The Deckhand newsletter · Issue 2 · Energy Street

Jack-up site-specific analysis

Prepared: Analyst Deckhand (AI assistant) · Checked: Editor Deckhand · Approved: Vamsee Achanta · 3 November 2026

On 24 October 2026, a jack-up drilling unit sank offshore Gabon. Of the 115 people on board, 110 were accounted for and brought ashore [1, 2]. Press reports of the dead and missing differ and await official confirmation [1, 2]. Our thoughts are with everyone affected, and with their families and colleagues.

Gabon's Ministry of Petroleum and Gas has ordered a technical investigation [1, 2]. The rig owner, Borr Drilling, said on 25 October 2026 that "preliminary information indicates that the rig experienced a punch through event during preload activities" [18]. The investigation's findings are awaited. Apart from the rig owner's statement, nothing in this piece bears on the cause of the loss. This piece is to demonstrate and progress complex engineering methods and workflows. We would like to use this opportunity to develop reusable engineering for the jack-up and the liftboat, in a bid to learn and also to help with future site studies for similar structures.

1 Public facts on the loss offshore Gabon

Each statement on the loss is entered in a register with its source and date (Table 1). The register is checked against its sources again on the day the page is published.

Table 1 - Public facts register for the loss offshore Gabon. Sources dated 25 and 28 October 2026, read again on 3 November 2026; [18] read on 4 November 2026.

Figure 1 shows where the loss happened, as reported. No position has been published, so the whole country is shaded.

The sections below use no data from this loss. They apply to any jack-up or liftboat at any site.

2 Jack-ups, liftboats and wind installation jack-ups all stand on legs

A drilling contractor's annual report counts 494 jack-ups in the global fleet at the end of 2025 [9]. On 1 August 2022, 77 US-flagged liftboats were in active service [10]. We found no public world count of liftboats or of wind installation jack-ups.

The three types of unit work in the same way:

• A jack-up is a mobile unit with a floating hull and legs that it lowers to the seabed. It then raises the hull clear of the sea.
• A liftboat is an offshore supply vessel with movable legs capable of raising its hull above the surface of the sea [7]. It has three or four legs and its own propulsion, and it serves oil platforms and wind turbines [10].
• Wind installation jack-ups, or wind turbine installation vessels, are "self-propelled heavy-lift jack-up vessels designed for the installation of offshore wind turbines" [11].
• All three preload their legs to test the soil before they raise the hull to its working height [4; 12; 13, p. 77].

3 Serious jack-up and liftboat accidents, 1999 to 2022: 35 events in three public sources

Liftboats and wind installation jack-ups have an accident record like that of drilling jack-ups. A 2019 review of self-elevating platform incidents finds liftboat incidents "identical to Jack-up incidents" [12]. For wind installation jack-ups, the 2010 MMS report states: "Much can be anticipated about incidents and accidents by looking at the track record of jack-ups in the North Sea and liftboats in Gulf of Mexico" [13].

Figure 2 shows all 35 serious accidents in three public sources, by year and initiating hazard [10, 13 to 17]. The MMS report lists 14 accidents of jack-up construction vessels (construction jack-ups below), mostly at wind farms, from 1999 to 2008. The 2021 review lists 17 of the worst drilling jack-up accidents from 2012 to mid-2021. Four NTSB reports cover one liftboat each.

By our count of Table 2, 17 events are on drilling jack-ups, 13 on construction jack-ups and 5 on liftboats. By our hazard grouping (Note 1), 4 start with storm or weather, 11 with punch-through or foundation, and 4 with leg, jacking or structural failure. Another 4 happen in transit or tow, and 12 are other or not stated.

By yearBy hazard

Note 1: the hazard groups are ours. An event under tow or in transport is transit or tow. Other events follow the source's cause code or wording; where the source states no hazard, the event is other or not stated.

