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Subsea Separation Emerges as the Best Subsea Technology in Demand

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Subsea separation ranks as the most targeted technology for rapid development and application due to its huge potential for cost savings by moving some of the traditional topsides fluid processing to seabed, according to a recent survey of subsea technologies conducted by officials with FMC Technologies Inc.

Dr. Phaneendra Kondapi, an engineering manager for flow management at FMC and KBR Inc. adjunct professor of subsea engineering at the University of Houston, and Randi Moe, also with FMC, evaluated and updated the status of the top 30 existing and developing flow assurance technologies to assess their maturity level, effectiveness and solution type, including thermal, chemical, hardware, operating and software.

Kondapi reported on the findings of the study, "Today's Top 30 Flow Assurance Technologies: Where Do They Stand?", at the Offshore Technology Conference (OTC) in Houston in early May.

Subsea separation improves oil production and recovery and boost company earnings. This technology improves flow assurance such as hydrates, wax and slugging with less chemical injection.

"More companies are driving towards utilizing this technology to increase hydrocarbon recovery with development of challenging and deeper subsea fields," Kondapi commented.

Key technology areas still in the experimental or embryonic stage include cold flow, subsea coolers and subsea compression, while subsea separation and real-time flow assurance advisory software are at the growing yet evolving, or emerging stage, of development, according to the evaluation results.

The first pilot-separation system was installed at the Troll field in 1999 for liquid-liquid separation and in 2001 for gas-liquid separation. Subsea separation projects delivered to date include oil-water separation projects, Statoil ASA's Tordis offshore Norway field and Petrobras S.A.'s Marlim field offshore Brazil, and gas-liquid separation projects, including Royal Dutch Shell plc's Perdido in Gulf of Mexico, Shell's BC-10 offshore Brazil and Total S.A.'s Pazflor offshore Angola.

However, a number of challenges remain for subsea separation technology, including achieving liquid-liquid separation and gas-liquid separation from heavy oils. Other challenges include:

Realizing the optimum combination of pump acceptance criteria with respect to gas-liquid separator design for heavy oil applications
Cost and installation challenges and opportunities to reduce bulky and heavy equipment
Disposal of the separated water
Improving and maturing an efficient compact design

Subsea cooler technology has received more attention recently from the industry mainly due to cost benefits realized by reducing or controlling temperatures. Subsea cooling is often coupled with other subsea processing systems such as subsea separation, subsea multiphase boosting, subsea compression, or can be used on a standalone basis at high temperature fields.

Subsea coolers can allow for lower cost, less exotic materials to be used in downstream pipelines and risers and reduce field development costs. While a long uninsulated flowline is the simplest and most matured cooling device, more efficient multi-pipe cooler units have been developed and qualified for subsea use. A multi-pipe solution has been used subsea offshore Australia at Exxon Mobil Corp.'s Kipper field and is a required unit for the ongoing development of subsea compression.

One fast-growing technology for large fields requiring pressure boosting is subsea gas compression technology, which improves production and recovery from the reservoir by reducing back pressure on the wells. Subsea compression can be used to extend production from mature fields or provide initial support for production for remote fields with long tiebacks.

Statoil's Asgard compression project will become the first subsea compression project upon its completion in 2015. The Ormen Lange gas compression pilot is underway and will likely pave the way for subsea compression at Ormen Lange if Statoil selects this option.

While real-time online monitoring and flow assurance advisory systems (FAS) have been around for the past 15 to 20 years, FAS software remains a growing technology as they are incorporated with newer modules that are customized based on specific field characteristics.

"Flow assurance technologies are becoming increasingly important, and are required to enable particular applications in deepwater and in challenging Arctic environments," Neil Saunders, senior vice president of subsea systems products & projects at GE Oil & Gas, told Rigzone. "This is particularly important for those applications that require complex flow over long distances and at relatively low temperatures."

Developing and future flow assurance technologies can be broadly segmented into:

Fluid management and treatment, or chemical injection and direct electric heating (DEH)
Pressure boosting and separation
Power supply, or long distance DEH and local power generation
Modeling and analysis tools, or improved prediction and accuracy
Flow remediation tools such as depressurization and subsea pig launching.

Some key flow assurance technologies benefiting from further development include:

Rheology modification, or flowing hydrates
Long distance direct electrical heating
Monoethylene glycol (MEG) loop optimization
Low dose inhibition

"Some flow assurance technologies have been demonstrated to be very effective over relatively short distances," Saunders commented. "Many of these technologies need further investment and development to enable future applications where, for example, multiphase transport is required over long distances. There is a huge difference in cost, technology and performance requirements between 3.1 miles and 310 miles (5 kilometers to 500 kilometers)."

