Carbon dioxide flooding of oil fields around the world is proven as a successfully adopted practice in increasing oil production particularly in marginal wells with low production rates. However, the limitations of this technology lie in the limited supply of carbon dioxide, high capital cost, and infrastructure corrosion. In this work, we present an alternative CO2 flooding method which generates CO2 inside the reservoir to increase oil recovery. The process involves the injection of a concentrated CO2 producing solution of ammonium carbamate (AC). Chemical solvent CO2 capture technology was widely used for years. Carbamates were formed when aqueous amines absorbed CO2. The new proposed in situ CO2 generation EOR technique provides a way to directly apply the product of the CO2 capture technology for outstanding tertiary recovery.
Ammonium carbamate (CH6N2O2), highly water-soluble chemicals, can dissociate at reservoir temperature producing carbon dioxide and ammonia. The carbon dioxide migrates to the oil phase, causing oil phase swelling and reducing oil viscosity, and therefore increasing oil production. The ammonia dissolves in the water, and the ammonia-water solution increases the water wettability of the rock.
Flow experiments were conducted using 6" Ottawa sand packs. The experiments demonstrated that the decomposition of a 35% AC solution injected to the sand packs resulted in further lowering of the residual oil saturation following a standard water flood. The tertiary recovery in the high-pressure sand pack experiments was found to average 27%.
In the proposed process, AC can be dissolved in produced reservoir fluids or seawater and injected into the reservoir to generate CO2 in situ and increase oil production as it decomposes. The benefits of this process compared to CO2 flooding lie in the simplicity of adapting this technology to an existing waterflood, and the lack of the complicated infrastructure needed in a typical CO2 project, such as compression and gas handling facilities. An additional advantage lies in the ability to deliver the CO2 in the form of a room temperature solid, alleviating the need for a pipeline.