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Wellbore Ballooning
27 May 2020
Hi All,

 We are drilling 8.5" hole depleted zones (2-4 ppg PP) at 72 deg inclination. We use 10.5 ppg SBM with pre-treated 40 ppb bridging material.

The first depleted sand we drilled through was experienced with 200 bph dynamic losses and reduce to 80 bph in few minutes. We picked up off btm and pumped 30 bbls of 150 ppb LCM pill through PBL port and performed ECD squeeze and then the lost rate reduced to 2 bph.

We continued drilling through the second depleted sand and experience with total lost return. We did pump 30 bbls of 150 ppb LCM pill and performed ECD squeeze, but this time the hole react differently. As soon as we complete the ECD squeeze, we did flow check and we got flow back from the hole. We shut the well in three times and got 0 psi on casing and the flow back rate was reduced to static after three hours.

This condition suggest us the wellbore is ballooning.

We continued drilling with losses and stopped before entering the next depleted sand. The hole is is still ballooning when the pumps off.

What is the good option to go to cure wellbore ballooning?

Will cement plug help curing the ballooning?

Appreciate your valuable feedback.


16 answer(s)
Snr Drilling Engineer
Medco Energi
Total Posts: 6
Join Date: 10/03/09
Thanks all for your feedback. When we drilled about 5 more stands to the bottom part of third depleted sand, we observed total lost and no more ballooning. We did pooh drlg BHA to surface and RBIH w/ OEDP and spot 600 ft of cement plug. The well is static. We tagged TOC about 300 ft from bottom. The hole condition was stable so far. We skidded over to other well for completion job and come back again in a week or two. We are reviewing geomechanic study and MW reduction possibility, renew WBS formulation and drilling practices. We did have contingency string and slimmer completion design. However, the pushback is the first production from the well.
Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 462
Join Date: 10/01/05
This is another case where without all the evidence being provided. Lots of prescription is being provided without that ability to review and analyses to offer due and diligent diagnosis. 

What spread forum should do is issue a investigative ‘LCA’ type guideline of how to get her all the key evidence needed before raising a post. Where it is then likely those in the know is specific subject matters can then offer some assistance and support. 

Where people evidence is often the most important and where this  generally evaporates the fastest. 

Personally this is not ballooning, An induced fracture was foolishly decided by people for what ever reason. Weakest or porous permeable formations were supercharged. What was lost was then returned. 

The end result was a problem on a problem. 

Poor problem resolution and further bad decision making this is how wells fail further and exposes from the line people further. 

Like all problems I suggest you go several stages back review and analyse all evidence to identify reasons why lost circulation resulted and why there was not a better plan b / c in the first instance. What was initiated base on what evidence had been provided was far from being considered a best practice in my view..   

senior operations engineer
SPREAD Associates
Total Posts: 4
Join Date: 17/08/17

Hi Army,


·         How much ballooning out?

·         What is the depth?

·         Do you have knowledge in the area structure? Nearby faults, directions?

·         Do you have any Geomechanics study done in this area to know MEM or stress regime in terms of magnitude and directions?


Most probably the ballooning occurs in cracked L.S reservoir and it is belonging to the pumping rate and pumping shut down.


Good luck

Amr Youssef

Consultant Well Engineer and Trainer - HPHT, Deepwater and MPD Well Delivery and Well Control,
Welltrain Limited
Total Posts: 18
Join Date: 09/12/09

To those advocating running casing to resolve this problem I would urge caution.  Ballooning / wellbore breathing takes many forms.

Where you are having to increase mud density in response to increasing pore pressure, the borehole pressure against shallower formations in the open hole may start to exceed the fracture opening pressure due to increasing hydrostatic and annular friction pressures.   In this case, setting a casing will isolate the weaker formations and hopefully eliminate the wellbore breathing problem.

That does NOT appear to be the case here.  The problem appears to be on bottom due to penetrating significantly depleted permeable formations which in teriun have significantly reduced fracture pressures, 8-9ppg vs a static mud weight of 10.5ppg.   The last shoe was only set 200ft above the top sand!.  

