Preventing Naphthenate Stabilised Emulsions and Naphthenate Deposits on Fields Producing Acidic Crude Oils

摘要

Naphthenic acids in a crude from field A in West Africa in combination with high pH connate waters cause severe problems during the separation of oil and water. The neutralization products of those acids with basic components in the water tend to form very stable water-in-oil emulsions and insoluble sticky naphthenate sludge. These phenomena considerably hamper oil production and result in high treatment costs using acetic acid. This paper discusses the ways problems were prevented during a large field trial with a combined demulsifier/naphthenate inhibitor based on a physical and chemical approach. Innovative technology in surface-active chemistry has demonstrated an effective way to reduce or eliminate the problems described. In addition, lab tests were performed on an instrumented bottle test that enables the different phases of decantation (Coalescence, sedimentation, dense emulsion) to be measured. Two conventional demulsifiers used in the field were tested and compared to this new combined demulsifier/naphthenate inhibitor. The new chemical prevented the formation of dense emulsion and resulted in better water quality. Further experiments demonstrating the unique challenges associated with naphthenates in different fields around the world are also presented.