(363e) Reservoir Based Hydrothermal Reforming of Hydrocarbons

Enhanced Oil Recovery (EOR) operations may offer a potentially clean and economical method for hydrothermal production of syngas or hydrogen as useful product or energy vector. EOR operations usually employ in situ combustion (using oxygen or air), steam injection and/or CO2 injection. In situ combustion has been studied for a number of years, e.g. the THAI process invented in 1993 by M. Greaves. In this process an air injection well is used to combust heavy oil and thus provides local heat to reduce oil viscosity. The oil is then driven towards a producer well (toe to heal). It is suggested that approximately 80% ooip recovery may be accomplished with the additional benefit of some in situ oil upgrading. Air injection results in the release of an equal amount of CO, CO2 and hydrocarbons. This of course begs the question whether the return gas, which would be used to provide the required electricity for the compressors, could be converted into syngas/hydrogen and thus lead to the production of a clean energy vector. Indeed, is it conceivable to employ, for example, redundant production wells as hydrothermal reactor systems with the explicit injection of oil, steam and air/oxygen and thus remove the need for above ground reformers? In the present work a basic parametric equilibrium study has been carried out on the reactions between crude oil and EOR fluids (air, steam, and CO2) using HYSYS and employing the embedded Gibbs Reactor model. This model allows the thermodynamic analysis of the effect of the molar flowrates of injection fluids (ratio of injection fluid to oil), reservoir pressure, reservoir temperature and water cut on the composition of the produced syngas. Only a few similar investigations have been reported in the literature (Ye et al., 2009, Ersoz et al., 2003, Jeon, 2008). These studies do not normally include crude oils containing sulphur compounds, nitrogen compounds and asphaltenes. Adiabatic steam/air reforming has been compared with adiabatic CO2/air reforming and adiabatic partial oxidation in terms of product distribution, temperature, and compression load. The goal was to identify conditions under which hydrogen production is maximised (Figure 1). It was found that steam, containing 20% O2, may potentially provide the highest yield of H2, the lowest yield of CO2, with reasonable compression load compared with air or CO2. The main challenge of air injection is the huge compression load, due to its high N2 content, which can reduce its cost-effectiveness. On the other hand, the main challenge with CO2 reforming is the huge rise in the CO2 compared with the very low H2 yield, which may add additional cost for separation of CO2 above surface. In situ sequestration of CO2 underground before reaching the wellhead might be feasible.