Date of Award
August 2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Chemical Engineering
First Advisor
Ali S. Alshami
Abstract
Mineral scale deposition is a persistent and costly flow-assurance problem in oil and gas production, where sparingly soluble salts such as calcium carbonate precipitate on pipe walls and equipment, restrict flow, and force costly intervention. Managing scale effectively requires understanding the full life cycle of a deposit: how it forms, how it can be prevented, and how it is removed. This thesis addresses that life cycle, with a focus on green, environmentally acceptable chemistry.Following a critical review of scale types, formation factors, inhibition, and dissolution, the thesis develops a tiered laboratory framework for evaluating scale dissolvers and applies it to screen thirteen candidate chemistries, selecting glutamic acid N,N-diacetic acid (GLDA) as a biodegradable base dissolver that complexes both calcium and iron across a wide pH range, an environmentally preferable alternative to mineral acids and to poorly biodegradable chelants such as EDTA and DTPA.
The central experimental contribution is a controlled flow-loop study of calcium carbonate deposition. Using synthetic brine at a fixed flow rate, the independent effects of temperature (28 to 90 °C) and pH (7 to 11) on the areal deposition rate are quantified, and the deposits are characterized by scanning electron microscopy, infrared spectroscopy, X-ray diffraction, and profilometry. The deposition rate rises roughly sixfold with both temperature and pH, the surface roughens markedly, and the scale is predominantly calcite with a minor vaterite fraction at high pH; an apparent activation energy near 28 kJ mol⁻¹ indicates transport-influenced mixed control.
In a collaborative inhibition study, a matched series of five surface-functionalized carbon quantum dot formulations was evaluated as green calcium sulfate inhibitors, with the candidate contributing the performance evaluation: NACE TM0374 calcium-retention testing with EDTA titration, zeta-potential analysis, and SEM and FTIR characterization of the recovered deposits. Carboxyl- and phosphonate-functionalized dots retained essentially all dissolved calcium (approximately 100% inhibition) at 10 to 50 ppm, whereas sulfonated and nitrogen-doped dots achieved only about 6 to 22% yet strongly modified the gypsum crystal habit, a split explained by surface charge and binding denticity. Together, the formation, prevention, and removal studies connect operating conditions to scaling severity and provide green chemistry for managing scale across its life cycle.
Recommended Citation
Abdelaziz, Hesham, "Green Management Of Mineral Scale In Oilfield Industry: Formation, Inhibition, And Dissolution" (2026). Theses and Dissertations. 13857.
https://commons.und.edu/theses/13857