When the fish in the Pixar movie “Finding Nemo” finally escape to the sea from the dentist’s aquarium, they find themselves floating in plastic bags filled with water atop the ocean, and the angel fish mastermind asks, quite rightly “Now what?”
Sometimes it seems as if the North Sea is in a similar situation – floating in an ocean of huge geological potential, but bound by intangible barriers beyond its control. So where does it go from here, facing a Pandora’s box of decommissioning and low prices?
See the UK 30th Rd page for further discussion
The history of the Northern and Central North Sea is anchored in the Tertiary and the Jurassic. These are the reservoir intervals that have delivered (by far) the bulk of the resource. Paetoro takes the view that if there is a future for the North Sea, this history is the best guide to it. There may be no one single answer, and who knows what new frontiers or plays may come into being down the line, but surely, in terms of probability – the odds are in favour of these proven intervals.
To be worthwhile now, potential has to be big. Not only that, but the time to cashflow can’t be decades. Supermajors might have portfolios that can sustain exploration in really frontier areas now, but not many others can. In the UK, the West of Shetland petroleum province has struggled at least in part for this reason – the time until first production’s landfall is just too long to be commercial. Areas which are even more distal would seemly strictly the reserve of the big boys with big global portfolios and bank balances to match. If something is big enough, an FPSO on top of it will of course work almost anywhere, but the risked resource in those truly frontier areas where source rock is an issue, and the long time to first production - means it is only a game for the biggest and boldest.
Yet in mature areas there is the opposite problem. There is so much infrastructure, much of it aging, and almost too many players. I have witnessed many a possible venture fall through simply by virtue of commercial complexities. When that isn’t the case, the costs of sustaining aging infrastructure often kill anything that isn’t big. The geology may be singing, but twenty mmbbl is difficult to make work when there are four partners who can’t agree, and an FPSO is turning a nice rusty orange colour.
In that sense, the North Sea has matured from an infrastructure led approach to almost an anti-infrastructure led approach, or at least one where you have to be very choosy about the infrastructure present. It’s not that you want to be so far from infrastructure that you can’t tie in somewhere fairly quickly, but neither do you want to be saddled with huge decommissioning and repair costs. That is a big driver in where to look.
Infrastructure and commercial realities have to be a big part of any exploration strategy – of course few would disagree with that. What of the geoscience then? Some of the world’s best geological minds have poured over data from the North Sea for over half a century. Why could there be something new in these existing plays?
Technology is the simple answer. It’s not the whole answer because workflows and concepts in Earth Science change too, but it’s a big part of it. The improvements in imaging are simply flabbergasting. Broadband for instance brings a new paradigm. What improvements in technology mean is that subtleties never previously visible in these old plays are starting to be seen. Structural and stratigraphic subtleties, and their combination, are behind most of the largest North Sea discoveries in recent decades. Drilling the bumps in the Tertiary is almost a distant memory. The Tertiary play today is largely one of stratigraphic subtleties. As such it is typically the domain of the rock physicists, who are best able to make sense of the stratigraphic subtleties that can still surprise – for better and for worse.
With its structural roots, Paetoro is focussing on the Jurassic. Even in recent years, the potential remaining in this play has been evident. Like the Tertiary it has no shortage of stratigraphic subtleties to explore, but the structural complexity is much greater. There-in lies the difficulty – it’s a harder problem for seismic to answer definitively – due to both depth and structural complexity. Fault seal has an important impact on both migration and trap. Yet there-in also lies the opportunity – it is much more likely to have larger resource remaining undetected as these difficult variables, somewhere, work together for good.
What of other plays? Well yes, fractured basement, Triassic, Rotliegend, chalk, even hopes for the Lower Cretaceous, all figure in the North Sea story. Anyone who has looked at the chalk over time will know of the many tantalising hints of hydrocarbons distributed throughout them. Chalk though requires huge investments for complex developments, and at low permeabilities, very large HC columns are a prerequisite to get useful saturations. The Lower Cretaceous from a point of view of production has only worked very locally in the Outer Moray Firth. Anywhere else it is something to investigate on the way down to another target and cannot justify well-costs on its own risking merits. The Triassic can work, but reservoir quality is much less - so very hard to predict/resolve at those depths, meaning it is largely a gas play - and high pressures can make it tough. It’s nice to have as a secondary target, but it’s the Jurassic potential that really attracts. The Rotliegend and fractured basement are interesting, but the migration story from a stratigraphically shallower Jurassic source requires large fault juxtapositions for them to work, limiting the areas where they can feature without calling on poorly understood deeper source rocks.
From a structural perspective, it is also the Jurassic basin configuration which has a controlling influence on virtually all of these plays in the central and northern North Sea. Even within the Tertiary, the compaction related changes in thickness associated with deeper sub-BCU faulting can be enough to cause syn-depositional changes in sea floor gradient and associated deposition. When you understand the Jurassic structures there, you understand a whole lot more.
For that reason it remains the Jurassic of the central and northern North Sea with still excites PAETORO the most. There is no shortage of North Sea locations to chase this potential, but we have opted to start with quads 210 and 211 in the Northern North Sea and quads 22 and 29 in the Central North Sea. These are quadrants which still have reasonable access to younger infrastructure, and which PAETORO feels still offer enough underexplored stratigraphic and structural complexity to harbour big finds. They also all have areas on the margins of the basin that are a bit less explored. The greater Catcher area has illustrated longer distance migrations within Tertiary plays, and while it is a much tougher call at Jurassic levels where structural continuity is far less assured, these quadrants nevertheless offer that potential too as an added bonus in the Tertiary and Jurassic.
PAETORO is happy to work with clients in any areas, but given the need for focus, it will be working initially to review the available databases of quadrants 22, 29, 210, and 211. It’s base camp for future efforts. We are undertaking a ranking exercise in these areas with both the 30th Rd and a longer term view in mind. See the UK 30th Round page for more detail.