Location: Papa Terra field
Region: Southern Campos Basin, Brazil
Water depth: 1,200 meters
Barge: Muliceiro -X
Vessel: DOF Subsea Skandi Skolten
Clients: Petrobras and Chevron
In March 2010, Petrobras hired InterMoor to install drilling and production conductors using InterMoor’s patented conductor installation methodology. WORK SCOPE: All operations were performed off of the rig’s critical path and included the fabrication of 17 well conductors; the design, fabrication and installation of five templates; and the provision of the installation barge. The dimensions of the conductors were 36 in (91.44 cm) – OD x 1.5 in (3.81 cm) wall x 193.6 ft (59 m). Fifteen of the conductors were driven to client specifications. Additional survey work was completed including surface navigation and Long Base Line (LBL) positioning.
Beginning with the fabrication phase, stringent welding qualification procedures were employed by Petrobras in adherence with Det Norske Veritas (DNV) standards. These standards are typically used for welding rigid risers; subsequently, allowable flaw sizes were exceedingly tight. The challenge was further complicated by the turnkey nature of the endeavor; design, fabrication and installation of the conductors to strict inclination, position and height tolerances. Additional concerns on location included the positioning and installation tolerances which were within 11.8 in (30 cm) of the conductor target position at less than one degree of inclination and a stick-up tolerance of +/- 3.9 in (10 cm). Timeframe was also tight. InterMoor had to fabricate and install 15 of the conductors in 365 contract days with 160 of those days used by the pipe supplier to fabricate and deliver the pipes to Morgan City, La., USA.
InterMoor manufactured all 17 of the 36 in (91.44 cm) conductors at its Morgan City, La., USA, facility to DNV-OS-F101 standards and client specifications. Engineering Critical Assessment (ECA) studies determined whether a given flaw was safe from brittle fracture, fatigue, creep or plastic collapse under the specified installation and service life loads. InterMoor inspected all conductor welds using Automated Ultrasonic Testing (AUT), a very sensitive non-destructive testing system. A special configuration for the AUT equipment was required and specifically designed for this project due to the J-bevel joint profile, 1.5 in (3.81 cm) pipe thickness and allowable flaw sizes defined by the ECA study. InterMoor designed and fabricated five individual templates in cooperation with Claxton Engineering and the InterMoor survey and fabrication team. Each of these 35-ton templates measured 78.7 x 14.8 x 4.9 ft (24 x 4.5 x 1.5 m), and each guided three conductors.
Seventeen conductors and five templates were fabricated, inspected and approved at InterMoor’s Morgan City, La., facility. The offload in Brazil was performed incident free two days prior to the arrival of the installation vessel. InterMoor then began the high-level logistical process of the safe transportation of these materials to Rio de Janeiro, Brazil. The barge, Muliceiro X, was used to transport and launch the conductors. The barge was modified by the installation of a custom shuttle system that elevated and transported each conductor to the barge’s side. The conductors were connected by a tow line to the installation vessel and side launched from the barge by the shuttle system. The conductors were pre-installed before the arrival of the drilling rig.This technique had been applied in deepwater once before and proved to be beneficial. The pre-installation of the conductors enabled the utilization of lower cost platforms to support offshore installation and also prevented the operator from paying drilling spread rates which allowed additional cost savings. All 15 conductors were batch set in one field visit, this required only one hammer launch. InterMoor used the MENCK MHU 270 T deepwater hammer spread. The hammer drove all conductors in one session and was recovered. This approach saved substantial time offshore and minimized risks. Installation was completed in the first quarter of 2012 after removal of the templates and final as-laid survey. A final as-laid survey confirmed that all conductors were correctly installed inside the tolerance, inclination and stick up.
This project was successful in all aspects: finance, logistics, time, operations, mechanics and especially Quality, Health, Safety and Environment.