In the offshore oil and gas exploration business, safety, reliability, environmental concerns and costs play vital roles. Gas compressors have been widely used in offshore applications to meet a wide range of duties such as gas lift, injection, export and separation. Traditionally, gas turbines have been chosen as the driver for gas compressors. However, with the advancement in technology, electric motors are now being utilized as an alternate solution to drive these gas compressors. The advancement in offshore power generation and power from shore technologies has shown that a centralized offshore power generation utilising larger prime movers based on electric motors or aero derivative multi-spool gas turbines provide advantages in both size and weight.
This paper explains selection of the drive for gas compressors specifically making a choice between gas turbines and electric motor drives. Both technologies are proven to be mature are able to cater for various power ranges, applications and environments. Nevertheless, the selection process for offshore gas compressor drivers is still considered a grey area due to various aspects that influence and affect the selection of driver for an optimized offshore solution. The harsh nature of offshore locations warrants robustness to ensure high reliability and availability, minimal maintenance, clean emissions, small footprint, low fuel consumption and low initial investment. A parametric study based on an actual operating offshore facility was performed to evaluate the advantages and disadvantages of each driver type.
An existing offshore facility that utilized gas turbines as the driver for both power generation and gas compression was set as Base Case for this study. The Alternate Case required that the gas compression system utilize electric motor drives as the driver and upsizing of the power generation system to cater for the motors electrical load was now increased. The optimum driver was determined based on cost (CAPEX and OPEX), reliability, availability, efficiency, power requirement (electrical system, power generation & distribution), dimension, layout and emissions.
The findings of this study are expected to be a benchmark reference for driver selection for future offshore gas compression systems of similar operation and power range.