Asphaltene deposition in production tubing is 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, HSE risks and operational issues. In a worldwide first, Kuwait Oil Company (KOC) has addressed this challenge using Fiberglass (GRE) Lined Production Tubing. This technology was implemented in two trial wells. This paper chronicles the different mitigation strategies employed by KOC and presents the findings of the above-mentioned successful trials. Tendency of scale to stick on smoother, non-metallic surfaces, is known to be less than on bare steel surface. KOC had trialed internal coating to mitigate Asphaltene deposition in tubing, but the experience was not satisfactory. KOC has been successfully using GRE lined tubing for corrosion protection and scale prevention in oil and water wells. Considering GRE's smoother surface, lower zeta energy and thermal insulation, it was decided to conduct a trial of GRE lined tubing in wells with Asphaltene deposition problems. Frequency of cleanout and Well Head Pressure (WHP) trends, before and after installation of GRE Lined Tubing, were compared for evaluation. The paper chronicles the trial results and provides a comparison of implementation costs against currently employed tubing cleanouts by Coiled Tubing (CT) using a Diesel-Toluene mixture. Two wells, requiring frequent tubing cleanout of Asphaltene, were selected as candidates. Trends over a period of 13-15 months after installation of GRE lined tubing showed up to 74 % reduction in WHP decline rate compared to pre-installation periods. Cleanouts were avoided against an earlier frequency of 3 to 3.5 jobs per year. This resulted in following benefits: (1) Direct annual operational savings of 519,750 US $ per well (2) Additional production by increased uptime of 1 to 1 ½ months (3) Avoidance of Coiled Tubing sticking, occurring in similar wells, and the resultant workover cost (4) Eliminating production deferment due to this workover (5) An environment friendly and safe methodology not requiring handling of toxic, highly flammable Toluene, used for the clean outs. Comparison of the economics show clear-cut benefits of GRE lined tubing over tubing cleanouts. In view of the applicability in most of their high API gravity Jurassic oil wells, KOC has decided on wide scale implementation of this technology. As this is the first known case of its kind worldwide, we expect that this paper will be highly beneficial to operators faced with challenges in producing Asphalteinic oil and those engaged in CO2 EOR campaigns. Besides sharing experience, the authors aim to generate global operator engagement to optimize this new solution, possibly combined with other solutions, to tackle Asphaltene deposition as efficiently as possible.
Asphaltene deposition problems in Kuwait have become a serious issue in a number of reservoirs during primary production in different fields, resulting in a severe detrimental effect on the economics of oil recovery. Hence, one of the mitigation approaches in the field is using remedial solvent treatments, such as Xylene or Toluene, which is very costly and harmful to the environment. Kuwait Oil Company (KOC) is planning to produce from asphaltinic Marrat wells that have been shut down due to low bottom-hole pressure (BHP), by artificial lifting technique using an Electric Submersible Pump (ESP) supported with continuous chemical injection, as a pilot. The main objective of this study was to investigate in the lab the effectiveness of various concentrations of toluene/diesel (T/D) mixtures on Marrat reservoir fluid in order to mitigate asphaltene deposition problem during the actual pilot implementation. Preliminary screening tests were conducted on the surface oil sample using Solid Detection System (SDS) "laser technique" to determine the optimum dose of the T/D mixture ratio. The results showed that pure diesel accelerated the asphaltene precipitation; however, mixing T/D inhibited the precipitation process. Series of pressure depletion tests was then conducted on live oil, single phase samples, to determine the Asphaltene Onset Pressure (AOP) with and without adding various ration of T/D solvents at different temperatures from reservoir to surface conditions. The results revealed that using 15% (by volume of oil) from the (50T:50D) mixture reduced the AOP close to the bubble point pressure. Furthermore, the amount of the precipitated asphaltene was physically quantified using a bulk filtration technique. It was observed that, based on blank sample, the wt% of the precipitated asphaltene was minimized at the AOP and maximized at the bubble point. However, using the recommended mixture of 50T/50D, the amount of asphaltene that precipitated was almost negligible. Therefore, from a health, safety, and economic point of view, this study recommends using a low dose of 7.5% (by volume of oil) from toluene mixture with diesel (50%:50%) rather than using pure toluene to prevent the precipitation.
Produced fluids, from a tight deep carbonate reservoir extended laterally from West to South East Kuwait experienced severe asphaltene deposition along production tubing. This flow assurance challenge significantly increases well operating cost, risk and production deferment periods due to frequent Coiled Tubing (CT) cleaning jobs using considerable amount of expensive organic solvents. This flow assurance challenge is caused mainly due to the absence of any of strong reservoir aquifer support, continuous decline in reservoir pressure and high draw down across this tight reservoir in order to meet production targets. The objective of this pilot trial was to provide a long term solution with redundancy feature to convey chemicals safely from surface to down-hole through capillary tubes and pressure regulated chemical injection valves. Different techniques have been introduced since 1980 including batch chemical squeeze treatment, coated tubulars and Radio Frequency Vibration tools. Results of these trials have shown either short term production gain or no improvement on asphaltene build-up rate and well productivity. In order to dynamically mitigate this challenge, a dual in-situ chemical injection system was installed to convey chemicals deep inside the well on a continuous basis. The system was successfully installed and has provided a safe & reliable field qualifying tool to verify chemical performance at different injection parameters. The novelty of this technology is the ability to provide a continuous asphaltene management system to achieve production sustainability using dual injection conduits and down-hole pressure regulated valves utilizing relatively small amount of chemicals. This paper highlights the adopted approach of continuous asphaltene management system from hardware design & installation prospective to chemical qualifying process in the field and also shed light on the pilot trial lessons learned.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.