Evaluation of Anti-fouling Surfaces for Prevention of Lead Sulfide Scaling in Single and Multiphase Conditions

Formation of mineral scale is one of the primary complications affecting production in the oil and gas industry. Soured reservoirs contain hydrogen sulfide (H2S) that can prompt the formation of exotic sulfide scales, leading to detrimental fouling that negatively affects the production of oil and gas. The mode of precipitation and deposition of lead sulfide (PbS) scale on a variety of anti-fouling surfaces for potential application in oilfield systems is examined in this paper. Previous sulfide scale work has reacted H2S derived from sodium sulfide (Na2S) with lead chloride (PbCl2) brine. However, the design of a rig for implementation of H2S gas into a reaction vessel resulted in a more accurate simulation of the processes occurring within sour reservoirs. Multiphase conditions induced by introduction of a light oil phase within a turbulent emulsion were used to simulate the presence of crude oil within a production line prone to sulfide scaling. The results showed that the presence of a light oil phase within the system caused the homogeneously-precipitated lead sulfide to reside at the interface between the oil and water phases, increasing its propensity to adhere to surfaces and promoting the dominant adhesion process. The wettability of anti-fouling surfaces had a significant bearing on the degree of lead sulfide deposition in a multiphase system.