Large Scale Laboratory Tests for Calcium Carbonate Scaling in Sliding Sleeve Valves

Abstract

Abstract Downhole carbonate scaling is a major concern in offshore scenarios, where workover operations are associated with very high costs. Intelligent completion concepts are also a requirement for reservoir management optimization. These systems however, introduce several elements in the production string which may constitute hotspots for scaling. The goal of this work is to present pilot scale test facilities and procedures designed to mimic real field situations. Results presented include pH, conductivity and particle size distributions from samples taken along the pipe length and along periodic time intervals. Severe, but representative of some of Brazilian pre-salt scenarios, scaling conditions (S between 3 and 3.4 and pH around 7.5) enable comparative results with a reasonable test volume. Pressure drop on the valve and along the pipe length is also discussed. The scale adherent to the pipe wall and on the valve have been dried and weighted after the experiment. X-ray diffraction and scanning electron microscopy have been used for further characterization of the scale structure. The role of flow rates, water composition and valve opening (creating different localized pressure drops) is experimentally investigated. A discussion on scaling mechanisms is presented. Additionally, the use of non-chemical strategies to delay pressure drop increase is also shown. Results show the present experimental set up is able to reproduce hydrodynamics and scaling conditions of downhole scenario. In this work reproducible large scale test procedures have been established. The flow loop allows the evaluation of chemical injection devices besides non chemical mitigation alternatives, including coatings and physical strategies.