BG Group's Mediterranean Scarab Saffron project was a class example of deepwater completions at the limit. An estimated savings of US $20 million were made by optimizing working practices during the completion phase of the project.

The project featured a long distance tieback to shore from eight gas wells in water depths ranging from 1,312 ft to 2,132 ft (400 m to 640 m). Well completion work involved a fast learning curve with several days of work saved on the last well in the program and massive savings in cost.
Omar Y. Mohamed, James G. King of Baker Oil Tools and El Metwally W. Toubar of Rashpetco explained how.

Scarab and Saffron were completed for the Burullus Gas Company - a joint venture between BG (25%), Egyptian Government Petroleum Company (50%) and Petronas (25%) - in late 2002 in the West Delta Deep Marine (WDDM) concession area in the Mediterranean Sea off Alexandria. The project marked two significant advances for the Egyptian offshore industry, as the first major deepwater gas development, and the first advanced subsea project.

"The learning curve was scaled quickly with the last of the eight subsea completions being run in less than 14 days and resulting in estimated savings of more than $20 million in overall drilling and completion costs," Mohamed, King and Toubar reported.

BG Group adopted best industry practices to achieve it. "The success of the project owes itself to the BG Group's total value drilling initiative," they said, plus best in class performance from Baker Oil Tools.

This was partially achieved by optimizing well design to cut operational sequences and reduce required rig time.

Also learning gained from the operation is due to be used for a new well campaign commencing mid 2004, as BG and its partners further develop the WDDM area.

The Scarab and Saffron wells, five on Scarab and three on Saffron, presented a challenge in that daily operating expenses for completions were put at $200,000.

Development of the fields featured vertical wells completed at total vertical depths (TVD) ranging from 5,906 ft to 6,890 ft (1,800 m to 2,100 m). Production design rates needed to be over 100 MMcf/d of gas for deliveries of between 70 and 100 MMcf/d of gas.

Standardized equipment was required for reliability, and for success, the project also required 20-year well life completions. Well designers had to overcome openhole shale instability, sand control sections for unconsolidated formations; gravel packing in openhole completions, the facility for reservoir isolation after installation of the sand face completion and for landing uphole completions subsea.

Work began early 2000 by Baker Oil personnel on the well completion design, using reservoir characteristics, production and operational requirements as the starting point. Actual completion operations began April 2002, using openhole gravel packs for sandface completions to provide high flow rates and to prevent sand production.

Reservoirs in Scarab and Saffron are unconsolidated and highly permeable Plio Pleistocene sands of 1,000 md to 1,300 md.

"Data obtained from logs and wells tests showed the formation would produce sand even at low drawdown pressures. Therefore the need for sand control was an integral part of the design," said Mohamed et al, writing in Baker's In Depth magazine.

One of the development's primary lessons was to minimize risks with openhole section shale instability. To tackle this, modified brine was use to carry gravel, and Baker's proprietary DirectPak alternate path screen was used.

One of the major reasons given for the choice of openhole gravel packs were their previous successful application in other deepwater production wells, the large inflow and filtration rates possible. It provided 300 ft to 400 ft (91 m to 122 m) of 81/2-in. openhole and 51/2-in. screens, plus the reliability of this system coupled with the minimal drawdown pressure necessary to achieve the required high production rates.
Originally 36 days were budgeted for each well completion operation. Toward the end of the program, revised budgets varied from 32.06 down to 18.58 days.

On one of the Saffron wells, the revised budget was 20.98 days; the actual outturn was 15.04, saving 5.94 days.

From the mudline, the wells were completed with a horizontal xmas tree as follows:

• 7-in. or 51/2-in. 13 chrome tubing
• 51/2-in. subsurface safety valve
• 7 or 51/2-in. 13 chrome tubing
• 51/2-in. downhole pressure/temperature gauges and venturi flow meter
• 95/8-in. production packer
• 7-in. or 51/2-in. 13 chrome tubing
• 9 and 5/8 in. openhole gravel pack packer and extension
• RB bi-directional multi-cycle reservoir isolation valve
• 51/2-in. 13 chrome premium [sand] screens

A CS 300 openhole gravel pack system was deployed in the wells, to achieve hole stability and it is a tool already field proven in the North Sea and in deepwater offshore Brazil. The project also featured a mechanical bi-directional isolation valve in the gravel pack assembly. It was fitted between the gravel pack packer and screen to isolate the reservoir after gravel packing was completed.
First gas was delivered from Scarab and Saffron March 2003 with an initial daily contract quantity of 440 MMcf/d of gas. Production is exported via two 36-in. and 24-in. diameter gas pipelines approximately 56 miles (90 km) to shore.

Since then, Baker has been awarded further work by Burullus to tap more gas in the concesion area.

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