Wettability and hydrophilicity of Fengcheng terrestrial oil sand
LIN Botao1, SHI Can1, YU Guangzhe2, JIN Yan1
1 College of Petroleum Engineering, China University of Petroleum-Beijing, Beijing 102249, China 2 McKetta Department of Chemical Engineering, University of Texas at Austin, Austin 78712, USA
The terrestrial oil sand reservoirs in Fengcheng are characterized by their high viscosity and micro fracturing stimulation followed by SAGD has been commonly implemented. In order to understand how the injected fluid and the steam condensate infiltrate the reservoirs, the wetting and hydrophilic mechanisms of the oil sand must be interpreted. To this end, this study investigated oil sand sampled from Fengcheng for its wettability and hydrophilicity under various pressure gradients and acidities, through a series of laboratory studies including XRD, ESEM, contact angle and NMR tests. It was found that the oil sand develops a loosely packed microfabric, with bitumen forming the cementing agent between sand grains rather than wrapping the grains. The oil sand tends to be water-wet, with the wetting saline existing as both a water film and pore water in the matrix. Either increasing the pressure gradient or acidity/alkalinity is able to thicken the water film or increase the pore water amount. In summary, the Fengcheng oil sand is water wet and hydrophilic. An increase in the injection pressure gradient can bring in more steam or water into a reservoir, while adding chemical ingredients will not cause harm to the injectivity of the reservoir.
