A Precise and High-Throughput Technique for Asphaltene Inhibitor Screening

A novel asphaltene deposition apparatus and method are developed that focuses on the diffusion-based, heptane-induced deposition of asphaltenes and enables the screening of asphaltene inhibitors with low oil consumption and with high repeatability. The apparatus comprises a simple 254 mm-long vertically oriented deposition tube with an inner diameter of 4.6 mm that is filled with a mix of oil and n-heptane for 2 h, after which the deposit can be recovered. Optical spectroscopy was used in place of gravimetric analysis to quantify the deposit, which increased the resolution and decreased the oil consumption by decreasing the required surface area relative to other methods. Three oils were tested to validate the method. The repeatability (standard error) in the measurement for a baseline deposit was 5% for two of the oils and 1% for the third. Inhibitor screening and dosage rate studies clearly demonstrated the method’s ability to identify inhibitors that prevent the deposition of asphaltenes in ambient conditions. A comparison between the novel asphaltene deposition method and asphaltene dispersion testing was performed. The results further confirmed that actual deposition should be generated and used instead of precipitation methods when testing inhibitors.