Diluted Bitumen Water-in-Oil Emulsion Stability and Characterization by Nuclear Magnetic Resonance (NMR) Measurements

Abstract

Canadian oil sands represent a huge oil resource. Stable water-in-oil (W/O) emulsions, which persist in Athabasca oil sands from surface mining, are problematic, because of clay solids. This article focuses on the characterization of water-in-diluted-bitumen emulsions by nuclear magnetic resonance (NMR) measurement and the transient behavior of emulsions undergoing phase separation. An NMR restricted diffusion experiment (pulsed gradient spin−echo (PGSE)) can be used to measure the emulsion drop-size distribution. Experimental data from PGSE measurements show that the emulsion drop size does not change much with time, which suggests that the water-in-diluted-bitumen emulsion is very stable without an added coalescer. The sedimentation rate of emulsion and water droplet sedimentation velocity can be obtained from NMR one-dimensional (1-D) T 1 weighted profile measurement. Emulsion flocculation can be deduced by comparing the sedimentation velocity from experimental data with a modified Stokes' Law prediction. PR5 (a polyoxyethylene (EO)/polyoxypropylene (PO) alkylphenol formaldehyde resin) is an optimal coalescer at room temperature. For the sample without fine clay solids, complete separation can be obtained; for the sample with solids, a rag layer that contains solids and has intermediate density forms between the clean-oil and free-water layers. Once formed, this rag layer prevents further coalescence and water separation.

NMR relaxometry and diffusometry in characterizing structural, interfacial and colloidal properties of heavy oils and oil sands

“…These include investigations into wettability [21], viscosity [22], fluid saturations [23] and emulsions [24]. In the present article, a brief overview of the relevant NMR theory (full details of which can be found in established texts, e g., [25][26][27]) will be followed by an evaluation of the literature, in conjunction with some new experimental results.…”

“…In addition to the PGSE techniques, T 2 relaxation population distributions have been used to study emulsions [24]. The T 2 value for the dispersed phase can be related to the droplet size using [81,82] …”

“…PGSE NMR was used to estimate the droplet size distribution of a waterin-heavy oil emulsion at three temperatures [83]. Other workers have demonstrated the use of NMR to investigate time-dependent stability properties of water-in-oil emulsions under different conditions [24].…”

“…The contrast between the bitumen and water phases in these profiles is generated by the different relaxation times of the respective phases. Profiles were obtained over time and used to monitor sedimentation and coalescence of the emulsions [24].…”

Experimental evaluation of different strategies for improving oil recovery at high-water-cut by quantitative etched-glass micro-models

“…The scale of distinguishability can reach up to 0.1 mm; and the clarity of images is far more satisfying when compared with CT. NMR has been intensively applied in petroleum research for the past 20 years. These applications include investigation on viscosity, emulsions, wettability, and fluid saturations (Bryan et al, 2003;Hum and Kantzas, 2006;Jiang et al, 2007;Kantzas et al, 2005). Etched-glass micro-model can be used to mimic the pore structures with high distinguishability (Sun and Qu, 2004;Sun and Tang, 2006).…”