DUPLICATING NORTH SEA LIVING QUARTERS SAVES GULF OF THAILAND PLATFORM COSTS

Pierre Guyonnet Total Oil Marine plc London To save costs and increase comfort, the living quarters for the Bongkot, Gulf of Thailand, offshore development project were based on designs proved on the North Sea's Alwyn North project. The Bongkot accommodation platform is about 180 km (112 miles) southeast of the Erawan gas field, 150 km off the eastern coast of Thailand, and 180 km northeast of the town of Songkhla. Bangkok is 600 km to the north (Fig. 1).

May 3, 1993

9 min read

Pierre Guyonnet
Total Oil Marine plc
London

To save costs and increase comfort, the living quarters for the Bongkot, Gulf of Thailand, offshore development project were based on designs proved on the North Sea's Alwyn North project.

The Bongkot accommodation platform is about 180 km (112 miles) southeast of the Erawan gas field, 150 km off the eastern coast of Thailand, and 180 km northeast of the town of Songkhla. Bangkok is 600 km to the north (Fig. 1).

Two remote wellhead platforms (WP2 and WP3) and a floating storage and offloading terminal (FSO) are 3 km north of the Bongkot production center (Fig. 2). The center includes a wellhead platform (WP1) connected by a two-level bridge to the production platform (PP).

The production platform is designed to handle 300 MMscfd of natural gas. Process and compression facilities are on the northern side segregated by a fireproof wall from utilities and offices on the south side. From there, a two-level bridge leads to the living quarters platform, which has a helideck.

Production is expected to start in July.

Total Exploration & Production Thailand (30%) is operator of the Bongkot field on behalf of a joint venture consisting of Petroleum Authority of Thailand Exploration & Production (Pttep; 40%), British Gas Thailand (20%), and Statoil Thailand (10%).

Total Oil Marine plc holds a 331/3% interest and operates the Alwyn North field. The remaining 66 2/3% interest is held by Elf Exploration UK plc.

ACCOMMODATIONS

As defined during the conceptual design of the offshore facilities, field operations required accommodations for about 100 persons on a dedicated platform, bridge-linked to the production platform.

At first, the design of the living quarters platform was based on the classic floor layout with bedrooms at the periphery, and most of the common shower and toilet facilities in a central position. Moreover, each bedroom was designed to suit the number of occupants; i.e., for one, two, or four persons, depending on the position in the organization and the duration of stay offshore.

Only a few cabins were equipped with private shower and toilet facilities. This design was typical of what was commonly available on most floating or fixed offshore accommodations.

After finalizing this scheme, the efficiency ratio, which is the useful area for accommodation divided by the total fabricated floor area, was calculated and compared with the ratio corresponding to the living quarters module recently commissioned for the Alwyn field in the North Sea (Fig. 3).

The Alwyn living quarters were designed along an entirely different concept. There, all rooms are identical. Each is equipped with two fixed beds for normal occupancy, and one foldable bunk that can be lowered for peak occupancy. Also, each room has access to one small toilet/shower block.

The comparison of efficiency ratios surprisingly showed a slight advantage for the more comfortable Alwyn design when calculated for normal occupancy, but a much more significant advantage for peak occupancy. The Alwyn design was the only one that offered 50% extra capacity for peak occupancy.

This result led Total to analyze the benefits for using the more comfortable and proven Alwyn design but still build the living quarters at less cost than the standard design.

The Alwyn living quarters, after a very meticulous design, had been in operation for several years; therefore, operational experience was available. The quarters had an excellent reputation among all users. At the same time, it was not an old fashioned design, and both the designer (Doris Engineering) and the company architect were available.

The 200 personnel normal capacity of Alwyn was easy to adjust to the 100 personnel normal capacity required for Bongkot. The similarity of all bedrooms, together with the concept of prefabricated bathroom units, made it an excellent candidate for low construction cost.

After the analysis it was clear that duplication of the Alwyn design was better and would cost less.

The Bongkot living quarters (Fig. 4) are an integrated deck, 1,600 metric tons lift weight, that includes the quarters and support utilities, i.e., helideck, water production and storage, emergency generators, fire fighting equipment, and life boats.

The topsides cost of about $30 million includes engineering, procurement, and onshore fabrication. This represents about 10% of the overall project cost, excluding drilling.

Table 1 compares the Bongkot and Alwyn North projects.

OCCUPANCY

For short periods of time, the Bongkot field will have a higher level of activity that demands additional capacity for the living quarters. This can happen when a field starts up or during large maintenance programs when a large number of vendor representatives and construction personnel need to be housed.

Living quarters very often are designed for normal occupancy only, and extra personnel have to be accommodated on a crane barge or a "floatel." The drawbacks are the availability, the cost of mobilization, the cost of running floating accommodations, and the risk of maintaining a floating vessel alongside a fixed platform.

