Effect of Mud Rheology on Cuttings’ Transport in Drilling Operations

Abstract

Settling of solid particles in drilling fluids represents a major problem, necessitating effective removal of drilled cuttings to the surface of the well to maintain safe and profitable drilling operations. Experiments were conducted using two group of drilling fluids, Newtonian (water, gas-oil, kerosene, and ethyl-glycol) and Non-Newtonian (Carboxyl Methyl cellulose (CMC)) in four different concentrations. Four cutting sizes were used, with diameters 0.212, 0.445, 0.672, and 0.853 cm, taken from the Garraf area of the Nasirya oil fields. The test results showed lower Reynolds numbers within the laminar flow region compared with the Turbulent flow region. The drag coefficients decreased with increasing particle Reynolds number, and small particle sizes gave higher drag coefficients and lower Reynolds numbers, while large particles gave lower drag coefficients and higher Reynolds numbers in both Newtonian and Non-Newtonian fluids. The results indicate that an increase in CMC concentration will decrease NRep and increase the drag coefficient for different particle sizes. For non-Newtonian fluids, the settling velocity decreases with increases in CMC concentration due to increases in the viscous forces that oppose settling of particles, while in Newtonian fluids, the settling velocity increases with increasing particle size due to gravity forces increasing. The low CMC concentrations (low n, and high k) offer higher settling velocities, while larger particle sizes give lower drag coefficients than smaller ones.

High energy dissipation-based process to improve the rheological properties of bentonite drilling muds by reducing the particle size

“…In its stationary state or at a low shear rate, mud must have high-viscosity characteristics and high yield stress such that crushed rock fragments are suspended in support and drilling equipment to avoid sedimentation [14] . Failure to support rock fragments and drilling rigs can cause circulation losses, high rotational torques, and excessive bit wear [15] . At a high shear rate, mud transportation through the internal circulation of a drilling rig or through its pipeline, where low viscosity is required to reduce the power requirement [16] , is necessary.…”

Fluid Flow Regimes Analysis on Drilling Fluid Circulation for Cuttings Lifting in Vertical Drilling Oil Wells

“…The regime of this flow can express how much pressure loss occurs. In addition, the regime of the fluid flow in the annular affects the value of the velocity at which the cuttings drop [7].…”

“…In addition, the slip velocity of cuttings also affects the success of cleaning well holes against cuttings. The velocity at which the cuttings falls (Vs) is explained through the stokes law expressing the velocity of deposition or terminal velocity (Vt) of an object that is in diameter 𝑑 𝑐 and density 𝜌 𝑠 in a fluid medium with density 𝜌 𝑓 and fluid viscosity 𝜇 which can be written mathematical equations as follows [7]:…”