Settling Behavior of Fine Cuttings in Polyanionic Fiber-Containing Drilling Fluids for Hole Cleaning

Abstract For efficient drilling operations, cuttings transport within the oil and gas wellbore is fundamental. Inadequate hole cleaning results in many problems including reduced rate of penetration, increased torque, bit wearing, and stuck pipe. The addition of fiber aids the cleaning performance of drilling sweep with a minor change in fluid rheology. However, our understanding of this complex fluid is very limited. Especially, the impact of polymer anionicity (solution negative charge density) on the hole cleaning performance of these fluids has not been investigated. The objective of this work is to examine the effect of anionicity and fiber on cutting carrying capacity of polymeric suspensions. This study presents results of an experimental study conducted on the settling behavior of fine cuttings in base fluids with the addition of polymers such as xanthan gum (XG), carboxymethyl cellulose (CMC), and polyanionic cellulose (PAC), and inert fibers. Moreover, the effect of cutting sizes (0.125 and 0.250 mm) was also assessed. Results showed that, in addition to the viscosity, the anionicity of base polymer influences the carrying capacity of the suspensions. The increase in anionicity improved the cutting carrying capacity of suspensions as indicated by Total Suspended Solids (TSS) measurements. The improvement of carrying capacity due to polymer anionicity is because of increased particle-particle and particle-polymer repulsion forces. Besides this, a small amount of fiber (0.08%) added to the base fluids enhanced the carrying capacity with minimal effect on fluid rheology. The enhancement due to fiber originates from the mechanical hindering effect of the fiber network and hydrodynamic interactions between cuttings and fibers. This study findings reveal that the hole cleaning performance of water-based drilling fluids with fine cuttings (0.063 to 0.500 mm) can be improved by increasing base fluid anionicity and adding fibers.