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Ulstein Presents Benefits of Its SX121 Design

Advancement in technology is permitting the offshore oil and gas industry to move into progressively deeper and colder waters in remote locations. ULSTEIN supports this development by providing products and solutions that contribute to safer, smarter and greener operations.

A case in point is the versatile and flexible OCV/subsea vessel design SX121, which ULSTEIN is currently building customized versions of for GC Rieber Shipping and Island Offshore. The design can be tailored for a multitude of offshore construction and subsea operations in deep and ultra-deep waters both below and above the Arctic Circle.

Deepwater and ultra-deepwater projects occur outside of the continental shelf at water depths between 400 and 1,500 metres and depths greater than 1,500 metres respectively. Deep waters mean remote locations, harsh weather conditions and sensitive ecosystems. This type of environment requires vessels that are reliable and safe, cost-efficient and environmentally sound.

“We aim to develop ships that can operate reliably, safely and efficiently in harsh conditions with as small an environmental footprint as possible. The robust configuration, system integration and X-BOW® hull line of the SX121 ensure safety and comfort for the crew, an increased operational window and significantly reduced environmental impact,” says sales manager in Ulstein Design & Solutions, Lars Ståle Skoge.

Currently, there are four sailing SX121 vessels designed and built by ULSTEIN. The vessels, which operate in different segments such as offshore construction, riserless well intervention and inspection/maintenance/repair, have received very good feedback.

Gordon L. Wilkinson in Veolia ES said the following about ‘Viking Poseidon’’s work in the Gulf of Mexico: “She is the Queen of the Gulf.”

At the end of 2012 shipowner Island Offshore, together with their American partner Edison Chouest Offshore, ordered another SX121 vessel from ULSTEIN currently under construction at Ulstein Verft. “We’ve received very good feedback on our two operating vessels of this design, ‘Island Constructor’ and ‘Island Intervention’,” says Technical Manager in Island Offshore, Trond Hauge. “I’m confident that this type of vessel is a safe and comfortable platform for the performance of advanced work in the years to come.”

Optimized for heavier installations

“The SX121 is a compact vessel that can perform deepwater and ultra-deepwater operations for which currently larger vessels are frequently used, thus providing the customer with a more cost-efficient solution,” says Håvard Stave, Sales Manager in Ulstein Verft.

“The typical SX121 vessel operates at depths down to 3,000 metres, which comprises most current oil & gas activities. The need to deploy heavier equipment in deep waters such as offshore Brazil and Africa and in the Gulf of Mexico, has spurred market interest in OCV vessels with a 400-tonne crane, which we’ve now incorporated in the SX121 design.”

ULSTEIN has drawn on experiences from its latest SX121 projects, and optimized the utilization of the hull with regards to work from deck as well as crane construction work, resulting in an even more versatile OCV/subsea vessel.

The robust platform is optimized for efficient operations in deep waters with a crane capacity of up to 400 tonnes and a substantial remaining deck loading capacity, and it can be configured for a variety of mission equipment. There is a large deck area of 1,750 m2, and the area around the main moon pool is reinforced in order to sustain a VLS or module handling system. The ROV installation is designed and chosen for operations in significant wave heights of 4.5 metres or more. Two heavy-duty work ROVs are situated in the enclosed hangar, one to be deployed from the starboard side, the other through a dedicated moon pool.

Extended redundancy

A reliable vessel is key for cost-efficiency, as down-time and aborting on-going operations are costly affairs, particularly when operating far from shore.

The SX121 vessel meets the highest standard for position keeping, DYNPOS-AUTRO, with redundancy on all major components. Featuring the ‘Operation+’ concept, an increase in redundancy in AUTR operations if a single major failure occurs, the vessel will still maintain system redundancy throughout the most critical areas. The typical configuration is diesel electric propulsion powered by six identical medium speed main generator sets. The switchboard system, propellers and diesel motors can be configured in groups of two, three or four. If a major failure occurs, the vessel will only lose one third of its power and propulsion. The combination of system architecture and power stations, three side thrusters and three main thrusters, ensures that the operation can be safely completed using two thirds of its capacity.

