An In-depth Study of Calcium Carbonate Scale Formation and Inhibition

Abstract A fundamental study of scale formation of calcium carbonate (CaCO 3 ) for producing oil wells has been carried out. This article presents the study of the prediction of salt deposition in two different synthetic formation waters and investigates the effects of temperature and pressure on calcium carbonate precipitation. The dependence of the induction period of the precipitation of calcium carbonate on the concentration of calcium ions was studied. In order to study the chemical scale inhibition, the most effective inhibitors, which are based on the risk analysis of scaling and laboratory reagent selection, were examined for evaluating the performance of salt inhibition. In this work, a new multi-component inhibitor was made and its scale effectiveness was evaluated at different concentrations. The developed inhibitor was mixed with other inhibitors to prevent calcium carbonate precipitation. The observations showed the synergetic inhibition effect on the scale inhibition at different concentrations of scale inhibitors. The new inhibitor provided high scale effectiveness at specific concentrations and low corrosion activity

Prediction and Inhibition of Inorganic Salt Formation under Static and Dynamic Conditions – Effect of Pressure, Temperature, and Mixing Ratio

As a result of waterflooding, inorganic salt precipitation occurs in the different parts of an oil production system, thereby leading to damage of production equipment. Different parameters affect the kinetics of salt precipitation. Scale inhibitors are widely used to prevent inorganic salt formation. In this study, the effect of reservoir pressure, temperature, and mixing ratio of injection to formation water on calcium sulfate and barium sulfate precipitation was investigated. For this purpose, two different formation waters and one injection water were used. In addition, the effect of temperature and mixing ratio on inhibition performance was studied. Four different existing industrial scale inhibitors and one new scale inhibitor were used. The performance of the scale inhibitors was determined under static and dynamic conditions. Results of the study showed that calcium sulfate precipitation increased with an increase in temperature and a decrease in pressure. Barium sulfate precipitation was found to increase with a decrease in the temperature. The effect of pressure on barium sulfate formation was negligible. The developed scale inhibitor showed the highest performance for the prevention of calcium sulfate and barium sulfate formation. A change in temperature from 60°C to 120°C reduced the inhibitor performance by 3%. In the cases of calcium sulfate and barium sulfate, the minimum performance of the scale inhibitor was observed when the mixing ratios of injection to formation waters were 60:40 and 50:50, respectively

Experimental and modeling analysis on the performance of 2-mercaptobenzimidazole corrosion inhibitor in hydrochloric acid solution during acidizing in the petroleum industry

Abstract In this work, the corrosion inhibition of carbon steel in 1 molar HCl solution was evaluated by experimental and modeling approaches using 2-mercaptobenzimidazole (2-MBI). To this end, an experimental design for the weight loss method using response surface methodology (RSM) was carried out and the corrosion rate (CR) and inhibition efficiency (IE) were determined. The study was completed at various values of temperature, exposure time, and inhibitor concentration to determine the optimal conditions for corrosion prevention. Using experimental data on the corrosion rate and inhibition efficiency of 2-MBI, new models were developed, the significance of which was tested using ANOVA-analysis of variance. The developed RSM-based CR and IE models were highly accurate and reliable, and their P-values were less than 0.0001. The novelty of this study lies in the newly developed model for the evaluation of 2-MBI inhibition performance and its application to high-temperature conditions in the petroleum industry. Besides, the R 2-statistics (R 2, adjusted-R 2, and predicted-R 2), adequate precision and diagnostic plots were used as main measures to verify the accuracy and adequacy of both CR and IE models. In addition, it was observed that inhibitor concentration had the most impact on both CR and IE models compared to other parameters due to its largest F-values (561.65 for CR and 535.56 for IE models). Moreover, the results indicated that adding 140–150 ppm of 2-MBI at low-level temperatures of 30–35 °C had the most interaction effect on the performance of the corrosion inhibition process. In this case, the CR was less than 0.9 mm/y and the IE more than 94%, even after a high exposure time of 105 h. Furthermore, numerical optimization of the corrosion inhibition process for 2-MBI showed that the optimum conditions for maximum IE and minimum CR were achieved at a concentration of 115 ppm, temperature of 30.7 °C, and exposure time of 60.4 h. Under these conditions, the efficiency and corrosion rate were 92.76% and 0.53 mm/y, respectively. Finally, the adsorption of 2-MBI on the sample surface was studied at various exposure times and temperatures. In all cases, the adsorption behavior obeyed the Langmuir isotherm. In this case, the Gibbs adsorption free energy varied from − 33 to − 37 kJ/mol, which reflects both physical and chemical adsorption of the corrosion inhibitor at all tested temperatures and test times

Prediction of barium sulfate precipitation in dynamic tube blocking tests and its inhibition for waterflooding application using response surface methodology

Abstract Scale precipitation is one of the major problems in the petroleum industry during waterflooding. The possibility of salt formation and precipitation should be monitored and analyzed under dynamic conditions to improve production performance. Scale precipitation and its dependence on production parameters should be investigated before using scale inhibitors. In this study, the precipitation of barium sulfate salt was investigated through dynamic tube blocking tests at different injection rates and times. For this purpose, the pressure drop caused by salt deposition was evaluated at injection rates of 1, 2, 3, 4, and 5 mL/min. The software determined the worst conditions (temperature, pressure, and water mixing ratio) for barium sulfate precipitation. Moreover, during the experiments, the pressure drop caused by barium sulfate precipitation was measured without using scale inhibitors. The pressure drop data were evaluated by the response surface method and analysis of variance to develop a new model for predicting the pressure drop depending on the injection rate and time. The novelty of this study lies in the development of a new high-precision correlation to predict barium sulfate precipitation under dynamic conditions using the response surface methodology that evaluates the effect of injection rate and time on the possibility of salt precipitation. The accuracy and adequacy of the obtained model were confirmed by using R2 statistics (including R2-coefficient of determination, adjusted R2, and predicted R2), adequate precision, and diagnostic charts. The results showed that the proposed model could fully and accurately predict the pressure drop. Increasing the time and decreasing the injection rate caused an increase in pressure drop and precipitation of barium sulfate salt, which was related to the formation of more salt due to the contact of ions. In addition, in a short period of the injection process, the pressure drop due to salt deposition increased sharply, which confirms the need to use a suitable scale inhibitor to control salt deposition. Finally, the dynamic tube blocking tests were repeated in the presence of two well-known scale inhibitors, which prevented salt deposition in the tubes. At the same time, no pressure drop was observed in the presence of scale inhibitors at all injection rates during a long period of injection. The obtained results can be used for the evaluation of salt precipitation during oil production in the reservoirs, in which barium sulfate is precipitated during waterflooding. For this purpose, knowing the flow rate and injection time, it is possible to determine the amount of pressure drop caused by salt deposition