Introduction of a New BCC Continuous Stirred Tank Reactor Inhibitor BCIn Screening Method for Chemicals in Controlling Inorganic Scales in Oil/Gas Production

Abstract

Abstract Inorganic scales such as calcite, barite, gypsum, celestite are some of the most common scales found in oil field brines. The scale problems are generally treated with different types of inhibitors depending upon the reservoir conditions. In this paper, a newly developed BCC Continuous Stirred Tank Reactor Inhibitor screening method BCIn method will be discussed that uses Continuous Stirred Tank Reactor (CSTR) theory which has been demonstrated to work for analyzing inhibitors efficiency on the inorganic scales formed in oil/gas production. The method has been shown to be more accurate and efficient than the methods commonly used in industrial laboratories. The BCIn CSTR method varies the inhibitor concentration so that constant feeding of the same background solution maintains a constant supersaturation and volume as the inhibitor concentration exponentially decreases. The inhibitor concentration decreases exponentially to below the critical nucleation concentration (Ccrit) and thereby supersaturated brine tends to precipitate rapidly. The induction time is used to compare the efficiency of the inhibitors. The apparatus is designed so that the partial pressure of CO2, pH, temperature (T)and saturation index (SI) can be precisely controlled which makes it suitable for most of the inorganic scales including calcite, barite, CaSO4's etc. The BCIn method was used to rank 18 common inhibitors under various brine conditions, including the effect of SI, T, pH for sulfate scales and additionally ratio of Ca2+/HCO3− for calcite and was investigated by comparing the critical concentration (Ccrit). It was also found that the critical concentration (Ccrit) from CSTR method has a good correlation with the MIC from batch tests so that it can be used as fast ranking to estimate minimum inhibitor concentration (MIC) values. This study provides a simple and reliable solution for conducting scale inhibition tests in an efficient and economical manner.