Smart and safe

In order to optimize capacities and performance of the vessel, the freeboard has been increased by one metre compared with the previously built vessels of this design. This increase also improves safety and ensures a dry work deck. In addition, the helideck has been moved further back in order to increase the weather window for helicopter landings.

The vessel’s X-BOW provides good motion characteristics for safe operations. It also reduces the vessel’s environmental footprint through lower fuel consumption and reduced emissions. With optimized resolution of the power generation plant, the vessel will have high fuel efficiency in all operational modes.

The vessel accommodates a crew of 130 and complies with all international requirements for comfort and safety.

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WWCS, DOF Subsea Conduct Subsea Services in US Gulf Of Mexico

Wright’s Well Control Services (WWCS) completed a riserless subsea plug & abandonment (P&A) using tubing to pull out of the hole from a Multi-Service Vessel (MSV) in 1,250’ WD in the Gulf of Mexico. DOF Subsea USA provided marine and subsea services. New tools where custom engineered specifically for this project and successfully deployed.

One of the initial challenges addressed by the WWCS team was the one-of-a-kind tree found at the site with an annulus monitoring valve at a 35° angle. After finding no Remotely Operated Vehicle (ROV) tooling on the market offering the ability to nipple down and up on a subsea flange, WWCS designed and built a new torque tool. The new tool unbolted the flange and bolted in a new flange with a 2” hot stab.

The next step was to design and build a hydraulic connector that would allow WWCS to pull away from a section that might have issues while leaving a modified Tree Running Tool (TRT) subsea. This connector was designed to engage and disengage a subsea Blowout Preventer (BOP) and lubricator for additional barriers as needed without time consuming trips to the surface to add and remove the TRT.

WWCS also modified a Tubing Hanger Pulling Tool (THPT) to pull tubing with a crane subsea. The tubing was removed with a bull string on the deck of the MSV with a ROV for guidance as the segments where pulled out one at a time. One of the MSV’s moonpools was used to run the coil string and the umbilical while tubing and casing were pulled from a secondary moonpool.

Steps in the plug & abandonment procedure included: setting six (6) 16.4 ppg Class H neat cement plugs, setting three (3) Cast Iron Bridge Plugs (CIBP), cutting and pulling 37 joints of 3½” tubing, cutting and pulling 750′ of 9⅝” casing, cutting and pulling 13⅜” casing, cutting and pulling 20″ x 30″ casing with a mechanical cutter below mudline (bml), flushing a 6″ pipeline of 3890 barrels (bbls) of fluid with a modified 4” connector, recovering the umbilical tension assembly (UTA) and pipeline end manifold (PLEM), and setting a modified plumbers plug and submar mats on the lines.

“This project was a great success for everyone involved at Wright’s Well Control Services,” said WWCS president David Wright. “In 30 days we successfully executed a very challenging subsea P&A utilizing four new subsea tools including a jumper to flush the pipeline that we designed and built while on location. I’m proud of our crew and support staff. The techniques and tools deployed on this job may change how subsea P&As are conducted going forward.”

“It was great to work with WWCS on this innovative subsea P&A project,” said Brent Boyce, vice president of operations at DOF Subsea USA. “The new tooling designed to flange and re-flange the subsea annulus monitoring system interfaced perfectly with our ROVs. We were able to remove and reinstall the device even at 35 to 45° angle.”

Wright’s Well Control Services offers comprehensive surface and subsea offshore services for clients in the Gulf of Mexico. Wright’s specializes in cost effective rigless applications including patent-pending hydrate remediation, subsea BOP and plug & abandonment technologies. WWCS was founded in 2006 by David Wright who has 25 years of offshore and onshore engineering experience including work at Halliburton, The Red Adair Company and ATP. Wright’s is a privately held company employing 75 people with corporate offices in Humble (Houston), Texas and an operations facility is Lake Charles, Louisiana.

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