Bit Balling « Thread Started on Oct 3, 2009, 3:39pm »
Hey Guys,
I'm curious to know more about defining BIT BALLING.
To my understanding is if you have a consistant or significant drop in ROP coupled with reduced torque is basicaly somewhat related to Bit's being balled up.
To confirm this condition, one will pick of bottom & pump at high rates with rotation, go back down & see if any progress is made.
But then again being in drilling fluids the first instance of balling they would refer to the MUD. Yes if you have poor inhibition, lubricity etc etc.
Can anyone help to get a better picture on the matter!!!!!!! Seems hard defining the issue!!!!!!!
Joined: Jun 2003 Gender: Male Posts: 188 Location: PERTH WESTERN AUSTRALIA
Re: Bit Balling « Reply #1 on Oct 5, 2009, 2:24am »
The lack of ROP and a associated reduction in torque may be due to bit balling. But not always. Bit balling is due to the cuttings agglomerating on the bit. Depending on whether you have a PCD or roller cone bit the methodology will change but the phenomena will be the same. Bit balling does not occur in hard rock it is in the shales. It is the result of some clay types adopting new characteristics due to the relationship between the clay drilled and drilling fluid. - Bit balling is unusual in OBM. If you suspect Bit Balling in WBM the material adhering to the Bit must be removed. I have heard that pumping 'Walnut Husks', an LCM material often kept on the rig will help. There is no point in persevering with the slow ROP. I usually pull the bit and have a look. If it is very deep, a Pipe Lax soak will help shrink the clays and often is a cheaper solution than a round trip. In spite of which way you approach the removal of balling the entire mud system will need to be modified to address this problem and stop it from recurring. Additional inhibition provided by an addition of KCl will often reduce the occurrence. Cuttings that have a propensity to balling will display this characteristic on the shakers and the cutting will be described as 'mushy'. That is the time to address the mud recipe before the balling occurs.
Re: Bit Balling « Reply #2 on Oct 5, 2009, 2:50am »
Don't try this at home on your own, check first if allowed. Years ago I knew a driller who pulled slightly off bottom and went back down with a whack. How high off bottom and how hard I do not recall. But it always worked and the effect lasted for a hours and most times for that entire formation sequence. Formation was shaley with a sandy component and the bit was a roller. Don't know if this is allowed these days with sensitive electronics etc in the BHA. No alterations were made to the mud. Can't guarantee what effect it did to the cones and their bearings.
Another driller checked the shakers and if lumps of plastic shale were surfacing he pulled back about 10 stands to shear the mud. Went back down drill ahead and rechecked the mud condition, this also worked. Again nothing else was done to the mud.
Joined: Apr 2006 Gender: Male Posts: 56 Location: rockhampton qld
Re: Bit Balling « Reply #3 on Oct 6, 2009, 7:39am »
Hi Guys, I have been drilling some holes with what we call the "fort coopers" in them and it has a tendency to ball up. I would normally use a mud mixture of liquid polymer and clay coat but to no affect. I was talking to another driller and he just uses a detergent product so I tried this on my current hole and no problems with balling of the bit.
Joined: Oct 2009 Gender: Male Posts: 3 Location: Queensland, Australia
Re: Bit Balling « Reply #4 on Oct 9, 2009, 12:44pm »
Hi Guys, I have found in recent situations, keeping the viscosity low, no higher than 32 seconds, using a detergent in conjunction with KCL or a KCL replacement tends to work well. Bit choice is important too. The higher the viscosity the slower the ROP tends to be.
Re: Bit Balling « Reply #5 on Oct 12, 2009, 6:37am »
Clayballing occurs in shale formation when the shale is allowed to effectively remain in the "Plastic Zone" therefore it's important to know the age of the shale (Young or Old) in order to select the drilling fluid that will perform well from the offset.
Bit balling can be avoided by moving the shale into the Dry Zone using dehydration option (KCl inhibited mud), so the shale when drilled remains reasonably hard and firm, or again depending on the age of the shale use the Liquid Zone option (Dispersed Mud) where the clay becomes too wet to stick to the BHA and will wash off.
The key is to keep the shale out of the Plastic Zone and one way to help do this is to minimize the amount of mud filtrate spurting into the formation. Bit-balling of young, shallow shales can be made worse by dehydrating them, ie taking them from the “liquid zone” into the “plastic/balling zone” so make sure you check the age of the shale you are drilling and they type of mud being used.
Minimise the amount of API Filtrate level in the mud to prevent too much free water being embibed into the clay platelets within the shale structure, and use the correct level of KCL determined by shale analysis and other laboratory tests for example. Severe to minimal accretion/ bit balling problems are dependant upon appropriate water based mud system design & selection so it's important to get that right prior to drilling.
