Modification of the paraffin crystallization and flow ability of waxy crude oil is of vital importance during transportation and restart processes at low temperature. To investigate the influence of pendants in comb-type copolymers on the cold flow ability of crude oil, maleic anhydride-α-octadecene copolymer and its derivatives with octadecyl (MAC), phenyl (AMAC), or naphthalene (NMAC) pendants were synthesized. These derivatives, when added to waxy crude oil, change the size and quantity of the paraffin crystals observed by polarizing light microscopy (PLM), improve the flow ability of waxy oils by reducing the viscosity and yield stress revealed by rheometer, and decrease the paraffin crystallization temperature and quantity of wax precipitation determined by differential scanning calorimetry (DSC). AMAC had the greatest effect followed by MAC and NMAC, respectively. It seems that small aromatic pendants improve the flow ability of waxy oils by adsorbing on the surface of asphaltenes, while large aromatic pendants impair the assembly of copolymers with asphaltenes by a higher steric hindrance.

Waxy crude oil containing large amounts of paraffins often results in various difficulties in extraction and transportation, especially at low temperature. Comb-type copolymers with phenyl pendants were found to be able to improve the flow ability of waxy oils effectively. To investigate the influence of spacer length between phenyl pendant and polymer backbone in comb copolymers on the flow ability of waxy oil, poly­(α-octadecene-co-maleic acid phenyl alkyl amide)­s with various spacer lengths were synthesized by modification of poly­(α-octadecene-co-maleic anhydride) with aniline, phenethylamine, phentermine, and phenyl-undecanoicamide. Their effects on the morphology and crystallization of model and crude oils were observed by polarized light microscopy and DSC. The flow ability of both oils in the presence of copolymers was studied by means of rheology, including measuring yield stress, viscosity, and thixotropic properties. It is found that the spacer length remarkably affects the rheology and wax crystallization behaviors for both oils. The copolymer with a longer spacer can provide better flexibility of phenyl pendants to disperse asphaltenes more effectively, and the long spacer can cocrystallize with long-chain paraffins.

Liaohe extraheavy oil is a kind of special crude oil with high paraffin and asphaltene contents and a pour point of up to 60 C. To improve its flowability, comb-type poly(maleic alkylamide-co-a-octadecene) copolymers (MACs) with various amidation ratios were synthesized and used. Model oils containing paraffin mixtures with the same average carbon number to Liaohe extraheavy oil with and without asphaltene were prepared to explore the effect of the MACs on paraffin crystallization and asphaltene dispersion, respectively. We found that MACs reduced the yield stress, changed the size and shape of the paraffin crystals, and obstructed the paraffin crystallization for both model oils and extraheavy Liaohe oils as observed by rheology, polarizing light microscopy, X-ray diffraction, and differential scanning calorimetry. The MACs seemed to be an ideal candidate for improving the flowability of Liaohe extraheavy oils.