Development and evaluation of an acid emulsion system for the removal of paraffin containing CaCO3 deposits in oil production systems

Abstract

This study develops and evaluates a W/O acid emulsion system for treating CaCO3 paraffin mixed scale in oil and gas production systems. Scale samples were characterized by SEM, EDX, and XRD analyses, revealing a complex structure containing inorganic and organic components, with CaCO3 content of 30.33%, organic/paraffin fraction (LOI) of 54.19%, and an average crystal size of 5.60 nm. The scaling tendency of produced water was assessed using Langelier Saturation Index (LSI = 0.38) and Ryznar Stability Index (RSI = 6.2). Two acid emulsion systems, HC30 and VC35, were successfully prepared and evaluated. Both systems exhibited suitable emulsification and phase separation behavior at 70°C. Among them, HC30 showed superior scale removal performance, achieving 96.25% dissolution efficiency after 4 h, compared with 88.88% for VC35. The corrosion rate of the selected system was 1.0049-1.0507 mm/year, below the acceptable limit of 2 mm/year. The HC30 system demonstrates high potential for CaCO3 paraffin scale treatment in Vietnamese oil and gas production wells.