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Drilling and completion
20 February 2019
Dear fellow members

I got the following from my friend in Algeria and they're thinking about running ABL.....

"We have a hole problem plenty cavings and big size, the hole not stable And we want to run 7" liner 1350 meters in open hole!

No way to cement this liner!  We will get pack off on hanger and PBR as well We had a pocket below 9⅝" shoe and the 8½" section started after 50m below the shoe.

That means bellow shoe we have a 12¼" hole  for 50 m then started 8½"

 This all pocket is claystone The inclination is 3.5° degree And drilled 30m with RSS and got vertical That mean 3°/100ft dogleg.

SO WHAT DO YOU THINK HERE ?! URGENT MATTER"
Documents uploaded by user:
IMG-20190220-WA0005.jpg
IMG-20190220-WA0006.jpg
8 answer(s)
PaulHowlett
CEO
Sudelac
Total Posts: 94
Join Date: 10/04/08
Sidi, I cannot help you with the wellbore stability, but don’t assume running the liner will be a slam dunk. Set your 7” liner up for success. Run sufficient good stand off rotating centralisers. Run a Deep Casing Tools turbine powered reamer so you don’t have to rotate the whole string to ream to TD, sounds like you’ll have lots of fill at TD.
Have a QAQC professional watch the whole liner hanger workshop preparation especially all pre job shear screw tests and pressure tests and torque ups. 
Pauljackson
Drilling Engineer / Supervisor
CONOIL PRODUCING LTD
Total Posts: 2
Join Date: 15/11/18
Sidi,

From the pictures you posted, it is clear indication of geomechanical instability resulting from the use of very low mud weight. It is not unusual, I have experienced it several times. 

The caving is from shale. From the shape, it does not look like an overpressure zone ( it is not a splintery shale). The only issue is that your mud weight is low.

You can still comfortably run your 7" line to bottom but you have to first raise your mud weight to the right MW, do not exceed the fracture gradient. 

Condition your mud, and circulate hole clean until the caving stops. Prior to pulling out of hole the drill string, spot about 300 ft of Weighted HiVis pill on bottom. 

I bet you, you will smoothly run the liner to bottom and carry out a good liner cementation job.

Note that the cement recipe and weight must be adjusted as well.

 
DavidCastillo
Director
Insight GeoMechanics
Total Posts: 1
Join Date: 03/08/18

Hi Sidi,

The angular cavings is a smoking gun that you have anisotropic breakouts where the well has intersected pre-existing plane of weakness.  For a vertical well, these planes of weakness are most likely part of a steeply dipping natural fracture system (unless your bedding is tilted to near vertical). Once the damage started, increasing the MW worsens matters because the increase in BHP from a higher MW forces drilling fluids into these planes of weakness, splits the cement between the planes and produced more angular, platey, and blocky cavings. Problem is that you initially drilled the well with too low of a MW (need modern geomechanics to estimate the optimal MW) that caused the anisotropic breakouts. Isotropic breakouts, which produces splintery cavings, responds well to MW increase. The same is not true for anisotropic breakouts. I’m afraid your well might be toast already. The best one can do (probably too late) is add massive amounts of cellulous mud additive to the mud system to plug the tips of the cracked planes. Other than that, it’s pretty hard to defuse a bomb if it has already exploded.

 

Good luck.

 

David

 

*********************************

David A. Castillo, Ph.D.

Insight GeoMechanics Pty. Ltd.

Perth, Western Australia

 


Fernando
Drilling Manager
PetroMasila
Total Posts: 6
Join Date: 09/09/13
Sidi,

I suggest you consider running 7" casing all the way to surface, in order to have enough annulus area to circulate the hole; be prepared to wash few joints before reaching bottom. If you are able to quantify the volume of sloughing on surface, it will help you to calculate the requirement for excess of cement.  

This type of sloughing is difficult to be mitigated by mud weight or any other means such as shale control mud products.

I have been in similar situations while drilling in the Central Foothills of Colombia (pictures attached) where, in fact, we were drilling parallel to a shale formation with almost 90º dip.

Hole cleaning is not the problem; if you are able to lift pieces of formation that size with minimum indication of being re-worked; the cleaning capacity of your mud should be fine.
Documents uploaded by user:
Sloughing.jpg
Sloughing 1.jpg
Sloughing3.jpg
Fernando
Drilling Manager
PetroMasila
Total Posts: 6
Join Date: 09/09/13
Sidi,

I suggest you consider running 7" casing all the way to surface, in order to have enough annulus area to circulate the hole; be prepared to wash few joints before reaching bottom. If you are able to quantify the volume of sloughing on surface, it will help you to calculate the requirement for excess of cement.  

