School of Engineering Marine Arctic Technologies Department Offshore concrete structures in Gulf of Mexico. Problems and perspectives Master student group M3119шпс – Beliaeva T. D. Checked by Candidate of Tech. Sc.– Makarova N.V. Program supervisor, professor – Bekker A.T. 2020 Contents • • • • • • • The Gulf of Mexico Tension Leg Platform Tendon forces Prestressing and Concrete Quality Examples of TLP Olympus TLP Conclusions 2 The Gulf of Mexico The Gulf of Mexico [10] is a major source of oil and natural gas in the United States: Maximum water depth is 6800 m [7] Number of platforms is 1862 (as of April 2019) [1] 3 The Gulf of Mexico Scheme of the approximate location of all existing platforms in GoM [11] 4 The Gulf of Mexico Many platforms in the GoM are TLP. Gulf of Mexico TLP projects include Auger, Mars, Ram/Powell, Ursa of Shell, BP, etc. [2] 5 Tension Leg Platform TLP is a vertically moored floating structure, particularly suited for water depths 300-1500m Norwegian oil fields (1st concrete-hulled TLP was designed initially for North Sea Heidrun field [4] Jolliet TLP in the GoM, installed in 1988 with production beginning in 1989 [9] 6 Tension Leg Platform The hull of TLP contains [4] about 23,400 m³ of lightweight aggregate concrete total reinforcing and prestressing steel weights are 6,400 mt and 475 mt [4] 7 Tension Leg Platform. Material Properties 1. High-strength, lightweight aggregate concrete (LWC) 3. Concrete unit weight of 1.92 t/m³ 5. The normal reinforcing steel has a yield strength of 500 MPa [4] 2. Concrete compressive cylinder strength of 50 MPa 4. Concrete long-term unit weight of 2.15 t/m³ (including reinforcing steel and an allowance for water absorption 6. The prestressing steel has ultimate strength of 1860 MPa 8 Tension Leg Platform. Tendon forces The tendon forces [4] were calculated taking into account the following contributions: • tides and storm surge; • setdown due to platform offset; • first order wave forces; • steady overturning moments due to wind, waves and current; • foundation positioning tolerance (0.25m); • pretension margin (2.5%). 9 Tension Leg Platform. Prestressing The hull is designed [4] as a partially prestressed, reinforced concrete structure. Prestressing (posttensioning) is used to ensure watertightness and enhance of fatigue resistance. [4] 10 Tension Leg Platform. Prestressing Normal reinforcing steel augments the prestressing [4] to meet ultimate strength requirements control crack widths 11 Tension Leg Platform. Prestressing The minimum thickness [4] required to achieve highquality construction 40 cm 30 cm for walls with two curtains of reinforcing steel and one layer of prestressing for walls with two curtains of reinforcing steel only 12 Tension Leg Platform. Concrete (1) – U.S., compressive strength requirement in 90 days; (2) – Norway, compressive strength requirement in 28 days [4]. [4] 13 Tension Leg Platform. Concrete • very low permeability and water absorption; • very durable; • excellent corrosion protection to reinforcing steel; • good fatigue resistance; • limiting heat buildup during hydration of the cement [4]. [4] 14 Tension Leg Platform. Examples [6] The Magnolia TLP is located in the water depth 4,700 feet [5]. 15 Tension Leg Platform. Examples [3] Olympus, Shell’s seventh, and largest, floating deepwater platform in the Gulf of Mexico, Mars B field [8]. 16 Before Olympus [13] The Perdido spar works at water depths of around 2,300-2,800 m and has the 170-metre cylindrical spar [12]. 