vs. the recovery achievable by producing the field naturally or by other IOR technologies. Operators have studied key oil-producing regions and have identified many instances in which mudline boosting is the most-viable alternative.