Scale Deposition and Hydrodynamics - Benchtop to Pilot Rig

Abstract

Scale deposition in oilfield production systems is influenced by thermodynamic supersaturation and kinetics, but also by hydrodynamic effects such as surface shear stress and turbulence. Results from experimental work investigating the impact of these hydrodynamic factors on scale location and correlating them to field flow regimes are presented. Laboratory tests have been conducted using both a benchtop jet impingement method and large-scale, high flow rate "pilot rig" apparatus. Both of these systems result in high shear stress conditions and can simulate hydrodynamic regimes representative of those expected in devices such as inflow control valves, inflow control devices, and sand control screens. The pilot rig is able to reproduce field-representative flow rates and fluid flow dynamics through full-size test pieces containing nozzles and restrictions. The results of this work demonstrate that the hydrodynamic regime has a significant influence on scale deposition. Increased levels of surface shear stress and turbulence result in a greater potential for scale formation than low shear, laminar flow conditions. This is particularly apparent in systems which are mildly supersaturated. The location of scale deposits was found to correlate with local shear stress and the pilot rig tests confirmed field observations that zones experiencing the highest level of shear are not necessarily those with the greatest deposit; the induced scale may deposit downstream in areas of lower surface shear. Additionally, the presence of these high shear locations upstream of the lower shear regime may lead to scaling in the lower shear region which would otherwise not be experienced. Supportive Computational Fluid Dynamic modelling of fluid flow within the pilot rig system correlated with the experimental findings is also described. This work allows a greater understanding of the hydrodynamic factors, in particular surface shear stress, influence oilfield scale deposition and has demonstrated the utility of both benchtop and pilot-scale methods for testing under appropriate conditions.