Vertical-tube evaporator system provides SAGD-quality feed water

Water treatment and steam generation methods for heavy oil recovery processes have evolved rapidly. Traditionally, Once-Through Steam Generators (OTSGs), driven by natural gas, have been used to produce about 80% quality steam (80% vapor, 20% liquid) for injection into the well to fluidize the heavy oil, especially for cyclic steam operations. However, the more recent Steam-Assisted Gravity Drainage (SAGD) method requires 100% quality steam for injection. The use of OTSG for SAGD applications requires a series of vapor-liquid separators to produce the requisite steam quality. For both SAGD and non-SAGD applications, pre-treatment of the OTSG feed water has consisted of silica reduction in a hot or warm lime softener, filtration and hardness removal by Weak Acid Cation (WAC) ion exchange. In most cases, the OTSG blowdown is disposed by deep well injection. As the use of SAGD increased, the traditional produced water treatment and steam generation methods were re-evaluated...