Fiberglass-Lined Tubing Helps Prevent Asphaltene Deposition in Oil Wells

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 21441, “First-Time Worldwide Application of Glass-Reinforced Epoxy-Lined Tubing for Prevention of Asphaltene Deposition in Tubing in Oil Wells: A Case Study From Kuwait,” by Reji E. Chinnappan, SPE, Milan Telang, SPE, and Riyad Quttainah, SPE, Kuwait Oil Company, et al., prepared for presentation at the virtual 2021 International Petroleum Technology Conference, 23 March–1 April. The paper has not been peer reviewed. Copyright 2021 International Petroleum Technology Conference. Reproduced by permission. Asphaltene deposition in production tubing represents a major flow-assurance challenge. Common strategies to mitigate asphaltene deposition downhole include mechanical or solvent cleanouts and chemical inhibition. These are associated with production deferment, high job costs, safety and environmental risks, and operational issues. An operator has addressed this challenge using production tubing lined with glass-fiber-reinforced epoxy (GRE). This technology was implemented in two trial wells. The paper describes the different mitigation strategies employed by the operator and presents the findings of successful trials. Background Jurassic wells of a Kuwait Oil Company asset are producing light crude from a tight matrix-type reservoir located at a depth of 13,000–15,000 ft. Reservoir pressure has depleted from approximately 9,500–10,000 psi to approximately 6,000 psi because of sustained production in the absence of any significant pressure support. Oil production rates per well have diminished to the 500- to 1,000-BOPD range. The oil features high asphaltene onset pressures (4,000–5,000 psi). When considering time-lapse plots of caliper logs from a well where asphaltene deposition used to occur, the plot indicates that significant asphaltene deposition in the well took place below 4,500 ft and progressively increased over time. In approximately 5 months, the average internal diameter of the tubing reduced from 2.75 in. to less than 2 in., thereby constricting the flow significantly and requiring cleaning of the tubing. In extreme cases, the tubing string could be fully plugged. Many field trials with different tools and chemicals using batch and continuous treatment have been conducted in past years to solve this problem but without satisfactory results. Application of GRE-Lined Tubing for Asphaltene Control The operator decided to apply a novel strategy of using tubing internally lined with GRE based on its established ability to retard, and even eliminate, scale nucleation and deposition. The technology uses a thin-walled, solid-filament-wound GRE/fiberglass tube run inside carbon steel production tubing. Cement is pumped into the annulus between the steel tubing and the GRE liner. The ability to prevent asphaltene from sticking to the inner wall of the tubing is attributed to the smoother internal surface. It is also corroborated by a higher Hazen Williams coefficient value of 150 for GRE as compared with 110 for carbon steel pipe, which provides for lesser frictional pressure loss during flow. The GRE liners used by the operator have a surface roughness of 0.00011 in., which, unlike bare steel, is retained over the life of the GRE. The GRE-lined tubing proved to withstand temperatures of up to 280°F and hydrogen sulfide concentrations of up to 50%. This is comfortably more than the process conditions for the trial wells in consideration.