Paper: Paraffin Wax Deposits and Chemical Inhibitors

The accumulation of paraffin wax in petroleum reservoirs and production equipment remains a continuous problem and expense in the production of oil. These problems have been remedied in the past by scrapers, hot-oil treatments and solvents. However, with the advent of extremely deep production, offshore drilling, and the possibility of ocean floor completion, the application of remedial measures becomes economically prohibitive. As a result, the use of chemical additives as paraffin deposition inhibitors has become necessary. Since no one additive has been proven universally effective, the problem of selecting an efficient additive for a specific application is presented. In order to define a suitable additive, a better understanding of the mechanisms of inhibition is necessary. Previous work showed that high molecular weight fractions from crude oil significantly affected paraffin crystal growth and subsequently retarded or prevented paraffin deposition. Some investigators found that these fractions were preferentially adsorbed to a metal surface and that a reduction in deposition occurred. In addition, it was noted that decreased deposition could be attributed to modifying the paraffin wax crystals or changing the wetting characteristics of the pipe surface. Although there is considerable experimental evidence to support each mechanism, there is no way to predict which mechanism and chemical inhibitor is the most efficient way to prevent wax deposition for any given crude oil system.