Economics Of Steam Generation For Thermal Enhanced Oil Recovery

Steam Generation for Thermal EOR Three methods of steam generation have been considered (Fig. 1): • Fuel-fired once-through steam generator (Boiler) • Cogeneration (Cogen) with a power plant by use of a oncethrough heat-recovery steam generator • Solar steam generator (Solar) by use of concentrating solar power (CSP) The first method, Boiler, burns fuel directly to generate steam. Boilers have the most-flexible operations, but are most dependent on fuel costs. The second method uses the high-temperature flue gas from the gas turbine (GT) as “waste heat” to produce steam in a once-through heat-recovery steam generator (Cogen). Cogen steam production is linked to the power production of the GT. Operators sometimes add supplementary firing to the Cogen, called duct burners. The steam produced from duct burning has the advantage of rebalancing the electricity vs. thermal demand, but it is linked directly to fuel price. The third method, Solar, uses mirrors to concentrate the sun’s energy to generate steam. Three solar steam plants have been built: The 21Z in California (2011) and the Amal SSGP in Oman (2012) use enclosed-trough technology, and the Coalinga project in California (2011) uses tower technology. Coalinga ceased solar operations in 2014. In July 2015, a 6,000-tons-of-steam/D (1-GW) enclosed-trough solar plant (Miraah) was announced in Oman. Solar has the highest capital expenditure (Capex) of the methods considered, but consumes no fuel. The pros and cons of these three methods are summarized in Table 1.