Onshore Modular Land Rig

The Challenge:

CCI wanted to expand their onshore drilling & workover assets by developing a fully modular onshore drilling rig.

The Solution:

Cube Offshore were engaged to develop the conceptual structural design.

The modular drilling rig complied with the following codes & standards:

• API Spec. 4F – Drilling & Well Servicing Structures
• NZ1170:5 – Earthquake Actions – New Zealand
• DNV-ST-E273 – Portable offshore units (lifting strength R30)
• NZ Transport Agency – Factsheet 53a, Overdimension vehicles and loads

The drilling rig comprised of the following modularised units.  All of which complied with the road transport requirements of New Zealand and DNV 2.7-3 R30 lifting requirements.

• Upper Module
• Mid-2 Module
• Mid-1 Module
• Lower Module
• Sub-base Module
• Spacer Modules (x4)
• Skid Beams (x2)

Jacking Loads = 460,000 lbs

BOP on skid cart = 35t

Total weight estimate = 162.5t

The Scope:

The following was delivered as part of an integrated project approach:

• Basis of Design & Functional Specifications
• Concept development
• Staad.Pro structural analysis
  • Operating
  • Storm – Expected
  • Storm – Unexpected
  • Seismic
• Navisworks 3D model

GA & Elevation of Land Rig Concept

BOP Skidding Capability

3D Navisworks Model

The Challenge:

The underdeck drain access platform on VOGA’s WNB platform was severely corroded and required replacing.

The Solution:

Cube Offshore were engaged to develop a modular replacement concept and carry out detailed structural design of the replacement access platform.

The design encompassed the following attributes:

• modular design to minimise handling and offshore construction
• component design to fit through existing under deck scaffold
• full structural design compliance with the revised VOGA WNB Basis of Design

The Scope:

The scope of work included:

• Basis of Design
• Functional Specification
• Concept development
• Detailed engineering design in accordance with ISO 19901-3 including:
  • Operating (5yr non-cyclonic) – ULS-A
  • Extreme (100yr cyclonic) – ULS-B
  • Accidental (2000yr) – ALS
  • Extreme Seismic – ELE
  • Abnormal Seismic – ALS
  • Component lift design to DNV 2.7-3 R30 rating
• 3D modelling, fabrication drawings & dxf files
• Modular construction for transport & offshore lifting
• Fabrication specifications.

Early modular concept                                                             Staad.Pro analysis model

Staad.Pro analysis output                                                          3D CAD model – exploded view

Component lift analysis (DNV 2.7-3 R30)                             Component lift design (DNV 2.7-3 R30)

The Challenge:

CCI own a Hydraulic Workover Unit (HWU) which they deploy offshore onto production platforms for cost effective down-hole intervention.  Upcoming onshore contracts required an Onshore Support Base to be designed & fabricated to support the HWU on land over the well head.

The Solution:

Cube Offshore were engaged to develop the concept and carry out detailed structural design of the Substructure.

The arrangement comprised the following components:

• 4no. corner Support Pods to transfer loads into the ground
• 2no. Spreader beams to span between the Support Pods and provide support for the loads above
• 1no. Sub-Base Module sitting atop the Spreader Beams:
  • Supporting the 191t jacking loads
  • Supporting a 35t BOP
  • Support the HWU tower above c/w all dead, personnel & functional loading
• All components were configured to be road transportable throughout WA without the need for a pilot
• All components were liftable in accordance with DNV 2.7-3 R00 requirements
• Ease of assembly with minimal use of bolting, instead adopting clamped, bearing and turnbuckle connections
• Design compliance with API Spe. 4F – Drilling & Well Servicing Structures

The Scope:

The following was delivered as part of an integrated project approach & full collaboration between design engineering, fabrication and client:

• Basis of Design & Functional Specification
• Concept development
• Detailed engineering design & 3D modelling
• Fabrication drawings, dxf files and NC files
• Fabrication support
• Assembly procedures

1. Staad.Pro structural analysis                                                                  2. Staad.Pro 3D model

3. AutoCad 3D model exported to Navisworks                4. Completed structure assembled for operation

5. BOP suspended under Sub-Base Module

Challenge:

Seadraulics (formerly Specialist Offshore Services) required structural, piping & geotechnical engineering design support to deliver the structural “module” component of their SHFM design.  The SHFM subsea structure had demanding specifications such as deployment to seabed at (-)4000m, electrical/hydraulic ROV interfaces, 2 x chemical dosing bladders, flooding system & filters, loading arm and pressure testing facilities.

Cube Scope:

• Structural design in accordance with DNV 2.7-3 / AISC 360-10
• Piping design to ASME B31.3
• Geotechnical design to API RP 2A / DNV-RP-C205
• 3D interchange of CAD files between mechanical and structural models and Inventor / Solidworks for full clash check

Outcome:

Critical file management of the 3D Mechanical models in Inventor and Structural models in Solidworks for weekly integration and clash checking allowed for a seamless design process.  Structural design incorporated Chinese steel sections for COOEC fabrication.  No clash problems with fabrication as a result of integrated approach to combined 3D module models.

Extensive design & analysis engineering scopes in support of the clean-up, salvage, decommissioning and float-away of the West Atlas jack-up drilling rig after major blowout over the PTTEP Montara WHP.

Multiple design, lifting & seafastening scopes to remove debris prior to jacking down of West Atlas and towing away.  Innovative and practical approaches required for the following scopes in particular:

• Cutting & removal of the West Atlas cantilever beams
• Support grillage for 110t mobile crane lifted onto the pipe deck
• 2 no. access towers suspended from the West Atlas rig to provide support to gangway and access to the topsides from the Seatrucks J25 construction vessel.
• Miscellaneous installation / decommissioning aids, seafastenings, lift analysis, rigging design, damaged steel assessment, etc.

