A full scope of tubular solutions
to support Moho Nord Project
Building on experience supporting Total’s operations in Angola, Nigeria, Gabon, and previous projects in Congo, Vallourec provided drill string engineering, high performance drill pipe, oil country tubular goods (OCTG), drill pipe risers, and welding services for the Moho Nord field, 75 km off Pointe-Noire, Republic of Congo.
Total planned the Moho Nord field to produce from two separate reservoirs. The Albian reservoir will be accessed by 17 dry tree wells on Total’s first tension leg platform (TLP) in Africa. The Miocene reservoir will be developed with 28 subsea wells, including Phase 1 Bis. All of the Moho Nord wells will produce to the Likouf floating production unit (FPU), which has two separate processing trains (handling H2S and CO2 along with oil, gas and water) and the capacity to export 100,000 BOEPD via pipeline to Total’s Djéno onshore terminal. Drilling began in 2014 and first production came ashore in March 2017.
Drill String Engineering
To prepare for the project, Vallourec’s drilling experts began working with Total engineers in 2012 to design drill strings for the challenging wells that would be drilled from the TLP in 800 m of water, with departures as long as 6,000 m and measured depth of 7,500 m. Total engineers provided parameters for each planned well, including well architecture, trajectories, and mud properties to be used in each hole section. Vallourec engineers, with in-depth knowledge of drill string components and their application, used proprietary software to analyze torque, drag, tension, compression and well hydraulics to design the optimum drill string. Tapered strings with high strength mechanical properties would be required on most wells.
Total provided the resulting specifications to the rig contractors, and Atlantica was selected for the rig on the TLP. Atlantica acquired the entire drill string from Vallourec. This included the VM-150 DP high-strength drill pipe with the field-proven VAM® Express connection. This connection provides torque capacity that averages 150% to 200% of API connections, improved hydraulic performance, and quick makeup for improved rig floor efficiency.
Oil Country Tubular Goods
The OCTG specifications for the Moho Nord project were very stringent on account of the reservoir conditions, requiring material to be both high strength, to support the well loads, and corrosion resistant (H2S and CO2). To confirm the high level of performance of connection and materials, Vallourec conducted specific laboratory tests at its dedicated Research Center in Aulnoye, France, including accelerated corrosion testing using fluids from the Albian and Miocene reservoirs.
OCTG provided for the Moho Nord project was manufactured in France and Germany using Vallourec’s super chromium proprietary grade VM 110 13 Cr SS as well as some high collapse sour service grades to withstand the corrosive fluids produced from the two reservoirs.
Moho Nord is one of the first major projects to take advantage of the high performance characteristics of Vallourec’s latest generation of premium connections, the VAM® 21. Qualified to API RP 5C5: 2017, the most stringent connection qualification procedure, VAM® 21 is gas tight and is as strong as the pipe body under compression and tension. VAM® 21 is now the reference threaded and coupled connection for deep offshore projects. In addition to OCTG, Vallourec manufactured a variety of custom-designed accessories including pup joints and crossover subs for the project. Through innovative engineering, careful material selection, and in-house fabrication, Vallourec produced made-to-measure components that met the challenging specifications at significantly reduced cost for Total.
Drill Pipe Riser
Vallourec provided its high performance drill pipe riser, VAM® DPR HP, as part of Aker’s subsea package for the Miocene wells drilled in up to 1300m of water. Drill pipe risers provide an efficient means of installing upper completion, subsea trees and other components as well as performing well interventions. The VAM® DPR HP drill pipe riser incorporates a proprietary double-shoulder connection design, with a gas-tight metal-to-metal seal, and is rated up to 10,000psi working pressure for safe operations on high-pressure wells. The 6 5/8” OD VAM® DPR HP drill pipe riser delivered to the project is manufactured using VM 105 DP MS proprietary sour service grade. It provides a quick, cost-effective means to connect service rigs to subsea assets to reliably install equipment and perform through-tubing or wireline operations. Total has already utilized the VAM® DPR HP drill pipe riser system on other deepwater fields including Usan and Egina in Nigeria.
Vallourec will provide over 20,000 metric tons of OCTG for the Moho Nord project between 2014 and 2019. To manage this quantity of OCTG, Vallourec helped Total optimize the operation of its large-scale pipe yard in Pointe-Noire. Vallourec experts audited the yard and made recommendations for its layout, equipment, and best practices for storage and handling with the objective of avoiding safety hazards, minimizing damage to the OCTG, and maximizing efficiency for the duration of the project. Vallourec also trained all people involved with tubular management. Vallourec’s local VAM® service licensee, SPIE Oil & Gas Services, and pipe yard personnel were familiarized with the new products, including the VAM® 21 connection. Vallourec experts also conducted training for the Total’s drilling, subsea and QA/QC teams on the drill pipe, drill pipe riser and the OCTG. Vallourec also trained and qualified local inspection companies on how to inspect OCTG and drill pipe connections.
Welding on pipelaying vessel
In addition to providing tubulars used in Moho Nord’s wells, Vallourec also contributed to the installation of the project pipelines. Working aboard the Technip FMC Global 1200 pipelaying vessel, Serimax, Vallourec’s pipe welding subsidiary, successfully performed approximately 20,000 welds on 225 km of line pipe.
Total brought the Moho Nord field on line from FID to first oil in less than four years. In the process, the operator leveraged Vallourec’s international scope of technical and manufacturing capabilities. To date, Vallourec has met all scheduled deadlines on the project without any safety incidents, and has kept its tradition of designing quality products, testing them in real life conditions, and providing Total the quality products that perform in very challenging conditions.
Article first published in TOTAL MOHO NORD supplement to Oil & Gas Journal.