The performance of paraffin inhibitors from several chemical families was evaluated using two model waxy oils in bench-top tests such as cloud point and pour point, and in small-scale deposition rigs using a cold finger and a flow loop. In addition, rheological characterization of the inhibited systems was conducted to provide additional insights into the function of the paraffin inhibitors. Similarities and differences in the response of the model oils to the paraffin inhibitors are discussed along with the correlations between the results from bench-top tests and the observed wax deposit inhibition performance.The model waxy-oils were formulated using blends of commercially available waxes dissolved in a paraffinic solvent or a mixture of paraffinic and aromatic solvents. The wax blends were chosen to represent a broad range of carbon number distributions including one highly polydisperse distribution with an extended distribution of high carbon number waxes exceeding C50. Candidate paraffin inhibitors were initially evaluated for their impact on cloud point and pour point in these model oils. Subsequent testing of the inhibited systems included rheological characterization over a range of temperatures, cold finger deposition tests and flow loop deposition tests in a pipe-in-pipe geometry. All results are compared to the baseline results for the uninhibited model waxy oils.While changes in cloud point and pour point gave a good indication that a particular paraffin inhibitor was impacting the wax crystallization process, this did not guarantee a significant reduction in deposits of the inhibited system. Moreover, the experimental conditions used in the small-scale deposition tests also affected the observed performance of paraffin inhibitors, indicating that temperature gradients (i.e., oil temperature and coolant temperature) must be optimized to achieve the highest discriminating power. This study highlights the degree of correlation and the areas of departure between bench-top test results and the main objectives of deposit reduction, and yield stress reduction in flowing systems. It also discusses the advantages and risks of using only the bench-top test results for the selection of paraffin inhibitors.

In this paper, we explore the correlations between the effectiveness of several wax inhibitors and physico-chemical properties of crude oils. First, the effects of the type of fluid was studied by dissolving refined paraffin waxes in non-waxy crude oils-here termed ЉdoctoredЉ crude oils-of different properties and comparing the wax appearance temperature and pour point of the doctored crude oils to those determined for a model waxy fluid used in previous studies [1]. After treating the doctored crude oils with wax inhibitors, the ability of the chemicals to depress pour point was examined. Even though the paraffin waxes in these fluids were exactly the same, marked differences in the effectiveness of the chemicals were observed. The doctored condensate was very responsive to the inhibitors in a similar manner to that observed for the model waxy fluid, while doctored crude oils from the Middle East showed a significantly reduced response to most inhibitors. The results are discussed in terms of the differences in solubility of the paraffin waxes, and the chemical composition of the crude oils.Secondly, the influence of a wide range of crude oil properties on the effectiveness of wax inhibitors was investigated by treating seven (7) crude oils of different geographical origin with five (5) wax inhibitors and evaluating their performance to reduce wax deposits in a cold finger experiments. Distinct crude oil behaviors were observed in terms of their responsiveness to the wax inhibitors. Some crude oils were equally responsive to wax inhibitors, while others showed moderate response, and one was not responsive at all. The results are clear examples of the crude oil ЉspecificityЉ, and demonstrate the risks of using model waxy fluids, or even different crude oils, to extrapolate the performance of wax inhibitors. Additives that worked well in model fluids might not work at all in real crude oils.Lastly, physical properties of crude oils and molecular characteristics derived from high-temperature gas chromatography (HTGC) were used to seek a correlation to wax inhibition performance using chemometrics tools, specifically, principal component analysis (PCA). Preliminary results from the PCA approach indicate that several crude oil properties affect inhibition efficiency. The analysis suggests that the efficiency of the inhibitors studied here increases for crude oils with lower wax appearance temperature, lower pour point and lower carbon number distribution. It could also be inferred that inhibition efficiency was improved in crude oils containing higher amounts of asphaltenes but low wax content.

One of the most serious flow assurance challenges encountered during oil and gas production is the deposition of paraffins on formation surfaces, flowlines, as well as on other processing equipment. Paraffin deposition can cause problems in the production system that includes blocked pipelines, lower production rates, solids-accumulation, and increased remediation time and costs. Several thermal, mechanical, and chemical methods are used to mitigate these challenges, and, of the chemical techniques available, paraffin inhibitors are deployed to mitigate the deposition problem. Several classes of polymers have been developed into paraffin inhibitors to delay the onset of paraffin precipitation and alter the crystal morphology of the precipitated paraffin particles – these combined phenomena reduce the extent of deposition. While these polymers control wax deposition, several challenges remain for their use in both cold and deep-water environments. Many of these polymers exhibit reduced solubility in common solvents used to formulate treatment products, and, as a consequence can only be blended at low concentrations for use in harsh environments. A real demand exists for new paraffin inhibitors that have enhanced formulation-stability at much higher concentrations suitable for use under low-temperature and high pressure environmental conditions. This paper describes the developmental work and performance evaluation of a novel series of polymers specifically developed for use in low-temperature environments.