Integrated Design Development of a Low Motion Semisubmersible Hull Form

Transcription

1 Integrated Design Development of a Low Motion Semisubmersible Hull Form

2 Contents The Semisubmersible as a Deepwater Concept Hull Form Development and Optimization Hull Motion and Structural Verification Platform Features Hull Topsides Mooring and Riser System Conclusions

3 The Semisubmersible as a Deepwater Concept Advantages System components adaptable to ultra-deep water Concept supports wide range of topside payloads Track record of proven design and fabrication and methods Proven offshore installation methods with minimal risk Quayside Hook-up and Commissioning Limitations Currently, the concept is limited to applications with subsea wells

4 Hull Form Development Work Flow Path Functional Requirements Practical Aspects Hull Form Optimization Design Verification TOPSIDES DRILLING PAYLOAD CONSTRUCTION TRANSPORTATION INSTALLATION OPTIMIZED MOTIONS AND STEEL WEIGHT ANALYSIS MODEL TESTING RISERS HULL OPERATION

5 Functional Requirements Basic Requirements Basis Range of Application Location Gulf of Mexico Adaptable to other regions Water Depth 1830 m > 3000 m Topsides 100 KBOPD 150 MMSCFD Drilling 26,000 Tonnes Can be re-configured for larger topsides (>40,000 Tonnes) Riser System Steel Catenary Risers: 6 Production 2 Test 2 Water Injection 2 Export 18-inch Maximum Dia. 4,500 Tonnes vertical load Flexibility to accommodate additional risers and/or larger diameter

6 Practical Considerations Draft Limitation Operating Draft (Max.) = 27.5m Structural efficiency Stability / tow-out draft Deck Installation Transit Draft (Min.) = 12m Flexibility for Deck Integration Access to yards Column Configuration Four-column and Six-Column configurations studied Six-column solution selected: Structural benefit from reduced deck span Improved rectangular deck layout (safety, piping, etc.) Increased flexibility for deck construction Ring Pontoon Omni Directional Motion Response

7 Cycle III-Operating Period (sec) CG, Hdg=0 CG, Hdg=90 Cycle III-Operating Period (sec) Pitch, Hdg=0 Roll, Hdg=90 Hull Form Optimization Pontoon Weight Coefficients Draft = 22.5 m Heave (m/m) Angular Motion (rad / m) MOTION RESPONSE MODEL HULL WEIGHT MODEL Volumetric Weight Coeff. (t/m3) Draft = 27.5 m Draft = 32.5 m Pontoon Aspect Ratio Variables Draft Columns (number, size, spacing, shape, inclination) Pontoon (length, aspect ratio, bilge radius, shape) Cross bracing / ring pontoon configuration SOLVER OPTIMIZED HULL Constraints Target motion RAOs Heave natural period Motion/Acceleration at Riser Attachment Minimum GM Deck area requirement Minimum trimming ballast Pontoon span / depth ratio Maximum Draft Transit draft

8 Hull Form Optimization Motion Response Model Xsp + Dco Morison Element formulation for heave pitch and roll motion Added mass and inertia (wave) forces calculated assuming hull as an assembly of slender Morison elements h_toc H_taper * (draft_r - Hp) draft_r Closed-form equations for pre-integrated forces along longitudinal, transverse and vertical slender members Db_Dt * Dco Db_Dt * Dci Hp Motions are de-coupled by calculating angular motions about an estimated center of rotation Dco Dci pon_xtrans * Xsp Wpi Cant Wpo Special treatment (added mass corrections) at connections between elements and element ends to obtain reasonable correlation with results from 3-D radiation / diffraction analysis Ysp/2 Yi Xpon_Ytrans * Yi Xsp/3 Xsp/3 Xsp rad_col * Dci Wpx rad_col * Dco Example of Hull Idealization

9 Hull Form Optimization Steel Weight Calculation: Pontoon Weight Coefficients Steel Weights defined on a volumetric basis Correlated to actual and preliminary designs Adjustments for draft / column (tank vent) height Adjustments for pontoon height and aspect ratio Coeff. (t/m3) Volumetric Weight Coefficient Draft = 22.5 m Draft = 27.5 m Draft = 32.5 m Increasing Draft Pontoon Aspect Ratio Pontoon Aspect Ratio a/b = 2 a/b = 3

10 Hull Motion And Structural Verification Motion Response Prediction Comparison to Production Semi s and MODU s Model Testing Structural Verification

11 Hull Form - Key Features Six-columns Ring Pontoon Pontoon Shaped to Reduce Motion and Provide Omnidirectional Response Enlarged Center Column and Pontoon Section Pontoon Aspect Ratio Maximizes Added Mass Contribution Pontoons Consist Entirely of Flat Plate Construction Columns Rounded to Reduce Wave Run-up

