Design of a Drilling Mud Agitator System for Small-scale Petroleum Operations

Abstract

Drilling mud agitation is a critical process in oil and gas drilling operations; inadequate agitation leads to solid particle settlement, inconsistent mud density, and degraded rheological properties that increase non-productive time (NPT) and operational safety hazards. This study presents the complete analytical design of a mechanically agitated drilling mud system comprising an 83-litre cylindrical tank and a discharge pump, sized for a process fluid of density 1,200 kg/m³ and dynamic viscosity 0.10 Pa·s. The design was executed using standard engineering equations for impeller geometry, power consumption, shaft torque, shaft sizing, motor selection, pump hydraulics, and mixing time estimation. A two-blade pitched-blade turbine (PBT) with an impeller-to-tank diameter ratio of 0.40 was selected, consistent with the CAD model and the fabricated prototype. The design yielded an impeller diameter of 182.9 mm rotating at 1,148.6 rpm, a Reynolds number of 7,684, a shaft power of 516.8 W, a shaft torque of 4.30 N·m, a rated agitator motor power of 0.75 kW, and a mixing time of 7.12 seconds. The pump system was redesigned with a 76.2 mm (3-inch) discharge pipe diameter, yielding a pipe velocity of 1.82 m/s, a total dynamic head of 2.14 m, and a rated pump motor power of 0.75 kW—demonstrating the significant hydraulic advantage of adequate pipe sizing. Parametric sensitivity analyses confirm that tip speed governs power cubically, impeller diameter governs power quadratically at fixed tip speed (and to the fifth power at fixed rotational speed), and mixing time is linearly proportional to tank volume. A prototype of the agitator was fabricated and mechanically operated to confirm assembly feasibility; the analytical results were compared with published mixing and agitation literature and provide a scalable design framework for small-scale petroleum engineering applications.