Water Separation Performance in Bitumen Recovery from Athabasca Oil Sands: Implementation of Separation Efficiency Index

Theoil (diluted bitumen)-water separation efficiency atsteam-assisted gravity drainage (SAGD) process conditions has beenevaluated in a laboratory environment by using a custom-built batchgravity setup, using SAGD field fluids and commercial gas condensateas a diluent. The key parameters and conditions investigated are solventamount, shear conditions, water-to-oil ratio, and the presence andwettability of fine solids. The results demonstrate the complexityof the oil-water separation process, affected by the dependenceof the investigated parameters from one another. A new quantificationapproach is introduced to facilitate the oil-water separationefficiency evaluation, based on the proposed descriptor, referredto as a separation efficiency index (SEI). Defined as the averageof the residual water-in-oil and oil-in-water indices, SEI rangesfrom 0 to 1, where 1 represents a "perfect" (complete)separation and 0 corresponds to a complete emulsification. The SEIallows one to describe the separation efficiency throughout the entireseparation vessel volume, using discrete vertical water distributionprofiles, and represents the separation efficiency with a single number,regardless of the experimental approach taken. The findings show thatin the range of solvent concentrations of 30 vol % or lower, the mixingspeed affects the separation performance and becomes predominant atthe relatively low solvent concentrations of 10 and 20 vol %. Theamount of solvent added becomes predominant in the oil-waterseparation process and overcomes all other effects in the highestsolvent addition (40 and 50 vol %) range. The presence of water-wetsolids improves the separation performance, while the presence ofoil-wet solids impedes the oil-water separation. The resultspresented in this study, in particular the proposed SEI, are importantfor improving the oil-water separation efficiency and can beused to develop operational envelopes and new solvent injection strategies,in terms of location, amount, and stages, further improving the qualityof the oil product obtained in SAGD.