Jim Britton Deepwater Corrosion Services Inc. Houston, TX. UTC 2008 Bergen

Transcription

1 Smart Cathodic Protection Retrofit Methods for ROV Installation Jim Britton Deepwater Corrosion Services Inc. Houston, TX.

2 Presentation Outline Introduction Key Factors to Consider Anode System Tie-Back System Monitoring & Verification Project Case History Outlines Northern North Sea Pipelines Gulf of Mexico Subsea Field Development Gulf of Mexico SPAR Risers & Wellheads

3 ROV friendly methods were developed d out of necessity to fix GOM gaffs water depth. Introduction ROV usage is on the increase irrespective of water depth. Sacrificial systems presented, but ROV s have successfully retrofitted ICCP

4 Anode System Design Considerations Constraints Size suitable for onshore and offshore transportation Weight to be deployed by RSV Can or cannot protrude above seabed

5 Anode System Optimization Anode Design Goals Work within physical constraints Optimize current availability Minimize number of installations Fulfill design life requirement Minimize mutual interference between anodes in an array Provide stability at installation site Minimize installation time

6 How NOT to do it Mutual interference maximized, low current 200 yr life!

7 Seabed Deployment Allows rapid deployment of large amount of anode material Simplifies ROV intervention Keep anodes in water if possible Large long parallel geometries for sub bottom arrays

8 Typical sub-bottom bottom deployed rigid sled used for pipeline retrofit

9 Tie-Back Systems The electro-mechanical connection between the anode array and the structure is critical Connect fails! CP system fails! Must be ROV friendly Options Mechanical clamp Generally favored by most operators based on cost and reliability Friction Welding Expensive and tough to control Explosive Studs Difficult for ROV, not suited to pipelines Wet Welding Operators tend to shy away very difficult for ROV

10 The RetroClamp family

11 Clamp Options Can carry anode payload directly Usually connected with flexible cables

12 Tieback Clamp Design Features Range of configurations have been used they all have common features. Single action easy location onto target Holding mechanism to hold position while torque is applied Contact element held with constant tension Variety of contact tips for connection to Structural Pipeline / Process Pipelines with coating variables

13 Variety of types used in project examples Structural Tubular / Square Tubing Pipeline Thin film FBE Pipe Flange Bolt circle engagement

14 Different geometries Bolt Circle Engagement Square Tubing

15 Verification / Monitoring Temporary installation reader Indicates clamp contact Permanent monitors Show anode current or potential shift Portable Probes Before / after measurement

16 The temporary reader system Surface installed Monitors artificially depressed clamp potential ROV recover and re-use

17 Permanent electrodes with ROV light powered readouts

18 Conventional CP Probes

19 Project A N. North Sea Meters Reason for Retrofit Pipelines showing advanced anode depletion, draining CP to platform jackets. Pipeline boost required. Scale of Retrofit 17 Anode arrays 34 tiebacks 10 Pods 7 Sleds 4 locations CWC removal ROV s 2 x Triton WC / 1 Seaeye Tiger IC Offshore Retrofit Duration 238 Hrs Average / Array 14 Hrs.

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24 Project B Subsea Field GOM Meters Reason for Retrofit New wells, flowline anodes consumed, life extension required. Scale of Retrofit 19 Pods 38 Tiebacks 4 Flowlines 5-15 Km each, 2 nd ROV excavating several areas. 8 Subsea Hardware Pieces ROV s 2 x WC Offshore Retrofit Duration 72 Hrs Average / Array 4 Hrs.

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29 Project C SPAR Subsea - GOM 1515 Meters Reason for Retrofit TSA consumption of production risers draining to well casing (dry tree system). Low potentials deep and need to preserve TSA. Scale of Retrofit 6 Risers / 6 Wells 3 SmartPods 2 wells / pod. ROV s 1 x WC Offshore Retrofit Duration 24 Hrs Average / Array 8 Hrs.

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35 Summary & Conclusions ROV can be very efficient at anode retrofit Project planning critical Use proven hardware solutions As this type of maintenance becomes second nature new equipment can go safely to post installed CP.

36 Ende