12 Motion Characteristics Heave Rao Pitch / Roll Rao deg (Head) 45 deg (Quartering) 90 deg (Beam) Roll (Beam Seas) Pitch (Head Seas) Heave Amplitude (m/m) Roll/Pitch Amplitude (rad / m) Period (seconds) Period (seconds)

13 Motion Performance Comparison Heave Rao Heave Response Heave RAO, Hdg = 90 (Beam Seas) HEAVE CG, Hdg=90 (Beam Seas) 2.0 KBR Drilling and Production Semi 0.60 KBR Drilling and Production Semi Production Sem 2 Typical 5th Generation Drilling Semi Production Semi Production Semi 2 5th Generation Drilling Semi Heave (m/m) Sig.Heave / Hs (m/m) Production Semi YR HURRICANE Period (sec) Tz (sec)

14 Motion Performance Comparison Roll Rao Pitch Rao Roll RAO, Hdg = 90 (Beam Seas) Pitch RAO, Hdg = 0 (Head Seas) KBR Drilling and Production Semi Typical Production Semi 5th Generation Drilling Semi KBR Drilling and Production Semi Typical Production Semi 5th Generation Drilling Semi Roll (rad/m) Pitch (rad/m) Period (sec) Period (sec)

15 Motion Performance Comparison Vertical Acceleration At Riser Porch Locations Heave Acceleration at Riser Porch #1, Hdg=45 Heave Acceleration at Riser Porch #2, Hdg= Sig.Heave.Acc'n / Hs [ (m/s^2)/m ] Production Semi #1 Sig.Heave.Acc'n / Hs [ (m/s^2)/m ] Production Semi # Production Semi # Production Semi # KBR Drilling and Production Semi Tz (sec) 0.00 KBR Drilling and Production Semi Tz (sec)

16 Model Test Verification Heave Rao Correlation DIFFRACTION ANALYSIS Model Test (soft mooring) Model Test (full mooring) 3.00 Heave Amplitude (m/m) Period (sec)

17 Structural Design Process Hull Framing and Scantling Calculations Hydrodynamic Analysis (WADAM) Global Hull FE Model (Patran): Various Wave Headings & Periods Map Wave Pressures and Inertial Loads onto Global FE Model Shell & Bulkhead Plating Pontoon & Column Web Frames Column Deck Flat Plating & Girders Shell and Bulkhead Stiffeners ( Lumped ) Dummy Members for Risers Porches, Fairleads, etc. Determine Design Waves Squeeze-Pry Load between the Pontoons Global Torsional Moment Longitudinal Shear Force between Pontoons 123, , , , , ,958 Global Topsides Model (Patran): Primary Transverse Trusses Primary Longitudinal Trusses Primary Deck Girders and Plating Global Strength Analysis (SESAM) Stillwater + Hydrodynamic Loads Yield Checks Buckling Checks (SESAM-Platework) Static and Mooring/Riser Loads (Patran): Hull Dead Weight and Operational Loads, including Ballast Topsides Dead Weight and Operational Loads Mooring Line & Riser Tensions Fatigue Analysis (SESAM) Screening Level Stochastic Fatigue Analysis using a Blanket SCF and one or more S-N Curves with G.o.M Scatter Diagram Detailed Fatigue Analysis of Critical Areas using Refined FE Models (e.g. t x t )

18 Hull Structure Scantlings in accordance with Class Rules (confirmed by Global Strength and Fatigue Analysis). Shell Plate Thickness Limited to 22 mm, except 30 mm in way of cross pontoon connections. Plate thickness and stiffener size variations minimized (8 plates sizes and 7 stiffener sizes, excluding local reinforcement at foundations). Option for bulb or angle stiffeners. Frame Spacing: mm. Stiffener Spacing: mm. 355 MPa (50 ksi) Materials. Typical Pontoon Framing Transv. Bhd. Plating, Stiff & Girders Long. Bhd. Plating & Stiff. Shell Plating & Stiff. Web Frames

19 Hull Structural Design Hull design has adequate strength and meets stress/buckling criteria using reasonable plating and stiffener sizes All areas have fatigue in excess of 200 years (based on Gulf of Mexico Criteria) Castings used in corner region to provide sufficient fatigue life Casting Detail Global Structural Model

20 Platform Configuration TOPSIDES Process Capacity: 100 KBOPD 150 MMSCFD Dimensions 60 x 96 x 14m Number of Decks: 2 Operating Weight: 26,000 tonnes Accommodation & Utilities Drilling Derrick Process Facility HULL Overall Length m Overall Breadth m Height (t.o. column) m Draft m Air Gap (to deck) m Moorings Risers

