Moho-Bilondo gets Congo’sdeepwater mojo working
  from: Offshore Engineer
  by: Darius Snieckus
  Friday, September 05, 2008

Moho-Bilondo, brought onstream by Total earlier this year, marks Congo’s first foray into its deep water,with expectations that the landmark FPU development will produce some 230 million barrels over its life. First flow was hard-won. It has taken free-thinking by the partners to drill up and develop reservoirs that had long been stymiedby marginal economics. Darius Snieckus reports on a project ‘opening a new lane’ into the West African deeps.

Think deepwater West Africa and it is most likely the names Dalia, Greater Plutonio, Bonga, Kizomba and Agbami that are among the first to come to mind – all multibillion dollar floating production vessel based developments collectively flowing many billions of barrels of crude from the offshore province that sits at the easternmost point of the so-called Golden Triangle. But while Angola and Nigeria may monopolise much of the international oil and gas industry’s time and energy in the region, there are a number of neighbouring states that have emerged to form an active second tier increasingly well-represented by novel deepwater field developments: think Okume off Equatorial Guinea, Espoir off Côte d’Ivoire, and, most recently, Moho-Bilondo, the Republic of Congo’s maiden deepwater project, brought into production earlier this summer by Total E&P.

Though now ramping up toward forecast plateau production of 90,000b/d of oil, the latest addition to the West African deepwater fraternity was for many years by no means a dead cert. For Moho-Bilondo, located 81km off the Congolese coast in water depths ranging from 540m-730m, has presented more than the usual set of challenges posed by a deepwater development, challenges perhaps best understood, according to project director Claude Cahuzac, in terms of ‘diffèrence’.

Start with the reservoirs being developed. Two, the ‘utterly heterogeneous’ tertiary Miocene Mobim and Bilondo, are the first of four discovered between 1995-2004 that are being tapped by Total and its partners, Chevron and the Société nationale des pétroles du Congo (SNPC), as part of a $2.5 billion first phase of the stepwise development. Covering an area of 72km2 in the Moho-Bilondo’s southern zone, Mobim and Bilondo’s ‘amalgam of channel sands and clay deposits present a wide range of facies’ that for several years frustrated attempts to fashion a development plan that struck a commercial balance between ‘guaranteed optimal recovery’ and drilling the fewest possible wells at the field.

‘That the Mobim and Bilondo reservoirs have a disconnected and composite character, which complicated our ability to predict the flow of the reservoir fluids, was the source of the principle uncertainties at the field,’ states Cahuzac, who has being running the project since 2001. ‘Fine-scale geological modelling, based on sedimentary concepts built on several years of research carried out by the partners as well as our [Total’s] wider experience developing similar fields in the Gulf of Guinea, was one of the main vectors in our ability to master these uncertainties.’

Arriving at the development concept ultimately chosen for Moho-Bilondo – a ‘compact’ subsea production system/ FPU/export line solution – has been hardwon. So much so in fact, that to bring the field to first flow, for Total, is said to represent nothing less than the ‘announcement of the new age in Republic of Congo production that is promised by its deep and ultra-deepwater oil and gas fields’.

‘When we kicked off the project we were on a rather different conceptual path from the one that finally took us to first production – and the economics of this first path led to the project being put on hold in 2003,’ recounts Cahuzac. Early thinking on the development had ranged widely, with front-running concepts including an FPU with twin mini-TLPs, a leased FPSO, and a standalone FPU for Bilondo with Moho tied back 18km to the Total-operated Nkossa floating production barge, and export route scenarios that made use of the nearby Likouala platform as a hitching post for oil transport to Djeno while gas was sent to Nkossa. In the final analysis, however, no one scheme proved commercially robust.

Having demobilised the project team, the field partners nonetheless decided to take a final look at the Moho-Bilondo area and the ‘very dissimilar architectures’ of the highly-fractured midsize Mobim and Bilondo reservoirs, the former characterised by ‘a succession of chalky sand and clay units’ and the former a pair of clean sand structures ‘distinctly dissociated’ by a thick shale barrier. ‘In parallel with the early development studies our G&G department had carried out, 3D surveys that extended into an area to the west of the core development had been shot but had not been closely analysed,’ Cahuzac explains. Through the lens of previously-shot 3D seismic surveys, a ‘potentially attractive’ reservoir was spotted.

