The Hole Problem: Sloughing shale
some mechanical occurrances that causing stuck pipe
5. The method of drilling wells to prevent sloughing which consists in causing fluid to flow into and through the well in
contact with the walls thereof during the drilling operation, said fluid having a freezing point below that of water, and
functioning as a vehicle to' carry off cuttings from the drill bit, recovering said fluid as it discharges from the well,
removing the cuttings from said fluid, recirculating said fluid through the well, and cooling said fluid before it enters the
well to a temperature above its own freezing point but below the freezing point of water, whereby water in the earth
formation surrounding the well will be frozen
1. The method of drilling wells through sloughing formation which consists in circulating refrigerating fluid through the well
during the drilling thereof, said refrigerating fluid having a freezing point below the freezing point of the fluid content of the
formation and functioning as a vehicle to carry off cuttings from the drill bit, and cooling said refrigerating fluid to a
temperature 'above its own freezing point but below the freezing point of said formation fluid, whereby the earth formation
surrounding the well will be frozen
2. The method of drilling wells to prevent sloughing which consists in circulating a brine through the well in contact with the
walls thereof during the drilling operation, and cooling said brine to a temperature above its own freezing point but below the
freezing point of water, whereby the earth formation surrounding the well will be frozen
3. The method of drilling wells to prevent sloughing which consists in circulating mud laden fluid through the well in Contact
with the walls thereof during the drilling operation, said mud fluid having a freezing point below that of water, and cooling said
circulating fluid to a temperature above its own freezing point butv below the freezing point of water, whereby the earth
formation surrounding the well will be frozen
4. The method of drilling wells to prevent sloughing which consists in circulating an emulsion through the well in contact with
the walls thereof during the drilling operation, said emulsion having a freezing point below that of water, and cooling said
emulsion to a temperature above its own freezing point but below the freezing point of water, whereby the earth formation
surrounding the well will be frozen
6. The method of drilling wells through dry sloughing formation which consists in supplying water to the well to cause it to seep
into said formation, then circulating through the well in contact with the moistened walls thereof a fluid at a temperature below
the freezing point of water, whereby the formation surrounding the well will be frozen
I’m glad when the drilling process runs well and fast.
No drilling problem or accident occurs. .
01 mmmmmmmmmmmmSo far, loss and kick are things that I’m still worried about. It’s so damn tiring! I used to work like crazy at
that time. When dealing with loss, I tired of making a lot of LCM, pumped it down, mixing it again, and so on.
The stressful thing at that time was mud level in thanks was getting down and down.
Sure I cannot let it be as the worst problem possible come when hydrostatic pressure is less than the formation pressure: Kick and
Blow out. Oh God, it’s so nightmare! That’s why I called the well which susceptible to get loss as the wild well.
So with the kick, I was sick of it because I have to raise MW in very limited time.
Well, I thought these are the only hazard that possibly happed in drilling an oil well. Apparently not. There’s any problem that
should be keeping an eye of, the sloughing shale.
first time got BHA stuck then seeing cutting size in shaker. Oh God, I was shock!
Actually, I Love drilling the shale formation as it commonly drill down much faster than any other formation.
It is soft. In a day I could have reached like 200 meter even more.
But still keep in mind that all mud properties must be on allowable range particularly the mud weight.
But, I’ve work in shale formation with no excitement at all coz at that time it turns to be another horrible problem: Pack off due to
The Sloghing Shale! Oh,,all problem was just the same, it’s stressful.
Simply, sloughing shale happened when there’s no adequate mud weight to control subsurface pressure or too bad mud salinity that
cause undesirable osmotic pressure. It causes borehole collapse then stuck the drill pipe or BHA .
The sloughing shale is one of the mechanical occurrences that Causing the stuck pipe.
Operators worldwide lose billions of dollars every year — sometimes millions in a single well — due to such of drilling problem.
Stuck pipe increase NPT, lose expensive tools in the hole (mud motor, bit, collar, NMDC, MWD tool, etc) and forced to make
Oh, it so nightmare! The sloughing always happened in clay-rich shale formations.
A combination of stress and pore pressure conditions around the well bore, related in part to incorrect drilling fluid salinity and type
and improper mud weight.