Each source covers its own scope and period, so the chart dates these events; the rates below come from the 2021 review. Over a longer span, that review counts 90 liftboat losses, with 56 deaths [14]. It puts the liftboat loss rate at 2 to 3 times that of drilling jack-ups [14]. On jack-ups, deaths per operating rig-year fell from 0.07 to 0.007 over 61 years of records [14].

Table 2 - the 35 accidents behind Figures 2 and 3, with the source of each

Year	Unit	Unit type	Location	What happened (source wording, shortened)	Initiating hazard (our grouping)	Source
1999	Aarsleff Jack	construction jack-up	Horns Rev, Denmark (wind-farm centroid)	Overturned	other or not stated	Compiled list: MMS report, Table 1 [13]
2000	Wijslift 6	construction jack-up	Blyth, UK (wind-farm centroid)	Hull dropped	other or not stated	Compiled list: MMS report, Table 1 [13]
2003	Excalibur (ex Wijslift 6)	construction jack-up	North Hoyle, UK (wind-farm centroid)	Broken leg	leg, jacking or structural failure	Compiled list: MMS report, Table 1 [13]
2003	MEG-JB1	construction jack-up	North Hoyle, UK (wind-farm centroid)	Crane collapse	other or not stated	Compiled list: MMS report, Table 1 [13]
2003	Skate II	construction jack-up	Gunfleet, UK (wind-farm centroid)	Punch-through: hull dropped	punch-through or foundation	Compiled list: MMS report, Table 1 [13]
2004	Skate III	construction jack-up	Brighton, UK (town anchor)	Wrecked	other or not stated	Compiled list: MMS report, Table 1 [13]
2005	A2Sea Ocean Ady (now Sea Energy)	construction jack-up	Scroby Sands, UK (wind-farm centroid)	Leg damage	leg, jacking or structural failure	Compiled list: MMS report, Table 1 [13]
2006	Octopus	construction jack-up	Orkney, UK (islands anchor)	Ran aground during tow	transit or tow	Compiled list: MMS report, Table 1 [13]
2007	JB-104	construction jack-up	Milford Haven, UK (town anchor)	Capsize, 1 fatality; alongside the dock, not in wind farm service	other or not stated	Compiled list: MMS report, Table 1 [13]
2007	Smit Lisa	construction jack-up	Robin Rigg, Solway Firth, UK (wind-farm centroid)	Punch-through: hull dropped	punch-through or foundation	Compiled list: MMS report, Table 1 [13]
2008	Dredging barge	construction jack-up	Mallorca, Spain (island anchor)	Abandon ship by helicopter operations	other or not stated	Compiled list: MMS report, Table 1 [13]
2008	Jakup	construction jack-up	Teesside, UK (town anchor)	Wrecked	other or not stated	Compiled list: MMS report, Table 1 [13]
2008	Russell W. Peterson	liftboat	about 14 miles off Rehoboth Beach, Delaware, USA (town anchor)	Wrecked, 1 fatality, in a May 2008 nor'easter (press quoted in the report)	storm or weather	Compiled list: MMS report, Table 1 [13], quoting press; US Coast Guard report not found
2008	Titan 1	construction jack-up	Atlantic (position not public)	Lost overboard from a heavy lift vessel	transit or tow	Compiled list: MMS report, Table 1 [13]
2011	Trinity II	liftboat	Bay of Campeche, about 15 miles offshore, north of Frontera, Mexico, 84 ft water (position estimated from the NTSB text)	Elevated in hurricane-force conditions; stern jacking leg failed, vessel listed; 4 died	storm or weather	NTSB investigation report NTSB/MAR-13/01 [15]
2012	Hercules 2502	drilling jack-up	Gulf of Mexico (position not public)	Under tow: mat badly damaged by poor cribbing alignment on the barge for a dry tow; rig retired, declared a total loss in 2019	transit or tow	Published review: 2021 review, Appendix A [14]; cause code S (structural)
2013	Hercules 265	drilling jack-up	South Timbalier 220, Gulf of Mexico (position not public)	Gas blowout; fire in derrick; beams supporting derrick and rig floor collapsed	other or not stated	Published review: 2021 review, Appendix A [14]; cause code O (blowout)
2013	Perro Negro 6	drilling jack-up	Congo River mouth, Angola, 40 m water (anchor: Soyo town)	Capsized after punch-through, with 103 on board	punch-through or foundation	Published review: 2021 review, Appendix A [14]; cause code B (punch-through)
2013	Trident 15	drilling jack-up	Moragot 19, Thailand (position not public)	Port leg punch-through giving 7° list; many braces damaged	punch-through or foundation	Published review: 2021 review, Appendix A [14]; cause code B (punch-through)
