−1,500 m · WATER COLUMN · FIELD NOTES
BlogField notes
Short technical pieces on subsea and offshore engineering, written for people who will be asked to defend the numbers. Every post names its sources and links them.
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Seven Blocks, Seven Envelopes: What Brazil's Pre-Salt Auction Actually Priced
On 7 October Brazil awarded seven of thirteen production-sharing blocks, with premiums up to 494.64% over the floor. Every one of those premiums came from a single sealed envelope — no block had a second bid. The ANP's "average premium" of 108.38% is one way of averaging them; a simple mean of the seven gives 178.26%. And the bidding document has a neutral cell after all, which corrects our own post of 19 September and sharpens the point that matters to engineers — the State's share is indexed to output per producing well, a number the development concept sets.
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Subsea Connector Failure Rates: Five Times Lower Than the Pipe They Join
A study written for the Norwegian regulator puts numbers on something every subsea engineer has an opinion about and few have data for — how often mechanical connectors leak. On the OREDA subsea record for 2000–2017, flowline connections lost containment at 1.04 × 10⁻⁶ per unit-year against 5.18 × 10⁻⁶ for the pipe body; manifold connections at 1.35 × 10⁻⁶ against 4.75 × 10⁻⁶ for manifold piping and 6.89 × 10⁻⁶ for manifold valves. Eighteen events in about 3,000 connections, none a burst — seventeen filed as leakage and one corrosion case filed as "Other". And one unit label in the report that does not survive arithmetic.
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The Gas You Can Smell but Not Measure
Havtil published its investigation into a year of chemical exposure incidents at the plant that receives Snøhvit. The report puts the H₂S odour threshold at 0.008 ppm and the sensitivity of the H₂S sensor in the personal 4-gas detectors at 1 ppm — people were smelling what their instruments could not register. The leading suspected source — one of several Havtil considers likely to have contributed — is the atmospheric vent of a rich-MEG storage tank: the far end of a 143 km subsea hydrate-control loop that was assumed to release only nitrogen and water vapour.
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Seven Billion Spent, and the Bill Has Not Moved
The UK regulator's 2026 decommissioning update puts remaining UKCS decommissioning at £43.4 billion after a record £2.6 billion of spend in 2025. Held at one price basis, the same 2023-onwards programme has grown from £44.0 billion to £50.5 billion in four survey cycles. Wells are half the cost to 2032 and 40% of everything that remains; the largest single line is subsea well P&A; the binding constraint is six semi-submersibles.
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The Bid Is a Percentage. It Is Not the Percentage.
On 7 October Brazil auctions 13 production-sharing blocks on a single variable — the share of profit oil offered to the State. The regulator's own bidding document anchors that share to Brent at US$ 50.00 a barrel and to 10,000 bbl/d per producing well. The pre-salt averaged 18,365 — and at that productivity the annex adds some eleven percentage points to the winning share, on top of whatever the price does. The percentage that wins is not the percentage that gets paid.
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A Storage Site You Have to Sail To
On 18 September the Greensand project began commercial CO₂ storage in the Danish North Sea — 400,000 tonnes a year into a depleted oil reservoir 1,800 m below the seabed, delivered entirely by ship. The geology is the easy part. The interesting engineering is that nothing in this chain is continuous.
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The Pipe With No Steel to Crack
On 15 September Petrobras awarded a contract for thermoplastic composite pipe — water injection and gas lift, post-salt, to 1,500 m. Read next to the regulator's own alert on CO₂ stress corrosion cracking, the interesting part is not the pipe that was bought. It is the duty it was bought for.
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203 Wells, 82.4% of a Country
In July 2026 the Brazilian pre-salt produced 82.4% of the country's oil and gas from 203 producing wells, out of 6,724 producing wells nationally. That asymmetry is not a headline — it is a set of design constraints.