Wax Deposition in Crude Oil Transport Lines and Wax Estimation Methods

Abstract

Petroleum industry is one of the major industries serving the energy demands. Flow assurance is essential for providing continuous fuel supply. Wax deposition is the main issue that affects flow assurance or reduces the efficiency of transporting crude oil. As the maintenance cost of repairing and troubleshooting is very high, addressing issues related to flow assurance becomes critical in the petroleum industry. This chapter will explore methods used for reducing, cleaning, and monitoring deposition of wax. Wax dissolved in the crude oil gets crystallized causing accumulation across the pipe walls once the bulk temperature of the crude oil gets lower than wax appearance temperature (WAT). Mechanical, thermal, chemical, and microbial methods highlighting general practice in the industry are discussed in this chapter. Next, the direct techniques providing information about the numerical wax deposition models used along with scientific measurement techniques are emphasized. Later, the indirect measurement techniques are discussed providing information about the external probing and nondestructive techniques to obtain information about wax layer deposition inside the pipe. The role of artificial intelligence and use of fuzzy logic for effective wax prediction or in developing the existing wax numerical models are emphasized in the last section.

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

“…The heating can be done at different stations along the pipeline route [10]. The concept behind this method is to maintain temperature in the crude oil system for reducing wax buildup [35]The temperature should however be watched in other not to coke the crude oil which can damage the wellbore [6]. The various thermal methods include: hot oiling, hot water treatment and direct heating [1].…”

“…To be able to curb the effects of wax deposition in crude oil transportation through pipelines, there is need to estimate its buildup in pipelines. This is necessary to forestall sudden and/or total shutdown as a result of partial or total blockage of the pipeline flow area with wax [35]. Several methods propounded by researchers for wax detection and estimation include the pressure drop method, the heat transfer method, and the pressure wave propagation technique [26].…”

“…However, not many of them possess the required chemical resistance, mechanical strength and cost effectiveness [26]. Alnaimat et al [35] suggests the use of plastics as insulators to shield temperature drop in the bulk fluid. Although not quite popular, but its use has been reported and recommended by researchers [37].…”

Advanced Research on the Production, Transportation and Processing of High Waxy Oil. A Review

“…Crude oil transportation lines play an important role in ensuring a continuous supply of fuel, i. e., flow assurance. Since the maintenance costs of repairing and troubleshooting transportation lines are very high, solving problems related to flow assurance becomes critical in the oil industry 50 .…”

“…The deposited layer of wax in transportation lines can be observed as three sublayers: the top layer is more granular and softer, the bottom layer has a strong bond with the pipe wall and is considered a tightly adherent layer, and the intermediate layer contains mechanical impurities and high content of wax. Over time, the layers harden and move from the top to the bottom, thus reducing the effective cross-section of the flow 50 .…”