2014	Aquamarine Driller 5	drilling jack-up	off Miri, Sarawak, Malaysia (anchor: Miri town)	Serious punch-through (plus possible heavy-weather damage under tow)	punch-through or foundation	Published review: 2021 review, Appendix A [14]; cause code B (punch-through)
2014	Ensco 104	drilling jack-up	Malaysia (position not public)	2 crew killed when a lifeboat fell 150 ft to the sea during maintenance	other or not stated	Published review: 2021 review, Appendix A [14]; cause code N (falling object)
2014	Menadrill 1	drilling jack-up	Akal field, Gulf of Mexico (anchor: Cantarell field)	Fire in shale shakers or motor generator room	other or not stated	Published review: 2021 review, Appendix A [14]; cause code F (fire)
2014	Rowan Louisiana	drilling jack-up	Vermilion 366, Gulf of Mexico (position not public)	Well control problem during wiper trip; all non-essential crew evacuated	other or not stated	Published review: 2021 review, Appendix A [14]; cause code O (blowout)
2015	COSLGift	drilling jack-up	South-east Asia (position not public)	Serious punch-through	punch-through or foundation	Published review: 2021 review, Appendix A [14]; cause code B (punch-through)
2015	Rigmar 152	drilling jack-up	South Atlantic (position not public)	Sank under tow from Brazil to Gabon	transit or tow	Published review: 2021 review, Appendix A [14]; cause code K (flooding)
2015	Rumailah	drilling jack-up	Al Shaheen field, Qatar (field centroid)	Punch-through; 3 legs broken	punch-through or foundation	Published review: 2021 review, Appendix A [14]; cause code B (punch-through)
2015	Troll Solution	drilling jack-up	Caan Alfa well, Gulf of Mexico (anchor: Cantarell field)	Probable punch-through and tilt when positioning for maintenance on a well	punch-through or foundation	Published review: 2021 review, Appendix A [14]; cause code B (punch-through)
2016	SAR 201	drilling jack-up	beside Safaniya platform, Saudi Arabia (field centroid)	Punch-through (or jack failure) on port leg; deck at port stern dropped to nearly sea level; evacuated; 3 missing	punch-through or foundation	Published review: 2021 review, Appendix A [14]; cause code B/M (punch-through or jacking system)
2017	Maersk Interceptor	drilling jack-up	Tambar field, Norway (field anchor)	Sling lifting a pump broke; 2 drilling staff injured, 1 then went overboard, was recovered and died	other or not stated	Published review: 2021 review, Appendix A [14]; cause code L (lifting)
2017	West Titania	drilling jack-up	Manick 100-1A, Gulf of Mexico (position not public)	Jacking system failure; trim by stern and slight list; flooding of starboard stern main deck	leg, jacking or structural failure	Published review: 2021 review, Appendix A [14]; cause code M (jacking system)
2018	KS Java Star	drilling jack-up	next to Camar Seagull jacket, SE of Bawean Island, Indonesia (anchor: Bawean)	Rapid penetration of starboard leg when preloading; gas well fire on adjacent platform	leg, jacking or structural failure	Published review: 2021 review, Appendix A [14]; cause code M (jacking system)
2019	Kristin Faye	liftboat	Main Pass Block 64, about 18 nm east of Venice, Louisiana, USA, 35 ft water	Elevated liftboat overturned in under a minute after a crane boom was raised; NTSB: punch-through of one of three legs	punch-through or foundation	NTSB investigation report NTSB MAB-20/36 [16]
2021	SEACOR Power	liftboat	about 7 nm off Port Fourchon, Louisiana, USA, about 50 ft water	Capsized while under way in a severe thunderstorm; 13 died	storm or weather	NTSB investigation report NTSB MIR-22/26 [10]
2021	Velesto Naga 7	drilling jack-up	Salam-3 well, offshore Sarawak, Malaysia (anchor: Miri town)	Punch-through; fully submerged	punch-through or foundation	Published review: 2021 review, Appendix A [14]; cause code B (punch-through)
2022	L/B Robert	liftboat	80 nm SE of Lake Charles, Louisiana, USA, 217 ft water	Unmanned and elevated: gale winds and waves above the air gap moved the vessel; a leg slid into an adjacent can hole; vessel tilted	storm or weather	NTSB investigation report NTSB MIR-23-28 [17]

