Private Forums
Installation of 24" conductor pipe to 30m in onshore well
16 July 2020
Dear friends in this great community,

Any experience is greatly appreciated.

Our project is currently assessing various options for driving a 24" conductor pipe to 30m for a pad drilling project.

Here are a few of the key issues I would REALLY appreciate your advice on.
  1. We are aware that the standard length for this pie is 12m, but can 16m pipes of acceptable standard be sourced?
  2. Which method of connection is preferable, welding or use of couplings/ quick connection?
  3. For coupling, which, type of coupling is suitable?
  4. If coupling is used, is the significant risk of fatigue or damage due to piling and what piling parameters are preferable?
  5. When piling, which is the best method to minimise deviation on conductor pipe?
Thank-you so much

Lamech
5 answer(s)
Punch
Managing director Punch Energy Services
Punch Energy Services
Total Posts: 9
Join Date: 24/06/20
Hello Lamach,

1) Would go for standard, that being delivered faster and cheaper. perhaps you can purchase some surplus. Standard would be 12 mtr (40ft).

2) If Onshore and soil conditions permit piling, would get a mobile crane onsite (meaning prior rig operations on site) and pile conductors with BW preps (so welding).

3) No connectors, BW prep.

4) Carry out straightness checks. Make use of straightest joints first. If you purchase new, get a SR in the purchase stipulating straightness tollerance, you can stipulate tighter tollerance as per API 5L.

Good luck.

Best regards,
Marcel
Simon.Lucas
Well Engineering Mgr
Zenith Energy Limited
Total Posts: 8
Join Date: 13/09/07
Hi Lamech

You should be able to get 16m piles if you want them, but they would be "project special" with longer lead times. Offshore we often use 60 ft joints, but they need special transport at the docks as they do not fit  on a standard truck bed.

Driveable couplings make the conductor running faster, but pile capable connectors are expensive. If you are doing a batch installation with a crane to lift the pile driver, I think welded connections will be the cheapest solution, as the "spread rate cost" for the the civil eng installation equipment is low compared to a rig.

There are various couplings available from e.g. Vetco and Oil States - have a look their conductor connectors on their websites.  You can consider modified buttress, but in a standard BTC connection the pins do not shoulder out - it is only thread-to-thread contact, so they may not be strong enough for hard piling conditions.  The pins can "nose in" in the worst case.  Also look at offsets though - if they have piled with standard BTC and no problems, then look at repeating what they did.

Piling parameters - look at offsets.  The piling company should be able to advise on what size of hammer is needed for the soil conditions, and make a piling forecast.  If you are installing a lot of conductors then consider a soils geotechnical borehole down to 30m so you know exactly what the soil profile is - then you can design the pile installation very accurately.  After you drive the first conductor, you will have a blow count graph that you can use as a guide / optimise for the the next ones.

Minimising deviation - ensure pipe is vertical at the start, use tuggers / bull dozers to get the right alignment if needed. In my experience, if the pile starts of OK it continues OK, unless it hits a boulder - if that happens you get a sudden change in piling behaviour, you can drill out the soil form inside the conductor and try and drill the boulder and continue.  Often its cheaper to just pile an extra conductor though.

For large conductor array, have some redundancy -pile a few extra conductors so that if you find one has a high inclination for drilling you can move to another.  After piling, drill out the conductors down to the shoe and survey the inc / az near the shoe with a decent tool (gyro is more accurate than single shot).  Make sure the survey tool is properly centralised in the conductor - use a decent springbow.  A project I was involved with a few years ago would not take time/money to do this, and the top hole in the first well was later found to have deviated under the conductor array, it caused all sorts of directional drilling problems on later wells. 

Regards 

Simon Lucas



gpulkit
Drilling Consultant
Drilling Consultant
Total Posts: 7
Join Date: 02/12/14
Hi Lamech,

I have done this on several wells while pad drilling in India and Kenya. We always used a small water well rig to drill a 30" hole to 30m. 12m joints are better from handling perspective but otherwise it doesn't matter. We always welded our joints as water well rigs don't have capability to make up a BTC joint. Using quick connectors on a land job is just waste of money. Critical thing with this is cementing the conductor. One way is to drill hole with air, land the pipe on the bottom of hole and just dump slurry in the annulus. If you use water to drill the hole, after landing the pipe on bottom you can run 1-2" steel pipes in annulus and pump cement through them to displace the mud.

I would certainly not recommend piling given that surface soil on land is lot more compacted than offshore. If your location is in marsh/ swamp/ delta area than piling would make sense as soil would be loose. Even if you pile, like other said, couplers are not required.


PabloAU
Consultant
SPREAD Associates
Total Posts: 6
Join Date: 24/11/15
Lamech, Gordon has the good info in his response, from another angle consider the following:
  • Handling of 16m v 12m, risk assesment would be higher on personnel & equipment
  • Weld - Weld every time! I have been involved in 7 well's using coupler's & Piling & out of the 7 only 1 was successful.... believe me that piling & coupler's do not play well in the same space. It can be done, however just because it can doesn't really mean that you should
  • Geology has a lot to play, are you jetting as well?
Good luck
GordonDuncan
Technical Director / Trainer
SPREAD Associates
Total Posts: 10
Join Date: 31/03/20
Lamech,
In answer to your questions below and also a couple of pointers.
A. We did this on a few projects in the Middle East with great success, but we well aware of the depth of the bedrock, so were confident of achieving 30M
B. On another project we used a Water Well rig to drill 30M peepholes that we then installed the conductor and base plate ready for the drilling rig, thuis avoiding fitting driving hammers etc to a drilling rig and having to carry out frequent drops checks in the derrick.
1. Go with 12M lengths to allow for any premature standup to allow easy cut off.
2. Use couplings, we used heavy wall Buttress connections.
3. use heavy wall if possible
4.  The pipe supplier should be able to provide the parameters, https://www.ebicoilfield.com/drill-string/conductor-pipe-drive-pipe/

5. Ensure straight to start with and take time to monitor as can always nudge back straight with a D9 or the same crane using the drive Hammer

Jump to top of the page