Performance Evaluation of a Phased-Array Flowmeter for Use in Non-Newtonian Drilling Mud Flow

Managed pressure drilling (MPD) has become a cornerstone technique in modern drilling operations, enabling precise control of annular pressure and mitigating risks such as kicks, losses, and wellbore instability. A critical element in successful MPD execution is the ability to measure the flow of drilling fluids accurately and reliably under dynamic downhole and surface conditions. Real-time surface flow monitoring provides vital feedback for hydraulic models and control algorithms, but capturing this information accurately, particularly when dealing with complex fluid systems such as oil-based muds (OBM), remains a challenge (Turner and Wilson, 2014; Al-Khafaji et al., 2016). Traditional flow measurement technologies, while effective in steady-state or single-phase industrial applications, exhibit multiple limitations when applied to non-Newtonian, multiphase, or transient flow regimes. Coriolis mass flowmeters, often regarded as the gold standard in many industries, provide direct mass flow and fluid density measurements. However, they are constrained by pressure limitations typically up to 3,000 psi and are vulnerable to mechanical vibrations, especially in rig environments (Patel and Huang, 2021). Their performance further deteriorates under pulsating flow conditions, in fluids with significant shear sensitivity (Nguyen and Reyes, 2020), or when gas entrainment is present. In addition to entrained gas, Coriolis meters are susceptible to pressure-driven bubble formation (cavitation), which can occur even in nominally single-phase fluids due to sharp pressure drops. These bubbles interfere with the vibration of the flow tube, causing instability and substantial measurement error (Ross and Harvey, 2011). Differential pressure (DP) devices, such as V-cone and wedge flowmeters, rely on pressure drop across a known restriction and require stable density inputs to infer volumetric flow. These meters tend to drift over time due to erosion or scale buildup on the flow constriction and are susceptible to clogging when exposed to high solids loading, an inherent characteristic of drilling mud. Furthermore, DP meters assume Newtonian flow behavior in their governing equations, limiting their accuracy when used with shear-thinning or thixotropic fluids (Zhao et al., 2022).