The mud density and ECD is as low as can realistically be achieved without mud cap drilling or drilling blind.  Army  has not reported borehole stability problems in the formations above the depleted sands.  So…what exactly will running an additional casing achieve in this case (assuming the current losses will even achieve a decent cement job?)?  

Reduced hole size will probably increase annular friction pressures and this increase ECDs and thus BHP and wellbore breathing / losses issues.

 Unless additional borehole support is required to allow the use of a different approach (mud cap / blind drilling) then in this situation I would not advise an additional casing.  

 Best wishes


Drilling Engineer
Kuwait Oil Company
Total Posts: 1
Join Date: 01/11/18

Hi Army,

Key question:

What is the relative quantity of fluid pumped into the wellbore (LCM + Mud) and the fluid released back after ballooning?

Are you as a team familiar with ''Drilling with a mud cap''?

Sir Drilling Specialist
Total Posts: 9
Join Date: 27/03/17
Going through these depleted zones, Its probably similar to digging a hole and patching the hole walls at the same time. Reading from responses, Balloning is the hole reacting to the squeeze, as it cannot take that level of bullheading and return the fluids back, as the induced fractures closing back. Its pretty typical occurrence on welltests where bullheading the formation creates balloning which confuses everyone (kick?) , who will then most of the time, over react.
The other risks are how long have you stayed in the section, how is the hole cleaning, would you need a short trip up to shoe?
tripping out and/or backreaming may open up the patches.

Drilling Support Superintendent
Maersk Drilling
Total Posts: 11
Join Date: 15/12/05
Hi Army,

You have received some very good feedback here from the forum. I would just like to add a nugget from a philosophical view point. This is something one of my first Drilling Superintendents told me early in my career. "When designing a well, resist the urge to over-engineer and achieve too much in one wellbore as this can lead to expensive downtime down the road."

There have been many situations where the time and cost lost to managing wellbore stability / well control related challenges (e.g. a depleted zone followed by a pressure ramp followed by another depleted zone) could easily have paid for the extra casing.
I agree with @DougP, if this is an exploration / appraisal well and you are having difficulty fingerprinting and managing the loss-gain cycle, just set casing and slim down the well to final TD.

If this is a production well, your options might be a bit tighter as you would have already procured all the required completion jewellery and running equipment. There could also be an impact on productivity of the well.
In this case, follow the advice already provided by other esteemed contributors to this thread (MPD, Wellbore strengthening, fingerprinting, LCM, drilling practices) while understanding it will require patience and perseverance.
Good luck!
Engineering Manager
Total Posts: 1
Join Date: 17/09/18

Agree with all comments regarding this being a perfect application for MPD.

However, if MPD is not immediately available,  it might be worth getting the mud service provider to perform a wellbore strengthening modelling to determine the pore size and advise a customized strengthening treatment to seal off the loss zones

Good luck,

Snr Drilling Engineer
Medco Energi
Total Posts: 6
Join Date: 10/03/09

Many thanks for your valuable input Dave, Ghazanfar, Iain, Eric, Steve and Doug.

To answer Steve question:

  1. How far below the production casing shoe was the first depleted sand? +/- 200 ft
  2. You mention you have drilled into a second depleted sand.  How much separation is there between the two sands and what formation separates the two sands? +/- 200 ft
  3. Have you had any fracture pressure analysis performed for the depleted sand intervals? no but we did receive estimated FG 8-9 ppg at the depleted sand.
  4. How much extra BHP did you apply during the “ECD Squeeze”? +/- 100 psi
  5. Is the level being maintained in the mud, especially after the lost volume has been rebuilt? Yes

To answer Doug question:

1. How far do you need to drill to reach TD? 28 more stands

2. If you are in a known area with high confidence of pore pressures you could consider carrying on to TD and accept the flowback on connections? This is what we consider currently while drilling to the next depleted sand.

