BURIAL ASSESSMENT AND SUCCESSFUL CABLE BURIAL: OLD TOPIC, NEW - - PowerPoint PPT Presentation

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BURIAL ASSESSMENT AND SUCCESSFUL CABLE BURIAL: OLD TOPIC, NEW LESSONS

• R. Rapp, C. Carobene, F. Cuccio

Tyco Electronics Subsea Communications (TE SubCom)

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Presenter Profile

• Dr. Rapp is the Director of Cable Engineering and Technology at TE

SubCom in Morristown, NJ, where he manages the Desk Top Study, Route Survey and Engineering, Marine Liaison, and Geographical Information Systems (GIS) groups. Collectively the

• rganization engineers undersea telecommunications systems

around the world. Ron has worked in the marine field for over 30 years with a number of companies including AT&T Bell Laboratories, Lucent Technologies, and Chevron. He holds a BS degree in Mechanical Engineering from the Pennsylvania State University and a Ph.D. in Ocean Engineering from the Massachusetts Institute of Technology where he did research in deep water wave breaking.

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• Dr. Ronald J. Rapp

Director, Cable Engineering & Technology TE SubCom (Formerly Tyco Telecom) Email: rrapp@subcom.com Tel: (+1) 973-656-8215 Mobile Tel: (+1) 908-930-1146

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Topics

• Threats to cable security
• Ensuring cable protection through burial
• A refocus on tools and analysis to assess burial
• Burial Feasibility Study - plow operability
• More capable burial tools
• Case studies and lessons learned
• Conclusions

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Fishing and anchoring pose the greatest risk to cable security. Cable burial remains the most effective and economical method of protection against these threats.

• r

• n

• l
• g

Why Bury? Threats

• M. Kordahi, S. Shapiro, G. Lucas, “Trends in submarine Cable System Faults,” SubOptic 2007

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This paper focuses on understanding the full set of conditions that impact plow operations and performance and on the marine survey and analysis to assess these conditions and the burial feasibility. This remains crucial to installing a reliable system and has significant commercial implications.

Desktop Study Route Selection Survey, Seabed Assessment, Route Refinement Burial Feasibility Study Burial Operations Cable Awareness Program

Requires focus over the full project cycle! Requires focus over the full project cycle! Ensuring Cable Security

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• P. Mole, J. Featherstone, S. Winter, “Cable Protection –

Solutions Through New Installation and Burial Approaches,” SubOptic, 1997, San Francisco, USA. P.G. Allan, “Selecting Appropriate Cable Burial Depths – A Methodology ,”IBC Conference on Submarine Communications, Cannes, 1998

• R. Hoshina, J. Featherstone, “Improvements in Submarine

Cable Protection,” SubOptic 2001, Kyoto, Japan

• M. Jonkergouw, “Industry Developments in Burial

Assessment Surveying (BAS),” SubOptic 2001, Kyoto, Japan

• R. Rapp, R. Munier, I. Gaitch, G. Lucas, T. Kuwabara,

“Marine Installation Operations: Expectations, Specifications, Value and Performance,” SubOptic 2004, Monaco.

• R. Rapp, J. Mangal, R. Munoz, “Accuracy of Cable Burial

Depth Measurements: A Review of the Issues,” International Cable Protection Committee (ICPC) Plenary 2002, Naples, FL, USA.

• M. Jonkergouw, “Is BAS Still Necessary, and if so, Where

and How?,” SubOptic 2007, Baltimore, USA.

Introduction of Burial Protection Index (BPI).

Burial depth required to protect cable is a function of soil stiffness.

Threat penetration depths and protection methods Review of invasive BAS tools, E-BAS, C-BASS Accuracy of Burial Depth Measurements Limitation of E-BAS in shortened project cycles

1997 2007

Background

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Relatively flat homogeneous seabed 0.6m to 1.5m plows with moderate pull capability

Focus on Plow Operability and maximizing time

• n bottom.

Rocky variable seabed 1.5m to 3 m plows with high pull capability

Previous Now

Focus has been

• n soil stiffness,

depth of burial, burial protection index (BPI)

BAS tools to measure shear strength Use of complete suite of survey tools to fully characterize the seabed

Focus Is Now on Plow Operability

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Burial assessment cannot rely on any one tool or single piece of survey gear; it must be based on an integrated analysis of all data.

