Saudi Aramco experienced serious corrosion problems in oil production tubing in one offshore field, attributed to presence of H2S, CO2 and varying levels of water cut. In early 2002, the company installed on trial test basis Glass Reinforced Epoxy (GRE) or commonly known as fiberglass lined carbon steel tubing in three wells. The fiberglass lining was installed to provide a corrosion barrier to protect the steel tubing from internal corrosion. As far the technology, the fiberglass lining or sleeve is carried out joint by joint by inserting a solid fiberglass tube into the low cost carbon steel tubing and cement is pumped into the narrow annulus between the fiberglass liner and the carbon steel tubing. The connection area is protected by the combination of end flares and a corrosion barrier ring. The company examined various methods to evaluate the performance of the fiberglass lined tubing, without having to pull out the tubing from the well as these wells are oil producers. After review of the evaluation options, it was decided to run a multi finger caliper to evaluate the condition of the fiberglass lining and check for any internal corrosion in the steel tubing. The log showed the fiberglass lining to be in good condition with no damage indicating that the steel tubing was protected from corrosion. The other two wells had no tubing leaks indicating the GRE lining is providing corrosion protection. Based on successful trial test results, the company adopted the technology to protect tubing strings deployed in corrosive environments in oil producers, water injectors and water supply wells. Field experience has shown that the use of fiberglass lined tubing is a low "life cycle cost" solution compared to other options. There has been no workover in these wells since installation. Today fiberglass lined tubing is applied in Saudi Aramco in high water cut oil producers, water injectors and combined water source and injection wells. The paper shares the history of corrosion, challenges and lessons learned during the implementation of the solution, various performance assessment methods evaluated and the results and interpretation of the caliper log.
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.
ISO 15663 Lifecycle cost (LCC) analysis principles are commonly applied to evaluate the viability of downhole tubing materials. This includes the initial CAPEX, operating or maintenance OPEX, Replacement costs and Revenue impact of tubing failure. Increased implementation of Glass Re-informed Epoxy (GRE) Lined tubing has provided significant evidence of flow assurance benefits of the system. This paper will present a modern adaptation of LCC analysis based on operator data and quantification of these benefits and savings. With over 100,000 GRE Lined completions worldwide there are numerous reported cases of flow enhancements and savings besides corrosion mitigation. The paper is based on extensive research of data collected with agreement from operators representing cost savings or additional revenue that can be factored into LCC analyses with a fair degree of accuracy. Overall operational savings that operators have derived from flow assurance benefits of GRE Lined Tubing, such as improved thermodynamics, scale mitigation, reduced pressure drop, etc. are substantiated using field data from downhole logs, analysis of produced fluids and inspection of retrieved GRE Lined tubing. Operators have reported higher temperature at well head in Oil Producers after steel tubing was replaced using GRE Lined Steel tubing. This has been associated with savings in separation costs at the surface. There are several reports of higher flow rates and reduced pressure drop across GRE lined tubing which translates to higher injectivity or production. Operators have numerous references of improved and stable flow rates for longer durations when compared to bare steel tubing due to the mitigation of carbonate scale deposition which would impact flow dynamics. Such cases represent significant improvements to production efficiency and, consequently, the overall return on investment in the asset. The findings of research on multiple operator flow enhancement case references, while implementing GRE Lined Tubing, are illustrated graphically to represent savings and/or additional revenue in comparison with graphical representations of traditional LCC calculations models based on ISO 15663 key drivers i.e. CAPEX, OPEX, Revenue Impact and Replacement Costs. It is anticipated that this paper will influence a paradigm shift that guides operators to consider the impact of flow enhancement, improved thermodynamics, improved injectivity and/or production, simplification of surface facility requirements and other fringe benefits, in addition to CAPEX, OPEX and Revenue, while evaluating the LCC of tubing material alternatives.
In a first ever case within Shell assets worldwide, Badr Petroleum Company (Bapetco) - a Shell Joint Venture Company in Egypt, has embarked on a project of replacing a 20 km Water Injection network, originally constructed with Welded API 5L carbon steel pipe, with fiberglass lined API 5CT Threaded and Coupled tubing. The original network is a conventional pipeline system of welded pipes transferring brine from 3 Water Source wells to 23 Water Injectors through the Egyptian Western Desert. The water is of a high salinity of 180,000 ppm saturated with dissolved oxygen up to 1,000 ppb before chemical treatment. After injecting oxygen scavenger the concentration of the dissolved oxygen is 100 ppb. As a result, Bapetco has been facing severe corrosion related failures in Water Injection flowlines. The 20 km surface pipeline network had to be totally replaced approximately once every two years. Many of the Water Source and Water Injection wells in this network were completed using GRE lined tubing for internal corrosion protection. However, corrosion by-products from the carbon steel flowline were a cause for concern given the risk of plugging the reservoir. Basic remedial solutions such as clamps, chemical inhibitions, patches etc. were carried out on the flowline. Nevertheless a more manageable approach was sought especially after reviewing the life cycle costs of maintaining the network and the impact of frequent drops in injection rates on the overall production from the field. Bapetco embarked on an ambitious plan to use API 5CT Threaded and Coupled Steel Tubing internally lined with fiberglass for corrosion protection to replace the bare Carbon Steel pipeline. Shell's confidence in GRE lining has been established over 20 years of using GRE lined tubing downhole in 11 countries. This endeavor also helps Bapetco utilize unused inventory of tubing instead of additional capex required for flowline replacement with API 5L pipes manufactured from more exotic steel. The integration of API 5CT specification threaded and coupled tubulars into Pipeline Engineering design, considering flow dynamics and make up compatibility with standard valves and fittings, is a huge challenge given the lack of applicable design codes, standards and Engineering common ground. Special components were engineered to provide a transition between GRE lined tubulars and plain end unlined fittings and flanges. Also, pressure testing, pigging and connection make-up procedures were reviewed and/or revised to accommodate the use of GRE lined API 5CT pipes in flowlines. This paper chronicles the history of the Water Flood project, the nature, reasons and consequences of the multiple corrosion failures and the failed corrosion mitigation strategies. Furthermore, the paper will shed light on the techno-commercial analysis and engineering that forms the basis for this mammoth effort.
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