Track: Energy

Abstract

Waxy crude oil deposition in production pipelines often causes flow assurance issues in production operation. The issue further deteriorates during restarting of the waxy crude oil pipeline after an emergency shut down or planned maintenance. This is due to the obstruction caused by the solid wax in the pipeline, which requires additional pressure to disintegrate the solid wax before achieving a steady flow. The conventional equation used to measure the minimum pressure required for pipeline restart is overestimated, since thermal shrinkage, gas voids formation, and compressibility are neglected. The present study describes the effect of water bath temperature on the cooling time of the waxy crude oil and the effect of gas injection duration on the restart pressure of the waxy crude oil pipeline. The experiment was carried out using a waxy crude oil flow loop rig. It was observed that as the water bath temperature decreases, the cooling time increases, and the cooling rate decreases. When different gas injection durations were injected, a longer duration yields to lower pipeline restart pressure. Longer gas injection duration implies more volume of gas; hence compressibility is increased, which provides more space for the movement of the gelled waxy crude oil and its disintegration within the pipeline during the restart process. Hence, the restart pressure of the pipeline can be greatly reduced. At water bath temperature of 20°C, the highest restart pressure reduction, 40.48% is achieved, whereas at water bath temperature of 32°C, the highest reduction in the restart pressure attained is 33.52%.