Viscosity and Density Measurements Using Mechanical Oscillators in Oil and Gas Applications

Real-time monitoring of wellbore fluids is of crucial importance for oil recovery. During various operations such as drilling, production, stimulation, and intervention, the characteristics of the fluids being produced or injected into the well needs to be monitored to ensure safe operation or to optimize production. However, measuring their physical properties, such as viscosity and density, can still pose a great challenge when the fluids are part of a multiphase flow or are complex inhomogeneous fluids whose properties can vary largely with external parameters such as temperature, pressure, and flow rates. While commercial instruments that make comparable measurements can be found in other industries, a solution tailored to these oilfield challenges does not exist at the moment. In this paper, we demonstrate two examples of viscosity/density systems using tuning fork-based mechanical oscillators tailored to different measurement scenarios in the oilfield. In the first example, we use a miniature piezoelectric tuning fork which can be integrated in small-scale measurement platforms for downhole deployment. By using the tuning fork as the frequency-defining element of an oscillator circuit, fast measurements of viscosity and density are possible. This feature allows us to use this device in fast changing multiphase flows, such as those found in live producing wells. In the second example, we demonstrate a ruggedized tuning fork device for in-line measurements of viscosity and density of non-Newtonian fluids. This instrument is a robust permanent tool for surface installation with applications in quality assessment of drilling mud and other wellbore fluids. We discuss some initial studies in a water-based drilling fluid.