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

Abstract

The oil (diluted bitumen)−water separation efficiency at steam-assisted gravity drainage (SAGD) process conditions has been evaluated in a laboratory environment by using a custom-built batch gravity setup, using SAGD field fluids and commercial gas condensate as a diluent. The key parameters and conditions investigated are solvent amount, shear conditions, water-to-oil ratio, and the presence and wettability of fine solids. The results demonstrate the complexity of the oil−water separation process, affected by the dependence of the investigated parameters from one another. A new quantification approach is introduced to facilitate the oil−water separation efficiency evaluation, based on the proposed descriptor, referred to as a separation efficiency index (SEI). Defined as the average of the residual water-in-oil and oil-in-water indices, SEI ranges from 0 to 1, where 1 represents a "perfect" (complete) separation and 0 corresponds to a complete emulsification. The SEI allows one to describe the separation efficiency throughout the entire separation vessel volume, using discrete vertical water distribution profiles, and represents the separation efficiency with a single number, regardless of the experimental approach taken. The findings show that in the range of solvent concentrations of 30 vol % or lower, the mixing speed affects the separation performance and becomes predominant at the relatively low solvent concentrations of 10 and 20 vol %. The amount of solvent added becomes predominant in the oil−water separation process and overcomes all other effects in the highest solvent addition (40 and 50 vol %) range. The presence of water-wet solids improves the separation performance, while the presence of oil-wet solids impedes the oil−water separation. The results presented in this study, in particular the proposed SEI, are important for improving the oil−water separation efficiency and can be used to develop operational envelopes and new solvent injection strategies, in terms of location, amount, and stages, further improving the quality of the oil product obtained in SAGD.

Investigation of Unresolved Interface “Rag Layer” in Athabasca Oil Sand Bitumen In Situ Recovery

“…The quartz powder treated to render oil-wet was prepared by soaking for 2 h in a 5% solution of dichlorodimethylsilane in toluene, followed by filtration, sequential rinsing with toluene, acetone, toluene again, and deionized water, and drying. The wettability of these solids has been reported and discussed by Hristova et al…”

“…All experiments were conducted in the presence of a predetermined constant amount of proprietary SAGD additives, consistent with SAGD field operations. The use of these dewatering agents was necessary to achieve a separation performance representative of that achieved in the field, as determined during commissioning …”

“…In the literature, the widely accepted paradigm claims that water-in-crude oil emulsions are almost exclusively stabilized by asphaltenes. − This stabilization is attributed to changes in the rheology of the thin liquid film in the contact zone between adjacent water droplets from fluid-like Newtonian to gel-like non-Newtonian, rather than the surfactant-like behavior of asphaltenes. , Recently, Hristova et al have attributed the notable non-Newtonian film rheology to the transition of the oil-continuous phase to a gel-like formation in the contact zone, essentially due to the surface asphaltene precipitation without any noticeable bulk asphaltene precipitation. Moreover, Hristova et al claim that surface asphaltene precipitation may be initiated below the critical dilution for bulk asphaltene precipitation. ,, This is particularly important for SAGD operations, where care should be taken to avoid asphaltene precipitation.…”

“…In the current study, we investigate the “rag layer” formation that can become disruptive when it extends beyond the oil–water interface and occupies a large part of the treater volume. This study builds upon the recently gained knowledge about oil–water separation efficiency. ,, The experiments are conducted at a bench scale, using produced fluids originating from SAGD field facilities in a custom-built setup under process conditions, as well as in a SAGD field sampling activity over several days during “rag layer” occurrence. The unresolved interface visually appears broadened and has a diverse morphology consisting of both oil-in-water and water-in-oil emulsions with a distinct transition between the continuous phases.…”

Intelligent Devices Harnessing Underwater Superoleophobic and Underoil Superhydrophobic Quartz Sands for the Separation of Diverse Stratified and Emulsified Water–Oil Mixtures

“…Oil–water separation plays an important role in environmental protection, industrial production, , resource recovery, and other fields . Oil entering the natural water will cause great harm to the ecosystem, such as the Gulf of Mexico oil spill accident, which has seriously affected the survival and reproduction of marine life. − At the same time, as an important chemical raw material and energy source, the recycling of oil is conducive to reducing resource waste and aiding energy conservation and emission reduction.…”