Electromechanical Tuning Fork Resonator For Drilling Fluid Viscometry and Densitometry

Abstract

Drilling fluids are an integral part of drilling wells for oil and gas production. They carry cuttings from the bit to the surface, prevent collapse of the wellbore, and balance formation pressures to prevent reservoir fluids from entering the wellbore. Frequent measurement and adjustment of the viscosity and density of the drilling fluid is crucial for a safe and efficient operation. However, on most drilling rigs, these measurements are done manually. Here, we describe an automatic sensor, based on an electromechanical tuning fork resonator, for vibrational viscometry and densitometry. The device was integrated into an instrument that allows continuous measurements at the return tank of the mud circulation system. The electromechanical resonator is the frequency-defining element of an oscillator circuit, where a digital gain control system maintains a constant vibrational amplitude. The resonant frequency and the required gain are related to the density and viscosity of the fluid. This technique enables fast measurements limited only by the transient response time of the resonator, which is in the millisecond timescale for the obtained quality factors in liquid media. This feature enables further integration of such devices into in-line systems, where measurements faster than the typical flow-rates are needed.