1. Lesson Overview: Pipelines and Flowlines
Lesson: Pipelines and Flowlines
Topic: Lesson Overview
Sub-Topic:
Learning Objective:
Lesson Overview: Pipelines and Flowlines
New methods and high-tech vessels have brought major new capabilities and cost savings to the construction, installation and operation of pipelines/flowlines.
Introduction
Construction/Installation
Onshore Construction
Surface, Mid-Depth and Off-Bottom Tow
Reel Barge
Offshore Construction
S-Lay
J-Lay
Seafloor Topology and Current Issues
Subsea Connections
Repair
Flow Assurance
Inhibitor Injection
Pigging
Temperature Control
Slug Flow/Sand Erosion
As you progress through the lesson you will be given the chance to answer brief Exercises to see if you have learned the fundamentals of the material covered. Remember, at the end of the entire Deepwater module you will be required to take a final assessment, where your responses will be recorded.

2. Introduction Challenges
In deep water, several factors increase pipeline/flowline cost and technology challenges.
Challenges
Higher pressure and lower temperature at the seafloor
Production coming from deeper reservoirs at higher temperatures and pressures
Greater distances from subsea wells to floating facilities
Facilities farther from shore
Pipelines that carry hydrocarbons from offshore production locations back to shore have always been part of offshore installations.
In addition, there have been flowlines that carry product from subsea wellheads to manifolds and then to fixed installations.
Indeed, pipelines and flowlines have always been a major element in the capital cost of offshore installations.
We have seen that the number of deepwater developments using subsea completions is increasing. The advance in flowline technology is one of the factors driving this trend.

3. Flowlines reach extreme depth and distance
Subsea tiebacks are dominating deepwater development, reaching beyond 9,000 ft WD and almost 45 miles (oil) and 90 miles (gas) distance.
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4. Lesson: Pipelines and Flowlines
Topic: Learning Objectives
Sub-Topic:
Learning Objective:
Learning Objectives
Upon completing the Pipelines/Flowlines lesson, participants will be able to:
+ Recognize the importance of pipeline and flowline construction in deepwater exploration.
+ Name some challenges for pipeline construction in deep water.
+ Differentiate between onshore and offshore pipeline construction and installation.
+ Describe two techniques for laying pipe.
+ Recognize the effect of seafloor topography in laying pipe and give examples of how those challenges have been overcome.
+ Discuss subsea connections using both vertical and horizontal subsea connectors.
+ Describe a deepwater pipeline repair system using an ROV.
+ Give examples of natural impediments to oil flow.
+ What are the techniques used in flow assurance?
You will learn the current technology for deepwater pipeline/flowline:
Construction/installation
Repair
Seafloor Connection
Flow Assurance

5. What part do pipelines and flowlines play in offshore installations?
Pipelines carry product, usually partially processed, from offshore facilities to shore.
Flowlines transport product produced from subsea wells, either to manifolds where it is commingled or directly to a floating facility.
The illustration is a hypothetical drawing of multiple fields and deepwater platforms with flowlines connecting individual, subsea wells with manifolds and floating facilities. There are also pipelines transporting partially processed product to shore. Occasionally, in shallow water locations, a subsea installation may produce directly to shore.
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6. Pipeline/flowline construction and installation methods
Onshore construction followed by towing to the offshore site by:
Surface tow
Mid-depth tow
Near-bottom tow
Choice of the construction and installation methods depends on many factors, such as pipe diameter and insulation covering, water depth, topology of the seafloor, metocean (weather and currents) conditions, distance, availability, and cost of equipment. We will discuss some of these factors.
Onshore construction plus winding on a reel and then unreeling offshore from a reel vessel
Offshore construction (on the pipelay vessel) and installation by:
S-lay
J-Lay
We will now discuss each method.

