Combined heat and power plant on offshore oil and gas installations

Abstract

Implementation of energy efficient technologies is an issue of growing importance for the offshore oil and gas industry. Risingawareness of increasing levels of CO2in the atmosphere is a major driver in this move, with a main aim being to reduce theamount of released CO2 per unit of oil or natural gas produced. Subsequently, the addition of steam bottoming cycles toexploit exhaust heat from gas turbines offshore has become an attractive alternative. This paper will investigate two differentcombined cycle configurations, namely the extraction steam turbine- and the backpressure steam turbine-cycle. Both cycleswere modelled using the process simulation software Ebsilon Professional with a single GE LM2500+G4 gas turbine as atopping cycle, and a once-through heat recovery steam generator to exploit GT exhaust heat.At design, the steam turbinesproduced 8.2 MW and 6.0 MW respectively, achieving net thermal efficiency of 45.5%/42.1%. This was a 12.3 pp/8.9 ppincrease compared to the simple cycle GE LM2500+G4 configuration.The findings suggest that a backpressure steam turbine could be an attractive option for oil producing facilities with highdemand for process heat, while an extraction steam turbine configuration is more suited to gas producing facilities with lowerheat requirements and a higher demand for power and flexibility. Additionally, both cycles displayed a substantial reduction inemitted CO2 per MWh produced, with reductions 26% and 21% compared to the simple cycle configuration achieved for theextraction and backpressure cycle respectively.