MODULAR DESIGNS HIGHLIGHT SEVERAL NEW RIGS

Keith Rappold
Drilling Editor

A new platform drilling rig for offshore Trinidad and two new land rigs for the former Soviet Union feature the latest in drilling and construction technology and modular components for quick rig up/rig down.

The Sundowner 801 was mock-up tested in Galveston, Tex., a few weeks ago in preparation for its load-out to the Dolphin field offshore Trinidad.

The rig will work under contract for British Gas plc for about 1 1/2 years. This lightweight drilling rig is designed for quick rig up and rig down without a derrick barge. The rig can be taken down, transported to another nearby platform, and rigged back up within a matter of days, according to builder Sun-downer Offshore Services.

Two other new units, UNOC 500 DE series land rigs, were recently constructed and mock-up tested in Ekaterinburg, Russia, for upcoming exploratory work for RAO Gazprom, a large natural gas producer in Russia. These rigs are unique in that they were constructed from new components made both in the United States and in Russia.

Rig builder UNOC Equipment & Supply LLC is a partnership of three oil field equipment manufacturers, two from the U.S. and one from Russia.

PLATFORM RIG

The Sundowner 801 platform drilling rig, built by Sun-downer Offshore Services, is a new minimum-area, self-erecting platform drilling rig with a modular design and lightweight components for quick rig up. The rig will work under contract in the Dolphin field for a British Gas plc/Texaco Inc. natural gas development project offshore Trinidad. The initial contract is for 554 days.

The Sundowner 801 is designed to work on any platform offshore Trinidad without modifications to the platform or the rig (Fig. 1)

This type of minimum-area, self-erecting modular platform rig has an average rig-up time of 4 days, and the average time from release on one platform to spud on another is 8 days.

MODULAR DESIGN

The entire package-cranes, rig, and quarters complex-have a modular design with no component exceeding 65,000 lb, thus eliminating the need for derrick barge mobilization which can cost as much as $1 million, according to Sundowner. The rig's modular components have controlled size and weight to allow mobilization using standard supply vessels.

With two 65-ton modular "bullfrog" cranes for mobilization, the average Gulf of Mexico rig-up time for Rig 801-from release from one platform to spud on another-is 58 days (not including travel time between platforms), according to Sundowner. Prior to each move, one bullfrog crane is engaged in preparing the receiving platform to accept the rig while the other crane disassembles and offloads the rig from the releasing platform.

Compared to an average rig-up time of 12-16 days for a typical platform drilling rig, this substantial advantage in mobilization time can reduce the operator's revenue losses resulting from the requirement to shut in production from platform wells during rig up and rig down, according to Sundowner.

The versatility in "footprint" options provided by the rig's modular design and the component packaging allows for rig up in a variety of configurations to match the platform space available and minimize costly relocation of deck-mounted production equip- ment. This assembly versatility also allows for variable load management if necessary. The drill floor can be rotated on the sub-base as dictated by platform layout.

The modular 85-man quarters package is 50 ff x 50 ft, weighs 108,000 lb, breaks down into five modules of 28,000 lb, and can support a Bell 212 or Sikorsky S-76 helicopter. The quarters modules are constructed of extremely light-weight, noise- suppressing, composite materials with a B-30 fire rating (OGJ, Sept. 11, p. 45).

The Sundowner 801 is equipped with dual-fuel, supercharged engines, each capable of developing more than 1,500 hp on diesel fuel (or a combination of diesel and platform gas). The engines will automatically switch to 100% diesel should the gas supply become inadequate. In natural gas fields, the use of platform gas instead of diesel for power could result in fuel cost savings up to $3,000/day.

The modular rig design and component packaging have resulted in significant weight reductions. The rig's total dead weight is about 1,300 kips, excluding the drill-string. The rig has 1 million lb net hook load capacity with a simultaneous set back of 600,000 lb.

The rig sub-base contains the active mud system tanks, brake water cooling tank, blowout preventer handling equipment, test stump, mud pumps, air compressors, and stairs. Elevated sub-base extensions accommodate shakers, mud cleaner, desander, desliter, and centrifuge.

The rig is equipped with an electric top drive with maximum torque of 50,000 if-lb and maximum speed of 185 rpm.

FSU RIGS

A partnership of three oil field equipment manufacturers has completed construction of the first purpose-built, land-based oil and gas drilling rigs made with new components from both Russian and American companies.

The partnership, UNOC Equipment & Supply LLC, built the two rigs which were purchased by RAO Gazprom,a large natural gas producer, for exploratory drilling inside the Former Soviet Union.

The rigs, classified as the UNOC 500 DE series, will be deployed in the Astrakhan gas condensate field located on the northern tip of the Caspian Sea in the Russian province of Astrakhan. The rigs are expected to begin drilling in the Astrakhan field in January 1996.

UNOC is a joint venture company, with principals Caterpillar Inc., AO Uralmash, and National-Oilwell. It was founded in 1993 to construct advanced drilling equipment and retrofit existing Uralmash rigs.

UNOC will provide training to the Gazprom drilling teams which will operate the rigs. The rigs will be maintained in the field by Astrakhanburgaz, a subsidiary of Gazprom. The rigs underwent a complete rig-up and testing in August at Ural-mash's Ekaterinburg plant (Fig. 2)

The rigs are capable of drilling to 6,500 m, and each has a self-elevating cantilever mast with a 500-ton hook load capacity.

In addition, the rigs are designed to operate in harsh weather conditions from -45 C. to 45 C., according to UNOC.

Each UNOC 500 DE rig has three 1,180 kw triplex mud pumps capable of circulating heavy mud for salt domes and other difficult drilling areas. Radiators from the engine/ generator sets direct heat via air ducts to the housing enclosing the mud pumps to allow them to operate in severe cold conditions.

The rigs also feature a transportable, modular design that uses hydraulic, electric, and pneumatic connectors for quick connect/disconnect for easy rig moves, according to UNOC. Each rig has a box-on-box substructure.

Both 500 DE series rigs are equipped with a combination Russian/American manufactured drilling system, engine/generator set package, and mud treatment system (Fig. 3)

. Each rig has a 700-mm (27.5 in.) rotary table.

Four separate diesel-fueled Caterpillar 3512 engine/gen- erator set packages provide a total prime power generating capacity on each rig of 3.86 megawatts (6,000 kva). The generator sets and silicon-con-trolled rectifier (SCR) system enable the rigs to run at variable speeds and to operate at remote locations where utility power is unavailable.

Each package includes a high-speed, 12-cylinder engine rated at 1,370 bhp at a continuous speed of 1,500 rpm, a Caterpillar SR4 brushless 667-v generator rated to produce 965 kw at 50 hz, and a cooling system to maintain proper engine/generator set temperature under extreme conditions. Each package is contained in a 30-ft modular steel enclosure for cold-weather protection.

National-Oilwell provided a customized ac control house to work with a Uralmash SCR diesel-electric distribution system to match power requirements for each rig's Russian and American components, and Uralmash provided semi-automated pipe handlers to improve tripping operations.

For environmental safety, each rig is equipped with a closed-loop mud treatment package, which includes a sophisticated encapsulation system to eliminate potential contaminants, according to UNOC.

To meet operating conditions, the package has a total capacity of 3,400 bbl. The primary mud system components include mud tanks shakers, desanders, desliters, centrifuges, encapsulation system, and heavy-weight roll system.