Marine Technology Reporter Blogs - pumps

Atmocean’s wave energy system is unique in that each array of fifteen seawater pumps located up to 2 miles offshore produces pressurized water transmitted in a seafloor hose to the onshore turbine operating a generator. By using and underwater compressed air energy storage system a dramatic reductions in the net cost and availability of grid-scale energy storage is reached. Storing air at hydrostatic pressure, in equilibrium with the surrounding water allows the use of thin-walled storage vessels, and simpler, more reliable compressors. A simple, proprietary reversible air compressor runs at near-constant temperature and the heat of compression is stored in water and is restored during expansion of the air.

Water covers 71% of our world and holds a vast potential for clean renewable energy production. The American Society of Mechanical Engineers estimated in a 2010 report of Offshore Mechanics and Arctic Engineering, that there is an estimated potential of 3.7 terawatts of wave energy, almost double that of current world electrical consumption, yet although it may never be possible to harvest all this energy, very little of it has been harvested up to now. Waves are mainly created by winds blowing across the oceans. Waves are distinct from daily tidal surges created by the gravitational effects of the moon as the earth spins on its axis.

In any given subsea field there is a multitude of equipment, that need to be constantly monitored. Subsea Multi-Domain Condition Monitoring can be achieved by introducing additional hydrophones, specially designed for detecting sound from rotating machinery, subsea processing equipment, structural integrity, fluid flow rate variations among others. The latest high-end sensor systems ally acoustic condition monitoring with acoustic leak detection. This works in much the same way as surface-based acoustic emission monitoring and can be used to monitor rotating machinery to check speed tracking and resonant frequencies. It can also monitor rotational equipment in subsea plant such as bearing damage, unbalanced pumps, mechanical breakdown and reduced efficiency.

Enhanced Oil Recovery (EOR) can increase the volume of recovered oil from a well mainly through the use of two distinct techniques. One is water injection, which is increasingly being used in mature fields and another is CO2 injection which is mostly used in deepwater fields and according to Petrobras will be extensively used at many of the pre-salt fields in Brazil, as these fields usually contain significant amounts of CO2 along with oil and gas. These are secondary production processes. The production process always refers to oil that is recovered naturally from a producing well, that is without the use of pressure or flow stimulants, such as water or CO2.

Multiphase pump technology allows increased development of remote location, deepwater plays and for fields deemed uneconomical due to low flow pressure. With the ability to handle high gas volumes as well as potentially reducing the risk on the environment, multiphase pumps are being increasingly used for subsea and downhole applications. Selection of multiphase boosting options remains a bit subjective and is frequently influenced by the seller’s informationwhich may mask potential limitations of this emerging technology. Information on multiphase pumping tends to focus on a certain pump type for a specific field application, but does not provide more-generalized criteria for the selection of multiphase boosting solutions from among those available in the market.

Subsea gas-liquid separation coupled with liquid boosting can be an effective means of oil reservoir exploitation. Despite advances, multiphase pumping technology remains limited in its capabilities. Dynamic (centrifugal and helico-axial) pumps function with reasonable efficiency for single-phase, low-viscosity liquids. However, they become very inefficient when a high-viscosity liquid is combined with high percentages of free gas. While use of multiphase pumps is in many instances an effective solution, special consideration must be taken when challenging conditions exist such as are found in deeper water or with long tieback distances, or when heavy-oil production is involved. More effective oil reservoir exploitation can be achieved using subsea separation coupled with liquid boosting.