Table 2 - Serious jack-up and liftboat accidents in three public sources, 1999 to 2022, with the source of each. Locations in brackets give the reference point used on the map in Figure 3.

4 Past accidents on the map: 26 of the 35 events

Figure 3 places the 26 accidents with a public reference position on a world map. They lie off northern Europe and Mallorca, the United States and Mexico, West Africa, Qatar and Saudi Arabia, and South-east Asia. The other 9 have no public position; Table 2 gives only a sea area, country, field, lease block or well for them.

WorldNorthern EuropeGulf of Mexico

5 What a site-specific assessment covers

Before a jack-up works at a new location, a site-specific assessment checks the unit at that location [3, 4]. The assessment covers:

• The foundation: how the seabed at that location carries the footings at the foot of each leg (spudcans). SNAME 5-5A lists foundation hazards that include punch-through, settlement or bearing failure, sliding, scour and seafloor instability [4, Table 3.1]. In a punch-through, a leg breaks through a strong soil layer into weaker soil below and drops quickly.
• The structure: the strength of the legs, the hull and the holding system, the machinery that holds the hull at its height on the legs.
• Overturning and sliding: whether the whole unit stays upright and in place in the assessment storm, the extreme storm that the unit is checked against at that site.
• The air gap: the clearance between the hull and the highest wave crest.
• The moves: the stability of the unit while it floats, under tow or under its own power. For a jack-up, this follows the stability chapter of the IMO code for mobile offshore drilling units (MODUs) [6]; for a liftboat, the US Coast Guard rules [8].

In US federal waters, Title 30 of the US Code of Federal Regulations (30 CFR) covers the use of a MODU in section 250.713 [5]. Under 250.713(a), the operator must show the unit's capability at the proposed location, including the minimum air gap. Under 250.713(b), the operator must also show that the site-specific soil and oceanographic conditions can support a bottom-founded unit, one that stands on the seabed [5].

For a liftboat, we apply the foundation, structure and air gap checks as for a jack-up. Its overturning check must also meet the US Coast Guard's special rules for liftboats, sections 174.240 to 174.260 of Title 46 of the CFR [8]. For a liftboat in restricted service, 46 CFR 174.255(c) sets on-bottom stability: a continuous downward force on each footing under waves, currents and 70-knot winds in normal operation, and 100-knot winds in a severe storm [8]. The same sections set its stability afloat and its freeboard [8].

6 Site and unit data

A site study needs two groups of data: data on the site and data on the unit (Table 3).

Table 3 - Data for a jack-up or liftboat site study, and where public sources exist.

