| One method of Enhanced Oil Recovery is the injection of steam into a nearly spent oil reservoir. This technique produces large quantities of 'connate' water, which contain high levels of suspended and dissolved solids. To alleviate the cost of required water treatment, it was proposed to generate steam from the connate water. The crux was to accomplish this without severely fouling the boiler. This experimental work has examined the feasibility of such "brackish water boiling." Special attention was given to the mechanism of heat transfer during the fouling process, and how, if at all, this might apply to the 'clean' surface condition.;Two fouling experiments were conducted, one on each geometry. Based on the 'clean' database, an optimal set of operating conditions was found to be: pressure 0.8 MPa, massflux 300 kg/m;The experimental results were very similar for both geometries. Both fouled non-uniformly, with the highest fouling observed in the SLUG flow regime, and lowest in the ANNULAR flow regime. Fouling rates were also peripherally distributed, but were different for each geometry. Microscopic examination of the deposit structure showed the existence of steam chimneys just before, and downstream of an observed peak in deposit thickness. This peak was located just downstream of the saturation point. In the single-phase region, just upstream of the peak, steam chimneys were not found, and the deposit was non-porous. Downstream, the steam chimney diameter decreased both with axial position, and peripherally toward the TOP.;It was concluded that fouling could be minimized by establishing ANNULAR flow for the entire boiler tube length (possibly by steam injection at the inlet), and ensuring that dryout does not occur. (Abstract shortened with permission of author.);Prior to performing the fouling experiments, a 'clean' two-phase flow boiling database was established. In SLUG flow, the data were heavily scattered and the heat transfer coefficients were, on average, lower than in ANNULAR flow. The heat transfer coefficients from both geometries were well represented by the Chen (1966) correlation. |
