The Delaying Influence of Degradation on the Divestment of Gas Turbines for Associated Gas Utilisation: Part 1
An important feature of the exploitation of associated gas as fuel for gas turbine engines is a declining supply. So when exploiting this resource, the divestment of prime movers is very important as the fuel supply diminishes with time. This paper explores the influence of engine degradation on the timing of divestments. Hypothetical but realistic gas turbine engines were modelled with Turbomatch, the Cranfield University gas turbine performance simulation tool. The results were deployed in three degradation scenarios within the TERA (Techno-economic and environmental risk analysis) framework to develop economic models. An optimisation with Genetic Algorithms was carried out to maximize the economic benefit. The results show that degradation will have a significant impact. It will delay the divestment of power plants, while they are running less efficiently. Over a 20 year investment, a decrease of $0.11bn, $0.26bn and $0.45bn (billion US dollars) were observed for the three degradation scenarios as against the clean case.
 I. Allison, “Techno-economic evaluation of associated gas usage for gas turbine power generation in the presence of degradation and resource decline,” unpublished, PhD thesis, Cranfield University UK, 2014.
 2b1st Consulting, ‘‘Associated gas’’, 2012. Available at: https://www.2b1stconsulting.com/associated-gas/ (Accessed: 17 Dec. 2017)
 J. Kearns et al., ‘‘Flaring and venting in the oil and gas exploration and production industry: an overview of purpose, quantities, issues, practices and trends’’. International Association of Oil & Gas Producers, 2000. Available at: https://2ch417pds.files.wordpress.com/2014/04/flaring-venting-in-the-oil-gas-exploration-production-industry.pdf (Accessed: 19 February 2018).
 B. N. Anosike, “Technoeconomic evaluation of flared natural gas reduction and energy recovery using gas-to-wire scheme,’’ unpublished, PhD thesis, Cranfield University UK, 2013.
 Accounting Tools Incorporation, ‘‘Salvage value,’’ 2017. Available at: https://www.accountingtools.com/articles/what-is-salvage-value.html (Accessed: 22 January 2018).
 Bureau of Economic Analysis – United States (2003), ‘‘BEA depreciation estimates,’’ pp. 262-265, 1979. Available at: http://www.bea.gov/national/pdf/fixedassets/BEA_depreciation_2013.pdf.
 A. E. Ogiriki, ‘‘Effects of environmental factors on gas turbine engine creep life and performance,’’ unpublished, PhD thesis, Cranfield University UK, 2015.
 M. Obhuo, ‘‘Techno-economic and environmental risk assessment of gas turbines for use with flared associated gases,’’ unpublished, PhD thesis, Cranfield University UK, 2018.
 Anosike, N., El-Suleiman, A., and Pilidis, P., (2016), Associated gas utilization using gas turbine engine, performance implication – Nigerian case study. Energy and Power Engineering, 8, 137-145.