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Offshore operations

The main source of work for MEP contractors in the Gulf region originally came from the oil and gas industry. With work in this sector still going strong, just how do installations differ from those in construction? Alison Luke goes offshore to find out.

ANALYSIS, MEP

Known worldwide for its oil and gas industry, the offshore rigs in the Gulf remain a symbol of the region. Floating metal villages with giant drills seeking out oilfields below the seabed, the construction of these structures requires specialist techniques and integral to the success of their operation is the MEP services.

To maintain 24/7 operations safely and effectively, rig occupants must be assured of a continued supply of fresh air, water and power. And perhaps even more essential, the MEP services on a rig provide a means of ensuring the drilling equipment remains operational at all times by maintaining critical conditions. But how do these installations differ from their onshore counterparts?

Nothing can fail on the rig. You have to have redundancy, especially with the air conditioning.

Safety, standards, redundancy and co-ordination are key aspects to an offshore MEP installation explains Jean Pierre Halin, senior projects manager with Thermo Offshore and Industrial Division. Standing aboard the Thule Power rig in Sharjah's Hamriyah free zone, the first thing that strikes home is the huge scale and volume of equipment involved and the compact area in which it is all installed. Valves measuring up to 900mm diameter join air conditioning pipework and a reverse osmosis desalination plant producing 2000l of fresh water daily is positioned alongside the drilling floor on the 53m triangular rig.

Thermo won the contract for the installation of heating, ventilation and air conditioning (hvac) on the project in competitive tender. A large proportion of the firm's installation services the rig's two accommodation blocks, however its scope of works also includes ventilation for the machinery floor, engine room, transformer room and the central switchgear room, as well as air conditioning for the driller control room.

Owned by Norwegian firm Thule Drilling, Thule Power is a rebuild of the salvaged AD19, a 25-year old rig that previously operated in the Gulf. "[Rebuilding] is cheaper than building a new rig," explains Tony Kettlewell, project manager for main contractor QGM Group. The central structure has been kept, but the overall rig has grown in size and sophistication from its original form. "We have increased the size of the rig to add more deck load and accommodate more equipment and we have modified the drilling package," explains Kettlewell. "When it's finished this will be state-of-the-art in its own field and will be capable of drilling at greater depths."

The 6,000 tonne rig has a 1.2 tonne drilling derrick and tower that is attached to a cantilever section. For safety, this slides clear of the main deck during drilling. It can be sited in water of up to 71m deep and will be able to drill to depths of 9144m.

"You need some serious equipment to access the deeper [oil] reservoirs," explains Kettlewell. "Once you perforate that reservoir the oil is 1500°C and under pressure...the cantilever here must be capable of taking 1.6 million pounds of pressure," he adds. Also essential for this section of the rig is closely-controlled temperatures and fresh air supply in the drilling control room. To ensure this, two 35TR air handling units serve the room on a 100% standby basis. "This room must be kept in positive pressure incase of any gas leaks," explains Halin. This is to protect the drill operator's safety, but also to ensure that no equipment is damaged.

"We have people to keep cool, but more importantly there is essential equipment that can only operate under certain temperature criteria - and even more important, the control systems for these systems must be protected," states Kettlewell. The reasoning behind this is the need for autonomy during operation; when at sea the amount of maintenance possible will be limited - and costly. "Nothing can fail on the rig. You have to have redundancy, especially with the air conditioning for the main switchgear and areas like that," stresses Halin. "While the rig is drilling nothing can stop it, because depending on the depth being drilled they can lose all of the drill and that costs millions, so can be very harmful financially."

The rig is based on the Friede & Goldman Super M2 design, which features a layout with accommodation areas ‘wrapping around' the forward leg to give more deck space and a more efficient facility. Divided into two three-storey blocks connected by two bridges, the accommodation for 105 personnel is sited on the opposite side of the rig to the main drill floor.

The products and installation methods used for the hvac services on the rig are similar to those on a ship. All products must be to marine-grade specifications to counteract the environmental conditions to which they will be exposed. To ensure safety, certain products are also explosion and fireproof. "Some zones are classed as hazardous areas because of the possible existence of hydrocarbon gases," explains Halin. A comprehensive sensor and alarm system for gas and smoke ensure safety throughout and a ‘cascade' system provides a safe supply of oxygen for workers to plug masks into should a leak be detected.

The distribution of services had also to be carefully considered: "For the marine industry the rules and regulations are far more stringent in terms of installation," stresses Kettlewell. "[The rig] is treated as a ship so, for example, if the ventilation ductwork goes though compartments you must make sure that each penetration is watertight, otherwise if water does flood one area the rig will sink like the Titanic."