Re: Bit Balling « Reply #6 on Nov 3, 2009, 8:49pm »
Balling occurs when you are drilling through a relatively soft clay laden formation. The clays adhere to the wheels of a tri-cone and stop or impede them from turning and cutting effectively.With a PDC the clays cover the cutters. you are drilling with a bullplug, as the saying goes. When I was still chained to the brake handle and experiencing balling problems, I found that mixing a bag of sawdust over an hour would help. The sawdust particles inhibit the clay bond. , If it was a tri-cone bit it would get spudded on every connection to free the wheels. If it was a PDC I would shut the pump off for 2minutes whenever the balling problem occurred, the dry cutting removes the clay from the cutters (not an option with a motor, obviously)
Joined: Jul 2008 Gender: Male Posts: 28 Location: Marcellus/Rockies/Thailand
Re: Bit Balling « Reply #7 on Nov 6, 2009, 8:19pm »
Hi RAJ sorry for the late response. There are couple of problems working against you in a balling scenario, and a number of remedies to minimize them. Not only do clays stick to drill steel, but they also aggregate back onto themselves. John Robinson's post is pretty interesting, mushy cuttings are one of the first things I look for when I hit the shakers for a mud check. I have drilled South Texas but never the Gulf Coast, and only with OBM, but the gumbos surging across and blinding shakers down there are legendary. We can do quite a bit to minimize clay hydration and dispersion. 1. Manage ROP, TFA of bit, and pump rates to keep the bore clean. 2. Manage the fluid to maximize cuttings removal and perhaps limit ECD. 3. Create a wall cake or physical barrier between the fluid and formation. 4. Create a membrane or osmotic barrier to limit the transfer of water to cuttings or formation. 5. Limit the water activity or 'willingness' of the water to interact with clays. 6. Limit the activity or reactivity of the formation and prevent the dispersion of cuttings themselves. 7. Provide a fluid that coats the drill steel to prevent adhesion. I'll speak in terms of products used in the US and Gulf of Mexico, not as advertising, but because that is what I a familiar with. You can take this info reference it with you own tech data, or use the product cross reference World Oil publishes every year. This will give you someplace to start. ROP is out of the hands of the mud engineer, but managing the YP, and therefore the lift capacity of the fluid is not. A little gel goes a good way towards building a decent wall cake of consistently sized particles and we can fortify it with polymers like PAC, the starch-like AquaBloc, or a lower vis alternative like SPA. SWACO's UltraDrill System, Newpark's DeepDrill System, and the TerraMax System from Baker Hughes are all customizable WBM systems that address issues 4-7 and are designed to be environmentally friendly cost effective replacements for KCL or OBM. Bit balling and ROP are addressed specifically by NewEase 203 an ester based polyol that preferentially sticks to metal forming a lipophilic or 'fatty' coating, minimizing the sticking of clays, and helping to prevent clay aggregation. It also helps in the formation of a membrane at the bore / fluid interface inhibiting the hydration of cuttings. Baker's TerraRate is being used with success in the soft formations of the Marcellus Shale in West Virginia and Pennsylvania. It functions like NewEase preventing sticking and aggregation, but it's warning label and smell leads me to believe it has a solvent or mineral oil carrier. Salinity or ionic content of fluids can either swell the clays present in shales, or shrink them and allow them to become mobile, thereby turning a reactive shale into a highly reactive shale. Fluid pressure can accelerate this process. LST-Md, which is Soltex suspended in a polyglycerol, plugs micro-fractures and helps the creation of a semi-permeable membrane limiting water transfer. Baker's TerraCoat uses a deformable polymer to achieve similar results. DeepDrill the methylglucoside base fluid inhibitor and New100 a polyglycerol, combine to inhibit water activity of both the drill fluid and the water found in the formation. They also reduce clay reactivity. They enhance the semi-permeable membrane formed at the interface, balancing the transfer of water to and from the formation. MaxGuard in the TerraMax system reduces clay activity preventing aggregation due to hydration and formation breakdown due to clay swelling. Incidentally, Newpark Canada, in response to environmental concerns, pioneered the use of New100 as a non-saline replacement for CaCl as the internal phase of OBMs in use there. This gave them greater flexibility in waste disposal. So John and the other posters are right, the water activity must be minimized and balanced, and activity and even salinity of the formation must be known at least in general in order to minimize the transfer of water and hydration of clays and dispersion of cuttings. That's how I understand it. Hope this helps a little, good luck and stay busy.
« Last Edit: Nov 7, 2009, 4:19pm by changojaiyen »
Re: Bit Balling « Reply #8 on Nov 11, 2009, 8:28am »
Thanks for the feedback guys. I guess in terms of drilling fluid we can control required parameters to a certain extend, however what I mainly face in the Field is actually defining bit balling. For instance a consistent drop in ROP or torque etc. However there comes a point where the clients just jumps to conclusion & say lets pump some remedial fluids i'e Caustic Pill etc. It can very well be deter-mantle to the drilling fluid. My best bet will be to pump 10-15bbls Seawater depending if hydrostatic permits & see if we do get improved ROP's. Which will com firm if the bit is balled from the fluid side of things.
YP are generally linked to Viscosity of the mud. In terms of seawater due to it's very low vis causes enough turbulence to assist in clearing the bit also depending if the jets are not blocked.