We are still assessing MPD and its availability to meet our schedule.

In the meantime, we decided not to do cementing plug, but we are building reasonable surface mud volume to continue drilling to the next depleted sand and "accepting" wellbore ballooning. We use Geoservice mud logging company and we do not have specific EKD sensor currently. They have fingerprint software during connection so that we can compare the result with manual calculation.
Drilling Supt (Consultant PE)
SPREAD Associates
Total Posts: 2
Join Date: 15/08/17
I had a similar problem years ago in Trinidad.  (In ~1970, a well was completed and deemed non-productive (only 1000 bpd).  20 years and 6-7 completions later, that 1000 bpd looked pretty good and we were tasked to sidetrack the wellbore (maybe 9 5/8, can't remember the details, casing) and drill back and complete the interval with decent reserves left. 

I was in an unrelated meeting with Dowell, manager from Caracas, and asked if they could come up with a product that would provide "total damage" to a formation!  He asked, "You mean no damage!"  No, I want complete damage and explained the well. 

They came up with some products, pretty cheap, that we could add to our WBM, sidetracked the well and drilled to the shale above the top of the objective.  Set casing, cleaned the wellbore, pits, washed the DP out, etc, and drilled with our normal WBM into the pay and set a small liner.  

We had a great completion that was still producing when I left 2 years later!
Aberdeen Drilling Management Ltd
Total Posts: 20
Join Date: 18/08/05
Hi Army,

In my experience the only way to cure ballooning issues is to run and cement casing and then drill a smaller hole size.

How far do you need to drill to reach TD?  If you are in a known area with high confidence of pore pressures you could consider carrying on to TD and accept the flowback on connections?

IF you think you could do that it would be essential to closely monitor return flows on every occasion.  Mud loggers could fingerprint flowback along with basic checks by drill crew.  If returns rate drops off you could be confident the "influx" was not gas, oil or water (which would reduce hydrostatic column and cause increase in flow rate).

MPD could possibly be a great solution but only if you could get experienced and competent MPD people on site to "manage" it! Remember you cannot have managed pressure during total loss events you must have a full column to apply and manage surface pressure.

Consultant Well Engineer and Trainer - HPHT, Deepwater and MPD Well Delivery and Well Control,
Welltrain Limited
Total Posts: 18
Join Date: 09/12/09


Hi.  I have a couple of questions. 

  1.  How far below the production casing shoe was the first depleted sand?
  2. You mention you have drilled into a second depleted sand.  How much separation is there between the two sands and what formation separates the two sands?
  3. Have you had any fracture pressure analysis performed for the depleted sand intervals?


Is it possible that the hole behavior you are seeing is from a shale lying between the sands.  This might explain why you are seeing different wellbore behavior.

Before you can decide how best to proceed it is important to consider the mechanism causing your losses.   When a permeable formation is depleted, not only does the pore pressure drop but also the fracture pressure.  As a rough rule of thumb the FP reduction is around 30% of the depletion below the original pore pressure.  Under these circumstances, severe losses initiated in such a formation will usually be associated with the creation and propagation of a fracture  in the formation rather than the loss of mud or mud filtrate into the pore space of the sand.   If this is indeed the case then traditional LCM material designed to form a enhanced filter cake that plugs up the pore throats will not be successful.  Similarly, the opening and closing of such a fracture at different bottom hole pressures (pumps on/off) will result in the flow back you are seeing.

How much extra BHP did you apply during the “ECD Squeeze”?  If you picture the losses as a fracture growing away from your wellbore, you may consider that this action is actually counter productive..and also guaranteed to generate flowback.

Bridging / wellbore strengthening / stress caging material is intended to combat losses caused by fractures rather than matrix losses.  The exact mechanism of how it works is the matter of hot debate but essentially you are trying to prevent hydrostatic pressure reaching the “tip” of the fracture and so allow a reduction in the stress at this point and prevent the fracture growing further.    

