Wax deposition process: mechanisms, affecting factors and mitigation methods

Abstract

Crude oil transportation in the pipelines of the cold environment is affected by the low temperature causing a problem such as wax deposition. The flow assurance in the hydrocarbon pipelines is very important due to the precipitation of the solid phase of wax on the pipe wall creating pressure abnormalities and causing an artificial blockage leading to a reduction or interruption in the production. Wax can precipitate as a solid phase on the pipe wall when its temperature (inlet coolant temperature) drops below the wax appearance temperature (WAT). In this review, wax deposition process is discussed. Also, proposed wax deposition mechanisms are outlined including molecular diffusion, shear dispersion, Brownian diffusion and gravity settling. Furthermore, the factors affecting the wax deposition process are explained, such as pipe wall temperature (inlet coolant temperature), crude oil composition, crude oil temperature, ambient temperature, flow rate, thermal history, time and pressure. There are several mitigation methods were used in the different oil fields around the world to reduce wax deposition such as pigging, inhibitors and thermal insulation.Citation: Theyab MA. Wax deposition process: mechanisms, affecting factors and mitigation methods. Open Access J Sci. 2018;2(2):109-115.

Occurrence and Characterization of Paraffin Wax Formed in Developing Wells and Pipelines

“…Various methods for prevention and/or removal of paraffin wax deposits have been performed to deal with wax problems. These methods include active heating, fused-chemical reactions, insulation, pigging, chemical treatments, wax-repellent surfaces cold flow technologies, and biological treatments [13].…”

“…Crude oil content is one of the potential factors that influences on deposition of wax significantly and is liable for the viscosity and pour point reduction [13]. In addition, it contains small amounts of sulfur, nitrogen, and oxygen compounds [4].…”

Crude oil and the problem of wax deposition on pipeline systems during transportation: A review

“…Among all flow assurance issues, the formation of waxes during the production and transportation of crude oil remains the greatest issue [28]. It affects numerous oil companies across the world and can even cause production sites to shut down [29]. At shutdown, the estimated cost of replacement and downtime is pegged at $30,000,000.00 (thirty million dollars) [11] The problem of wax solution is amplified by the fact that most oil production sites are moving deeper and deeper offshore [13].…”

Molecular interaction study on Gemini surfactant and nanoparticles in wax inhibition of Malaysian crude oil

“…WAT is defined as the temperature at which the first wax crystals begin to form in the crude oil during a cooling process. 12 Above WAT, paraffin is soluble in crude oil where less solid wax is present. Weaker vdW interaction at 308 K suggests less wax aggregation and higher wax solubility than 288 and 298 K.…”