The three graces: on time, on budget and on station

The Delta House semi-submersible FPS has an initial production capacity of 80,000 b/d of oil and 200 MMcf/d of gas. First oil was produced April 2015. Photograph courtesy of Audubon.

In 2010, a joint venture group of partners and their majority shareholder, LLOG Exploration Co. (LLOG), acquired approximately 20 deepwater leases in the Gulf of Mexico’s Mississippi Canyon area. But there was a catch: drilling had to begin within 36 months or the leases would expire. So with the clock ticking, LLOG hired Audubon Engineering Solutions (topsides engineering contractor) and EXMAR Offshore (hull engineering contractor) to design a floating production system (FPS) to be ready to get production assets on station and ready for first oil.

In traditional oil and gas operations, after a discovery is made, delineation wells are drilled and a thorough examination of reservoir characteristics is conducted. Only after commercial viability has been established, does the process of FEED, bid tendering, detailed design, and construction begin. In the case of LLOG in the Mississippi Canyon area, time was not a luxury. So they decided to start work on the design of a production platform before a discovery had even been made.

Normally, production platforms are tailored to the particular characteristics of a reservoir and the hydrocarbons it contains. However, with no detailed data available on either of these, the Delta House semi-submersible deepwater FPS would have to be able to operate with a wide range of reservoir types.The tight lease deadline, coupled with a greater return on investment (ROI) from quickly bringing the FPS online and moving on to other endeavours, was enough to convince LLOG that the benefits of this approach outweighed the disadvantages of employing a more generic platform design. The strategy proved sound, with production beginning two to four years earlier than comparable conventional deepwater projects in the region.

With the platform designed before well characteristics were defined, there was a possible risk that the flow rate could exceed the nameplate capacity of 80 000 b/d. However, LLOG’s cost-benefit analysis revealed that if the required processing capacity was exceeded, it would be more economical to temporarily curtail production, expand the existing unit, or even build a second production platform. Conversely, if the flow rate was less than expected, the company could lease out the spare capacity, allowing other producers to tie their wells into the FPS.

AVEVA PDMS: enabling technology

In order to make this strategy a success, LLOG Exploration, Audubon Engineering Solutions, and EXMAR Offshore adopted a flexible ‘one size-fits-most’ design approach so that the platform would be versatile enough to handle a wide range of hydrocarbon profiles. And to help them achieve this on such a demanding timeline, they used AVEVA PDMSTM.

‘One of the primary business benefits of AVEVA PDMS is increasing our capability for multi-disciplinary design on large projects,’ said Denis Taylor, Managing Partner of Audubon Companies. ‘CAD systems have limitations in project size and speed; and as the project grows, the model becomes slower and more prone to crash and hinder progress. This invariably seems to happen just before a critical milestone. With its own 3D graphics engine and a specialised database, AVEVA PDMS handles big projects very well, allowing us to maintain progress throughout the life cycle of the project.’

Denis also explained how Audubon Engineering Solutions’ use of PDMS opens the door to working with larger clients who prefer, or even mandate, that design be done in PDMS, a proven software for offshore design, construction, and visualisation.

The prêt-á-porter platform- With a production capacity of 80 000 b/d of oil and 5.7 MMcm/d (200 MMcf/d) of gas, Delta House will operate in an average water depth of 1372 m (4500 ft). The reservoirs themselves range in depth from 3658 m to 5629 m (12000- 18500 ft). Delta House will operate most efficiently with crude ranging from 28° to 37° API, with some reduction in capacity outside of this range.

‘To meet the aggressive schedule of this project, we kicked off the design of all major modules and deck areas simultaneously,’ added Marcus Martin, Project Manager at Audubon Engineering Solutions. ‘The work was split between our Houston and New Orleans offices by deck area and process, whereby each office had vertical scope, including project management, engineering, design, and procurement. This would normally be very difficult to interface, but AVEVA PDMS enabled us to execute the design seamlessly across the multi-disciplinary teams in the two locations. Using one live PDMS model was critical to achieving this, and because any design team member in any office could see the work progress in real-time, it minimised errors, clashes, and rework.’

Time-saving strategies

Many offshore platforms are designed in tiers. So if one piece on a lower level needs rework, systems on higher levels cannot be installed, which can often delay the construction process. Using a design philosophy employed on Who Dat – another platform operated by LLOG in the Gulf of Mexico – Delta House was designed as a single level, with most of its processing equipment installed on the main deck.

In almost every instance, performing work on systems and components in the construction yard instead of on the platform is a safer and more economical option. So Audubon Engineering Solutions designed the topsides to allow for this. The onshore work included fitting of all the piping and cabling, thus enabling the completed deck to be lifted and set on the hull with minimal work to complete integration.

Sharing data with other contractors

To avoid overloading the heavy lifting device (HLD) used to hoist the topsides deck, centre of gravity (CG) calculations were critical. Audubon Engineering Solutions needed to work closely with EXMAR Offshore to ensure design compatibility and accuracy. To achieve this, information exchanged between the two companies was based on a model swap schedule. Once a week in Houston the design coordinator would physically load a drive with the PDMS database and update it with the latest hull model.

AVEVA PDMS enabled Audubon Engineering Solutions to collaborate with EXMAR, monitor the CG, and make adjustments as required. Similarly, they had to work closely with Kiewit Offshore Services (who was responsible for the fabrication of the topsides integration on site) to ensure that the overall weight of the design was within the limits of the HLD. Hyundai began cutting steel for the hull in its yard in South Korea in March 2013, and a year later the hull was offloaded at the Kiewit yard. Two weeks after that, the integrated truss deck and topsides were added to the hull. At 9580 t, it was the heaviest single lift the Kiewit yard had ever executed. The operation was flawless, taking less than five hours, which included the initial positioning of the hull, right through to the release of the load.

The next step

‘Audubon Engineering Solutions has always strived to be at the forefront of technology, so the adoption of AVEVA Everything 3DTM (AVEVA E3DTM) is definitely in the cards, especially because we can introduce it side by side with AVEVA PDMS to avoid a ‘Big Bang’ approach,’ added Taylor. ‘It has all of the qualities that have made PDMS so valuable plus some impressive new features that can make our project delivery even more streamlined.’

Denis went on to explain that, while making the move to AVEVA 3D is a possibility, its adoption would have to occur without negatively impacting Audubon Engineering Solutions’ ability to meet client needs. ‘Staying competitive is the goal of every company and to do that, risks and benefits must be carefully weighed,’ he said. ‘The move to AVEVA E3D will be about minimising risk and maximising opportunities. Our goal would be to capitalise on the advantages it provides without affecting project schedule.

To expedite the construction process, Delta House was designed as a single-level platform. Lead time from sanction to installation was approximately 30 months. Photograph courtesy of Audubon Engineering Solutions.

Delta House success

At the moment, work on Delta House 2 is already under way. Because the Delta House concept can be used on so many different types of projects, Audubon Engineering Solutions is implementing an approach that reuses as much of the design as possible. Though very similar, Delta House 2 will take lessons learned from Delta House 1 to create an even more cost-efficient platform.

‘We have already begun replicating the best parts of DH1 onto DH2,’ Martin explained. ‘AVEVA tools make duplicating an intelligent model quick and painless, whether it’s just one piece of equipment or an entire project.’

Meanwhile, Delta House 1 is already in operation, having produced first oil in April 2015 – two full years earlier than what is typically expected for similar platforms throughout the globe.

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Adapted from an article from AVEVA by Louise Mulhall

Published on 08/10/2015

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