Experimental screening of various asphaltene deposition inhibitors for utilization in flowlines

Abstract

This study presents a systematic experimental screening approach to scrutinize the efficacy of various inhibitors for two distinct crude oils (named A and M). The crudes possessed relatively high asphaltene content suffering from asphaltene deposition issues in flowlines. For this purpose, a set of static and dynamic tests were conducted for 16 chemical inhibitors. Modified asphaltene dispersion test (ADT) was mainly used for synthetic oils of SM and SA, made up of crude oils M and A, respectively. The samples were later subjected to inhibitors to monitor their inhibition performance, and thermal stability. DBSA was observed to outperform other chemicals, with an efficiency of 97%. However, its applicability was limited in fields under consideration where both water production and asphaltene deposition occur simultaneously. Branched DBSA, palmitic acid, and phthalic acid, at 1000 ppm, showed 52%, 41%, and 39% efficiencies, respectively. A lower centrifugal force, applied during ADT, improved the efficiency of 110, a commercial chemical, by over 2.5 times to 71%, suggesting its superior dispersion capabilities over inhibition. Thus, it was revealed that the ADT-based method at strict centrifugal conditions would underestimate the performance of dispersants. Furthermore, using the modified ADT on crude oil M revealed that DBSA, branched DBSA, and phthalic acid, at 1000 ppm, had 74%, 65%, and 58% efficiencies, respectively. Time scan turbidimetry showed also 67%, 51%, 49%, and 42% suspension of particles after 80 min in the presence of 66.6 vol% n-C7 for DBSA, branched DBSA, dispersant 110, and phthalic acid. Finally, results obtained from the capillary deposition flow (CDF) test at 70 °C, showed that dispersant 110 would have the most promising performance since 50% reduction for pressure drop was experienced. This chemical is deemed suitable due to low efficiency of DBSA in cases where water would co-produced with oil.