The proposal to design the Alwyn living quarters for a 200 person normal occupancy and 300 person peak occupancy was welcomed by the operations division because it increased flexibility without significantly affecting the operating cost.

The limited additional capital cost for additional peak occupancy was more than offset during the first year of operation. Because there is a foldable bed in each room and all services and safety systems are in place for peak capacity, everything is available to increase manpower. The only additional expense is a minimal increase in the catering crew.

Additional space and comfort for the occupant is available under normal occupancy. This is one incentive for returning as soon as possible to normal occupancy levels.

COLOR

The selection of a color scheme is usually not made by the designer. Typically, many color possibilities are explored and then a number of themes are chosen for each area of the living quarters.

To approach the real colors, shape, pattern, and size, each theme is shown in graphical form using as many selected samples of material and fabric as possible.

The first proposals are presented to several small groups of future users. Comments are then incorporated and the final proposals presented to the company management and to the partners for a decision.

For Alwyn, the proposal included one distinct color code for each floor. This was to ease identifying the location and ultimately to increase the comfort level for moving around the living quarters.

The final selection, from the top floor down were:

Blue-The helicopter reception room
Green -One bedroom floor
Orange -The other bedroom floor
Red-The kitchen, restaurant, and recreation room floor
Brown-Services, change room floor.

To everyone's surprise, the Bongkot partners did not completely favor the color scheme selected by Alwyn management for each of the bedroom levels.

For both Alwyn and Bongkot, green was regarded as peaceful and graceful. But the opinions were dramatically different for the other two alterative colors, orange and blue.

For the middle of the northern North Sea on Alwyn, there was a clear preference for orange that was considered as giving a cozy and warm atmosphere. Blue was not retained because it was felt to be too cool.

But for the middle of the Gulf of Thailand, the preference of the Thai partners was immediate and unanimous in favor of blue. They praised it for creating a comfortable and cool environment. A definite asset when the outside humidity approaches 100% and the temperature is greater than 30 C. (86 F.).

LIVING QUARTERS

The living quarters design starts by identifying the required functions. Early on, it was established that Bongkot was very similar to Alwyn and that almost all the conclusions of the studies made for Alwyn were readily applicable to Bongkot.

The main functions and their respective locations (Fig. 5) for Bongkot can be summarized as follows:

Bedrooms, located on two floors, Levels 3 and 4, have to be isolated as much as possible from noisy areas (helideck on Level 6 and diesel fire pumps and emergency generators on Level 1).

Kitchen, food storage, restaurant, and main recreation room are, for logical reasons, on one floor on Level 2 with easy access to the production platform office (same level). This area is considered as a quiet area and can be used as a buffer between the services area on Level 1 and the bedrooms on Level 3.

Services such as the heating/ventilation/air conditioning (HVAC) plant, the water treatment plant and pumps, the diesel fire pumps, and the emergency diesel generator were all regrouped on the lowest floor, below the kitchen/restaurant. This was as close as possible to sea level (pump shaft and heavy mechanical equipment) with easy access to the production workshop and warehouse.

Access from the floor, classified as a "dirty area," to the upper floors, classified as "clean areas" (restaurant level, bedroom levels), is through a change room where greasy overalls and boots can be left and showers taken. Lifeboats, which are as close as possible to the sea, are located on the lowest floor.

The helicopter reception, telecommunications, and sports room are on Level 6 below the helideck and serve as a buffer for the bedroom floor, located below.

The helideck on top has standard landing and safety equipment as well as refueling facilities. To reduce the volume of hydrocarbons on this living quarters platform, jet fuel and the associated pumps are located on the production platform. Jet fuel is delivered through a fixed closed-loop stainless steel piping system.

BEDROOM LEVEL

The two bedroom levels, and all 25 bedrooms on each level, are identical. This enabled a lower-cost design, procurement, and fabrication as well as easier maintenance.

Each room has two fixed beds that correspond to normal occupancy. A third, foldable bed can be placed in each bedroom for peak occupancy.

The room equipment is designed for three persons. This allows more comfort for normal occupancy.

Each room is equipped with a shower/toilet block which is fabricated and fully equipped in the factory. All piping connections (hot, cold water, and drainage) are accessible from the corridor outside the bedroom. This permits easier connection, testing, and maintenance.

Before fabricating living quarters, a normal practice is to assemble a mockup cabin. This costly and time-consuming exercise was not necessary for Bongkot because of the existing 106 identical cabins on the Alwyn North platform.

For the restaurant and kitchen level design, a systematic study of Alwyn led to the Bongkot layout. Flows of personnel, food, and waste are straightforward, rational, and never cross one other (Fig. 6).