Multiphase metering based on Vx technology is the answer for many of the challenges in heavy oil exploration and development. Accurately evaluating reservoir productivity is a challenge, especially during the early stages of exploration. Well testing using a separator has limitations in measuring gas and liquid flow rates because of poor separation among the three phases. In a heavy oil environment, standard separators cannot always acquire accurate flow data in certain difficult environments—extremely low gas rates, low density contrast among liquids, contamination of the different effluents after separation, and well instabilities leading to carryover or carry under. PhaseTester and PhaseWatcher multiphase meters provide a simple, compact, and robust solution to many of the common problems in these challenging environments, without requiring separation for flow rate measurement.
Efforts to extend the operating envelope in the field have led to the creation of special procedures, refined over time, and gradually resulting in a more accurate interpretation model, including fit-to-purpose fluid properties packages. Certain of these well testing procedures have achieved better results in heavy oil: heating the flowing effluents to bring viscosity within the operating envelope and developing improved in-place processes to measure high oil viscosities. In sum, the overall envelope has been expanded to cover a wider range of situations. Based on this experience in heavy oil well testing worldwide, Schlumberger created a database of best practices.
In a heavy oil environment, the most appropriate meter in most cases is the PhaseTester 29-mm multiphase flowmeter. However, even with modified processes in place, heavy oil scenarios often remain outside the fluid properties standard black oil model, which is based on a series of well-known correlations. In such environments, a significant data enhancement can be achieved by adding the PVT Express onsite well fluid analysis service to increase the accuracy of the final flow rate measurements by removing the uncertainty caused by fluid properties. This portable, modular system is specifically designed to produce rapid and reliable PVT results on site. Sample analyses are produced using less than 50 cm3 of reservoir fluid, collected during bottomhole or surface sampling. In addition, the PVT results can be downloaded to the PhaseTester meter, allowing onsite computation of accurate flow rates at standard conditions. This combined service improves wellsite data quality and enables more rapid decision making.