Simultaneous Determination of Asphaltene Deposition and Corrosion under Dynamic Conditions
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Asphaltene deposition is one of the major flow assurance problems that could plug the production tubing, significantly impeding oilfield productivity. Conventional asphaltene dispersants are supposedly used to improve the stability of oils, thereby preventing asphaltene deposition. Currently, the injection of asphaltene dispersants has shown mixed results in the field. In this work, a multi-section packed bed deposition apparatus, which is designed to not only directly quantify the deposited asphaltenes but also investigate the deposition profile, is used to assess the performance of asphaltene dispersants at ambient conditions. Results indicate that the dispersive performance of the inhibitors is not directly related to their ability to prevent asphaltene deposition. In some cases, the chemicals with the highest dispersive efficiency produce the largest amount of asphaltene deposition. To determine asphaltene deposition under realistic production conditions, the development of a novel stainless-steel packed bed column deposition system is presented. The new design allows the feasibility of investigating a variety of factors affecting the deposition process under a wide range of temperature (20 – 300 ℃) and gauge pressure (0 – 3,000 psi). The impacts of operating temperature, type of precipitant, degree of asphaltene stability, and chemical additives on the deposition tendency of asphaltenes are discussed. Upon formation of the deposits, solvent wash is commonly used to re-dissolve the deposited asphaltenes in the well. In this work, a re-dissolution test apparatus using the packed bed column is introduced to evaluate solvents for in-situ asphaltene deposition remediation at high temperature and under dynamic conditions. Results suggest that screening of chemical solvents based on their solubility parameters may not provide an accurate indication of the selection of solvents. Furthermore, the effects of aging time, occluded oil, soaking temperature, and soaking time are investigated on the re-dissolution of asphaltene deposition. Besides asphaltene deposition, corrosion is a coexisting problem in the production tubing. Asphaltene inhibitors and corrosion inhibitors are usually injected into the well to solve the corresponding problem. In this dissertation, an integrated approach containing the critical micelle concentration measurements, the rotating cylinder electrode tests, and the packed bed column experiments is developed to evaluate the compatibility of the selected asphaltene inhibitor and corrosion inhibitor for oilfield applications. Results reveal that the corrosion inhibitor not only provides effective corrosion prevention, but also acts to mitigate asphaltene deposition. On the other hand, the asphaltene inhibitor fails to reduce deposition. It interacts and weakens the performance of the corrosion inhibitor injected simultaneously. The current research work introduces a new technology to not only determine the asphaltene deposition and corrosion tendencies on the metallic surfaces, but also assess the performance of asphaltene inhibitors and solvents for field applications. It will contribute to the development of advanced simulation tools to predict asphaltene deposition under realistic production conditions and cost-effective approaches to mitigate asphaltene deposition and corrosion simultaneously.
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Kuang, Jun. "Simultaneous Determination of Asphaltene Deposition and Corrosion under Dynamic Conditions." (2018) Diss., Rice University. https://hdl.handle.net/1911/105910.