Access Tower being lifted into position.  Pre-Installed landing frame on the West Atlas allowed for rapid set-down and removal of crane.

Gangway landing on J25 landing on Access Tower

110t mobile crane on support grillage over West Atlas pipe deck

Heat damaged internal framing column.

Cube were selected to develop an innovating strengthening design to improve the structural integrity of an existing topsides module on the Woodside NGujima Yin FPSO.

The following design characteristics were achieved:

• Phase 1 strengthening work was all bolted and carried out during normal operations
• Phase 2 strengthening work (deck remedial scope) was welded and scheduled for future shipyard implementation
• Full integration with the offshore construction team to develop a sympathetic design for access, handling and installation operations
• All analysis carried out using Bentley SACS
• Limit state ULS / ALS (ISO19902) combined with ship motions, environmental loading and deck deflections.
• CAD models integrated with Point Cloud survey data for clash checking
• Significant reduction in module primary steel and deck utilisations achieved

Photo comparison with Point Cloud image.

SACS analysis showing original high structural utilisations prior to remedial bracing.  Deck not modelled.

SACS analysis showing topsides with remedial bracing & reduced utilisations.  Preliminary deck steel modelled showing high utilisations

SACS analysis showing extended deck model and longitudinal bracing to redirect and reduce deck utilisations.

Phase 1 – bolted bracing / strengthening to improve topsides integrity – implemented on station during normal operations

Phase 2 – welded longitudinal bracing to improve deck integrity – implemented in the shipyard during scheduled maintenance visit

Cube were engaged by Woodside to provide independent Review & 3rd Party Verification services for their NRA Caisson Removal Project.

Challenges included corroded caisson sections with limited survey detail inside guide locations with a risk of dropped object during removal.  Engineering adopted a risk-based approach with mitigations designed into the removal methodology.

Woodside’s gas compression trains up in Karratha are key to their continuous delivery of NWS gas to customers.  In order to keep it that way, critical spare rotor shafts must be available and is a preserved condition for whenever needed.  To ensure that this happens, Cube Offshore developed, manufactured & tested a range of 5no. dedicated Rotor Cocoon Skids designed for the following criteria:

• Rotors secured inside cocoons using adjustable restraints
• Pressurised containment of Nitrogen gas inside cocoons to preserve rotors
• Horizontal lifting, upending and vertical lifting (Woodside & DNV 2.7-3 specifications) c/w rotor under pressure
• Road transport & forklift handling

5no. Rotor Cocoon Skids in vertical storage position:     

Vertical lift of Rotor Cocoon Skid due to careful lift point placement:

Rotors secured inside cocoons for all loading scenarios:   

Progress photo during manufacture:   

Rotor Cocoon Skids – 3D CAD model representation:

Vertical lift analysis extract showing plate stress and member utilisations:

Challenge:

As part of the INPEX Ichthys phase 2 drilling campaign, the Casing Setback Area needed to be raised by 1.5m.  Design loading was 436t, no offshore hotwork allowed,  the platform was to be easily removable and overhead lift access on the rig was restricted.

Scope:

• Interface with INPEX and Maersk Drilling stakeholders to resolve BoD & concept
• Concept development & detailed design for operating & installation load cases
• Manufacture & testing of 3no. casing Setback “pods”
• Design, manufacture & testing in accordance with DNV 2.7-3
• Certificates of Conformity for Lifted Equipment

Outcome:

After early liaisons with INPEX & Maersk Drilling personnel, a comprehensive Basis of Design was agreed and a 3-part “pod” concept developed to aid both functionality & installation limitations.  The individual “pods” were safely lifted into position then connected together to form a single Casing Setback Platform.  No hotwork was required for the installation of the platform and lifting analysis for a vertical lift and side lift provided for lifting options.  Cube further proposed that all timbers be pre-installed & secured which greatly reduced offshore installation risk & effort.

Offshore Lift

Client feedback:

Great work all and thanks to Andrew, Emily and Steve especially for coordinating.  That was a great late in the day call to pre-install the wooden blocks.

Malcolm Reid

INPEX Drilling Superintendent

Challenge:

As part of the Woodside Ngujima-Yin FPSO modification & upgrade for the Greater Enfield project, three highly critical riser valve stacks (2.5m and up to 6t) needed to be transported offshore, lowered into the turret area and installed onto the buoy.  The turret area was highly congested with vertical and side access.

Scope:

• Detailed 3D modelling of the entire turret area with installation lift paths clash checked
• Design, manufacture & testing of a 6.5t WLL lifting davit to be mounted onto the buoy swivel pedestal.
• Design, manufacture & testing of 3 x dedicated valve stack lifting frames (DNV 2.7-3)
• Detailed Lift Plans for the installation of all valve stacks & equipment (x 7)

Outcome:

By importing a range of different software model files to create a single model, Cube Offshore produced a highly detailed & accurate digital 3D space of the FPSO turret area.  3D models of the valve stack installation paths were developed to establish the lift plan and generate a detailed 3D clash check.  This significantly reduced risk for the offshore installation operation.

Subsequently, Cube Offshore applied their design, manufacturing and lifting knowledge to deliver fully certified mechanical handling equipment and detailed Lift Plans.  At all stages, Cube actively communicated and integrated with the Woodside team to incorporate existing knowledge and lessons learned.

Client feedback:

Hi Gents,

I was going to send a note back to our contracting office letting them know how good a job Cube has done on the Greater Enfield scopes. ..

Thanks,

Scott Cranston
Completions Lead
Offshore Commissioning & Start-up Team (OCST) 

Greater Enfield Project
Woodside Energy Ltd.