Abstract
Total indirect greenhouse gas (GHG) emissions from oil and gas operations today are around 5,200 Mt of carbon dioxide equivalent (CO2-eq) yearly, 15% of total energy sector GHG emissions. Most of these emissions occur due to natural gas leaks. Methane, a much more potent GHG than CO2, is the most significant single component of natural gas and, therefore, of these emissions. Part of these emissions results from routine operations such as flaring and venting, representing both an economic and an environmental issue. Many solutions have been developed to recover and use this natural gas instead of venting and flaring it. Three possibilities were simulated with AVEVA PRO/II, and a preliminary economic assessment was carried out with Guthrie’s method. 30 kmol/hr of natural gas fed was assumed, according to average site data, therefore, small-scale plants are suitable. A first solution based on compression, though requiring high OPEX (> 280 k$/y), produces very low emissions yearly (1,140 t CO2-eq/y). Another possibility is to couple flaring to a microturbine for energy generation, but this solution is both uneconomical and has a high environmental impact (> 10,000 t CO2-eq/y). The last technology analysed is thermal methane pyrolysis. This possibility, often disregarded in environmental studies, involves the production of turquoise hydrogen and carbon black. Although characterised by high capital costs (almost 3 M$), it can reduce gaseous emissions since it stores the carbon part of hydrocarbons in the solid matrix that is formed.
