Dynamic Remote Control System for Subsea Well Stream Boosting
Authors: Queseth Per Olaf , Dahl D.G. , Theobald Mike 
Published: October 2008

This paper is based upon the advanced stage of work underway to produce a control system for a prototype of a subsea process facility. This facility is developed to boost the production from subsea oil and gas wells and is particularly suited to enhancing production from remote or otherwise marginal satellite oil and gas reservoirs. Fig. I KBS Mechanical Configuration is a detailed mechanical drawing of this facility.

Component selection occurred as a result of substantial analysis via computer model simulations of both the process and mechanical functions. System development and design emphasised use of proven techniques to meet the results of the analysis with modifications being applied where required for subsea adoption. 1

Substantial testing is presently underway to verify correct component selection. The distinctive design of this work provides for the placement of a complete liquid and gas separator combined with pump and compressor modules as a single unit for subsea installation. Variable speed pump and compressor motors, submerged hydraulically actuated gas compressor anti-surge system, monocyclonic gas scrubber and associated computer monitoring and control items are adapted from successful surface based systems.

Development work by others has involved subsea separation of liquid and gas with liquid pumping as well as multi-phase pump designs. However, none of these concepts involve single phase gas compression.

Knowledge of these potential reservoir enhancement systems can allow off-shore field planners to provide additional resources to their inventory of assets that would otherwise be unavailable. Marginal wells can now be profitable and more surface processing can be moved subsea.

Introduction

Our philosophy has been to thoroughly test individual components prior to assembly of these into larger modules and systems. Further, the larger units are thoroughly tested to ensure quality before integration into the fmal booster. These component test results conclude that the concept is functional.

Individual components tested, involving simulation studies, include:gas filled variable speed electric motor.water filled variable speed electric motor.pump and compressor impellers.control system routines.

These results differ from others in that they are based upon a very advanced state of actual function tests.

New information revealed concerning the control system is:subsea process control is now feasible given the advanced stage of development of systems particularly the compressor.use of proven surface based concepts in a subsea environment is viable.

practical subsea equipment control functions are attainable for:continuously variable speed electric motors.hydraulically positioned compressor gas re-cycle valve including analogue positional feed back.anti-surge protection computer. separator liquid and foam analogue level monitoring, via nucleonic means, with proportional liquid level control.

Significance of Subsea Well Stream Boosting Control

Future economic and safety benefits are provided by moving processes subsea and thereby operating by automatic and remote means. The subsea location of process facilities offers the potential of:reducing off-shore manning requirements.increasing overall personnel safety.safeguarding production equipment.eliminating disrupting the view of the environment.

Additionally locating working equipment subsea takes advantage of t