Effective separation of water and oil dispersions is considered a critical step in the determination of technical and economic success in the petroleum industry over the years. Moreover, a deeper understanding of the emulsification process and different affected parameters is essential for cost-effective oil production, transportation, and downstream processing. Numerous studies conducted on the concept of dispersion characterization indicate the importance of this concept, which deserves attention by the scientific community. Therefore, a comprehensive review study with critical analysis on significant concepts will help readers follow them easily. This study is a comprehensive review of the concept of dispersion characterization and conducted studies recently published. The main purposes of this review are to 1) Highlight flaws, 2) Outline gaps and weaknesses, 3) Address conflicts, 4) Prevent duplication of effort, 5) List factors affecting dispersion. It was found that the separation efficiency and stability of dispersions are affected by different chemical and physical factors. Factors affecting the stability of the emulsions have been studied in detail and will help to look for the right action to ensure stable emulsions. In addition, methods of ensuring stability, especially coalescence are highlighted, and coalescence mathematical explanations of phenomena are presented.

No abstract

No abstract

Thermal stability of water-based drilling fluids is an essential factor especially through drilling geothermal and deep oil and gas wells. The chemical and physical properties of a drilling fluid system are substantially affected by high temperature and consequently lead to excessive gelation and formation damage issues. As a result of high temperature, formation damage might result from high fluid losses and reaction with formation fluid salts and hydroxides. This study is an attempt to investigate the thermal stability of clay base drilling fluids using thermal cycle testing. This test is a part of stability testing that allows determining if a fluid system remains stable under various conditions. This type of test can be applied to the drilling fluid systems and puts the sample through a series of extreme and rapid temperature change encountering in during fluid circulation in a geothermal well. Less toxicity as well as commercial and economical availability of clays make them an inevitable component for drilling fluid systems. A type of sepiolite clay taken from Eskisehir in Turkey and Wyoming bentonite as the API reference clay were considered to prepare freshwater weighted, unweighted, and solid contaminated fluid systems. API recommended and oscillation amplitude sweep tests were firstly carried out to evaluate the mechanical stability of selected fluid systems. The samples were then subjected to five thermal cycles from 25° C to 150° C. The relative change of the viscosity value compared to the value at the start of the thermal cycles was used as a measure of the structural changes in the fluid systems. The sample that shows a small value for the relative structural change at the end of the thermal cycles has the lowest decrease in the viscosity and hence the highest thermal stability. Discovery Hybrid Rheometer (DHR-II) was used to apply the oscillation and thermal cycle testing. Results revealed that sepiolite based muds formulated in this study tolerate stability problems resulted from high and rapid temperature variation. Obtained appropriate thermal rheological properties as well as thermal cycle test results were strong indicators for the effectiveness of sepiolite muds. This study can help the oil and geothermal industry to be more familiar with a high-temperature stable sepiolite clay to prepare high-performance drilling fluids.

No abstract