Effects of Clay Wettability and Process Variables on Separation of Diluted Bitumen Emulsion

Abstract

Initial processing of bitumen froth obtained using a water-based extraction process from Athabasca oil sands yields stable water-in-bitumen emulsions. When the bitumen is diluted with naphtha to reduce its viscosity and density, almost complete separation can be obtained with a demulsifier in the absence of clay solids. However, a "rag layer" persists between the oil and free water layers when clay solids are present. Effects of the naphtha/bitumen (N/B) ratio, demulsifier selection, and silicate dosage on the rag layer formation and product quality have been studied. Emulsions with a N/B ratio of 0.7 are more stable than those with a N/B ratio of 4.0. This can be partially attributed to the difference in viscosity and density affecting the sedimentation velocity. The residual water and solid contents in the oil layer decrease with the addition of silicate. This behavior is attributed to the effect of silicate on clay wettability. Clay solids have toluene-soluble organic contents, which vary as follows: in the oil layer > in the rag layer > in the bottom layer. This result indicates that the solids are the most water-wet in the bottom (water) layer and the most oil-wet in the oil layer. In the same layer, samples with a N/B ratio of 0.7 have a higher toluene-soluble organic content in solids than those with a N/B ratio of 4.0. At 80 °C with a N/B ratio of 4.0, emulsion adding 200 ppm of demulsifier PR 6 and 4 Â 10 -4 M sodium m-silicate had 0.3-1.5% water and 0.9% solids in the oil layer, with the water content decreasing with an increasing height above the rag layer.

Kaolinite and Silica Dispersions in Low-Salinity Environments: Impact on a Water-in-Crude Oil Emulsion Stability

“…From results of zeta potential measurements, silica with 3 µm in diameter in 0.01 MLB at pH~11 has a higher zeta potential in absolute value (−26.23 mV) than at pH~3 (−1.88 mV), which is close to ZPC [20]. …”

“…Neutral conditions are more favorable to formation of stable emulsion than acid conditions. It is found that the edges of the kaolinite are positively charged, which may adsorb negatively charged carboxylate components of the oil and turn that portion of clay solids partially oil-wet [20,21]. As Figure 13a shows, the clay particles are simply depicted as round and most of it is in the continuous phase (oil) due to their hydrophobicity.…”

Role of Caustic Addition in Bitumen–Clay Interactions

“…13 The attached clays to the bitumen surface can also cause problems in bitumen froth treatment by forming a rag layer. [14][15][16] The mechanism for bitumen slime coating has recently been studied in detail by Masliyah et al using atomic force microscopy (AFM) and zeta potential distribution measurement. 12,[17][18][19][20][21][22][23] While oil sands ores are a complex mixture of clays including kaolinite, illite, chlorite, montmorillonite, not all the clays cause slime coating.…”

Understanding Mechanisms of Asphaltene Adsorption from Organic Solvent on Mica

“…While pipeline deposition can lead to pipe plugging, adsorption onto clay solids modifies their wettability, decreasing efficiency of oil liberation from the solids and increasing solids partitioning at the oil-water interface. [14][15][16][17][18][19][20] In oil production, the formation of a complex multiphase dispersion layer in the middle of oil-water separation vessel, known as rag layers, is frequently encountered. 21,22 The rag layers are extremely stable multiemulsions with the stabilizing species identified as surfactants, asphaltenes and inorganic fine particles.…”