Investigation of a solid particle deposition velocity in drag reducing fluids with salinity

Abstract

Optimal and cost-effective drilling operations in extended-reach horizontal wells depend on efficient solid cuttings removal from the borehole. Several solids-suspended multiphase processes such as crude petroleum transportation, separation, and processing of oil and gas streams also require the efficient removal of these solids. The terminal settling velocity (Vts) of the solid particle is a vital parameter that controls the removal efficiency of these solids. In a drilling scenario when there is a hold on fluid circulation such as connection time, the accurate estimation of Vs provides the driller with time available to prevent solid deposition. In severe conditions, this can result in a stuck pipe, especially for extended-reach horizontal wells. In this work, both spherical and non-spherical particle deposition were experimentally investigated in several fluid rheology and salinity. Two concentrations (0.1vol% and 0.05vol%.) of partially-hydrolyzed polyacrylamide (PHPA) were used as a drag-reducing additive for water-based drilling mud. The PHPA drag-reducing fluid (reduced pressure loss) acts as a turbulence inhibitor. The PHPA polymer chain suppresses any turbulence in the flow, reducing the turbulent eddy viscosity. The effects of salinity (3wt.%NaCl and 3wt.%CaCl2 contamination) on solid particle settling velocity (Vs) in drag-reducing fluids were also investigated. Terminal velocity was achieved for all experiments and seemed to increase with increased diameter/sphericity. However, cases when this trend was not consistent were observed and therefore a new parameter of Φ (sphericity index × diameter) was proposed. Vs increases with Φ value for all cases. During drilling, PHPA also aids in sealing the fracture in the formation. With and without salt in the fluid, how lowering drag affected the settling velocity of solid particles (drill cuttings) could be observed. The settling velocity tests will be improved in drag-reducing PHPA solutions with the knowledge from this study.