Re: Bit Balling « Reply #9 on Nov 11, 2009, 5:40pm »
I have had good results in pumping a " Nut Plug" or ground walnut hulls pill down to the bit, which just sand blasts the bit. The hulls have no effect on the mud properties and just go over the shaker.
Re: Bit Balling « Reply #10 on Nov 12, 2009, 3:39pm »
Raj, I don't know of a sure-fire way to diagnose balling, though it's usually confirmed when the bit is pulled and has cuttings wrapped all over it.
Very good comments above, especially from changojaiyen. To those comments, I'll add:
Jet configuration plays a huge role in bit balling. With WBM, you need a HSI of at least 2, and much more if possible. There is a balancing act when allocating pump pressure between flowrate and HSI. In other words, do you open up the bit and allow more flowrate for hole cleaning, or jet down the bit to get more HSI (and pressure loss) to the bit? More HSI gives better instantaneus ROP, but if hole cleaning is inadequate, average ROP will ultimately suffer. The mud guy who knows hydraulics can become very valuable in making the best choice for optimization.
A word on dialatency... When a chip is formed, the rock is crushed. This creates tiny voids in the forming cutting. As the PDC bit turns, the chip is sheared, or slid upon itself. This causes the voids inside the chip to become enlarged. This dialating void creates a suction effect that causes the cutting to become very sticky, resulting in long "ribbon" cuttings that ball up the bit. A good ROP enhancer, such as TERRA-RATE, coats the steel and prevents those ribbons from sticking to the bit/BHA--but beyond that, it can actually penetrate into the cutting and break the seal around the dialatent voids. Likewise, it can penetrate between the face of the cutter and the forming cutting to get beneath the chip and actually reduce chip hold down pressure. I don't know if other ROP enhancers can do this, but TERRA-RATE uses patented technology to accomplish this. By the way, it does use a mineral oil carrier. Baker Hughes also has a version that uses an IO carrier for offshore, that is called PENETREX.
There are many other factors affecting ROP but aren't necessarily related to balling (so I won't go there!). For balling, there are a lot of "quick fixes" that can be tried for temporary relief, but the best fix is to use good fundaments: an inhibitive mud, optimal hydraulics, and a quality ROP enhancer.
Joined: Aug 2003 Gender: Male Posts: 60 Location: Netherlands
Re: Bit Balling « Reply #11 on Nov 13, 2009, 11:20am »
Raj,
to diagnose a bit balling problem, you would first look for a drop in ROP, possibly combined with signs of nozzle plugging and some change in torque. In itself this is not enough, you need to wait for confirmation from the mudlogger when cuttings come to surface. If severe enough, you would see the shaker plugging up and overflowing. If less severe, the mudlogger would still be able to identify plastic clay cuttings. Once you work the bit by rotating fast off bottom and reciprocating the string to shake off the clay coating, you should get again confirmation of (nearly) plastic cavings coming over the shaker.
If bit balling is first noticed during a check-trip, the indications might look a little different. Cavings would still be plastic on the outside, but might be dry inside which can confuse an inexperienced mudlogger.
If you suspect you might enter a zone of bit balling soon, but haven't seen it yet, you could ask the mudlogger to run a methylene blue test to look for swelling clays - this could give you an early warning before the bit or the nozzles are clogged up.
Whether all of this helps you avoiding a roundtrip is another question. If you can't generate sufficient hydraulic horsepower to keep the bit free, you have to slow down rop to avoid digging yourself deeper into the problem and continue to pick up and shake/rotate the string. You also need good annular velocity to keep the string free until any correction of mud properties or additives will show an effect.
I have seen in the past many cases where mud property adjustments and change of hydraulics were not enough to solve the problem sufficiently. Once the shale has been hydrated enough to swell, you can only slow down further swelling/hydration but not undo the damage. Therefore it might be a good idea to do a roundtrip anyway to change bit and nozzles and loose any jewelry in the string that might prevent optimum hydraulics. This of course only if the expected remaining section to be drilled is long enough and you can effort to blast past the problem without trajectory control. Most of the time people wait with such roundtrip decision too long.
I had one case on the rig (Netherlands), and one case monitoring a well from the office (Central North Sea) were we were dealing with really, really bad bit balling and soldiered on, trying to get the section out of the way. Of course this didn't work, and when the BHA came back on surface we had to scrap off a 1-1.5 inch thick clay coating with shuffles from the entire BHA. On one of the stabilisers we found within the clay coating one half of a septaria nodule (a whitish cavity in the clay, surrounded by drying cracks and filled with small crystals) of ca 10 inches length that made a beautiful paperweight for my desk.
Joined: Aug 2003 Gender: Male Posts: 60 Location: Netherlands
Re: Bit Balling « Reply #12 on Nov 13, 2009, 11:47am »
Sorry, I forgot: if you are unsure whether bit balling is your problem, you can also call the office and ask them if they can see something. Thick sections of plastic clay can show up on seismic, and especially in some areas of the North Sea the seismic interpreter can look for socalled "polygonal faults" as indicators for tricky shales. Also, if cuttings from a offset well are still available, the lab can run tests even on old cuttings if they haven't done so for the mud design.
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