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Collaborating Authors
Results
Combined Inhibitors - A New Experimental Method for a Simultaneous Assessment of Scale and Corrosion Phenomena
Sanders, Laura (University of Leeds) | Hu, Xinming (University of Leeds) | Mavredaki, Eleftheria (University of Leeds) | Eroini, Violette (University of Leeds) | Barker, Richard (University of Leeds) | Neville, Anne (University of Leeds)
Abstract The formation of calcium carbonate scale and the occurrence of corrosion in CO2-saturated environments in different parts of oil and gas facilities are both phenomena that have been extensively studied. However, to date, very limited work has been carried out on evaluating combined products in a combined scale/corrosion methodology. This paper presents the results from a new combined bulk jar scaling/bubble cell corrosion test. The aim of this project is to investigate the effect of two combined chemicals in a new experimental setup; to study the corrosion and scale interactions which occur simultaneously. Two combined products were assessed at 5 ppm concentration at two temperatures (60°C and 80°C) in a CO2-saturated brine. Bulk scale precipitation was monitored using a turbidity meter and the corrosion rate measurements were made using the linear polarisation resistance (LPR) technique. Scale deposition and corrosion mechanisms have been studied using surface analyses. The performance of the two combined products has also been tested to measure: (i) the increase in the induction time of the calcium carbonate formation in the bulk, (ii) the change of the morphology of the crystals and (iii) the formation of a partial protective layer on the sample. According to this study, the new experimental method has enabled the corrosion and scale deposition on pipeline steel (X65) and the bulk precipitation process to be studied simultaneously. Detailed scale deposition mechanisms on the material surface in the presence of corrosion processes and combined products are addressed from this study.
- North America > United States > Texas (0.28)
- North America > United States > California (0.28)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Abstract Calcium carbonate and iron carbonate scales are widely observed in oil and gas production. Scale formation can be useful for corrosion control; however, excessive scale buildup can lead to severe production loss. What is called calcite scale in the field is almost always a solid solution of iron in calcite. Yet little attention has been paid to the precipitation of these mixed calcium-iron carbonate scales. As a result, knowledge of the formation and inhibition of mixed calcium/iron scales is very limited. Normally, calcite scale formation is readily inhibited, whereas siderite inhibition is notoriously difficult. The solid-solution transition from predominantly calcite to predominantly siderite properties is unknown. Besides, although the solubility of mixed scale can differ by several orders of magnitudes from the solubility of its pure salts, scale prediction models are normally developed based on the data from pure solids. Finally, the incorporation of iron into calcite solid dramatically alters the kinetics of scale growth, as will be illustrated. A series of experiments were performed to precipitate mixed iron-calcium carbonate (FexCa1−XCO3), ranging from calcium-rich to iron-rich. The experiments were conducted at 7.3±0.2 pH in 0.5 M NaCl at 55 °C. The work was performed with a new constant composition method, modified to handle oxygen sensitive ferrous carbonate scale and solid solutions. Based upon the experimental results and a flux-based theoretical derivation, a new correlation in a form of a logistic function has been developed to predict the composition of FexCa1−xCO3 as a function of the aqueous composition. The model is an excellent representation for all of the experimental results, with R greater than 0.97. The correlation and methods developed in this work can readily be adapted to other mixed scale systems. Laboratory results will be compared with field observations and the consequences discussed.
- Asia > Middle East > Saudi Arabia (0.28)
- Europe > Norway > Norwegian Sea (0.24)