A practical method for the separation of high quality heavy oil and bitumen samples from oil reservoir cores for physical and chemical property determination

We describe a mechanical extraction method, referred to here as “the plunger”, for the recovery of heavy oil and bitumen samples, equivalent to produced oil samples, from clastic and carbonate reservoir cores. We demonstrate the efficacy of the plunger relative to the centrifugation method through comparing the physical properties and chemical compositions of the heavy oils and bitumens recovered from oil sands cores. Over the dead oil viscosity range from 21,000 cP to 1.4 × 106 cP at 20 °C and 9.6 × 106 cP at 25.5 °C, the plunger consistently yielded correspondingly lower viscosity oils compared to the oils recovered by centrifugation from the same sample material, as well as lower sediment fines and water content. For an example of extremely viscous oil, the plunger yielded 3.3 g of 9.6 × 106 cP oil (25.5 °C), while centrifugation produced only 50 mg of fluid, adequate for geochemical analysis but insufficient for viscosity and density determination. unger has many advantages that favor its use over centrifugation such as successful recovery of highly viscous oil from cores, lower oil sediment fines/water content and faster sample extraction (typically 30 min to 1 h versus 2 h). The plunger has also been operated at the rig site to generate oil viscosity logs immediately following core recovery (prior to or during petrophysical logging) affording real time data acquisition to support decisions for conducting production flow tests while drilling rigs are onsite. Incidentally, due to the improved preservation of physical properties controlling volatile liquid components, repeated plunging of larger volumes of sample core can be used to recover large enough volumes of heavy oil or bitumen for PVT or specialist assay analysis. Since the plunger is operated under a sealed system the device may be configured in such a way to interface with a PVT cell. Gas introduced into the plunger system ultimately can lead to the production and collection of “enlivened oils” for viscosity measurements.