Driller thriller

‘The work they performed showed that there was a reservoir that might be worked into a new – much more compact and lower cost – development concept for the now larger field,’ he continues. ‘We restarted Moho-Bilondo in 2004 using this more compact concept and it afforded us the possibility of drilling a further exploration well targeting a tertiary Miocene turbidite complex, and this led to our development efforts being ultimately successful.’ In July of that year, the ‘resoundingly successful’ Mobim-1 well was spudded, breathing new life into a field now foreseen likely to produce over 230 million barrels of crude.

Development drilling of the two reservoirs, contracted to Transocean and assigned to its semisubmersible GSF Rig 135, convinced the project team to opt for a campaign of highly deviated wells, some as sharp as 70°, guided by real-time measurement while drilling and logging while drilling technology, to hit targets more than 3000m below the seabed. ‘What we were after, during development drilling, were two clusters of wells as close as possible to the FPU,’ says Cahuzac. ‘But not so close as to make the drilling so highly-deviated as to be next to impossible.We needed equilibrium between drilling distance and drilling angle.’

Keeping an eye on ‘optimal productivity’ from the wells drilled so far in Moho-Bilondo’s ‘unconsolidated sand’ reservoirs, Total is applying frac-packing treatments on Mobim and installing open-hole casings and sandscreens on Bilondo. To the seven appraisal wells already drilled on Moho-Bilondo, a further 14 wells will be completed by 2010.

The phase one development plan approved for Moho-Bilondo by the field partners and Congolese authorities in August 2005, almost exactly one year after drilling Mobim-1, is based around 14 wells: nine producers (five on Mobim and four on Bilondo) and five water injectors (three on Mobim and a pair on Bilondo) equipped with vertical christmas trees and housed in two templates located 2800m apart on the seabed – together making up the subsea production system delivered in 2007 by FMC Technologies under a $115 million turnkey contract.

Bottomhole gas lift, common in shallower environments but getting its deepwater premiere for Total on Moho- Bilondo, is being used hand-in-hand with a programme of water injection to boost recovery at the field by 20%. Production of the field’s wellfluids – which originating from different-aged source rocks at different depths flow different chemistries of crude, at 29°API Mobim is seven times more viscous than Bilondo at 22.9°API – is via two of Acergy-subsidiary NKT’s 8in dynamic flexible riser bundles, each outfitted with an electrohydraulic control umbilical and a gaslift and methanol inject line to prevent wax and hydrates build-up, up to the FPU. The 188m-long, 28,000t floater is moored in 600m of water using an 12-point catenary line system, front-end engineered by Doris Engineering and Haakonsen and supplied by APL.

Through the FPU, designed by Doris and built by Hyundai Heavy Industries at its Ulsan yard under a $400 million first-time ‘hull-and-topsides’ EPCI deal to handle 90,000b/d of oil, 45mmcf/d of gas and 75,000b/d of produced water, crude is being exported some 80km to the Djeno onshore terminal via a new 16in pipeline. A 6in line is piping gas to Nkossa, while one 18km 8in line injects water from the Nkossa installation into Bilondo and another 5.6km line does the same for Mobim via the newbuild production unit. Acergy was charged with installation and pre-commissioning of a total of 88km of flowlines and oil and gas export pipelines as part of a $280 million assignment awarded in 2005.

As with any deepwater development, flow management has been a key concern during planning. Doghouses installed at key ‘cold spots’ in the subsea infrastructure, including the flanges between the jumpers and around christmas trees, are being used along with methanol injection to ensure the temperature of produced flow does not drop below 20°C as it is cooled by the effect of the gaslift. At the onshore Djeno terminal – Congo’s only oil receiving facility, which was processing some 250,000b/d before Moho-Bilondo – two new processing trains have been added to the handle the field’s heterogeneous flow.

Near horizons

On 27 April 2008, only 33 months after the signing of the main construction contracts, Moho-Bilondo reached first oil. As OE went to press, two production wells had been brought online, one on Mobim and the other on Bilondo, with expectations that 60,000b/d would be flowing from the development by yearend. Going forward, according Cahuzac, Total’s strategy is bifocal: one eye will be trained on hitting output of 90,000b/d by 2010 and the other on drilling up new reserves from some of Moho-Bilondo’s surrounding reservoirs in order to extend what is foreseen to be a ‘rather short’ four-year production plateau.

