Rock-physics characterization of bitumen carbonates: A case study

Bitumen carbonate is an important source of bitumen, and knowledge of its properties needs to be improved. Owing to its high viscosity, most production methods of bitumen involve thermal techniques. Bitumen properties change tremendously during thermal production, which can inevitably affect the properties of bitumen carbonates. Moreover, the high pressure applied for steam injection can also impact the properties of bitumen carbonates. The variations of reservoir properties are indicators of a steam-affected zone, and thus they are significant for reservoir monitoring. To reveal the responses of bitumen carbonates under different pressure and temperature conditions, two bitumen carbonate samples are measured in the laboratory. We first develop a method that enables the estimation of porosity and bitumen saturation simultaneously. Then, the samples are exposed to various differential pressures, covering the in situ effective pressure range, to study the influence of pressure on velocities. Afterward, different temperatures are used to test the temperature sensitivity of the two samples. A histogram analysis of the velocity variations is also conducted to investigate the effects of distinct porosity and bitumen saturation. After washing off the bitumen, the clean samples are also measured and compared with the as-is samples, so as to check the impacts of bitumen on the carbonate samples. We have determined that porosity, bitumen saturation, pressure, and temperature can all have a noticeable influence on the velocities of bitumen carbonates. Although the research is in its initial stage, it can help improve our understanding of bitumen carbonates and also assist in monitoring the steam-affected zone during thermal production.