Within the accommodation block the main distribution route is above ceiling in a central corridor. Fresh air is fed into each room from above ceiling units then exhausted through a grill in the door and via a main exhaust in the corridor. This airflow pattern is again to ensure the health and safety of the onboard operatives. "We have to keep a positive air pressure in the bedrooms; this is to avoid humid and warm air entering, but also to keep any potential leaking gas outside the rooms. There is a 24/7 operation on the rig so we must make sure that the air is kept clear for the people sleeping," stresses Halin.

The division of services into several small hvac and electrical systems each serving a dedicated area ensures continued use of the accommodation blocks. "There is a non-centralised system, so only a quarter of a floor would be affected if there was a problem with the air conditioning or power," explains Halin.

"Safety is the most focal part of any of this work," adds Kettlewell. "Maritime, industrial and offshore standards, plus rules for safety of life at sea and for the protection of people are applied. [MEP installations are] driven by rules and regulations regarding the number of men in a room and the lighting lux levels needed, for example. We have to meet all of these regulations fully in order for the rig to be permitted to leave the jetty and be used," he stresses.

There are three main standard organisations for rig building: The American Bureau of Shipping (ABS), Norwegian-based DNV and the UK's Lloyds Register of Shipping. Thule Power is being built to ABS standards and daily checks are made by an on-site ABS engineer to ensure conformity. In addition, all work carried out on the rig must meet several other sets of standards.

Environmental regulations are also enforced. For the hvac system, one if these is the use of refrigerants. "Our operatives are specially trained concerning environmental protection in the use of refrigerant gases. We are equipped to recover the gases for official disposal," explains Halin. Gases of particular concern are those refrigerants such as R22, the use of which is now banned or restricted in many countries. As well as ensuring the environmental impacts are minimised, this is important when seeking work. "If the rig is to be used in a country that has signed the Kyoto Protocol, the systems must meet these standards," Halin explains. A firm found illegally venting such gases may find itself banned from future work on oilfield projects.

Fitting the services

The need for upfront designs and co-ordination between members of the construction teams were vital on the project. The main structure had to be largely complete prior to installation of the hvac services beginning, which meant all distribution routes and location of plant and equipment had to be agreed early in the process.

"If you don't have proper co-ordination on a project like this it can't be done, because everything is much tighter than in an onshore building," stresses Halin. "You have false ceilings, but they may only be 30cm deep and you have to pass everything in there, so if you don't have the proper co-ordination you will have clashes everywhere, which is a waste of money and a waste of time."

Co-ordination was carried out using AutoCAD; each subcontractor supplied their installation drawings to the main contractor and these were superimposed to ensure clashes were eradicated at design stage. Once installation began, with working spaces tight, co-ordination was just as vital. "Most of the time we ask for priority for the MEP services, especially in tight spaces...we dealt with space issues by designing the ductwork first then adding the pipes and finally the cables," explains Halin. "Co-ordination is quite a heavy cost initially, but if you do it well at the beginning it pays at the end," he adds.

Ductwork was prefabricated onshore in sections of up to 2m diameter and 1.5m long, with ductwork walls ranging from 3-12mm thick depending on the area in which they were used. These were craned in sections from the adjacent jetty. Many of the products used were sourced from Europe and the USA, with lead times of six to eight weeks for standard products and 12-14 weeks for the more specialised explosion-proof equipment.

At peak Thermo had around 100 staff on the project. With around 80 permanent staff in the division this meant the firm had to recruit additional operatives. The solution was to engage staff from owner group Thermo's construction division in Dubai. "The extra staff are mainly used for helping the permanent operatives," explains Halin. "They are not specifically skilled for rig work so we mix them in groups with our full-time staff." All staff are given intensive health and safety training and this is continuously updated.

Thule Power is due for completion in August 2007. Saudi Aramco has already signed a five-year contract to lease the rig.

Project: Thule Power

Client: Thule Drilling

Main contractor: QGM Group

MEP contractor: Thermo Offshore and Industrial Division

Contract details

Tender date: September 2005

Construction start date: June 2006

Contract period: One year

Completion date: 31 August 2007

Suppliers

Air conditioning: Carrier

Controls: PLC-TSG

Ductwork: Gmamco

Extract fans: Airtrade, Rucon

Floor grilles: Technalco

Insulation: Kimmco

Pressurisation: Carrier

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