7. Towing Pipelines on the Surface
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Towing Pipelines on the Surface
Pipelines can be fabricated on the beach, then towed out with buoyancy attached. When the buoyancy is reduced on location, and/or the pipe is flooded, it submerges.
Onshore fabrication followed by tow out to location is attractive where the water is calm, because severe waves can damage the pipe. The pipe sections can be fabricated to the required lengths for making offshore connections to facilities and wellheads.
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8. Towing Pipeline Mid-Depth and Off-Bottom
To prevent damage from wave forces, the pipeline may be towed submerged.
Off-bottom
Depth controlled by buoyancy and dragged chains
For mid-depth tow, the pipeline is suspended between two boats (Figure 2).
For off-bottom, vertical chains are added to drag on the seabed to effect a neutrally buoyant pipeline (Figure 1).
Mid-depth
Suspended between two boats
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9. Onshore Flowline Construction and Laying from a Reel Vessel
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Onshore Flowline Construction and Laying from a Reel Vessel
Smaller diameter line is fabricated onshore and then wound onto a large reel, as much as 200 ft in diameter. It is deployed offshore from a reel vessel, straightened as it is laid.
Use of reel vessels has greatly facilitated laying flowlines and smaller pipelines. Onshore fabrication substantially reduces cost and increases quality control. These videos make clear how meticulous each step must be to ensure that the pipe will be able to withstand installation and the hazards on the seafloor. For example, there is a thorough inspection of the pipe before delivery, the welds following welding, and the protective coating.
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The first video (WV-10) is a horizontal reel vessel capable of laying two lines simultaneously. The second video (SS7-1) shows how the line is fabricated and loaded onto a vertical reel vessel.

10. S-Lay Technique for Laying Pipe
In the illustrations and videos so far, we have seen pipe deployed from the vessel by the S-lay technique. The pipe releases horizontally from the back of the vessel and then bends downward over a stinger. Tension is maintained in the pipe, causing it to bend gently back to horizontal when it reaches the seabed.
High tension on the pipeline prevents overbending.
Buoyancy may be added to reduce its weight in water.
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11. S-Lay Stinger
Stinger: A curved steel structure with rollers that protrudes from the stern of the pipelay vessel and limits the bending radius of the pipe
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12. Construction and Deployment from an S-Lay Vessel
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Construction and Deployment from an S-Lay Vessel
The first animation (WV-9) illustrates how pipeline/flowline is fabricated and laid as the pipelay vessel moves along the prescribed route. This is a typical method for laying larger diameter pipelines.
Pipelines can be laid from specially built offshore vessels that move along the route, laying the pipeline behind. This method is typical for larger diameter pipelines, greater than about 14 in. One video is an animation so you can visualize what’s happening. The second is actual footage from a pipelay vessel showing more details of the fabrication.
Notes:
Sections of pipe are loaded onboard from a barge.
Welding is automatic, followed by thorough inspection.
Protective, anticorrosion coating is applied following welding.
A stinger prevents excessive bending.
Tension is applied to the pipe by tractors. The pipe must be maintained in tension to prevent excessive bending at the seafloor.
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The second video (WV-14), shows details of the fabrication and inspection operations on an actual pipelay vessel, the Solitaire.
WV-9, WV-14

13. J-Lay Technique for Laying Pipe
A more complex method, J-lay is generally employed for deep water due to the high tension caused by the weight of the long, suspended pipe.
The pipeline is fabricated vertically in a gimbaled tower and lowered vertically to the seabed where it bends to the horizontal (assuming a J curve).
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The pipeline is fabricated vertically in a gimbaled tower and lowered vertically to the seabed where it bends to the horizontal (assuming a J curve). The tower is usually gimbaled to accommodate vessel motions without inducing bending stresses in the pipe.

14. J-Lay Technique, cont.
Two of the largest crane barges in the world, Heerma Balder and Saipem 7000, (shown) have been retrofitted with J-lay towers.
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Saipem

15. J-Lay on Crane Barges, cont.
These huge crane barges can J-lay prewelded, 160-ft joints of pipe, reducing the number of welds required in the tower.
Heerma
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Saipem 7000
The Heerma Balder can J-lay 30-in. diameter pipe in up to 10,000 ft water depth (2.6 MM lb).
J-lay video: This (WV-8) animation shows how fabrication is accomplished in the vertical tower. Notice the multiple set of tractors for supporting the pipe’s weight.

