Development of Dynamic Tube Blocking Test Method to Study Halite Scale Deposition and Inhibition

Abstract

Halite scaling has been observed in the oil/gas field with high TDS and low water cut. Due to its higher solubility, slight changes in temperature (T) and pressure (P) and evaporative effect could yield a large amount of scale, causing significant operational problems. Accurate prediction and control of halite scaling in the oil and gas production system have been a challenge. Therefore, this study aims to shed light on the prediction of halite scale formation, deposition behavior, and inhibition at close to oil field conditions. We have designed and developed a dynamic scale loop (DSL) test methodology that can be used at various T and P. The test method utilizes a change in temperature (ΔT) as a driving force to create halite supersaturation and follow with the scale precipitation/deposition. The tube blocking experiments suggest that the tube blockage can be caused by bulk precipitation and or deposition of halite precipitate. SEM analysis of the tube cross-sections indicated that tube blockage, presumably by bulk precipitation, could be seen at the beginning of the reaction tube, but deposition was observed towards the exit end of the tube. Similarly, various experimentation to simulate the water dilution at constant pressure and ΔT were conducted. The effect of the addition of water to prevent halite deposition was analyzed computationally by using ScaleSoftPitzer (SSP) software. Brine compatibility of several inhibitors were tested via bottle tests and autoclave tests and qualified inhibitors were tested in the tube blocking experiments to identify the performance of the inhibitor to treat the halite precipitation at high temperature and pressure. Overall, a robust test method was designed and developed for halite scaling under high temperature and pressure that can simulate the oil and gas production in the field.