17 Olympus, Mars B field shape of the column and supports [14] simplified the construction phase, and helped with process and personal safety 18 Olympus, Mars B field. Features 1. Connection to the One Shell Square via a fibre-optic cable 3. Export lines head to shallow water complex West Delta 143 2. Installation a remote-control room and opening the subsea well from the remote control room onshore in One Shell Square [14] 19 Conclusions Olympus and Magnolia are concrete-steel-hulled platforms. Of course, steel is convenient for using for some reasons: for example, more steel fabricators and steel designers are available. Reinforced concrete is obviously good material. Although reinforcing is a difficult process, concrete has its advantages: 1) Concrete hull of TLP is less expensive than steel hull; 2) Reduced costs for inspection and maintenance; 20 Conclusions 3) 4) 5) 6) 7) Concrete is simpler when discussing structure details; Good resistance to ambient water pressure; Low stress concentrations and long fatigue lives Reducing the applied moments on the tendons; The relative insensitivity to topside weight. 21 References 1. Bureau of Safety and Environmental Enforcement [Electronic resource] / Developer : U.S. Department of the Interior. – Access mode : https://www.bsee.gov/faqs/howmany-platforms-are-in-the-gulf-ofmexico#:~:text=As%20of%20April%202019%2C%20there,in%20the%20Gulf%20of% 20Mexico , free. – Screen title 2. Deep Water Shell Global [Electronic resource] / Developer : Shell Global. – Access mode : https://images.app.goo.gl/aWM9rMSESqKL12D48 , free. – Screen title 3. Drill, Spill, Repeat: Offshore Drilling Threatens North Carolina [Electronic resource] / Developer : Blue Ridge Outdoors. – Access mode : https://www.blueridgeoutdoors.com/go-outside/drill-spill-repeat-offshore-drillingthreatens-north-carolina/ , free. – Screen title. 22 4. 4. Lokken, R. T., Concrete Tension Leg Platforms for the Gulf of Mexico / R.T. Lokken, R.H. Gunderson, G.F. Davenport, S. Fjeld, M.O. Wold // Offshore Technology Conference. – 1990, 12pp. 5. 5. Magnolia Tension Leg Platform [Electronic resource] / Developer : McDermott. – Access mode : https://www.mcdermott.com/What-We-Do/ProjectProfiles/Magnolia-Tension-Leg-Platform , free. – Screen title. 6. Magnolia TLP 2003 [Electronic resource] / Developer : OSM. – Access mode : https://mapio.net/pic/p-46061648/ , free. – Screen title. 7. Map Showing Geology, Oil and Gas Fields, and Geologic Provinces of the Gulf of Mexico Region [Electronic resource] / Developer : U.S. Geological Survey. – Access mode : https://en.wikipedia.org/wiki/File:Gulfofmexico.pdf , free. – Screen title. 23 8. 8. Mars B/Olympus deep-water project [Electronic resource] / Developer : Shell Global. – Access mode : https://www.shell.us/energy-and-innovation/energy-fromdeepwater/shell-deep-water-portfolio-in-the-gulf-of-mexico/mars-b-olympus.html , free. – Screen title. 9. MC Offshore Jolliet TLP [Electronic resource] / Developer : Fact Harbor. – Access mode : https://factharbor.com/facility/mc-offshore-jolliet-tlp , free. – Screen title. 10. Offshore oil and gas in the Gulf of Mexico (United States) [Electronic resource] / Developer : Wikipedia: The Free Encyclopedia. – Access mode : https://en.wikipedia.org/wiki/Offshore_oil_and_gas_in_the_Gulf_of_Mexico_(Unit ed_States) , free. – Screen title 24 11. Oil & Gas Platforms in Gulf of Mexico [Electronic resource] / Developer : Esri. – Access mode : https://www.arcgis.com/apps/webappviewer/index.html?id=a71d6758535042dd9 69114fb6a356888 , free. – Screen title. 12. Perdido – Overview [Electronic resource] / Developer : Shell Global. – Access mode : https://www.shell.com/about-us/major-projects/perdido/perdido-anoverview.html , free. – Screen title. 13. Perdido Shell Global [Electronic resource] / Developer : Google. – Access mode : https://images.app.goo.gl/A96gGH5T3Lbbu9bi6 , free. – Screen title. 25 14. Platform for growth - Shell’s Olympus tension leg platform [Electronic resource] / Developer : World Expro. – Access mode : http://www.worldexpro.com/features/featureplatform-for-growth---shellsolympus-tension-leg-platform-4372724/ , free. – Screen title 26
