Flow Assurance Technical Section

All,

API 14 E is developed for erosional velocity prediction for tubing/pipeline but there exists some uncertainty in calculating erosional limits.

Is there any procedure to determine actual erosional velocity as a function of flow rate, temperature, pressure & gas-liquid ratio and material properties??

Further more "Prosper" calculate erosional limits based on empirical constant  "C" which is dependent upon produced fluid characteristics & target material properties (hardness, ductility & density).For sand free production: Is there any set of rules to select C values for different metallurgy (stainless steel, carbon steel, chromium alloy, etc) & downhole environment???

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Lajpat Rai
Petroleum Engineer
United Energy Pakistan Ltd
Karachi City
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C factor is a high level check to understand if there is a risk of erosion in a multiphase system. A better approach is to use the methodology described in DNV-RP-0501. We have used this technique in the past and believe it's a more effective way of checking erosion. I think DnV has now put a free download of erosion rate calculator at their website. 

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Majid Abedinzadegan Abdi
Lead Engineer, Facilities and Process
Husky Energy Inc
St. John's

Rai,

The API methodology is a first pass approach but it doesn't account for key factors, like the geometry of the system, having T's, bends, expansions, contractions are all critical when evaluating sand erosion.  DNV-RP-O501 considers these and other parameters making it a more accurate approach.

For detailed erosion calculations on small critical parts, like subsea chokes, CFD is recommended.

We recommend coupling multiphase transient simulations and the DNV method to realistically assess the risk of erosion in a production system.  

Best regards,

Luis Eljach

Senior Engineering Consultant, GATE, INC 

O: +1.832.500.3034  |  M: +1.713.560.4778

F: +1.832.500.3035

E: leljach@gateinc.com

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Luis Eljach
Production Engineer
GATE Inc
HoustonTX

Original Message:
Sent: Dec 19,2015 06:31 AM
From: Majid Abedinzadegan Abdi
Subject: Erosional Velocity Empirical constant "C"

C factor is a high level check to understand if there is a risk of erosion in a multiphase system. A better approach is to use the methodology described in DNV-RP-0501. We have used this technique in the past and believe it's a more effective way of checking erosion. I think DnV has now put a free download of erosion rate calculator at their website. 

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Majid Abedinzadegan Abdi
Lead Engineer, Facilities and Process
Husky Energy Inc
St. John's

Here is some commentary to give context to some of the previous answers.

By the sounds of it, the software mentioned in an earlier response might be an implementation of an equation similar to the one presented in a 1983 analysis of  the API 14E method:

Salama, M.M. and E.S. Venkatesh, Evaluation of API RP 14E Erosional Velocity Limitations for Offshore Gas Wells, in Offshore Technology Conference. 1983: Offshore Technology Conference, Houston, Texas.

Equation (3) from this paper gives an proposed explicit relation between fluid velocity and erosion rate. The former is a function of sand flow rate, fluid flow velocity squared, metal hardness, and pipe diameter.

For impingement erosion, applicable to gas-liquid flow through pipe bends, the authors found the relation too conservative compared to water jet erosion data. As a result they suggest using the C value of 300 in sand-free systems when using the API RP 14E approach for these systems. When the fluid carries sand they found the API RP 14E approach to show an erroneous trend.

A more detailed calculation method was proposed by one of the same authors almost two decades later for sand-laden fluids:

Salama, M.M., An alternative to API 14E erosional velocity limits for sand-laden fluids. Journal of Energy Resources Technology, 2000. 122: p. 71-77.

The more recent and elaborate recommendation for calculating erosion rate was completed in 2007 by Norwegian DET NORSKE VERITAS with collaboration from Amoco Norway, Conoco Norway, Norsk Hydro, and Statoil. Here is the link to the 2011 updated version on-line:

Erosive wear in piping systems: DNV RP-O501

If a quick simplified calculation like these is not sufficient for the nature/sensitivity of your project then the next level is a combination of laboratory tests and/or CFD simulations for estimating erosion rate. These are usually restricted by time/budget constraints, however CFD is becoming more widely accessible.

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Pablo Adames
Software Development Manager
Virtual Materials Group Inc
CalgaryAB

Original Message:
Sent: Dec 21,2015 09:37 AM
From: Luis Eljach
Subject: Erosional Velocity Empirical constant "C"

Rai,

The API methodology is a first pass approach but it doesn't account for key factors, like the geometry of the system, having T's, bends, expansions, contractions are all critical when evaluating sand erosion.  DNV-RP-O501 considers these and other parameters making it a more accurate approach.

For detailed erosion calculations on small critical parts, like subsea chokes, CFD is recommended.

We recommend coupling multiphase transient simulations and the DNV method to realistically assess the risk of erosion in a production system.  

Best regards,

Luis Eljach

Senior Engineering Consultant, GATE, INC 

O: +1.832.500.3034  |  M: +1.713.560.4778

F: +1.832.500.3035

E: leljach@gateinc.com

------------------------------
Luis Eljach
Production Engineer
GATE Inc
HoustonTX

Hello Lajpat,

Depending on company policy you may consider API, Norwegian or UK methods. All provide various fluid considerations.

A more recent 2015 DNV guideline is at  http://rules.dnvgl.com/docs/pdf/dnvgl/RP/2015-08/DNVGL-RP-O501.pdf
A good discussion from the UK Safety office is at http://www.hse.gov.uk/research/rrpdf/rr115.pdf
NORSOK P-001 is at http://www.standard.no/pagefiles/1130/p-001r3.pdf

For any design, if production velocity approaches design limit, regular inspection and monitoring with erosion probes is key.