Some future applications may lie in the upper part of that range and the technical and economic limits will continue to evolve with investment, Saunders noted. GE is working on a technology that limits hydrate agglomeration on pipe walls, reducing the probability of hydrate plug formation as well as improving the flow efficiency.

"Of course, the overall solution enabling complex flow over long distances will require integration of multiple technologies, some of which may be application specific," Saunders noted.

Normally, technology starts at the safer and easier side of oil and gas production and when applicable the technology is then developed and enhanced to migrate to more difficult environments once proven.

"However, sometimes challenging environments require a 'step change', something not tried before in order to solve an issue unique to that environment and in those cases the benefits that technology can deliver can then be applied to easier environments to deliver the same gains and that adoption path is normally faster, but happens less often because 'disruptive' advances are not common," Saunders added.

Maturing Technologies Find New Life Through New Applications

While the industry needs to forge ahead with advancement of new subsea technologies, the industry continues to find new applications for matured technologies like chemical and operating solutions, or technologies that have been around a decade or more, some of which have applications for both onshore and offshore production. These technologies have opportunity for incremental improvements to optimize for better processes.

Direct electric heating, the current applications for which are focused on hydrates, is both a matured and growing technology. DEH can keep fluid temperatures above the hydrate formation temperature and above the wax appearance temperature. DEH has mostly been used in North Sea fields, with DEH open loop technology used at Statoil's Asgard, Huldra, Kristin, Urd, Tyrihans, Alve, Ormen Lange, Morvin, and BP's Idun and Skarv fields. Closed looped DEH technology has been utilized at Shell's Serrano, Oregano, Nakika and Habanero.

"DEH technology is matured for shallow water applications and pipelines that are shorter than 31 miles (50 kilometers) but for risers, manifolds, longer pipelines and deepwater applications the technology is growing but needs to be extensively tested," Kondapi said.

One of  the chemical flow assurance technologies, scale inhibitor chemistry is a matured technology but its treatment applications are still evolving, and not only has been used offshore, but also has found onshore applications in recent years as hydraulic fracturing activity has picked up in the United States. Scale inhibitors have been used both offshore and onshore, in Alaska's North Slope, the Permian Basin, the North Sea, Western Siberia and West Africa.  Scale inhibitors offer several benefits, including treatment cost savings over basic dilution methods and operating expenditure savings.

Some key technologies that will benefit from further development include rheology modification, long-distance direct electrical heating, MEG loop optimization and low dose inhibition, Saunders commented.

GE has already seen some limitations on the use of certain chemical compounds in flow assurance that are effective in the inhibition of gas hydrates, Saunders noted.

"The drive for low environmental impact will continue, particularly in the Arctic where environmental sensitivity is such a big issue."

Agency Similar to NASA Needed to Advance Subsea Technology Development

The U.S. federal government should establish a national institute for subsea engineering in Houston similar to the National Aeronautical Space Administration (NASA) that would focus on development of subsea technology, an oil and gas industry official and subsea professor told attendees at OTC.

Federal funding will be necessary to help the industry develop new subsea technologies as oil and gas exploration moves deeper offshore, Kondapi told Rigzone.

"I see multiple reaping benefits," Kondapi commented. "It increases research and development capabilities in addition to developing new technologies. It will help in establishing much needed test facilities and finally enhance safety and reliability."

Kondapi also stressed the importance of joint industry partnerships along with university-industry research partnerships in developing and testing some of the technologies. A NASA-like agency would work in coordination with university-industry partnerships. Primarily, the agency should support the university research activities while enhancing fundamental research activities.

"I would say it is not in competition with joint industry partnerships or university-industry research partnerships but should collaborate with these partnerships to avoid duplication," Kondapi commented.

This collaboration will ensure that technology is not developed in parallel and efforts duplicated.

Kondapi sees funding for this type of agency garnering approval.

"In the wake of Outer Continental Shelf Governors Coalition for offshore energy development this will definitely grab attention and the importance can be addressed by the benefits like economic growth and creating more jobs in addition to the fundamental research in subsea engineering."

"Development of fundamental technology solutions for the most demanding applications, without doubt, requires significant investment not just in dollars but also in time," Saunders noted. "Support for fundamental research is always welcoming, providing the technology is made available to organizations that can ultimately deliver efficient applications."

Source:    Rigzone

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