Use of GPR (Ground Penetrating Radar) for buried pipe mapping in O & G Plant 1

[Meesamali512]

Dear All,
We have a project related to installation of CP system for a very prestigious Oil & Gas client for its live gas plant. Our company is taking care for the civil part which is mostly related to excavation works, reinstatement after installation of CP anodes, augering for various depths, small RCC foundations and all sorts of civil works to support the CP installation works. As per the strict guidelines of plant management, we can only dig up to 0.9m without any approvals or detailed surveys. For augering to depths more than 0.9m we need to do a subsurface scanning using ground penetrating radar "GPR" and then after making a map of existing facilities then we can proceed with excavation / augering. I want to know details about GPR and how it is used and what are the precautions related to it? Moreover is this latest technology or are there better technologies available? Need detailed insight on this topic as I have to prepare the detailed technical & commercial bid.
Any help / guidance is much appreciated.

Best Regards,
Syed Meesam Ali

 

[Ron]

Yes, GPR is appropriate technology for this application, however, you must understand that the method is not magic and relies heavily on the proper selection of equipment (there are numerous antennae for various applications), the proper operation of that equipment, and proper interpretation of the results. GPR scans can be confusing in congested areas and erroneous interpretations are possible if not probable.

I would suggest doing a physical correlation with the subsurface indications for one or two areas before you rely too heavily on the results.

 

[Meesamali512]

Thanks Ron for your quick reply. Actually we have mostly underground buried piping which consists of pipes for various utilities i.e. potable water, sewage water, contaminated water, gas lines, chemical lines etc. Most of these pipes are 6" dia or more and are spaced properly so hopefully congestion won't affect the results. Can you please recommend some brand which is most commonly used or some equipment? Any guidance about relevant codes / standards as I am totally new to this?

 

[Ron]

GSSI is the leading manufacturer of GPR equipment. Call them. They are quite helpful.

603-893-1109

http://www.geophysical.com

Note: I am not affiliated with GSSI except as a customer

 

[a2mfk]

Agree with Ron's assesment of GPR. Our company uses GPR all of the time, and you definitely need someone who knows how to operate the equipment and interpret the results. Also picking the device with the right frequency for that application is important, they can vary greatly.

But if you are looking for buried pipes 6" and up, space apart, GPR is a good choice.

 

[dik]

In addition to GPR... you might consider hydrovaccing...

Dik

 

[LittleInch]

GPR is a useful technology, but like many other systems, has its own issues. The key one that affects definition of depth is knowledge of the actual ground and its particular physical properties as these affect the speed of transmission and hence depth. This is why they work very well in concrete which is a homogeneous material. If what you're trying to do is find clear areas where you can excavate bases or drill augers then accurate depth probably doesn't matter very much. One thing you need to lok at is the differentiation of pipe sizes at different levels (tends to reduce with increasing depth)

It works best on flat prepared surfaces where you can make lots of lines back and forward to cover the area of interest.

Even then, once you've dug to you 0.9 m depth, I would suggest you Cat scan the bottom of the hole to pick up any small cables or pipes which may have been missed by the GPR.

You need to hire the operator as well as the machine to interpret the screens correctly.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Meesamali512]

Thanks LittleInch for your insightful review. Can you please give some more information about CAT Scan and how it is performed? Also any info about supplier is appreciated. For me the major restriction is that it is a LIVE plant and by no means we can afford to do even a slightest mistake. We have to work with extra care to make sure that we are not at all disturbing any utility pipeline, while carrying out excavation/digging/augering works. Our primary purpose is safely digging the marked areas, lowering of anodes and then back-filling. We are ready to hire / purchase any sort of equipment and personnel for this specialized job.