I was working in a well where the sloughing shale was happened.
I drilled shale formation with high ROP. I used a mud weigh as per program.
Everything went so normal, no anomaly or something like that.
After reaching casing point, we put Hi-Visc Mud down there to suspend cutting when we do short trip to casing Shoe. When run in
hole back, it stuck in certain depth. Oh God I feel so guilty. I was questioning about that. Was that the mud fault? But I have used the
proper mud properties during drilling that hole particularly the mud weight. But then, my senior said that I don’t to worry about that.
We’re working in a team. Nobody knows what really happened in the subsurface, right? Although you have applied the mud program,
but the kind of formation being drilled will possibly different. I was trying to free it by circulation. And apparently, I was shocked as I
found a lot of cutting coming out in shaker in horrible size. That was first time I see that kind of cutting size,. Really abnormal!
cutting evidence when normal and abnormal condition.
I raised mud weight gradually in attempt to cure it. Oh, it’s a tiring time.
Yes, I was not lifting all chemical sack but I was tired of asking a lot of people to help it (crane operator, the mud boy, etc.).
I’ve heard the term “bomp-ing” to help curing it quickly.
It means I raised mud weight quite drastically.
It’s been work in several well, my senior said.
The kind of shale I was dealing it is the brittle one which has micro fracture in it.
Raising mud weight gradually didn’t work well.
But at the time, the company men didn’t accept the offer.
He worried about getting worst which causing loss of circulation.
After raising almost 6 times (it takes 3 days ) then it’s getting better.
We used some chemical to help curing it: the asphaltic material.
It called shale stabilizer commonly.
Every company has its own name for it.
Use Hi-concentration to make it take effect.
The 3 days I’ve passed through was the stressful days.
U know, the BHA got stuck, can be moved vertically and rotated.
I was worried about unable to free it and have to use fishing service.
But then, it solved. Yeahhhh….I learned how to deal with it. What a precious experience 🙂
First Experience : Loss Circulation
Finally, I’ve worked in the last section of drilling phase here; the 6″ section.
This is a production zone. It is a small hole and is susceptible of getting some drilling hazard such as stuck pipe, loss circulation
How does it sounds? interesting, huh? 🙂
I was working in a development well in West Java, Indonesia.
I never thought that a place called Bekasi has that pretty big oil reserve.
It’s been drilled for the seventh. I’ve worked in well xxxx, the eighth well that was drilled. Historical data shows us that this field
was really susceptible to get loss of circulation (hereafter it called as “loss”).
Things that was happened in field A, from 4 well that have been drilled, most of them got a serious loss.
Just heard from the crew, that there’s one well that was discontinue drilling because of serious loss on it.
wow! can’t imagine how severe it is! It was stopped because of economic consideration.
A company man have told me that the first well is also got losses seriously, however it produce really big oil afterward (I don’t
know how much it actually is) and could covered the cost for the dry hole that have been drilled before in that area.
Hmm,,, sounds amazing, right? Well, just heard an information from my senior, the well that’s got losses on drilling is most likely
to get a good oil production (or may be contain oil at least)…It’s almost 90 % that this kind of well has that characteristics.
I think It’s just a gossip :mrgreen: . Hmmm,,,I have no idea regarding to that.
Oh I need to learn hard and got a lot of experience before write down that opinion. So, anybody know?
Well, I need to explain what’s actually a loss of circulation is.
It can be one of the more serious problems that can arise during the drilling of an oil well or gas well.
Circulation is said to be lost when the drilling fluid, known commonly as “mud”, flows into one or more geological formations
instead of returning up the annulus. . It is the loss of whole fluid, not simply filtrate, to the formation.
Losses can result from either natural or induced causes and can range from a couple of barrels per hour to hundreds of barrels in
Lost circulation is one of drilling’s biggest expenses in terms of rig time and safety.
Uncontrolled lost circulation can result in a dangerous pressure control situation and loss of the well.
The drilling of 6-inch section here is so risky.
Mud properties has a big deal and play a vital role on it, particularly the carrying capacity.
Therefore, The YP (yield point) and the funnel viscosity (actually it just indicates a changes in viscosity) must be on spec.
