Impact of Waxphaltenes on Overall Stability of Asphaltenes, Paraffins, and Emulsion

Abstract

Abstract Recent studies revealed that field deposits collected from production tubing of offshore wells often exhibit compositional variation pointing to more complex fouling process than original predictions based purely on asphaltene or paraffin instability. This deposit mixture generally comprises of 50-60% asphaltenes, 30-35% paraffin and remaining highly polar organics. The objective of this work is to understand the impact of Waxphaltenes co-precipitation on the overall performance efficiency of asphaltene inhibitors, paraffin Inhibitors, and Demulsifiers. Routine screenings and initial chemical treatments were found unsuccessful for both asphaltene and paraffin application. Firstly, the oil sample was fully characterized though Fourier Transform InfraRed (FTIR) spectroscopy and High Temperature Gas Chromatography (HTGC). A series of dispersion and deposition tests were then conducted in order to identify potential chemistries for treatment. For asphaltene application, dispersion testing was mainly carried out using Asphaltene Differential Aggregation Probe Test (ADAPT) technique, whereas deposition tests were conducted on a customized Asphaltene Dynamic Deposition Loop (ADDL) test. Crude oil characterization indicated presence of unstable asphaltene fraction within the analyzed crude oil sample. Dispersion efficiency with different asphaltene inhibitors revealed possible co-precipitation issue of other crude oil solubility fractions. Further characterization analyses highlighted heavier paraffinic components to have very high affinity towards the asphaltene clusters and creating waxphaltene precipitation issue. Efficiency of traditional asphaltene inhibitor chemistries were observed to not perform well for waxphaltene deposition. Similarly, paraffin application was tested using optical transmittance method and cold finger deposition setup. Moreover, rheological studies also highlighted issue of highly stable emulsion formation leading to complex fluid flow challenge. Improvement in the chemical treatment program and product development based on the knowledge obtained through this holistic work resulted in superior performing formulations. The deposition test results using the improved inhibitor chemistry was tested on ADDL and showed better performance than the traditional asphaltene inhibitor. Cold finger results also yielded softer deposit with overall lower mass on the fingers. Furthermore, considerable reduction in the emulsion stability was as obtained with addition of the combinatorial product. The new approach presents a unique opportunity to revisit the way we do product development allowing chemical treatment strategy to be adopted and aligned based on actual deposit characteristics. Findings from this work allows more objective and reliable strategy to be adopted for offshore production with flow assurance management challenges caused by waxphaltenes deposition.