Development and optimization of ionic liquid as a carbonate scale dissolver /
Muhammad Suhaimi Man
- xvi, 138 pages : illustrations (some color) ; 30 cm. + 1 CD-ROM
Faculty of Chemical and Process Engineering Technology
Thesis (Doctor of Philosophy in Chemical Engineering) -- Universiti Malaysia Pahang – 2019
Includes bibliographical references
Scale deposition have a lot of serious threat in petroleum field, and becoming menace to flow assurance, where it reduces the flow thus resulting in production losses. Existing scales need to be removed for proper functioning and operation of the well. The application of chemical method is the most cost effective and most successful in handling scale problem. The problem of HCl that usually used to remove carbonate scale is the corrosion effect toward pipeline. The lack of fundamental knowledge on dissolution of carbonate scale, which is the inability to explain the interaction at molecular level during dissolution process. Due to ability and unique characteristic of ionic liquid (ILs) act as ligand with metal ion to form metal complex is an alternative for the conventional chemical solution that have been used as scale dissolver. The aim of this study is to analyze molecular interaction during dissolution process between proposed ILs with carbonate scale. The experimental study was started with three cations and five anions were selected from COSMO-RS database to form 15 types of ILs. The performance of all ILs were evaluated through ability to dissolve carbonate scales. From 15 ILs were synthesized, N-pyridinium chloride ([Npy][Cl]) was selected as it was able to dissolve calcium carbonate (CaCO3) and dolomite (CaMg(CO3)2). One factorial at time (OFAT) method was used to screen five possible factors which is concentration of ILs, stirring effect, pH, temperature and salinity effect that influence the dissolution rate of carbonate scale. Only three factors which is concentration of ILs, stirring speed and temperature were identified as the most significant factors for dissolution rate of carbonate scales which proceed for optimization study. The optimization of dissolution rate was achieved using response surface methodology (RSM). The optimum condition for dissolution rate of calcium carbonate and dolomite is 80oC, 1000 rpm and 2M concentration. Gaussian software was utilized to predict the molecular interaction between [Npy][Cl] solution and carbonate scale. The molecular interaction occurs through ligand to form metal complex formation. The molecular interactions are then validated using Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Testing on model crude oil, salinity study and recycle of ILs was done to ensure the reliability of the study. Dodecane (n-C12) and toluene as a model crude oil does not have any effect on dissolution rate but for presence of salinity was affected toward dissolution rate. Recycling of [Npy][Cl] was studied to investigate the effectiveness in term of dissolution rate. The finding shows that by recycling [Npy][Cl] the dissolution rate decrease more than 50% compared to pure ILs. The corrosion test was done due to pH of [Npy][Cl] quite acidic but the result from corrosion test shows the weight loss of carbon steel does not exceed 1% from the total weight for 7 days compared to diluted HCl where the weight loss exceeds 22%. Based on the findings, it can be concluded that, [Npy][Cl] is alternatively suitable to be used as a scale dissolver in oilfield especially in dissolving calcium carbonate and dolomite scales.
Faculty of Chemical and Process Engineering Technology--Dissertations