Method And Device For Measuring Fluid Properties Using An Electromechanical Resonator

摘要

A method and device are described for making in situ measurements of the density and viscosity of downhole fluids at subterranean wells. An oscillator circuit is deployed in the well comprising an amplifier, a feedback loop, and an electromechanical resonator. The electromechanical resonator is a component in the feedback loop of the oscillator circuit, and has a resonance mode that determines the frequency of the oscillator circuit. The electromechanical resonator is also in contact with the fluid such that the density and viscosity of the fluid influence the resonant frequency and damping of the resonator. The frequency of the oscillator is measured by a microcontroller. In one embodiment, the oscillator circuit periodically stops driving the electromechanical resonator such that the oscillation decays and the rate of decay is also measured by the microcontroller. The density and viscosity of the fluid are determined from the frequency and rate of decay of the oscillation. This measurement technique provides a faster response time to fluid changes than is possible with conventional measurement methods, and the fast response time opens up new applications for downhole viscosity and density measurements, including determining PVT characteristics, phase diagrams, and flow rates.

主权项

1. A method for making an in situ measurement of downhole fluid properties at a subterranean well, comprising the steps of:
a. deploying an electromechanical resonator at the subterranean well such that an electromechanical resonator is at least partially immersed in a downhole fluid; b. causing the electromechanical resonator to oscillate at a resonance frequency by powering an oscillator circuit, wherein the electromechanical resonator is incorporated as a frequency-defining element of the oscillator circuit; c. measuring the resonance frequency of the oscillation produced by the oscillator circuit; d. measuring a damping of the oscillation produced by the oscillator circuit; and e. relating the frequency and the damping to a viscosity and a density of the downhole fluid by employing a processor configured by code to utilize at least one of:
i. theoretical equations relating frequency and damping to fluid viscosity and density; andii. empirical relationships based on curve fitting to calibration measurements of the resonance frequency and damping in reference fluids, wherein the viscosity and density of such fluids are known.