As the historical data in the previous well that susceptible to get loss, we need to prepare in mud tank an LCM and Kill mud in
Other important things is making sure that the stock of LCM and weighting materials (e.g barite) in the field must be enough.
The more stock, the better it is.
I was really lucky to have a field training here as it planed to have a coring program in this well.
Seems like need a separate chapter to tell since it rare and expensive to be applied.
Basically, the coring has an aim to take a rock sample in the prospective zone.
It is going to be use as a complete evaluation of that reservoir.
The depth that was targeted is defined by the wellsite geologist.
After the rock sample was capture, it’s then evaluated either in Lemigas. Hmm,,,it must be interesting to be learned.
Working on losses is not easy things especially for “a baby engineer” like me :mrgreen: .
It’s my first time working in this section and the loss has just occurred. almost for 2 weeks I was working there like crazy. I was really
really panic and suddenly forgot what I was supposed to do.
The rate of loss was reached 5 barrels per minute or more than 100 bbls per hour ( Oh my god, just realized that a severe lost!).
More than 10.000 barrels mud have been made was lost to formation and more than 600 bbls of Loss circulation materials (hereafter
it called “LCM”, and commonly it called like that) was spotted and doesn’t take effect unless just a little. It getting worst when there’s
no return at all ( Oh my god, That total loss! 😥 ) but fortunately it was happened just a couple minutes and not in my shift time.
Don’t know what would be happened in me when got that things. May be I’ll be super duper panic! Haha. But, that’s normal
anyway.. Things that make me more stressed in dealling with the loss is the material stock. That makes me more more panic. More
than 5 times, I have asked well next to mine to transfer some materials (barite, LCM, etc) because of its shipping from Jakarta
warehouse was delayed and found some problem.
Actually, at the first time there’s a discourse to have a cement plug if the LCM doesn’t work properly. But then, the wellsite geologist
doesn’t allow to do that as problem in the previous well which become a dry hole because of it. He was suspicious on cement plug
has an effect on production at that well although the cement itself is actually production friendly such as carbonate cement, etc.
Again, I don’t know what’s really happened at that time. But for sure, a mud engineer now have to be working hard to cure the loss.
They just rely on LCM due to fears of using cement plug.
Making mud in the situation of loss is tend to be incorrect. We mixed mud like crazy. Yup, every body knows that we worked with
limited time to fill up the annulus. It’s emergency! So, the mud properties that being our concern at that time just mud weight and
the carrying capacity ( although just by a funnel viscosity). If we didn’t keep the hole filled by mud, the hidrostatic pressure will be
gradually down as the mud level in the annulus is getting down as well. Consequently, when the hidrostatic pressure reached a point
that lower than the reservoir pressure then The Kick will be occurred which possibly create a blow out. Hmm,,could be so nightmare!
I made 100 bbls of mud for 30 minutes, whereas the optimum mud mixing for that volume is around 2 hours. The mixing of some
polymers that need 15-25 minutes per sack is now blended at once without any fears of getting fish eyes. Concequently, when the
loss is getting small and the mud pump line doesn’t use, the barite was settled and causing pressured drop :mrgreen: . so, we need a
long time before use the pump.
The loss was start getting slow when I spotted a higher concentration of LCM (100 ppb) including the KWIK-Seal.
That’s getting better when the mud weight is decreased from 1.24 SG to 1.08 SG gradually.
As higher LCM used, the MWD tool need to be lay down due to the max concentration can be accepted was 50 ppb.
So, the POOH is a must.
..rest for a while? Of course not! Coz I attempt to fill the hole with mud with same rate of loss. Oh what a day! after spotting the
higher LCM. It’s really work.
To minimize the loss I added LCM (CaCO3) continuously to active system.
Surprisingly, it’s getting lower and lower until it reached 0.04 bpm or almost nothing.
But then, as the more depth being drilled, the loss is again getting higher, but fortunately still in the attemptable range.
Finality, drilling section 6 inch was finished in the depth of 2975 meters. But, unfortunately, there’s a sudden crew change at
2950 depth drilling.
And I need to go home but, I feel better although sometimes feel upset.
why don’t they let me work here till the completion.
Though I was so stressed this drilling section, there’s a benefit I had.