‘Around the reservoirs that we are developing as part of phase one there are others in the southern zone,’ underlines Cahuzac. ‘Quite small ones, perhaps, but reservoirs that together will likely have something to contribute through a potential third production cluster.’

However happy a hunting ground the southern zone proves to be on Moho- Bilondo, there looks to be some big game lurking to the north, if the two discoveries made by Total in 2007 using Transocean MG Hulme are anything to go by. The operator made the finds in around 1000m of water in the development’s northern zone in April last year, with the Moho Nord Marine-1 well striking a 140m column of crude in a ‘high quality’ upper Miocene reservoir at a total depth of 2465m, and, some 1.5km away, Moho Nord Marine-2 encountering a pair of connected upper Miocene structures, one a 78m column of oil in an ‘excellent quality massive reservoir’ and the other a 22m column of oil in ‘good quality massive sandstone reservoir’, at a TD of 2340m.

Appraisal of the additional reserves contained in the three oil reservoirs encountered by Moho Nord Marine-1 and Moho Nord Marine-2 is under way ‘to determine their potential, and development plan studies have already been launched’. The three contending concepts being weighed up for Moho-Bilondo phase two are a standalone FPSO scheme, an FPSO with shuttle tanker offloading oil and gas piped to Nkossa, and a subsea solution that would pump oil to the newly-installed FPU and send gas to Nkossa. First production, according to current conceptual planning schedules, would be some time in 2013.

‘When we launched the project it was made up of five packages – drilling, the FPU, the SPS, the UFL [umbilicals and flowlines], and the integration of the Djeno terminal – and, to be sure, this was a heavy yoke to carry,’ offers Cahuzac. ‘But over the course of the development we proved that safety and quality standards could be balanced with strong management of project interfaces and overall operability and that this could be done while lightening the load of responsibility that usually rests with our contractors by being “interventionist” in our involvement in each package. This tactic shifted a great deal back onto our shoulders but – now that the project is successfully onstream – can be seen to have been the right strategic choice on all levels, not least for the interfaces.’

Beyond the triumph of commercialising this once uneconomic field, Total’s singular effort on Moho- Bilondo may well exert a positive ripple effect on future developments in the region. ‘This development continues to be strongly supported by the field partners and the Congolese government alike,’ he states. ‘At the time of Moho-Bilondo’s approval there were no other developments on the horizon for the state – it was a region in decline, with production coming only from mature offshore fields closer to shore. Moho- Bilondo should help change this trend.’

‘As Congo’s first deepwater development, the project has had a real impact,’ Cahuzac continues. ‘We have gone to great lengths to ensure this is a sustainable project and one that represents a positive change for the Congolese both in terms of direct training for local company personnel – a number were brought to South Korea to work and train in Hyundai’s yard during construction of the FPU – as well as through inward investments by Total, such as in HIV treatment programmes run by a mobile unit of the largest hospital in Pointe-Noire.’

Change appears to be the keynote for the Congo, a mature hydrocarbon province entering what Total reckons is a period of ‘new growth’ fed by deep and ultra-deepwater.

‘Today, the Congo is in a very different position from that which we saw when we first launched Moho-Bilondo,’ concludes Cahuzac. ‘We’ve drilled additional wells on Nkossa to add production, and other oil companies, such as Murphy, are moving ahead with interesting deepwater developments. There really is a renewal of the region under way.’

Commercial development of Moho- Bilondo, in Total’s view, will ‘enter the annals of Congolese oil and gas production as a project that opened a new lane for exploitation of its deep and ultradeepwater reserves’. The portents of greater things to come in the Congolese deeps appear promising.

Last November, in 2120m of water 185km off Congo’s coast, Total made a fifth discovery on its Mer Très Profonde Sud block with the Persée Nord Est Marine-1 discovery well. Drilled to a total depth of 4110m through found six oil reservoir levels in the Miocene, the latest find follows Andromède (2000), Pégase Nord (2004), Aurige Nord (2006) and Cassiopée Est (2007) and gives credence to the operator’s hopes of building an economically viable development ‘pôle’ on the ultra-deepwater permit, which ranges over an area of more than 5000km2 in waters between 1300m and 3000m deep. Field development studies for MTPS are to be launched ‘once the related reserves are assessed’. OE

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