Abstract
Mineral scale formation and deposition on downhole and surface equipment is a major source of cost and reduced production to the oil industry. One potential means of preventing losses due to scale is to prevent it adhering/depositing on key components in the production system (such as downhole safety valves and key parts of intelligent well systems). In general, the coatings proposed to prevent deposition of scales are made of low-surface energy materials. However, industry experience of non-adherent coatings is not good and a search of the literature suggests that there are a number of contrary reports on the effects of surface energy on solid deposition behavior. Some reports show that deposits attached preferentially to high surface energy surfaces, while others purport to show that deposits attach preferentially to surfaces with low surface energy. Numerous studies also indicate that there is little relationship between surface energy/wettability and deposition behavior. Obviously a sound theoretical explanation of the observed deposition behaviour on various surfaces is crucial for the development, and deployment, of low-deposition surfaces. In this paper, the extended DLVO theory is used to explain scale deposition behaviour on metal substrates, and on modified metal surfaces. The proposed theory is shown to agree well with the limited experimental data available and thus provides the basis for a sound theoretical approach to controlling and preventing scale adhesion on surfaces