21 Lower Hull Plan FLUID STORAGE TANKS (TYP) PA1A PA2A PA3A PA4A PA5A PA6A PF6A PF5A PF4A DRILL WATER PF3A PF2A PF1A UTIL. ELEV. SHAFT SHAFT ACCESS SHAFT W.T. DOOR ACCESS SHAFT ELEV. UTIL. SHAFT SHAFT PA1B PA2B PUMP ROOM PA4B PA5B P6B PF5B PF4B BASE OIL PUMP ROOM PF2B FUEL OIL PF1B PA1C VOID PF1C VOID PUMP ROOM (TYP) CROSS PONTOONS (VOID TANKS) CA1D VOID CF1D VOID SA1C VOID ACCESS TUNNELS SF1C VOID SA1B SA2B FUEL OIL PUMP ROOM SA4B BASE OIL SA5B S6B SF5B SF4B PUMP ROOM SF2B SF1B UTIL. ELEV. SHAFT SHAFT ACCESS SHAFT W.T. DOOR ACCESS SHAFT ELEV. UTIL. SHAFT SHAFT SA1A SA2A SA3A SA4A SA5A SA6A SF6A SF5A SF4A SF3A SF2A SF1A

22 Transverse Section At Corner Columns CHAIN JACK EQPT ROOM CHAIN PIPES VOID PIPING/UTILITY CHASE CHAIN LOCKERS VOID CROSS PONTOON VOID ACCESS SHAFT PUMP ROOM TANK FAIRLEAD

23 Transverse Section At Center Column COLUMN STORAGE CAPACITIES BULK TANKS VOID CHEMICAL STORAGE VOID Barite/Bentonite 425 m 3 (15,000 ft 3 ) Cement 340 m 3 (12,000 ft 3 ) Liquid Mud.4,000 bbls Drilling Fluid (Brine) 4,000 bbls Chemical Storage.4,500 bbls DRILLING FLUID STORAGE MUD TANKS TANK TANK ACCESS TUNNEL

24 Topsides Configuration Alternatives Integrated Deck Stiffened Plate Box Deck Floatover or Lifted Construction Modular Deck Truss Structure Lifted in 4,000 ton modules or larger INTEGRATED BOX DECK MODULAR DECK

25 Modular Deck Configuration PROCESS MODULE UPPER DECK MEZZANINE DECK LOWER DECK PROCESS MODULE

26 Topsides - Upper (Weather) Deck 96 m FLARE RISER RACK DERRICK FLASH GAS 60 m QUARTERS PIPE RACK GAS COMPRESSION LAYDOWN/ UTILITIES POWER GEN. PIPE RACK SUBSTRUCT. CEMENTING/ SACK STORAGE BOOSTER PUMPS 16.8 m m 22.1 m m 16.8 m

27 Topsides - Lower (Production) Deck UTILITIES MANIFOLD QUARTERS GAS TREATMENT MUD PUMPS OIL PROCESS AREA UTILITIES WATER TREAMENT MCC/ SWITCHGEAR MUD PITS

28 Hull - Deck Interface FE Model BOX BEAM

29 Modular Deck Construction

30 Mooring And Riser System UMBILICALS EXPORT RISERS MOORINGS RISER PORCHES PRODUCTION, INJECTION & TEST RISERS

31 Mooring System

32 SCR Interface - Production Lines CLEAR DECK AREA FOR VERTICAL ACCESS CHAIN JACK TO MANIFOLD CHAIN BASKET FIXED PIPING TOPSIDES MESSENGER CHAIN INSTALLATION SET-UP FLEX JOINT/BASKET SCR SCR LAYOUT CONCEPT

33 Summary The semisubmersible hull form provides low motion characteristics within normal draft limits and using a relatively simple hull geometry. Motion response verified by analysis and model testing Structural design and analysis to verify hull weight and construction. Efficient and functional deck layout. Flexibility to accommodate alternative deck construction methods. Flexibility to accommodate riser system

34 Integrated Design Development of a Low Motion Semisubmersible Hull Form Thank You

35 Contacts For further information on our designs and services please contact: Singapore Office: 39, Pandan Road, Singapore Tel.: Malaysia Office: 11, Jalan 14/2, Taman Tar, Ampang, Salangor, Kuala Lumpur Tel.: Mob.: Irvine Engineering Pte Ltd - Registered Address: 60 Paya Lebar Road, #08-43 Paya Lebar Square, Singapore Tel.: Dubai Office: Jumeirah Lake Towers, P.O. Box: , Cluster C, Goldcrest Executive Tower Office 706, Dubai. UAE. Tel.: Fax: Mob.: (Main Company Contact) enquiries@irvineeng.com