Ultra-Low Dose Asphaltene Inhibitors for Offshore Applications: Myth or Reality

Abstract

In recent years, long-distance subsea tiebacks have become a preferred field development option for deep and ultra-deepwater production. However, conditions such as lengthy umbilical systems, high pressures and variable temperatures conditions pose challenges for the continuous injection of various flow assurance chemicals. Severe operating conditions often require relatively high volumes of diluted inhibitors to be stored and injected offshore, resulting in high CAPEX costs for the installation of large topsides chemical storage tanks and their associated weight increases. Alliance Engineering estimates a deepwater platform's topsides installed costs are within the range of $35,000-$50,000/ton. It is possible to achieve significant capital cost savings on new platform designs if the dosage rates and subsequently offshore storage volumes of the highest usage production chemicals such as asphaltene inhibitors could be significantly reduced. This paper presents information on a new class of biosurfactants that are bio-based and eco-acceptable with potentials for development of ultra-low dose asphaltene inhibitors for offshore applications. Asphaltenes were extracted from chemical free crude oil samples and a curve of solubility with different ratios of heptane was obtained for each sample in order to determine the best conditions to perform the screening tests. A new class of glycolipid biosurfactants (GLP-U) was developed as an asphaltene dispersants effective at low concentrations for use in offshore applications. The new GLP-U biosurfactants are eco-acceptable and soluble in the organic solvents commonly used in offshore production chemicals. GLP-U were proved to be effective in dispersing and preventing precipitation of isolated asphaltenes at dosage rates as low as 25 mg/L (active substance), while for comparison a dodecylbenzesulfonic acid-based inhibitor provided inhibition at significantly higher concentrations (at least 40 times more).