- Bit Performance

8/2/2019 - Bit Performance

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bit performance

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Jan 10, 2012, 23:57

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:: DrillingMegaDeck Composite Mats The ultimate rig mats & portable roadway for oil/gas &pipeline projects :: Drill String and Bits :: bit performance

A ut ho r To pi c: b it per fo rm an ce ( Read 19 8 t im es)

mehranLeading Member

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b i t p e r f o r m a n ce Thread Started on Dec 13, 2011,9:36

Hi everybody;

I am managing a project in Sudan and I got a

complaint from my client regarding our RCB

performance. We are using Chinese KingDrill bits in

the 17.5" section with the following parameters:

1) WOB=4-10 tons2) RPM = 90-110 (no PDM)

3) GPM = 700-900

The ROP however does not exceed 6 mph and the bit

usually drills around 300 meters before we POOH.

Its dull condition is usually 3-4.

These parameters seem to me quite normal for

drilling surface hole and the bit isn't so worn out

that the ROP drops heavily (it basically drills its

whole 300 meter lifespan starting with around 5-6

mph and then dropping to 2-3 mph when we POOH).

I wonder if anyone could tell me if there is

something wrong with my parameters or is the bitsimply useless 9as my client insists that it is but

with the embargo in place I don't have much chance

of bringing US manufactured bits)

Cheers;

Mehran

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p u p j o i n tLeading Member

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Re: b i t pe r fo r mance Reply #1 on Dec 13, 2011, 12:16

Mehran,

I realize its top hole and generally less consolidatebut can you give us the type of formation drilled.

Was there a change in lithology as the bit

approached the end of the run ? Information of ROP

m/hr vs formation type, might help. Also can you

give us the full information for bit wear ie: I-O-D-

L-B-G-O-R. I 'm articularl interested in the

To Adve r t i se you r

comp any Cl i ck he re

Manufacturersof

Stainless:

ToolJointIdenfiers

StainlessSteelRulers

StainlessSteelGauges

CustomMadeRulers&

Gauges

Clickformoreinfo

Manufacturers

ToolJointIdenfier

withDepthGauge

Digital&AnalogCalipers

Dividers&Calipers

CustomBrassRulers

Protractors

Triangle&AngleRulers

CalibratedandCerfied

Rulers

CustomizedPocket

performance http://drillingclub.proboards.com/index.cgi?board=drillstring&action=d...

r 15 11/01/2012 00:17


2/15

*Logging

*ManagedPressure

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you've given us appears to be quite average.


adoub leukLeading Member

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Mehran,

Unfortunately you don't tell us what sort of

formations you're drilling, nor what IADC code the

bit is.

Regarding your parameters, I suspect you could

benefit from a higher flowrate, if possible.

However, assuming the bit is (nominally) suited to

the formation being drilled, given the ROP and the

dull condition after only 300m, my honest feeling is

that your client is correct, and the bits are rubbish.

Given their provenence, that wouldn't be surprising.

I don't know about the political situation and theembargo in Sudan, but bits carrying a reputable

brand name are manufactured in plenty of places

other than the US: Germany and Gt Britain, for

instance.

AK

CustomEngineers

Scales

Clickformoreinfo


r 15 11/01/2012 00:17


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Last Edit: Dec 13, 2011, 12:27by adoubleuk

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Thanks everyone;

The IADC code for the bits is: 117

The last dull grading was: 4-3-WT-A-E-NO-PR

The formation is medium to fine sandstone inter-

bedded with layers of clay-shale (around 3-4mthick)

I tend to agree with you guys that the bits are not

top notch but I keep wondering if we can squeeze

something more than a miserly 5-6 m out of them (I

am used to drilling surface hole with 20-35 mph and

this is really driving me nuts)

Any help and advice would be appreciated

Cheers;

Mehran


p u p j o i n tLeading Member

Re: b i t pe r fo r mance


r 15 11/01/2012 00:17


4/15

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I tend to agree with AK's reasoning but check the

shaker screens and formation samples under a

microscope for metallic debris...someone could have

dropped something into the hole, albeit it would be

substantial to hold back a 17-1/2" in top hole. How

deep is TD for this section ?

Last Edit: Dec 13, 2011,13:44 by pupjoint


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Dec 13 , 2011 , 13 :21 , m e h r a n w r o t e :

Thanks everyone;The IADC code for the bits is: 117The last dull grading was: 4-3-WT-A-E-NO-PRThe formation is medium to fine sandstone inter-bedded with layers ofclay-shale (around 3-4m thick)

I tend to agree with you guys that the bits are not top notch but I keepwondering if we can squeeze something more than a miserly 5-6 m outof them (I am used to drilling surface hole with 20-35 mph and this isreally driving me nuts)

Any help and advice would be appreciatedCheers;Mehran

Mehran,

An interesting situation. With extra detail you've

provided, there's more scope for ideas.

