Hydrogen solubility measurements in heavy oil and bitumen cuts

An indirect method for measuring gas solubility in liquid media such as heavy oil, bitumen, petroleum residue and low volatility model hydrocarbons is reported. The method is intended for use with an existing X-ray view cell apparatus. With this apparatus it is possible to verify the number of phases present and to ensure that the phases are well mixed. For example, vortices in the impeller region are readily observed using transmitted X-ray imaging, despite the opacity of heavy hydrocarbons to visible light. Gas solubility data is obtained by tracking the location of the liquid–vapour interface. The volume of the view cell, the number of moles of gas added to the cell and the mass of the liquid phase are known. Once the volume of the liquid is obtained, the dissolved gas fraction is computed by difference. The method is applicable over the range of conditions accessible with the view cell apparatus — from ambient conditions up to 450°C and 30 MPa. For sparingly soluble gases such as hydrogen, solubilities measured using this method fall within 5% of values reported in the literature for hexadecane and tetralin at pressures greater than 2 MPa. Measured values are repeatable to within 2%. Hydrogen solubilities in a light virgin gas oil, a heavy virgin gas oil, Athabasca bitumen vacuum bottoms and Gudao atmospheric residuum are reported over a broad range of temperatures (80–380°C) and pressures (0.5–12 MPa). The solubility values obtained for the four cuts differ significantly at low temperatures but fall within a narrow range at elevated temperatures where the values do not differ markedly from values obtained for much lighter fluids such as tetralin.