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Flow Assurance In Pipelines – An Introduction




For the last 4 to 5 weeks I am preparing a presentation on pipeline flow assurance for some young engineers of my company.

Now I would like to present an abridged form of that presentation on my blog for the benefit of the forum readers.

Here is how it goes:
"Flow assurance is an engineering analysis process to assure hydrocarbon fluids are transported through pipelines in an economical manner from the source to the destination in a given environment over the life time of the project.

Flow assurance covers the whole range of possible flow problems in pipelines such as hydrate formation, wax & asphaltene deposition, corrosion, erosion, scaling, emulsions, foaming, and severe slugging.

The avoidance or remediation of these problems is the key aspect of flow assurance that enables the design engineer to optimize the pipeline system for the complete operating envelope including start-up, shutdown & turndown scenarios.

Flow assurance is a recognized critical part in the design & operation of both onshore & offshore oil/gas systems.

Following are the flow assurance concerns that need to be examined:

  • Pipeline rupture from corrosion
  • Pipeline blockage from hydrates or wax
  • Severe slugging can damage separator
  • Large pressure drop in pipelines can cause lower flow than should be

Following are the flow assurance strategies that need to be adopted:
  • Hydraulic Analysis – acceptable pressure drops, pipeline size, erosion & corrosion limits
  • Thermal Analysis – temperature distribution, heat loss
  • Inhibition Analysis – hydrate inhibitors, wax inhibitors, corrosion inhibitors, scale inhibitors

When is flow assurance required?

The bulk of the flow assurance analysis is done during the Front End Engineering & Design (FEED) stage.

During detail engineering phase a verification process may be undertaken based on the following:
  • Changed product specifications including composition, phase change (GOR, water cut)
  • Change in pipeline routing
  • Changed operating procedures
  • Change in local health, safety & environmental regulation

Why modeling of pipeline systems is required for flow assurance?


Modeling is a cost effective & tested tool for flow assurance. Some benefits are:
  • Ease of studying & optimizing new and existing pipeline systems
  • Facilitates rigorous screening of various options in existing and potential systems
  • Reduce uncertainty in design & operation
  • Reduce downtime by giving a realistic picture of how the system will be

How is modeling of pipeline systems done?

Steady State Modeling:
  • Software such as PIPESIM & HYSYS can be utilized for steady state modeling
  • Objectives of Steady State Modeling
  • Determine the relationship between flow rate and pressure drop along the pipeline and decide the size based on the maximum allowable flow rate & the minimum allowable flow rate.
  • Check temperature and pressure distributions along pipeline in steady condition to ensure that the pipeline never enters the hydrate region during steady state operation.
  • Determine the maximum flow rate in the system to assure that the arrival temperatures do not exceed any upper by the separation and dehydration processes or by the equipment design

Transient Modeling:
  • Software such as OLGA and ProFES can be utilized for transient modeling
  • Transient Cases or Scenarios:
  • Start-up and Shut-down
  • Emergency shut-down
  • Blow-down and warm-up
  • Ramp up or down
  • Pigging / slugging
Objective of transient analysis is to ensure that the pipeline conditions are maintained to prevent dangerous surge conditions and to prevent conditions (pressure and temperature) for hydrate formation.

Comments from valued readers of the forum are most wecome.







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Qalander (Chem)
Nov 12 2010 12:52 AM
Dear Ankur Thanks,

I believe that this particular blog of yours is very much guiding and supporting for understanding even the flare system's issues as being discussed in one of the forums right now.

I do appreciate and suggest OP "ogpprocessing" to once again read through this blog entry.
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Best Regards
Dear Sir,
Thank you for this valuable thread.
I have a question, what is ramp up and ramp down?
Could you please explain with the simplest way as Im a beginner in flow assurance.

Your help is highly appreciated. Thank you.

Regards,
Iwan
Thank you so much. This is extreamley valuable.
If possible please share the presentation.

Thks in advance.
Photo
truongld_83
Dec 29 2011 04:17 AM
It is better to know If you share the presentation.
Looking forward to your presentation
Thank you, please i need
Flow Assurance In Pipelines complete
Photo
sondung4ever
Aug 13 2013 04:06 PM
Please give me some guidelines for Engineer beginner in flow assurance. - A Detailed List Of Books need to read - Work will do when study flow assurance Thank you
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zorro21072107
Aug 19 2013 03:44 AM

Dear Ankur, 

 

your post is very much appreciated

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vaibhav.poly
Sep 06 2013 02:13 AM

Dear Ankur,

 

very nicely explained. it cleared my fundamentals about Flow assurance study. I am new in this field. currently i am doing one off shore project and have one query.There are two existing platforms from which well fluid is going to onshore facilty. This is carried by existing sub sea header. Now two new platforms are erected. but the well fluid coming from these new platform is also connected to existing sub sea header.

Now client is asking us to do flow assurance study for new platforms. But my concern is that as there is already existing header for which client might have done FA study earlier. As now only flow quantity is increased does it really required to do new FA study. (All composition, pressure,temperature remains the same).

Your expertise will be highly appreciated. Thanks in advance.

vaibhav,

 

Any modification to a pipeline whether sub-sea or onshore requires a re-validation of the flow parameters which can be done through flow assurance. You definitely need to do a flow assurance study to ensure that the existing sub-sea pipeline is able to deliver economically with the new flow parameters.

 

Regards,

Ankur.

Vaibhav,

 

You have not mentioned  in which pahse well fluids are flowing, ( oil,  gas, or  multiphase). Though your subsea configuration is unchanged downstream of subsea header, you have to do the the flow assurance study considering additional flow through the header and check whether additional flow  is not violating your boundry conditions and desigh margins.

 

Regards,

 

Madan

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