16. Subsea 7 Ship
Like the Seven Borealis, below, some new vessels are equipped for both S-lay and J-lay.
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The large pipelay vessel shown in this animation (SS7-2) is capable of both J- and S-Lay operations. Its large capacity and simultaneous operations capability gives it cost advantage for the installation of deepwater fields with extensive pipelines/flowlines.

17. Exercise Define the J-Lay technique for laying pipeline.
Lesson: Pipelines and Flowlines
Topic: Exercise
Sub-Topic:
Learning Objective:
Exercise
Exercise
What is the difference between the J-Lay and S-Lay techniques for laying pipe.
How is pipe constructed onshore and offshore?
Which construction is more economical?
What is the purpose of a stinger?
What is the purpose of a gimbaled tower in the J-Lay technique?
When is onshore construction the better choice?
Which towing method uses two boats?
Define the J-Lay technique for laying pipeline.
Define the S-Lay technique for laying pipeline.
What are the two kinds of barges used in pipeline construction?
Why is deepwater pipeline construction so expensive?
What are two methods of towing pipe?

18. Seafloor Topology
The seafloor is often not flat and soft. Canyons, mounds, escarpments, even small mountains can present major obstacles for pipelines.
The seafloor is often far from flat. Major geohazards (canyons, mounds, escarpments, even small mountains) can present major obstacles for pipelines. The seafloor topology must be carefully surveyed before pipe laying so that a suitable route can be laid out.
There may be significant currents at the seafloor. Pipeline that is not buried is subject to hydrodynamic forces, and even VIV where the pipe spans a seafloor depression. One of the worst seafloor challenges was the Orman Lange project offshore Norway, seen in the video, where they installed vibration monitors.
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To avoid damage during pipe laying and to preclude long, unsupported spans, the seafloor must be surveyed to find a suitable pipeline route.

19. Seafloor Topology and Seafloor Currents
In many areas there are significant currents at the seafloor.
Hydrodynamic drag can move unburied pipeline on or near the seafloor.
Unsupported spans are subject to Vortex Induced Vibrations (VIV) that can lead to fatigue failure.
Orman Lange
Pipeline Span
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One of the worst seafloor challenges was the Orman Lange project offshore Norway, seen in this video (WV-25). Vibration monitors were installed to record any vibration.

20. Seafloor Topology and Seafloor Currents, cont.
When long spans and high seafloor currents are possible, the pipeline may be fitted with strakes to suppress VIV.
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RJ Brown
Even flowline jumpers may require strakes.
RJ Brown
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21. Subsea Connections
The ends of pipeline/flowlines are connected to seafloor facilities and wellheads by remote operations. Many ingenious techniques have been devised. Here are a few:
Vertical Connections
An illustration of a wellhead connected to a manifold with a jumper
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A subsea manifold
connected to many wellheads

22. Subsea Connections – Vertical
This is a J P Kenny scheme. (Kenny is one of the oldest names in offshore pipelines.) The jumper is prepared with downward-looking connectors that can be closed over the upward looking receiver with a hydraulically actuated tool that is in the connection tool. With ROV guidance, the jumper is lowered over the both upward-looking receivers simultaneously, one on the wellhead and one on the manifold. Both connectors are closed and locked hydraulically. The connection tools are then retrieved.
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1.The remote tools, carrying the ends of the jumper, are lowered over the upward-looking receivers.
2. The connectors are closed and sealed by hydraulic power.
3. The tools are retrieved.

23. Subsea Connections – Horizontal - I
The first pipe section was terminated a connector receiver and attached to a base with a guide post. The second pipe section was cut to precise length and the connector tool attached to it, with the guide sleeve. The tool and guide sleeve are lifted over the post with ROV guidance and assist. The connection tool closes, locks and seals the connector.
A previously laid line was terminated at a base with a guide post. First using the sleeve, then by fine positioning in the tool, the ends are merged. The connector is closed, sealed and tested.

