Review of the process integration alternatives for interconnecting solar steam generators into existing steam facilities, and resulting facilities costs, energy contribution (solar fraction), and net CO2 credits generated.
Siting and land footprints were chosen for several thermal recovery projects. Three integration options were studied: water preheating, constant-rate steam with balanced boiler turndown, and variable-rate steam distribution. Solar collector arrays were laid out and hourly energy production modeled. Aspen Hysys studies were carried out and line sizes, pressure drops, and facilities costs were estimated for the full path to the wellhead. Annual total contributions to steam injected (solar fraction) were evaluated.
Solar preheating of boiler feedwater required the least changes to existing facilities, and was economical especially at fields with lower temperature boiler feedwater; solar fraction was limited in most cases to under 6%. Constant-rate steam injection increased practical solar fraction to above 15%, while requiring changes only to the steam generator setting. Variable-rate steam injection involved facilities changes to wellhead rate control devices but allowed over 50% solar fraction with economical facilities costs.
In March 2014, the California Air Resources Board released an estimate that if 30% of California oilfield steam were solar, 3.7 million tons/yr of credits would be generated in the Cap & Trade program, and an additional 4.3 million tons/yr in the Low Carbon Fuel Standard program. Facilities and land constraints associated with achieving that target are reviewed.