First, I’m getting close with all rig crew from rig floor to rostabout.
Really! I miss that moment again .And then, I’m getting used to the same problem. I don’t feel panic again when hearing the
term “loss”. Ups, I forgot that I spent a lot of money and various brands of cigarettes just to entertain the crew mrgreen:
I still remember when dealing with high loss, the tool pusher just tell me “be patient dude, that’s really hard for a green
engineer like you”. Almost all people and gathered up in the tank to help me mixed thousands barrel of mud, some of them
help me to check the mud weight periodically, another else helped me load and discharge any kinds of mud material. Even the
company man stayed up in the tank and gives some instruction to help me.
to be honest, that’s really a interesting experience .
Crazy Stuck Pipe Experience
Stuck pipe is one of the more common and serious drilling problem.
If previously the problem that I was afraid of when I was doing a Job was Loss or kick, but now I have a new enemy called Stuck
Pipe. Yes, Stuck pipe is one of the more common and serious drilling problems.
Let's briefly review the loss cases that I experienced in the past.
The worst was when I was doing a job in Bekasi (Didn't expect that there was a drilling site in Bekasi? 🙂 ), more than a week I
didn't stop mixing mud, LCM pump (special mud to 'clog' loss), cement plug, etc. Still, the loss doesn't go away.
The rate varies up to 5 bbl/minute (300 bbls/hour).
In my opinion it becomes much more tiring than the 'total loss', if the total loss is just the water pump.
Huh, I'm annoyed, why do I have to be 'cured' all the time. 😥Now, I work on wells that are no less challenging.
The well is in the Madura Sea with a slope of 80 degrees (the trajectory is also steady) with unconsolidated sand formations,
shale and clay which are reactive. so hole cleaning is really a real concern.
Because there is loss sand, you need special mud (using special polymers) and reactive clay/shale, you also need mud that is
stable and somewhat safe. Cool? 🙂One day (the first day on-board) I found that the well was having a total loss in the Limestone
formation (In this area of Java, the limestone formations are incredibly crazy…it's the same on land and in the sea 😥 ).
That day was initially relaxed because the drill was using sea water, after that TD, after TD there was usually a wiper trip up to the
I don't know why at that time the wiper trip was only 1000 ft (not reaching the shoes) then it went down again to the bottom.
After that, I pumped LCM at the bottom before POOH.
It turns out that in the middle of the road there is stuck
As usual, as a personnel involved with the 'hole condition', I feel that I haven't succeeded.
Even though I have tried as hard as I can, the reality is different. I keep wondering Is it because the hole isn't clean? or is there a
Limestone ruins? differential sticking? Just dogleg? Hmm… the indications show that there was a collapse of the formation wall
Yes it is 😦 . We tried to be free first (work on the pipe all the time) a few hours after that, I don't know why suddenly there was
news that the string had broken. The problem is even more strange. maybe the driller is impatient :mrgreen:
The people of Jakarta were excited, meeting here and there. In the end, there was a decision to fish for DP and plant BHA, which
was incredibly expensive. Hopefully they don't think "it's not a problem, after all it's the state that pays," hehehe *joking* :mrgreen:
I'm sure, they have their own calculations, instead of paying expensive rent for a rig (can be up to 4M per day 🙂 ) and fishing can
take days -day. sad huhHowever, there is always a lesson behind disaster.
it was decided to use TESCO's CwD (Casing while drilling), now part of Schlumberger.
Thank God, I learned something new 🙂 , The well was also cemented with a plug.
After that they intend to drill only 600ft sidetrack, and leave the open hole filled with KCL-PHPA Mud. I don't quite understand what
it means by leaving the open hole long enough like that? 🙄 that's it,,,we-we in the rig just follow Jakarta's orders.
maybe make the way for the casing drilling later.
Turns out, STUCK back at 300 ft before TD 😯 . and Pack Off again.
it's getting worse and worse.
I asked to pump caustic pills (to dissolve the charges) and it worked! After that, because Rich didn't want to take any more risks,
there was no longer any drilling program until the casing drilling equipment arrived.
Drilling continues with TESCO's Casing while Drilling (CwD). Sophisticated and quite smooth until TD.
