Novel Modified Polycarboxylate Paraffin Inhibitor Blends Reduce C30+ Wax Deposits in South Texas

Abstract

Abstract A typical challenge encountered during shale oil and condensate production in South Texas is severe wax deposition on fractured rock surface near the wellbore and flowlines from wellheads to separators, potentially reducing surface areas for oil and gas flow. Commonly used surfactant dispersants and wax inhibitors such as comb shaped polyacrylate/methacrylate (PAMA) and alpha-olefin modified maleic anhydride (OMAC) sometimes fall short and do not always address challenges associated with C30+ waxy crude oil and condensate. This is typically due to the mismatch of molecular weights and the incorrect ratio of polar and non-polar groups between the polymeric additive and the targeted wax species. In this study, we present the findings of a new modified polycarboxylate and polyacrylate blend that provides a balanced approach of optimized non-polar and polar groups on the polymer backbone. Additionally, the inherent long polymer chains with a broad chain density distribution appear to interact well with C30+ waxy compounds, effectively lowering pour point, reducing wax appearance temperature (WAT) and suppressing wax deposition. A gradual reduction of WATs in polymer treated waxy deposit was observed via DSC/CPM measurements when the polymer blends were varied with polyacrylate/methacrylate/modified carboxylate ratios. Cold finger tests were performed at selected temperature differentials that closely represented field conditions in order to demonstrate the efficacy of the optimized blend, in which deposits of C30+ waxy compounds were significantly eliminated. It's commonly accepted that comb shaped polymers interact with wax crystals via incorporation and perturbation. The polymer blend presented here, with an optimized ratio of non-polar and polar groups, appear to enable a secondary mechanism that introduces a repulsive force between growing wax crystals, which is reminiscent of interfacial polarization of charged wax crystals under an external electric field. Through Zeta Potential, Cold Finger, Yield Stress, DSC, SARA and HTGC analysis, it was demonstrated that this additional interference rendered the comb shaped polymer blend much more effective, against other PAMAs, OMACs, and linear polymers such as ethylene vinyl acetate (EVA).