Flow assurance of waxy crude oil through thermal methods using nichrome wire and ultrasonic waves effects - Experimental investigation

When crude oil transportation stops for a certain period, the low temperature causes sufficient wax crystallization inside pipelines. During the crystallization, pipelines are exposed to a decrease in the inner diameter of the pipe, which leads to clogging and an increase in pressure drop. The higher pressure drop may require a huge pumping force to break the wax crystals and start the flow, increasing the level of risks and costs. Recently, many thermal and non-thermal methods have been used to alleviate wax deposition, such as surfactants, electric heating, and chemicals. In this study, flow assurance of heavy crude oil was investigated through pipelines using ultrasonic waves, nichrome wires, and combined methods. It includes conducting an experimental investigation on the ability of applying the ultrasonic effect and nichrome wires to improve the transportation performances of waxy crude oil through pipelines in a safe and environmentally friendly manner at the lowest costs while maintaining the characteristics of crude oil at high levels. The cooling rate was also studied at surrounding temperatures close to 30 degrees C, 15 degrees C, and 5 degrees C. An experimental setup was developed to study the efficiency of the combined method in heating the pipeline. It was observed that the combined method was found effective in heating pipelines to higher temperatures in a shorter time. When the surrounding temperature was 30 degrees C, the combined method was able to raise the temperature of the crude oil to 80 degrees C in just 9.96 min, while the nichrome wires took 25 min to raise the temperature to 73 degrees C. As for the ultrasonic, it took 28 min to bring the temperature to 65.6 degrees C. It has also been proven that the highest cooling rate occurs at the walls of the pipeline. Therefore, the deposition of wax begins on the walls first and then moves successively to the middle.