In terms of mud, it's quite challenging with casing drilling here, we drill using seawater and dumped overboard. Most also have to
sweep regularly to make sure the hole is really clean.
At some occasion, we added a type of Glass Beads, to reduce torque, because the CwD torque is terrible bro...
The next section that is no less challenging, the sandstone formation which is said to be somewhat unconsolidated is prone to
collapse and of course prone to loss.
plus the formation contains clay inserts which are said to be reactive. For this reason, the mud used here is rather special, the name is
MAX-BRIGE, essentially the same as KCl-PHPA but with the addition of fine and medium graphite and premium grade amine mixture
compounds. Also added CaCO3 mixture as LCM in it. It is hoped that this mud can seal and reduce the pore pressure in the formation.
Thank God... I also tried the weird mud... hehe 😎 .The results were quite encouraging, no losses were encountered during drilling,
but there were still quite a few tight spots when tripping. Pragmatic people will think that the Mud Engineer isn't right, they are
usually sarcastic and don't provide solutions. The under pressure is there. Just be patient 🙂 luckily the company man understands.
The trajectory is also challenging, bro, it's only natural that there are tight tights.The problem that arises is when the casing is
running, it turns out that the casing cannot enter to the bottom and cannot be removed either. stuck again. Three times got stuck in
one hitch. very stressful.
Finally, for the first time in my life, says running BLACK MAGIC spotting fluids, a special type of mud to melt mud cake.
Generally used for freeing stuck pipe caused by differential sticking (thick mud cake).
Actually, it's not stuck because the mud cake and mud have exceeded the mud program (fluid loss <4 cc, HTHP around 8 cc).
even though it could actually happen.
It's really messy mixing this Black magic.
Black Magic is spot on and left for 12 hours (ideally), only here it's only 4 hours, while working on pipe. After that, it couldn't even
circulate because the pack was off again. In fact it got even worse 🙄 finally the magic was able to get it out and it still didn't go away.
Ha ha ha. Investigate after investigate it turns out, when running the casing, the centralizer is installed in all the casing. He said it was
a bit unusual, especially for this semi-ringed well. Usually for directional wells, at least one centralizer for every 20 joint casings. he
said anyway :mrgreen: , So I think that's the suspect. But Allahu 'alam.So,,, THREE TIMES stuck in one well is enough to make 'trauma'
😆 The operator can lost millions of dollars just in a couple days of STUCK. It seems that this is indeed a problem that is feared by all
those who drill. However, A Smooth Sea Never Made a Skillful Sailor. And, for positive-minded people, nothing is useless.
Drilling Successfully Through Deforming Shale Formations: Case Histories
Shale sloughing and swelling are the two major problems encountered when drilling through shale formations.
Some areas are characterized by shale sections containing bentonite or other hydratable clays, which continually absorb water, swell and slough into
These types of formations are known as heaving shales. This problem, if left uncombined, results in high cost of drilling the hole and significantly, to
other hole problems (pipe sticking, excessive solid buildup in the mud and hole bridging), and sometimes abandoning the well because of the difficulty
of reaching the targeted or anticipated pay depth.
Drilling through shale formations can, many a time result to hole stability problems and may be aggravated the more when drilling through more than
one kind of shale lithology.
The existing literature addresses possible solution techniques to combat the shale problems based on laboratory studies but these techniques neglect
the existence of shale heterogeneities which may cause sloughing and swelling while drilling the same shale formation.
This paper examines the physical appearance of various shale samples with a view to (a) determining the physical properties which contribute to the
shales' undesirable properties, and (b) proposing methods to minimize their effects on drilling performance.
Five field cases are presented where sloughing and swelling shales were encountered.
These cases reveal that the heterogeneity of the shale formations can cause difficulties in controlling the sloughing and/or swelling problems because
of the variations in shale composition, ion exchange capacity, formation water content and shale strength.
Shales make up over 75% of drilled formations and cause over 90% of wellbore stability problems.
Shale instability in a borehole may be attributed to any or all of the following combination of forces:
degree of compaction at the formation
pore pressure in shale exceeding the hydrostatic pressure
rate at which the clays absorb water,
tectonic forces and
presence of micro fractures along cleavage planes on the clay platelets.
