Research on the Correction Model for Measuring the Rheology of Oil-Based Drilling Fluids in Straight Pipes Under Pulsating Flow

The currently common method for the automated real-time accurate measurement of drilling fluid rheology is the straight pipe measurement. However, the pulsating flow generated by the pumping equipment often leads to significant data errors in pressure difference and flow measurement, resulting in low accuracy of the calculated rheological parameters. To address the issue of data errors caused by pulsating flow, this paper proposes a correction model for straight pipe drilling fluid rheology measurement under pulsating conditions. Through research and theoretical analysis of the pulsating flow produced by diaphragm pumps, we derived the variation laws of outlet fluid flow rate, pressure, and diaphragm pump operating frequency, resulting in an expression for outlet flow velocity, which provides initial parameters for subsequent simulations. We then conducted 3D modeling and simulations of the measurement pipe in the actual experimental setup, obtaining a correction model for fluid rheology measurement under the influence of pulsating flow based on numerous simulation results. Finally, comparative experiments were conducted on a constructed experimental platform, comparing the results at different flow rates, viscosities, and temperatures against a rotating viscometer as the standard. The average deviations for the corrected rheological parameters were found to be 2.69% for apparent viscosity (AV), 2.362% for plastic viscosity (PV), and 3.056% for yield point (YP), effectively reducing the data errors in pressure difference and flow measurement caused by pulsating flow.