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Taras Makogon
HoustonTX

Hi All,

I can't seem to find how API RP14E defines "sand-free" flow in the standard. I have seen loading limits of <0.1 lbs/MMscf or <20 ppmw used to denote "sand-free" flow in gas dominant flows used but can someone point me to a proper reference for the same?

Thanks,

Saurav 

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Saurav Jha
Senior Flow Assurance Consultant
Wood Group Kenny
PerthWA

Original Message:
Sent: Dec 27,2015 04:52 PM
From: Taras Makogon
Subject: Erosional Velocity Empirical constant "C"

Hello Lajpat,

Depending on company policy you may consider API, Norwegian or UK methods. All provide various fluid considerations.

A more recent 2015 DNV guideline is at  http://rules.dnvgl.com/docs/pdf/dnvgl/RP/2015-08/DNVGL-RP-O501.pdf
A good discussion from the UK Safety office is at http://www.hse.gov.uk/research/rrpdf/rr115.pdf
NORSOK P-001 is at http://www.standard.no/pagefiles/1130/p-001r3.pdf

For any design, if production velocity approaches design limit, regular inspection and monitoring with erosion probes is key.

------------------------------
Taras Makogon
HoustonTX

Saurav,

API RP 14E doesn't exactly define the parameters for sand-free flow.

If you are designing a solution for a customer, you may have to check with them on their specifications. The normal practice is that operators define their own guidelines for empirical constant 'c', sand-free conditions and other modifications to the API RP 14E formula..

In SPE 88492, the authors mention less than 0.1 lb/MMscf as nominal sand free production and more than that as excessive sand production for gas wells.

HSE (UK) Research Report 115 has mentioned (from OTC 4484 - Evaluation of API RP14E erosional velocity limitations for offshore gas wells) a well producing less than 5-10 lbs/day as being considered as sand-free.

Even otherwise, this is a guidance and preliminary selection criterion. For severe or abnormal service conditions, you may have to carry out a detailed analysis with piping geometry and metallurgy, actual diameter, sand loading rates, angle of impact, grain size, upset conditions (max rates), etc. Accordingly, you may end up with a combination of prevention and monitoring methods like erosion probes, filters, acoustic monitoring, and regular thickness measurements from a CFD analysis or something similar.

For additional information you may also refer to DNVGL-RP-0501 (Managing sand production and erosion), HSE Research Report 115 (Erosion in elbows in hydrocarbon production systems), OTC 4485 and 8898 and SPE 88492, amongst others. 

Regards.

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Sudeep Roy
Oil & Gas Professional
Geneve

Original Message:
Sent: Mar 12,2016 07:36 AM
From: Saurav Jha
Subject: Erosional Velocity Empirical constant "C"

Hi All,

I can't seem to find how API RP14E defines "sand-free" flow in the standard. I have seen loading limits of <0.1 lbs/MMscf or <20 ppmw used to denote "sand-free" flow in gas dominant flows used but can someone point me to a proper reference for the same?

Thanks,

Saurav 

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Saurav Jha
Senior Flow Assurance Consultant
Wood Group Kenny
PerthWA

Hi Sudeep,

Thanks for sharing your insights and for pointing to the references for the sand-free sand loading criteria, much appreciated.

Starting with the operator specification is always the base criterion for selection of the preferred methods, provided they have one! Also, I completely agree with the detailed assessment required for complex geometries and fittings especially those within trees and structures; which we always perform.

With API seldom being used even for screening purpose, an understanding of the comparison between methods such as DNV and Tulsa SPPS (among other less popular models) becomes important for understanding the level of conservatism applied in the final design. Even with CFD, it is important to understand which model used leads to realistic results and the different safety factors that need to be applied to the predictions from these models.

Probably, I've deviated from the subject of the thread of C-factor selection if the API method is used, but it would be great to understand more about the deviations in predictions from these methods based on benchmarking in operating facilities with high velocities.

Regards

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Saurav Jha
Senior Flow Assurance Consultant
Wood Group Kenny
PerthWA

Original Message:
Sent: Mar 13,2016 08:16 AM
From: Sudeep Roy
Subject: Erosional Velocity Empirical constant "C"

Saurav,

API RP 14E doesn't exactly define the parameters for sand-free flow.

If you are designing a solution for a customer, you may have to check with them on their specifications. The normal practice is that operators define their own guidelines for empirical constant 'c', sand-free conditions and other modifications to the API RP 14E formula..

In SPE 88492, the authors mention less than 0.1 lb/MMscf as nominal sand free production and more than that as excessive sand production for gas wells.

HSE (UK) Research Report 115 has mentioned (from OTC 4484 - Evaluation of API RP14E erosional velocity limitations for offshore gas wells) a well producing less than 5-10 lbs/day as being considered as sand-free.

Even otherwise, this is a guidance and preliminary selection criterion. For severe or abnormal service conditions, you may have to carry out a detailed analysis with piping geometry and metallurgy, actual diameter, sand loading rates, angle of impact, grain size, upset conditions (max rates), etc. Accordingly, you may end up with a combination of prevention and monitoring methods like erosion probes, filters, acoustic monitoring, and regular thickness measurements from a CFD analysis or something similar.

For additional information you may also refer to DNVGL-RP-0501 (Managing sand production and erosion), HSE Research Report 115 (Erosion in elbows in hydrocarbon production systems), OTC 4485 and 8898 and SPE 88492, amongst others. 

Regards.

------------------------------
Sudeep Roy
Oil & Gas Professional
Geneve