The Virgo platform is one of the newest additions to Gulf of Mexico production facilities.
The platform sits in 1,130 ft of water in Viosca Knoll Block 823. Only three other fixed conventional platforms have been set in deeper water.
Elf Exploration is project operator. Coastal Oil & Gas Corp., Nippon Oil Exploration USA Ltd., and Pogo Producing Co. are partners in the development.
Enercon Engineering Inc., Houston, provided the conceptual and detailed designs for the four-leg, 12-skirt pile, drilling and production platform, which can handle 200 MMscfd of gas and 15,000 b/d of oil and condensate.
Enercon supplied the following description of the sequence of events covering the load out at Aker Gulf Marines's fabrication yard at Ingleside, Tex., near Corpus Christi, Tex., and the on-site platform installation:
- Aug. 2, 1999, 7:00 a.m.-Began pulling the 25,000-ton Virgo jacket from the Aker Gulf Marine fabrication yard onto the Intermac-650 launch barge.
- Aug. 4, 11:00 p.m.-Finished pulling jacket onto transport barge.
- Aug. 5, 8:00 a.m.-Template and pile barge departed the Aker Gulf Marine fabrication yard, arriving at the Viosca Knoll 823 location at 7:15 a.m. on Aug. 7. Installation began shortly after arrival. Template installation went according to plan.
No problems were encountered in engaging the template and stabbing it over the existing wells. The template sat level on the seabed, as verified by a remote-operated vehicle (ROV) readings of two bulls-eye level indicators. After docking piles were driven to grade, the template was retrieved and shipped to shore.
- Aug. 10, 8:45 a.m.-Virgo jacket departed from the fabrication yard (Fig. 1) and arrived on location on Aug. 14. After the jacket arrived, launch preparations began. Ballasting of the Intermac-650 launch barge began on Aug. 15 while pulling the jacket to the stern of Heerema Marine Contractors' semisubmersible crane vessel (SSCV) Balder.
The Balder is capable of a tandem lift of 6,300 tons and has an overall 154-m (505 ft) length and 86-m (450 ft) breadth.
- Aug. 16, 6:30 a.m.-Finished launch ballasting and cutting the sea fastening. The jacket was successful launched at 7:30 a.m. The floating attitude agreed with Enercon's original design. The jacket upending sequence started later in the morning.
- Aug. 16, 10:30 a.m.-Completed rigging the jacket to the Balder (Fig. 2), after which it was ready to be upended.
- Aug. 17, 7:00 a.m.-Stabbed jacket over the wells and set it on bottom.
- Aug. 17, 10 p.m.-Began lifting piles. The weather was good and the seas were calm while the crew prepared the pile-driving hydraulic hammers.
- Aug. 22-Finished driving-in the initial four piles to penetration and activated the gripper system, thus adding an additional level of protection against seasonal storms.
- Aug. 30-Finished driving all 12 piles. This was followed by the next phases that involved grouting operations using an ROV hot stab and umbilical system, and installation of the well conductors. The hot-stab packer inflation-grout system worked well. Grouting operations progressed without any delays. Well conductor installation went smoothly with all seven conductors installed to their design penetration by Sept. 11.
- Sept. 8-Load out the 4,000-ton Virgo production deck from the Aker Gulf Marine fabrication facility.
- Sept. 12, 3:00 a.m.-Brought deck, onboard the MWB403 transport barge, to the stern of the Balder.
- Sept. 12, 10:40 a.m.-Lifted deck with the Balder. Once on the hook, the barge was removed and the Balder winched itself to position the deck just over the jacket (Fig. 3).
- Sept. 12, 12:00 noon-Finished setting deck on jacket. During the following 3 days activities included: welding the deck, and installing the flare and drilling rig (Fig. 4).
- Sept. 15, 3:00 a.m.-Completed final acceptance walkthrough, followed by the signing of the platform acceptance certificate.
- Sept. 16-Pulled anchors and demobilized the Balder.
This was followed by drilling rig and facility hook-up tasks.
Initial production was expected in November 1999.