December 2004 Supplement    New Rig Designs

Flexible and modular drilling rig

FMWR-ES 1250 workover rig for well depths of 24,000 ft, to be installed on offshore jackets with a light crane.

France’s EIFFEL Construction Metallique will deliver to Eni Gas BV, from its yard in Fos-sur-mer, a workover rig for the Western Libyan Gas Project (WLGP). Designed by Sofindel, following the concept of a new drilling/ workover rig model called Fast Moving Workover Rig (FMWR-ES 1250) (FMWR), the compact rig has a footprint of only 12 x 30 m, depending on cap beam spacing, and an overall dimension of 28 x 36 m, that is both flexible and modular. The FMWR is intended for production and maintenance functions in two areas of application: workover operations on existing shallow offshore stationary platforms such as in the Persian Gulf and Lake Maracaibo, and combined oilfield developments. Its compactness allows installation on existing platforms and its flexibility does not require heavy logistics.

The rig’s design allows access to vertical or deviated wells of depths up to 24,000 ft (7,300 m). It can be mobilized/ demobilized via light crane and delivered by supply boats, for producing wells previously drilled and basically completed by a floating rig prior to jacket installation. The new rig then performs all workover operations and well connections, installs production pipes and carries out reworking drilling operations. Fully autonomous, the rig does not need assistance of a tender that immobilizes one side of the jacket, thus disrupting production facilities.

To be mobilized/ demobilized quickly with a light crane, the rig comprises a number of packages with limited weights. The objective is to demobilize the rig at the end of the campaign and replace it with a “killing unit” to ensure well safety and, at the same time, use it on other fields and mobilize it once again for specific operations. The rig is equipped with complete drilling instrumentation, telecommunication and gas detection systems, fire detection and an alarm system corresponding to safety requirements.

The operator concluded that a workover rig responding to these characteristics would save more than four months of the initial start up schedule for the platform and reduce capital expenditures by more than US$38 million, while providing a rig for other operations. The FMWR rig comprises four principal modules:

1. The electrical power plant and utilities (fuel oil, pressurized hydraulics and air)
2. Sludge tanks and return sludge treatment comprising the drillfloor support
3. A high-pressure sludge pump module serving as support for the rig’s own crane, and
4. A workstring support provided by the sludge tanks and the sludge pump’s structure.

Principal rig characteristics are:

• Mud tank capacity: 1,500 bbl
• Mud fabrication performance: two hoppers, each 175 mt/hr
• Drawworks: 250 mt hook capacity
• Mast capacity: suitable for 3-in. and 5-in. drill pipe
• BOP handling with double system of transfer, suitable for one BOP 11-in., 10,000 psi or 13-5/8-in., 5,000 psi
• Full communication, fire/ gas, alarm system
• Drilling shelter equipped with remote brake, full rig instrumentation and BOP panel
• Pipe rack capacity: 180 mt, suitable for Range 2 casing.

Development of existing fields requires rigs that are more high performance in terms of capacity without necessarily resorting to Tender Assisted Rig types. The FMWR ES 1250 responds in part to this market segment. The concept is the subject of a patent application.