Supersonic separator for cleaner offshore processing of supercritical fluid with ultra-high carbon dioxide content: Economic and environmental evaluation

Abstract

Offshore gas processing presents challenges, especially when high flow rates, high-pressure and high carbon dioxide contents are involved. The present scenario comprehends offshore processing of high flow rate of high-pressure natural gas with 68%mol carbon dioxide, which results from oil production and behaves as a dense supercritical fluid. The processing goals with this fluid comprise: [A] water dew-point adjustment; [B] hydrocarbon dew-point adjustment; [C] decarbonation of a small part to 20%mol carbon dioxide fuel-gas for power production; and [D] compression/pumping of the remaining fluid enriched with carbon dioxide from decarbonation for enhanced oil recovery. For these tasks the industry considers traditional well established processes such as molecular-sieves adsorption for water dew-point adjustment, Joule-Thompson expansion for hydrocarbon dew-point adjustment and membrane-permeation for carbon dioxide removal. However, conventional technologies can become cumbersome in such awkward conditions. Thus, unconventional solutions are sought for reliability, lower equipment size/weight, and better power consumption, emissions and environmental sustainability. Recently, supersonic separators have been analyzed in proof-of-concept researches for natural gas processing. In this regard, this work quantitatively proves that goals [A],[B],[C] are achievable using only supersonic separators, attaining 33% higher net value, 40% greater oil production, 10% lower investment and economic leverage to reach lower carbon emission relatively to conventional counterparts.