This type of sloughing is difficult to be mitigated by mud weight or any other means such as shale control mud products.

I have been in similar situations while drilling in the Central Foothills of Colombia (pictures attached) where, in fact, we were drilling parallel to a shale formation with almost 90º dip.

Hole cleaning is not the problem; if you are able to lift pieces of formation that size with minimum indication of being re-worked; the cleaning capacity of your mud should be fine.
Documents uploaded by user:
Sloughing.jpg
Sloughing 1.jpg
Sloughing3.jpg
Companyrep
Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 366
Join Date: 10/01/05
Sidi,

I suggest you go back three steps to gather all the evidence that will be present to first and foremost better understand why//how/who/when/what things started to go wrong and then deteriorated to the current state of wellbore problems you have.
These did not happen but were caused form where causes can be determined, evaluated and corrected. (who when how).

Unfortunately you have only painted half the picture needed to help and assist you.

Scant evidence provided, implies you set 9-5/8" shallow for some specific and evident reasons? Leaving a big rathole? Operations then re-started, drilling commenced (instability resulted) or was this a continuance form the previous section?

Pictures from shakers afforded suggest mud weight is too low wellbore breakout, collapse and instability resulted. Why this resulted could be quite complex as this is a function of geological strike/dip, physical, mechanical factors, formation type characteristics, mud type, weight, rheology used, practices used (and all human factoring evidence involved). 

Pictures at shakers provide suggest angular cavings from well break out from Hmin direction implicating mud weight is too low for wellbore pressure exposed (stress) regimes that exist. For me I would be taking this and all other evidence gathered to a geomechanics specialist and seeking peer advice assist and review to resolve matters. 

Optimal mud weight? to be used to be discussed should be somewhere between the max pore pressure and minimum fracture gradient (adopting an Aadnoys recommended mean mud weight principle geomechanics approach.).

With optimal mud weight agreed, several further discussions around best practices to employ when drilling tripping, running through and pulling out of these zones not to make matters worse should then follow. 

e.g. Spotting a high viscous pill across trouble zone may help/aid trips. Specific drilling, connection practices to use/emloy?. e.g. Try and avoid backreaming through these zones at all costs, this generally only makes matters worse is my experiential view.

How to investigate and learn from such events?, is needed at some point in time. To assure learning are translated and sustained without assigning blame, so similar future events will not recur on the next well is surely important. 

I recommend you check out 'Latent cause analysis' investigative methods, that is an simple, yet well evolved and advanced root cause analysis method  of how to investigate anything and everything that goes wrong without assigning blame. 

Note: I was enlightened to this method in 2014-17 and although 35years too late for me. This next generation of drillers and well engineers in a more complex world need these skills far more today than perhaps we ever did on the past. As wells are not getting any easier!

Wishing you success in your recovery and resolution of your current problems and assurance that you translate and sustain learning going forward.

 
Muhammad Abdulrehman
DRILLING SUPERVISOR
MOL Group
Total Posts: 3
Join Date: 17/01/19
This problem is not uncommon. You have to increase the mud wt as much as possible. It will help to stabilize the hole as well as improve the hole cleaning. You can also use some hole stabilisers such as max shield or G seal if available in time. With increased mud wt you may need to revise the cement recipe too.
amryoussef
senior operations engineer
SPREADAssociates
Total Posts: 2
Join Date: 17/08/17
I do not find serious issue in this case.
*Rat hole below the casing is normal practice but 50 m is too much. Is it planned or had to do so?
*I think it is shale not clay stone, flaky and may be you have a hole cleaning issues
*Hole cleaning in 8.5" hole is a critical application especially with shale and salt
*The hole is considered as vertical; 3.5 degree is not a problem. I think the RSS is used not to go to vertical but to keep it in vertical. What type of RSS is used?
*The main point is the hole cleaning:
#close monitoring on the gap between ECD and ESD.
#In case of shale like this, we need to determine the PP and monitor the variation while drilling.
#Drilling parameters; flow, what is he maximum permissible? you might need RSS with nozzle.
#what is the mud type? It is shale, so WBM is problematic but you can live with it through rheology
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