Subsea processing consists of a range of technologies for separation, pumping and compression that enable production from offshore wells without the need for surface facilities. Seabed processing systems have become increasingly accepted by operators as a solution to accelerate reserves, maximize production, and reduction costs. This maximization has led to the development of marginal fields, low energy reservoirs or reservoir with poor rock or fluid properties and multiphase boosting or combination of gas/liquid separation and liquid boosting has made this more economically feasible. Benefits can be found in later life reservoirs with high water cut that are produced into constrained topsides, in which subsea processing can lead to water re-injection by-passing water choke by backpressure to increase production. For example, reservoirs with main driving mechanism of water-flooding such as that in the Campos Basin in Brazil operated by Petrobas seek to use the subsea processing to tackle the increasing water content in stream once water breakthroughs.
Faced with such formidable conditions how do oil and gas companies operate at depths of 300 metres, or even 3,000 metres below the surface? The answer is subsea wells that produce hydrocarbons via installations on the seabed. With near-shore resources already well developed, these complex technologies are enabling us to take our pursuit for resources longer, further and deeper offshore.
Given recent advances in cost-reduction (compared to surface facilities), accessibility and efficiency, the use of subsea wells has increased. For example, half of Statoil’s production now comes from 500 subsea wells. Across the industry, analysts forecast global subsea hardware capital expenditure totaling $117 billion for the next four years – a growth of more than 80% over the preceding five years.
However, in comparison with conventional technologies, cost for equipment and operations have accelerated in recent years. In fact, as a result of the extraordinary growth of subsea, costs for installations have increased by 250% in the last 10-12 years. One of the main reasons for higher costs is due to operators working with suppliers on tailor-made solutions, on a project by project basis. Recognizing this issue, the industry is exploring standardization, which will deliver volume and drive down costs (excerpt from Statoil). We might see a move from the current point-to-point subsea powering systems to a high capacity subsea power grid in power distribution system architecture.
An example would be the AKPO field in block OML 130, 200km offshore Nigeria is in 1400m water depth. It is a gas/condensate field with high pressures and high temperatures. One of the greatest challenges is to ensure that condensate and gas in multiphase flow reach the production facilities without being stopped by hydrates and wax and scale deposition. The technical challenges alone are significant, but when set against the background of increasing oil prices and high commercial pressure on the suppliers from more than one operator and more than one field, the challenges take on a new dimension. Added to that for Akpo were the issues of resources of personnel and manufacturing capacity in a very buoyant market as well as the new challenge of manufacturing in Nigeria.
The second most important issue facing all Subsea decisions is the fact that the cost of installation - whether by Drilling Rig or by Installation Vessel - FAR exceeds (in most cases) the cost of the equipment itself. Added to that is the cost of the lost production. This cost is effectively tripled if equipment has to be retrieved and then re-installed. No Subsea Engineer ever wants to see their equipment return to the surface. Nevertheless - things do go wrong even on a single well - and in a system as large as Akpo, the opportunities for something to go wrong increase. Such is the inevitable nature of large Systems. The ability to recover and install was seen as vital. Design for installation was a vital strategy in the design process. This lead to design in order to minimize installation - and retrieval - costs. [2]
Standardization is the new song in the lips of the innovative juggernauts pushing this evenly gradually accepted subsea frontier in oil and gas exploration and production. The deep sea is a truly alien place where the temperature is close to freezing and for every 10 metres of depth you reach the pressure increases by 14.5 pounds per square inches. Divers rarely exceed 180 metres and if you want to go any deeper, submersibles, robotic or manned, become the only options [1]. Coming into deep water scenarios we can say that no two fields are the same and dealing with such high commercial pressures the industry is in dying need of a template, a set of client categorized models. At this stage we need a centralized knowledge bank with synergies made to full functionality when it comes sharing and implementation of experiences to tackle the rising challenges in moving the topsides to the seabed.
Industry collaboration
Successfully achieving standardization will depend on industry collaboration. Currently several joint industry partnerships (JIP) are underway, bringing together oil and gas producers focusing on various elements of subsea technology, including the interface, underwater grid, power solutions and more. The goal of these JIPs is to develop internationally agreed industry standards.
Collaboration to achieve standardization is innovation in an uncharacteristic form. Typical conceptions of innovation are limited to small and revolutionary start-ups, or large ‘game-changing’ technologies. However, for subsea, innovation is about ensuring the long-term feasibility of existing technology. In the world of subsea, standardization is the new innovation.
It's a stage in the evolution of overcoming new frontiers on the deep water end of this industry and the sooner standardization is birthed and accepted in future developments the earlier we can start to feel the economies of scale to a cost-benefit advantage.
[1] The FInal Frontier: Conquering The Seabed (2014) www.statoil.com
[2] AKPO: The Subsea Production System (2010) Stuart GrahamNelson (Total Upstream Nigeria)
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