Physical-mathematical model applied in the study and simulation of dissolution of sodium chloride particles in brines in upward flow in tubes

Abstract Drilling trough salt layers has been a challenge for the oil drilling industry. In this way, water-based muds are a friendly environment, although they tend to dissolve generated salt particles along with the wall of the well. Particularly, the particle dissolution may cause changes in the fluid rheology and physicochemical properties. Other problems related to this are the enlarging of the borehole, the excessive torque, the accumulation of salt gravels in the bottom hole, the well controlling issues, and some other operational situations. Thus, the controlling and prediction of the salt dissolution process in drilling fluids are of great interest. The main objective of this work was to study the dissolution of halite (NaCl) particles in brines at different concentrations on upward flow in tubes that simulate the borehole flow. An experimental apparatus was built, capable of reproducing some drilling conditions as the upward fluid flow where the data of NaCl concentration as function of position and time were obtained. A mass conservation mathematical model based on the continuum mechanic was proposed in order to simulate the process. The model was composed of two differential partial equations generated by the conservation law for the mass of salt in two phases: a fluid phase of salt dissolved in water and a solid phase of salt particles. The dissolution data were used to estimate the global mass transfer coefficient in different operational conditions and to validate the mathematical model. The total mean deviations were lower than 5 % for the proposed and validated model.