24. Subsea Connections – Horizontal - II
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A wire connected to the end of the new pipe pulls it close to the receiver on the facility.
The ROV guides the pipe head into the receiver as the wire pulls it.
The ROV then locks, seals and tests the connector.

25. Subsea Connections – Horizontal - III
This animation (WV-31) shows an elaborate North Sea technique for seafloor joining of two pipeline segments.
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26. Exercise Explain why and how a strake is employed.
Lesson:
Topic: Exercise
Sub-Topic:
Learning Objective:
Exercise
Exercise
Explain why and how a strake is employed.
Give an example of ROV use in subsea connector utilities.
3. What is VIV and how can it be dealt with?
4. Describe how vertical or horizontal connectors can be employed remotely on the seafloor.

27. Repair A major challenge is repair of damaged deepwater pipelines.
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Learning Objective:
Repair
A major challenge is repair of damaged deepwater pipelines.
The schematic shows cutting out a section of the pipeline containing the leak or damage, removing and replacing it with the help of an ROV*.
* Remotely operated vehicle
The schematic shows cutting out a section of the pipeline containing the damage, removing and replacing it with the help of an ROV*.
* Remotely operated vehicle
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28. Repair, cont. A crane lowers a section of pipeline for the repair.
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29. Lesson :
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Repair, cont.
Chevron has developed and fabricated a deepwater pipeline repair system. It is stored on the Gulf coast for shipment when needed anywhere in the world.
The modular system features:
Interchangeable parts
80,000-lb. lift capacity
Dual grip and seal hydraulic connectors
No debris left on sea bottom
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This video (WV-19) explains the Chevron Deepwater Pipeline Repair System, which is similar to other operations.

30. Lesson:
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Repair, cont.
In the Chevron video, we saw that damaged pipeline needs to be cut and the ends prepared for insertion of a new section. The Wachs® Subsea diamond wire saw, deployed by an ROV, was used.
The Wachs® Subsea diamond wire saw can be used with an ROV to:
Sever 12- to 24-in. diameter pipe
Bevel pipe internally and externally
Remove fusion bond epoxy (FBE) coating
Remove longitudinal weld seam
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This is a (WV-23) demonstration of the Wachs diamond wire saw which is capable of cutting pipe up to 24-in. diameter.

31. Exercise Describe the principles of Chevron’s DW PR system.
Lesson:
Topic: Exercise
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Exercise
Exercise
Describe the principles of Chevron’s DW PR system.
What is an ROV?
How is an ROV instrumental in deepwater pipeline repair?

32. Flow Assurance
All pipelines carrying crude oil and gas tend to become clogged, even on land and in shallow water. In deep water, low temperature and high pressure require various measures to assure pipeline flow. Very briefly, the problems are:
Gas hydrates are ice-like minerals that form crystals at the low temperatures and high pressures in the deep sea. Crystals forming inside pipelines or flowlines can clog the flow.
All crude oil contains some amount of wax (paraffin and asphaltene) that will solidify as the temperature drops.
Corrosion due to corrosive elements in the crude can damage or even breech the line.
Gas hydrates are ice-like minerals that form crystals at the low temperatures and high pressures in the deep sea. Crystals forming inside pipelines or flowlines can clog the flow.
Crude oil contains some amount of wax (paraffin and asphaltene) that will solidify as the temperature drops.
Corrosion due to corrosive elements in the crude can damage or even breech the line.