Subsurface shales have been dehydrated by the pressure of the overlying sediments.
Drilling a well relieves the lateral pressure and the formation imbibes water from the drilling fluid. This change can result in very high swelling
pressures which destabilize the borehole.
Thus, the stability of the borehole depends, to a large extent, on the interactions between the drilling fluid and the exposed shales.
Interactions between the drilling fluid filtrate and the clays present in potential producing formations may restrict productivity if the incorrect type of
drilling fluid is used to drill these formations.
Highly bentonite shale can absorb water, soften, and become incorporated into the drilling fluid, thus increasing the viscosity of the drilling fluid to
detrimental high values.
Sloughing shales or heaving shales were encountered in ATDM Gilsonite Co.
operations in the Hackberry Field, La. during the late 1960’s.
Numerous fishing jobs because of sloughing shales plagued drilling operations, and the costs of reaming tight holes and weighting
up the drilling fluids raised drilling costs substantially.
One of the most common solutions to the problem was the use of relatively high mud weights, but this resulted in slow penetration
rates, high mud costs, and high total well costs while drilling the normally pressured shale formations.
The Hackberry field is located in southwestern Louisiana on one of the many pier cement salt domes present in the Gulf coast area.
Wells included in this study are in the 9,500 to 12,500ft range.
The section is characterized by a long sand-shale sequence of recent to Miocene age formations from the surface to about 9,500 ft.
Below, a predominately Oligocene shale section of about 1,500ft long is encountered prior to penetrating the normally pressured
objective, the Camerina sand. It is this long shale section that has the tendency to slough and cause hole problems.
The formations dip in excess of 50° and it is believed that the high dip angle is at least partially responsible for the heaving problems
since equivalent age formations of normal dips have been drilled in other areas without problems.
The temporary solution to the problem was raising the mud weight, to 12.5 pounds per gallon (ppg) opposite a 9.0 ppg equivalent
This contributed to increase drilling costs because of low penetration rates.
Gilsonite is solution to shale
ATDM Gilsonite Co group was asked to find a solution to the shale problem.
One solution to the problem would be to add a material to the mud before the problem shale was penetrated to retard filtrate
invasion along the micro fractures and bedding planes.
The research group indicated that Gilsonite , a naturally occurring mineral, dispersed throughout the mud system as fine particles,
would extrude by a plastic-flow mechanism into the pores, bedding planes and micro fractures.
Once in place, it would reduce fluid invasion and bond the matrix of the formation to prevent sloughing.
Looking at the well temperatures, the lab recommended a softening point Gilsonite around 338°F along with a special wetting agent
they designed to prevent balling of the product.
The research laboratory indicated that Gilsonite was superior from both a temperature and purity standpoint than the blown
The recognition by the lab of the formation sensitivity to Gilsonite softening point and the development of a good surfactant was the
initial work on Gilsonite investigation which later led to the development of Bore-Plate , a blended Gilsonite with a strong surfactant.
As a result of the research center’s recommendation, Gilsonite was used successfully in the mud system without encountering any
problems of sloughing shale.
In 1970, a decision was made to begin lowering the mud weights from 12.5ppg in 0.5ppg increments to determine if the shale would
remain stable and determine what mud weights would be required using a treatment of 5.0 pounds per barrel (ppb) Gilsonite. 14
wells were successfully drilled with mud weights as low as 10.5ppg with no serious problems resulting from shale sloughing.
As a result, drilling penetrations were increased and borehole problems relating to shales were minimized.
The average cost per foot of the wells drilled with Gilsonite was reduced by 43.3% compared to the wells without Gilsonite.
ATDM reported savings amounting to $623,000 (1971 US dollar value).
A study of the shale cuttings from the wells indicated the Gilsonite performed by extruding into the bedding planes, voids, and micro
By this mechanism, the Gilsonite both inhibits mud-filtrate loss and bonds the shale together.
ATDM has used Gilsonite and later Bore-Plate in many other wells in southwestern Louisiana with success when experiencing
sloughing shale problems.
Normal treatments were 5-6 ppb.
Other case histories of the use of Bore-Plate to minimize sloughing shales have been demonstrated throughout the world in both soft
and hard formations.