U.K. Block 49/24a

Landmark: Early Use of 13-3/8" Drill-Through Wellhead System

Project Overview

• Contract Award: 1994
• Sales: Dunfermline, U.K.
• Fab. Trees: Dunfermline, U.K.
• Fab. Controls: Kongsberg, Norway
• Service Base: Aberdeen, Norway
• Host Type: Platform
• Contract Type: EPCI

Project Characteristics

• No. Trees: 3
• Water Depth: 30 m (100 ft)
• Tree Type: Vertical
• Tree Pressure: 5,000 psi
• Tree Bore Size: 5"x2"
• Hydrocarbon: Gas

Project Ownership

• ExxonMobil 50%
• Tullow 50%

Scope of Work

• Three (3) vertical 5"x2" 5,000 psi subsea trees
• Three (3) subsea control modules
• Vertical wireline access through annulus valves
• 13-5/8" 5,000 psi subsea wellhead systems
• Diver-assist trees
• External mechanical tree cap
• PSL-2 FF trim with CRA-protected seal surfaces
• Electro-hydraulic control system
• System integration testing, installation assistance, service and maintenance

Comments

Located in the Southern Sector of the North Sea, the Gawain project was a joint effort between Arco and Mobil. The wells were drilled and completed near a shipping lane, and therefore needed an overtrawlable fishing structure. The wells were drilled and completed with a jack-up rig and tied back to the Thames platform with a single 12" flowline approximately 15 km (9 miles) long.

The subsea drilling and completion hardware were completely concentric designs allowing for uninterrupted drilling and completion operations. The tubing hanger incorporated a concentric sliding-sleeve annulus valve and the ability to control the downhole SCSSV.

The project was one of the first EPCI contracts in the North Sea with Brown & Root and E.M.C. as the major joint-venture partners.