33. Flow Assurance: Inhibitor Injection
To prevent flow restrictions by hydrates and wax, and to inhibit corrosion, chemicals are injected into the flow. An extensive process is employed to specify the inhibitors and to design the injection system.
Extensive engineering analysis (example by Noble Denton) and design are required to specify the amount and method of inhibition. Elaborate systems of injection lines and fluid pumps are required to convey the inhibitors to the upstream ends of the pipelines/flowlines where they are injected. Instruments in the lines monitor the flow to ensure that the inhibitors are working.
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34. Flow Assurance: Pigging
In addition to inhibition, pigs are pumped through lines to remove the buildup of hydrates, wax and scale on a pipeline’s inner wall. Instrumented pigs can also measure the pipeline wall thickness, detecting corrosion before leaking occurs.
Pig launchers and receivers must be built into the pipeline during construction.
A pig* is pumped through the line, scraping the wall and pushing the buildup out through the pig receiver.
Besides scraping, “smart” pigs incorporate sensors to detect damage and corrosion, so it can be repaired before leaks occur.
* A device with blades or brushes inserted in a pipeline for cleaning purposes. The pressure of the oil stream behind pushes the pig along the pipeline to clean out rust, wax, scale, and debris.
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35. Flow Assurance: Pigging, cont.
Pigging Operations:
Pig launchers and receivers must be built into the pipeline during construction.
A pig is pumped through the line, scraping the wall and pushing the buildup out through the pig receiver.
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This video (WV-24) of the Pipeline Engineering Automatic Pig Launching System illustrates pig launching and retrieval.

36. Flow Assurance: Temperature Control
For long flowlines carrying very hot product from very deep wells, chemical injection and pigging may be insufficient or not cost effective.
Another option is to reduce heat loss by coating flowlines with insulation.
Constructed “pipe-in-pipe” uses the outer pipe to protect the insulation against the harsh environment of installation and seabed survival.
Extensive design analysis and testing are required.
Courtesy Bredero Shaw
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37. Flow Assurance: Temperature Control, cont.
Pipe-in-pipe construction protects the insulation during installation and in service.
For long flowlines carrying very hot product from very deep wells, chemical injection and pigging may be insufficient or not cost effective.
Insulated flowlines can reduce heat loss, thus reducing solidification of hydrates and asphaltenes.
Flowlines can be coated with insulation, or even constructed “pipe-in-pipe,” the outer pipe protecting the insulation against the harsh environment of installation and seabed survival. Extensive design analysis and testing are required.
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Designs of pipe-in-pipe insulated flowlines requires extensive thermal analysis and testing.

38. Flow Assurance: Temperature Control, cont.
Complex pipe-in-pipe designs can incorporate fluid and electrical heating sources to deal with highly viscous oil.
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39. Flow Assurance: Slug Flow and Sand Erosion
Two additional problems are slugs in two-phase flow (liquid and gas) and sand erosion. Solutions to these problems are more difficult in remote, deep water.
Slug Flow
Liquid collects at depressions in the pipe, cleared only when the gas pressure behind it builds up sufficiently.
Uneven flow results.
Rising and falling pressure causes pipe vibration and disruptive conditions at the pipe exit.
An active system of pressure sensors and variable chokes may be required to break up the slugs.
Liquid collects at depressions in the pipe, being cleared only when the gas pressure behind it builds up sufficiently. This leads to uneven flow, with rising and falling pressure causing pipe vibration and disruptive conditions at the pipe exit. An active system of pressure sensors and variable chokes may be required to break up the slugs.
This problem exists in all lines but remote, deep water complicates the solutions.
The same condition exists with the erosion caused by sand in the flow.
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40. Flow Assurance: Challenging Example
Anadarko’s new Independence Hub platform in 8,000 ft WD presents a major challenge to uninterrupted hydrocarbon flow.
20+ tiebacks (totaling over 176 miles)
Farthest tieback: 45 miles
Deepest wellhead: 9,000 ft WD
Pipeline: 135 miles to near shore terminal
Anadarko’s Independence Hub platform is moored in 8,000ft WD and has 20+ tiebacks (totaling over 176 miles) to gas wells reaching as far as 45 miles and going down to 9,000 ft WD, at the time of installation, the deepest water depth production.
IH’s 24-in. diameter gas export pipeline runs 135 miles to a near shore junction.
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Underwater view of Independence Hub in the GoM shows its flowlines and risers.

41. Exercise 1. What natural occurrences impede pipeline flow?
Lesson:
Topic: Exercise
Sub-Topic:
Learning Objective:
Exercise
Exercise
1. What natural occurrences impede pipeline flow?
2. What is a pig and how does it solve a problem in pipeline flow?
3. How can insulating the pipe help pipeline flow?
4. What is pipe-in-pipe insulation?
5. How did Anadarko solve its flow problems at great depths?