Phase Stability and Inhibition of Calcium Sulfate in the System NaCl/Monoethylene Glycol/H2O

SPE Journal ◽  
2011 ◽  
Vol 17 (01) ◽  
pp. 187-197 ◽  
Author(s):  
Haiping Lu ◽  
Kan Amy T ◽  
Ping Zhang ◽  
Jie Yu ◽  
Chunfang Fan ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Behavior ◽  
Calcium Sulfate ◽  
Oil And Gas ◽  
Gas Production ◽  
Inhibition Mechanism ◽  
Oil And Gas Production ◽  
Prediction And Prevention ◽  
Monoethylene Glycol ◽  
Kinetics Of

Summary Calcium sulfate is one of the major mineral scales in oil and gas production. Hemihydrate (CaSO4·0.5H2O) and anhydrite (CaSO4) are the predominant sulfate scales formed at high temperature, while gypsum (CaSO4·2H2O) scale may form at low temperatures (<~45°C). However, it has been shown in this study that anhydrite can form at low temperature in the presence of excess amounts of monoethylene glycol (MEG), and this may occur during offshore production with long tie-backs. The prediction and prevention of calcium sulfate scales requires knowledge of the phase behavior of the three major phases of calcium sulfate. The phase behavior of different calcium sulfate phases is related to the supersaturation state, temperature, and fugacity of water. In this study, the effect of a common hydrate inhibitor, MEG, on calcium sulfate solubility and phase behavior was investigated. This study was run with NaCl/CaSO4/MEG/H2O solutions at 0–6 molality (M) NaCl and 0–95 wt% MEG at 4–70°C. Three approaches were taken to determine the kinetics of calcium sulfate phase transition at various temperatures, ionic strengths, and MEG concentrations: (1) dissolution of gypsum, (2) dissolution of anhydrite, and (3) nucleation and precipitation of calcium sulfate by mixing calcium- and sulfate-containing solutions. The effect of scale inhibitors on phase transition was also evaluated. Phase transition of gypsum to anhydrite was observed in the presence of high concentrations of NaCl and MEG, regardless of the experimental approach. The transition boundary of temperature and concentrations of NaCl and MEG can be estimated from solubility of calcium sulfate and the fugacity of water. The inhibition mechanism of hexamethylene diamine tetra (methylene phosphonic acid) (HDTMP), one of the most effective inhibitors for calcium sulfate scale, was also tested by investigating the kinetics of precipitation and inhibition of calcium sulfate.

Evaluation of TG202 inhibitor for tubing steels in 15% hydrochloric acid by electrochemical noise technology

2021 ◽  
Author(s):  
Mi-feng Zhao ◽  
Juantao Zhang ◽  
Fangting Hu ◽  
Anqing Fu ◽  
Kelin Wang ◽  
...  
Keyword(s):  
Hydrochloric Acid ◽  
Corrosion Rate ◽  
Oil And Gas ◽  
Electrochemical Noise ◽  
Gas Production ◽  
Inhibition Mechanism ◽  
Oil And Gas Production ◽  
Effective Technology ◽  
Steel Tubing ◽  
Inhibition Performance

Abstract Acid fracturing is an effective technology for increasing oil and gas production. However, acid will cause serious corrosion to the tubing. In this paper, the inhibition performance of TG202 inhibitor for acidizing of high temperature and high pressure gas wells on N80 carbon steel and 13Cr martensitic stainless steel tubing in 15% hydrochloric acid was studied by electrochemical noise technology. The results showed that with the increase of TG202 inhibitor content, the noise resistance increased and the corrosion rate of tubing steel decreased. Under the same condition, the order of corrosion rate of tubing steels: 13Cr > HP-13Cr > N80 > P110. The pitting corrosion of HP-13Cr and 13Cr is significant. The research showed that TG202 inhibitor had a protective effect on tubing during acidizing. The inhibition mechanism of TG202 inhibitor was discussed.