7 How the methods serve future site studies

• Each site study starts from the same data list (Table 3). Each input is entered with its source and date, so a later study can see what was measured and what was assumed.
• Jack-ups and liftboats both raise their hulls on legs, so the checks of section 5 are set out for both; section 5 gives the checks that carry over to a liftboat and the US Coast Guard rules that add to them.
• The accident record of section 3 is kept beside the data list. Each new site study can then be read against the events seen on similar units.
• The inputs and results of each site study are kept with its prompt, for the next study of a similar structure.

Try it out: for your next jack-up or liftboat move, list each input to the site assessment with its source and date.

This piece leaves open which checks of a jack-up site study need changes before they apply to a liftboat.

Reusable prompts

Set out a site-specific assessment of a jack-up or liftboat at a new location: list the site and unit data it needs (Table 3), set out each check of section 5 with the edition and clause of each code it uses, and mark every input with its source. Then count the jack-ups and liftboats in service from public operator filings and investigation reports. Chart past serious accidents of all kinds by year, initiating hazard and unit type, and on a world map, each with its source. Name no cause for any event still under investigation.

Data: the public data sets for each input, such as the GEBCO grid, the NOAA National Data Buoy Center records and ERA5, are named in Table 3. The accident data set behind Figures 2 and 3 is jackup-accidents.csv. It holds 35 public events, each with year, unit type, location, position, hazard group and source. The sources are the MMS report, the 2021 review and four NTSB investigation reports [10, 13 to 17]. The fleet counts are from [9] and [10].

Readers are welcome to share their own site study results at support@aceengineer.com.

References

[1] World Oil, citing Reuters, 25 October 2026, news report on the jack-up loss offshore Gabon. [2] Marine Insight, 28 October 2026, news report on the search and rescue offshore Gabon. [3] ISO 19905-1:2023, Site-specific assessment of mobile offshore units, Part 1: Jack-ups. [4] SNAME T&R Bulletin 5-5A, Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units, Rev 3, August 2008. [5] US Code of Federal Regulations, 30 CFR 250.713, "What must I provide if I plan to use a mobile offshore drilling unit (MODU) for well operations?", eCFR, current to 30 October 2026, ecfr.gov. [6] IMO resolution A.1023(26), Code for the construction and equipment of mobile offshore drilling units, 2009 (2009 MODU Code), Chapter 3, stability. [7] 46 CFR 125.160, Definitions, "Liftboat", eCFR, current to 30 October 2026, ecfr.gov. [8] 46 CFR Part 174, Subpart H, Special rules pertaining to liftboats, eCFR, current to 30 October 2026, ecfr.gov.

References [9] to [17] were read on 4 November 2026. [9] Valaris Ltd, Form 10-K for the year 2025, filed 20 February 2026, sec.gov. [10] NTSB, Marine Investigation Report MIR-22/26, capsizing of the liftboat SEACOR Power, adopted 18 October 2022, section 1.1.1, ntsb.gov. [11] NREL, Offshore Wind Market Report: 2024 Edition, NREL/TP-5000-90525, docs.nlr.gov. [12] van der Kraan, "Self Elevating Platform (Incl. Liftboat) Incidents", Jack-up Conference 2019, conference paper. [13] Sharples, "Damage and Critical Analysis of Accidents ... Offshore Wind Farms on the OCS", MMS TA&R Project 633, May 2010, Table 1 and p. 77, bsee.gov. [14] Jack, Hoyle and Hunt, "Jack-up Accident Statistics - Yet Another Update", Jack-up Conference 2021, Appendix A, conference paper. [15] NTSB, Marine Accident Report NTSB/MAR-13/01, liftboat Trinity II, ntsb.gov. [16] NTSB, Marine Accident Brief MAB-20/36, liftboat Kristin Faye, ntsb.gov. [17] NTSB, Marine Investigation Report MIR-23-28, liftboat L/B Robert, ntsb.gov.

[18] Borr Drilling Limited, "Borr Drilling Limited - Prospector 5 Rig Incident", press release, Hamilton, Bermuda, 25 October 2026, distributed by PR Newswire, read 4 November 2026, prnewswire.com; copy at placera.se.