Mariculture farm on offshore oil and gas platforms

MOST of the offshore oil and gas platforms in Malaysia are built to last for approximately 25 to 30 years. The decommissioning of platforms is expected to be scaled up between 2013 and 2015, as 600 of the 900 offshore platforms are over 20 years old.

With the cost of decommissioning a conventional medium-sized structure at approximately US$3 million, oil companies are keen to find alternative options such as using the decommissioned platforms for other purposes such as marine culture, hotel and diving resorts, artificial reefs and rigs, marine research centres and control centres. Some of these ideas have been applied successfully, an example being the Seaventures Rig Dive Resort at Sipadan Island, Sabah, which was a platform turned into a hotel resort and diving centre.

The concept of using decommissioned oil rigs for mariculture (deep-sea fish farming) is realistic. The platform serves as an operational hub where all facilities related to farm fishing and crew are provided. It can easily support quarters for crew, storage for food and other supplies, docking facilities and a monitoring spot.

Besides reusing part of the structure as an operational hub, the structure of the platform can be used and manipulated as an anchor for mooring cages and nets near the platform. The structure can also be used as a hatchery, which will reduce transportation and operational costs. Indeed, the options are quite extensive.

Due to biological reasons, offshore mariculture on platforms help ensure clean and unpolluted oceanic water. Seawater surrounding offshore platforms or water at a distance of 3km from shore has low nutrition value and this characteristic is beneficial for fish farming as it reduces potential algae and phytoplankton bloom as well as other dangerous bacterium. This is beneficial especially in protecting the seawater and marine creatures from pollution and disease caused by bacterium.

In addition, the condition of seawater at most offshore platforms will promote less pollution due to the slow rate of sedimentation of pellets compared with onshore farming. The growth rate of marine species will also be rapid due to the constant year-round temperature and salinity. In addition, there is the capability to raise high-value marine species and greater harvest density due to higher dissolved oxygen rates. Financially, there are no pumping or aeration costs involved.

In general, fish farming activities do not require a high amount of energy, which means the energy required to operate the farming can easily be generated by using alternative energy such as wind, solar, tidal, wave and vortex-induced sea current. Since the farm will be located offshore in deep waters, the farm can be operated with minimal human interaction and will be able to internally generate required amounts of energy to support its operations for a considerable period of time.

At most offshore platforms, wind is available in a very high density in addition to having wind turbine structures that support the platforms. Therefore, the high cost for building wind generator structures can be reduced.

The climatic conditions in Malaysia are favourable for the development of solar energy. The key advantages of photovoltaic cells are that they can be integrated into platform structures so that no extra space is required, and as they are modular in nature, systems of any size can be installed depending on the demand. These benefits could be very beneficial to oilfield platform operations due to limited space and flexible power demands.

In addition, the solar panels can provide shade from sunlight. Such shade might be required for fish fry or for some other fish activities such as breeding. Vortex-induced energy can be generated using sea currents. It uses the physical phenomenon of vortex induced vibration in which water current flows around cylinders inducing transverse motion.

Multiple aquaculture activities with multiple types of fish can be integrated into a single platform operation including fish farming, oyster, mussel and seaweed depuration. Basically, these integrated activities require larger areas of farming systems to prevent diseases spreading between each farmed species. It also involves larger fish caging areas and more complicated managing systems as well as more facilities to support the activities. Integrated systems of alternative energy technologies for sustainable operations will also be required.

A research team from Curtin Sarawak comprising Dr Sharul Sham Dol (project leader and Department of Mechanical Engineering head), Dr Lisa Marie King (senior research fellow at Curtin Sarawak Research Institute) and Lim Chye Ing (mechanical engineering lecturer) and Dr Ulugbek Azimov (Northumbria University, United Kingdom) is currently working on a project to breathe new life into decommissioned offshore oil platforms by turning them into mariculture facilities.

The project team published and presented their preliminary study at the Science and Engineering Technology National Conference in Kuala Lumpur in July last year. Initial discussion has also been made with the local platform owner on the possibility of collaboration. They also hope to collaborate with oil and gas companies in the region as well as companies involved in aquaculture and mariculture businesses on the project.

Dr Sharul Sham Dol is Mechanical Engineering Department head at Curtin Sarawak’s School of Engineering and Science.