Developments on Calcium Sulfate Scaling Prediction and Control in Oil and Gas Production

2020 ◽  
Author(s):  
Samridhdi Paudyal ◽  
Sana Mateen ◽  
Chong Dai ◽  
Saebom Ko ◽  
Xin Wang ◽  
...  
Keyword(s):  
Calcium Sulfate ◽  
Oil And Gas ◽  
Gas Production ◽  
Oil And Gas Production ◽  
Prediction And Control ◽  
And Control

Measurement and Prediction of Thermal Degradation of Scale Inhibitors

SPE Journal ◽  
2014 ◽  
Vol 19 (06) ◽  
pp. 1169-1176 ◽  
Author(s):  
Wei Wang ◽  
Amy T. Kan ◽  
Fangfu Zhang ◽  
Chao Yan ◽  
Mason B. Tomson
Keyword(s):  
High Temperature ◽  
Thermal Degradation ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Gas Production ◽  
Gas Industry ◽  
Oil And Gas Production ◽  
Active Inhibitor ◽  
First Time ◽  
Kinetics Of

Summary As the oil and gas industry is making firm strides in deepwater and shale exploration and development, possible thermal degradation of scale-inhibitor molecules poses a great challenge for scaling control and flow assurance for high-temperature reservoirs. Although extensive research has been conducted to test thermal stability of scale inhibitors, little work has been devoted to study the thermodynamics/kinetics of thermal degradation of scale inhibitors. In this work, a novel and efficient testing approach based on inhibition kinetics has been developed and successfully applied to determine the fraction of the active inhibitor molecules in preheated samples of scale inhibitors with various generic chemistries. Moreover, for the first time, we have modeled the kinetics of inhibitor thermal degradation on the basis of the integrated first-order rate equation and Arrhenius equation, with good agreements between the model predictions and experimental data. The preheated scale inhibitors have been analyzed by nuclear-magnetic-resonance (NMR) spectroscopy for organic-compound characterization. Our results and predictions based on inhibition testing assay are consistent with the 31P/1H NMR analyses. This work has enabled an in-depth understanding of the time and temperature dependence of thermal degradation of scale inhibitors, and facilitates the rational selection and deployment of scale inhibitors for high-temperature oil and gas production.

Scale Prediction and Inhibition for Oil and Gas Production at High Temperature/High Pressure

SPE Journal ◽  
2012 ◽  
Vol 17 (02) ◽  
pp. 379-392 ◽  
Author(s):  
Chunfang Fan ◽  
Amy T. Kan ◽  
Ping Zhang ◽  
Haiping Lu ◽  
Sarah Work ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
High Temperatures ◽  
Oil And Gas ◽  
Gas Production ◽  
Scale Formation ◽  
Oil And Gas Production ◽  
Scale Inhibition ◽  
Kinetics Of ◽  
High Temperature High Pressure

Summary With the advance of new exploration and production technologies, oil and gas production has gone to deeper and tighter formations than ever before. These developments have also brought challenges in scale prediction and inhibition, such as the prevention of scale formation at high temperatures (150–200°C), pressures (1,000–1,500 bar), and total dissolved solids (TDS) (>300,000 mg/L) commonly experienced at these depths. This paper will discuss (1) the challenges of scale prediction at high temperatures, pressures, and TDS; (2) an efficient method to study the nucleation kinetics of scale formation and inhibition at these conditions; and (3) the kinetics of barite-crystal nucleation and precipitation in the presence of various scale inhibitors and the effectiveness of those inhibitors. In this study, nine scale inhibitors have been evaluated at 70–200°C to determine if they can successfully prevent barite precipitation. The results show that only a few inhibitors can effectively inhibit barite formation at 200°C. Although it is commonly believed that phosphonate scale inhibitors may not work for high-temperature inhibition applications, the results from this study suggest that barite-scale inhibition by phosphonate inhibitors was not impaired at 200°C under strictly anoxic condition in NaCl brine. However, phosphonate inhibitors can precipitate with Ca2+ at high temperatures and, hence, can reduce efficiency. In addition, the relationships of scale inhibition to types of inhibitors and temperature are explored in this study. This paper addresses the limits of the current predition of mineral solubility at high-temperature/high-pressure (HT/HP) conditions and sheds light on inhibitior selection for HT/HP application. The findings from this paper can be used as guidelines for applications in an HT/HP oilfield environment.

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