Abstract
Abstract
Phenolic resins are major class of polymeric compounds used for treating asphaltene instability related challenges. Such compounds often act like as artificial resins naturally present in crudes to prevent the aggregation of asphaltene molecules and therefore their tendency to deposit on solid surfaces. However, these phenolic resins are known to have toxicity and biodegradability issues. Aim of this work is to elucidate and compare cardanol ethoxylates derivatives as asphaltene dispersants in comparison with commonly used phenolic resins chemistries.
To characterize the effects of cardanol chemistries, a series of laboratory tests were conducted. The thermo-electric properties of the crude oils were studied both with and without chemical treatments to establish state of asphaltenes and their disaggregation. Optical dispersion testing confirmed whether cardanol formulations affected the sedimentation rate and particle size distribution of flocculated asphaltenes within the oil matrix. An Asphaltene Dynamic Deposition Loop (ADDL) test verified the effectiveness of the cardanol ethoxylates on the overall asphaltene deposition rate under flow conditions. Finally, the rheology and viscoelastic properties of the treated oil were examined at various temperatures and shear rates with specific focus on steady state and low shear environments. Results were compared against commercially available resin-based products.
In a thermodynamically stable crude oil medium, the asphaltene molecules exist in an equilibrium state and contributes least towards the overall thermo-electric reading of the test sample. Addition of an effective asphaltene inhibitor disrupts this equilibrium and disperses the polar asphaltene molecules within the crude matrix, leading to higher thermo-electric values. For the crude samples tested, it was observed that the addition of cardanol derivatives increased the thermo-electric response thus improving the asphaltene dispersion. Further validation of this improvement was confirmed with the optical dispersion test results. Relative to the blank or untreated sample, adding formulations with cardanol ethoxylates resulted in lower sedimentation rate and settling velocity of the heavy asphaltene fraction. Furthermore, effectiveness of cardanol as a surface-active agent that can avert the preferential sticking of the polar asphaltene fraction onto the metal surface of production and transportation flowlines was also assessed using the ADDL test. Lastly, the low-shear rheological analyses of the treated and untreated crude samples also corroborate synergistic efficiency of cardanol containing formulations to decrease the bulk sample viscosity.
Cardanol ethoxylates belong to a class of surfactants derived from renewable and sustainable raw materials that can be considered as a viable option for upstream oilfield applications. Results from this study are quite encouraging and could set the stage for development of new asphaltene inhibitors and improve our capability to control asphaltene flocculation in more complex fluids and production systems including high asphaltenic crudes.