Influence of Crude Oil SARA Composition on Flow Improver Performance: Toward Composition-Guided Additive Selection

Abstract Flow assurance in crude oil pipelines remains a major operational challenge due to wax precipitation, gelation, deposition, and asphaltene aggregation. Chemical flow improvers are commonly employed to mitigate these issues; however, additive selection remains largely empirical because structure-efficacy relationships based on crude oil composition are not well established. This study develops a mechanistic framework for composition-guided additive selection that considers both additive functionality and crude oil composition. In this work, six commercial polymeric additives were evaluated in four crude oils with varying SARA (saturates, aromatics, resins, and asphaltenes) compositions to identify SARA-dependent performance trends. The effect of radical initiator concentration, an often-overlooked parameter, was inferred from variations in additive performance, suggesting possible differences in polymer architecture, such as chain length and branching. Rheological (viscosity, yield stress, and gel point measurements) and microscopic analyses revealed that effective flow improvers consistently transformed needlelike wax structures into dispersed globular aggregates, suppressing network formation and significantly improving low-temperature flowability. The results further indicate that resin-stabilized asphaltenes remain largely dispersed and exert minimal influence on wax crystallization, whereas aggregated asphaltenes (asphaltene clusters) are inferred to promote heterogeneous nucleation and network formation, contributing significantly to increased viscosity and yield stress. Wax-rich, low-asphaltene oils respond best to additives with flexible backbones and compatible alkyl side chains that promote wax cocrystallization and morphological modification. High-asphaltene crudes require additives enriched in polar and aromatic groups that can disrupt asphaltene aggregation. Conversely, in low-wax, low-asphaltene systems, bulky or strongly polar additives offer minimal advantage, demonstrating that simpler, long side-chain and wax-compatible additives are both more effective and cost-efficient. Collectively, this work establishes practical mechanistic structure-efficacy guidelines, identifying backbone length and flexibility, side alkyl chain characteristics, polarity, and aromaticity as key design parameters. The findings provide guidance for composition-guided selection of flow improvers and may reduce reliance on costly, time-intensive empirical screening.