Multibeam Echosounder bathymetric mapping SideScan Sonar Sub Bottom Profiler Gravity Core Cone Penetrometer (CPT)

Survey Tools and Techniques

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Experienced and knowledgeable geologists provide accurate data interpretation to engineer best burial routes. Plow operations are considered in route design to maximize tool performance, improve cable burial and thus enhance cable protection.

Multibeam swath depicting pipeline Crossings south of Singapore

• sition

Sub Bottom Profiles Seabed Shear Strength to 3 m Core Samples Side Scan Sonar Image – Coral Heads

Survey Data Interpretation

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Burial Category: A: Cable burial to a target cover depth of 0.8 –1.0 m; B: Cable burial to a target cover depth greater than 0.4m but less than 0.8m; C: Cable burial to a target cover depth of less than 0.4m; D: Risk of uncontrolled cable burial to a cover depth of greater than 0.8m; E: Cable burial to a target cover depth of 1.5 m in water depths of 10-20 m; F: Cable burial to a target cover depth of 3 m in water depths of less than 10 m; G: Cable burial to a target cover depth of 3 m. Risk Category: 1: No identified risk of damage to the burial equipment due to seabed conditions; 2: Possible risk of damage to burial equipment due to seabed conditions. Scale of possible damage to be repairable on the installation vessel using shipboard equipment; 3: High risk of damage to the burial equipment due to seabed conditions. Scale of possible damage in excess of category 2.

Results of the integrated survey and analyses form the Burial Feasibility Study BFS is a guideline to predict burial likelihood and plow risk along the route Where seabed is not conducive to burial, consider uparmor if warranted by risk of external aggression

Example Only Deeper burial may be required in many cases

Key Elements of the BFS

• Seabed description
• Core and CPT

penetration depth

• Hazards such as slopes,

rock, boulders, coral, sand waves, soft sediment, pock marks

• Cable or pipeline

crossings

• Currents that may affect

plow or ROV deployment

• r operations

Burial Feasibility Study (BFS)

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Towed cable plows remain the industry standard for cable burial. Improved capability allow deeper burial and in more challenging seabed. The burial will be dictated by plow operations and reasonable endeavors guidelines. New burial tools are more capable and less sensitive to soil stiffness; seabed bathymetry and features are more critical to performance. New burial tools are more capable and less sensitive to soil stiffness; seabed bathymetry and features are more critical to performance.

Sea Plow 7 - 1.5m Plow MD3 – 3 m Plow EB Sea Stallion 3 m Plow ROV for Jet burial

Cable Burial Tools

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Recommendations and lessons learned were based on projects representing a range of seabed conditions; recent burial assessments were compared to the actual success of cable

• burial. (Blue ovals show areas of burial)

Case Studies

Selected TE SubCom Systems Installed over the past 3 years

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Goal is to obtain a strong correlation between the survey results, that describe the seabed, and the actual conditions ultimately encountered by the burial tools (plow and ROV).

Results and Correlation

Integrated analysis of seabed comprising sidescan sonar, multibeam echosounder, sub- bottom profiler, core and CPT

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Results and Correlation

Examples of well buried cable in sand and cobble sediments

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Results and Correlation

Plowing is not always recommended. Surface laid cable is well conforming to the seabed in areas not suitable for plowing.

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Burial assessment and feasibility is part of the integrated marine route survey program; it is not a separate operation or study. Contract scopes

• f work and technical requirements should be written with this in mind.

Seabed sampling intervals chosen to balance cost and cable protection. Missed features or inaccurate seabed characterization are often due to incomplete analysis of existing data or where an existing sensor was

• perated incorrectly.

Even small areas of mischaracterized seabed can cause significant downtime to repair a damaged plow or cable, and perform recovery, reroutes, and relays. Postmortems and feedback to survey contractor is crucial to process improvement, is often missed in the rush to the next project.

Lessons Learned

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There is no silver bullet or single tool that will improve the characterization of the seabed and conditions for maximizing plow performance. An integrated and disciplined system approach of survey and analysis is required where all sensors perform to required specification and are used to optimize the route for burial. Budgets must be in line with required survey line plans and seabed sampling intervals. A strong focus on Plow Operability and the full set of conditions that impact plow operations and adjusting the route and burial accordingly will maximize burial success and cable protection. A strong focus on Plow Operability and the full set of conditions that impact plow operations and adjusting the route and burial accordingly will maximize burial success and cable protection.

Conclusions

2010

Pacifico Convention Plaza Yokohama & InterContinental The Grand Yokohama 11 ~ 14 May 2010 www.suboptic.org

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The 7th International Conference & Convention

• n Undersea Telecommunications

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