Microfluidic Platform for PVT Measurements

Abstract In this work, we present a small-scale pressure/volume/temperature (PVT) cell which allows for the measurement of saturation pressure and phase-volume ratio using only a few microliters of reservoir fluid sample. This novel PVT measurement technique has been successfully tested on a wide spectrum of live reservoir fluids at elevated pressure (86 MPa) and temperature (150°C). In the microfluidic PVT platform, the small microfluidic device performs the same function as the laboratory-scale pressurized visual PVT system. At the heart of the microfluidic device is a long and narrow capillary, densely packed in a serpentine shape, embedded on the device. The capillary is nearly 1-m long and has a total volume of 5 μl. The microfluidic device is fabricated using glass and silicon which allows visual monitoring of a fluid sample at various pressures and temperatures. To acquire PVT data, the pressure in the capillary is systematically reduced to accurately detect the appearance of micron-size gas bubbles in a sample at saturation pressure. Due to the small thermal mass of the device, the temperature of the sample can be changed rapidly, which enables the measurement of multiple saturation pressures in quick succession. Below the saturation pressure, the growing gas bubbles form a segmented gas-liquid distribution in the capillary. The lengths of the liquid and gas segments are measured in real-time using an automated image capturing and analysis tool to determine the gas-liquid phase-volume ratio at a given pressure. Validation tests have proven this technique to be repeatable and feasible for rapid PVT measurements of black oils. The results presented in this study demonstrate that the microfluidic PVT system performs at the same level as the conventional PVT with significantly smaller sample volume and faster turnaround. The microfluidic PVT system is demonstrated to have the potential to become a reliable and portable measurement platform.