I note that you are already using bridging material.  Is the level being maintained in the mud, especially after the lost volume has been rebuilt?   You might want to discuss the size distribution of this material with you Mud Company..  finer seems to be better!

Under these circumstances you also have to keep in mind minimum BHPs required to maintain borehole stability in the impermeable formations elsewhere in the open hole.

As others have commented, MPD can help you manage the change of BHP during connections although the degree of overbalance is severe and you can only reduce the mud hydrostatic so far.  It is also unlikely to be able to help you in this instance.   

You might want to examine your hole cleaning capability vs pump rate to see if you can operate at a reduced flow rate.  Similarly, streamlining your BHA and drillstring can reduce ECD.  Anything that can reduce the change in BHP between pumps off and on will reduce your ballooning tendency.

Fingerprinting of the flow back characteristics after turning off your pumps  has been mentioned and this is really the best option to gain confidence in the behavior of the well.   Also keep an eye on the “big picture” of losses and gains.  The Driller commonly resets his PVT gain/loss when back on bottom and circulating.  Thus  flow back is always seen as a pit gain.   Get the mud loggers to track total mud lost and recovered from pumps off back to pumps off.  That will give you a better picture of the status of your well.   Obviously a net gain is not a good sign.

Hope this is of some help,


Best wishes 


Fluids and Cement Superintendent
Assala Energy
Total Posts: 13
Join Date: 19/10/14
Temperature effects

Rock Mechanic issues, Ballooning, Breathing, are very often linked to temperature effects.

To make it simple, just an example, at 2000m you pump in front of your formation a fluid 20°c below the formation temperature at that time, it is stress-wise for the formation equivalent to an increase of 0,5 sg (+4,15ppg) of ECD, you may start loosing.

As you continue circulating, your mud will warm up and the open fractures will slowly close, also probably not fully, your losses will ease.

When you stop circulating your induced fractures will close even more, giving you back their internal volumes, as the formation comes back to its static temperature.

A close footprint over the whole sequences could validate this possibility and for sure open some new approaches on mitigation practices.

PS: Addition of LCM can (according to LCM type) force these thermal fractures open in the similar way proppant is used in unconventional shale oil. My two cents.

Lead ERD Advisor / Engineer / Instructor
Merlin ERD Limited
Total Posts: 15
Join Date: 04/05/16

without going into what Dave & Ghazanfar have already mentioned too much. MPD is probably your best option, but not something you can immediately utilize if you are currently drilling. Who are you using for mud logging? Do they have  software to finger print the flow back at connections? This would at least give you the confidence with regards to making your decision as to whether you are suffering ballooning or taking a kick.

Regards, Iain

Drilling Performance Engineer
International Petroleum Corp
Total Posts: 1
Join Date: 30/12/19
I agree with Dave, it's a perfect application for MPD. Should have planned the well with MPD if multiple depleted zones were known.

In the current situation, not many options left but few options to consider: 
- Shut-in and monitor the well.
- Callout MPD service right away. Rig will go on standby for few days but that is unavoidable.
- Cement pumping is an option but it will not work if there are multiple depleted zones. There will be heavy losses while pumping cement also. Cementing is not a good option if this is a reservoir sand.
- Check with mud company if they have Ez-Squeeze product, it is kind of plaster. Spot it in the depleted zone and let it soak and get hard. try drilling again. For this one to work you must know the length of the depleted zone and correct volume should be pumped. 

Good luck!!
Ghazanfar Shahid
Managing Director (
Relentless Pursuit Of Perfection Ltd.
Total Posts: 460
Join Date: 10/01/05
Hi Army

This would be a great application for a simple MPD application, since you would be able to apply "ECD" when shutting the pumps down.

From what (little) I know, there are some very good flowcharts to use to manage wellbore breathing.  As I understand it, shales "balloon" and sands etc "breathe"

I'll leave it up to those with recent operational, or well control experience, to respond.  If not, I'll post a few flowcharts that come up when we run a DWOP for such a challenging well.

Kind regards

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