First off, if you're pulling bits with worn teeth graded


r 15 11/01/2012 00:17


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being the case, get brave and run 'em just a tad

harder, so they're completelyworn out by the end of

the section. More WOB, more pump. I wouldn't

advise increasing RPM, though.

Secondly, the intercalated formation brings other

thoughts to mind, regarding the way the guy on the

brake is reacting. Does ROP suddenly increase in theshale bands, with the driller 'chasing' it, then really

slow down at the next sandstone layer? It might be

a good idea to instruct him to take it slightly easier

through the soft stuff, if that's the case. You may

have a bit-balling problem.

Thirdly, (and I know this might sound corny to the

mud engineers), check your mud properties. If

you're in Sudan and it's top-hole, I'd assume you're

using water-based mud, and not much polymer. If

that's so, make sure your ph is high, something like

10 or so. It may help. Also, keep the mud weight as

low as you safely can, by dilution if necessary,

though that means adding more products to keep

things stable. However, bentonite and caustic arecheap.

Are you encountering high torque?

Regarding PJ's comment, I agree, but only in part.

Because if you're seeing this trend over a series of

runs, it can't always be attributable to potential

junk, especially as your dull grading makes no

mention of junk damage. But (apologies to the

mud-men once more), certainly keeping a very close

eye on what's coming over the shakers is important.

Are you pumping low/high vis sweeps from time to

time? If not, try it, and see what happens when the

sweep comes back. It will indicate whether you havea hole-cleaning problem or not. 900 GPM in 17 1/2"

hole sounds low to me.

But without wanting to seem overly discouraging nor

chauvinistic, the possibility remains that your client

is correct, and that the bits themselves are to

blame. I don't trust anything 'made in China'

downhole, no matter how cheap it is, nor plentiful

the supply. I don't trust their surface stuff neither

(rigs, pumps, etcetera). Nothing against the

Chinese, it's just that they're on a steep learning

curve, but with a long way to go before they

manufacture any oilfield equipment worthy of the

name. Right now they're producing junk which ought

to go straight to the cutting-torch. It might look likea dog and go 'woof', but that doesn't mean it's

necessarily a dog. It might be a wolf. Though when

it comes down to good bit perfomance it's a Wolf you

want, not a Shar-Pei.

AK



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Thanks guys for all the feedback;

Let me answer a few more questions so that thesituation will be come a bit clearer:

1) this phenomena has been observed in 3 wells so

possibility of junk is quite remote

2) The interval in question is roughly from 30-600

mRKB.


r 15 11/01/2012 00:17


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drops when we get to the clay/shale beds.

4) We do indeed have a bit balling problem in some

areas and that just cuts the ROP down to 1-2 mph,

but even when we are drilling in a relatively long

stretch of Sandstone (20-30 m) the ROP remains at

around 3-5.

I was quite interested in the part mentioned by AKregarding the mud. The parameters of the mud are

generally reported as follows:

MW=8.9 ppg

Funnel vis = 45 seconds

PV = 11

YP = 28

Gels = 8/10

PH = 9.5

and the mud itself is a simple bentonite mud. My

shaker screen sizes are 40, 40 and 60

Since I am not a mud expert I wonder if anyone can

tell me if these properties can be somehow improved

Cheers and thanks again;Mehran


Rebel Too lLeading Member

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Joined: May2010Gender: MalePosts: 223Location: UK


As everyone keeps mentioning, you seem very light

on the flow. Are you limited by surface equipment?

Normally for 17-1/2" hole I would be thinking

1500gpm, at least something way over 1000gpm.

The kind of flow rates you quote are more typical of

12-1/4" hole drilling.What kind of jets are you using? The old rule of

thumb always used to be to try and use 60% of your

hydraulic horsepower across the bit. That seemed to

fall out of fashion as there was push for more and

more annular flow rates for hole cleaning, but you

don't seem to be in either camp. Are you sure that

you are using enough hydraulic impact to clear any

cuttings away from the bit (you mention bit balling

which seems to confirm my suspicions) and enough

flow to get the cuttings up the annulus. In 17-1/2"

hole, and assuming that you are using 9-1/2" drill

collars, you are very unlikely to get enough AV to go

into turbulent flow with the light thin mud that you

are using.


r 15 11/01/2012 00:17


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b js taa lMember

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Joined: Mar 2003Gender: MalePosts: 1Location: Cairo -

Egypt


Mehran,

I would definitely look into the hydraulics as stated

already in the emails.

Furthermore, if you are managing this project, go

and have a look how they are drilling. What you

read and what you see may be two different things.

Check offset bit data (if available) in your area. I

have never run a Chinese bit and maybe never will;

you have to realise that bits are cheap compared to

your overall rig spread rate. I suggest you run youreconomics too and try perhaps a Western bit

manufacturer. First get your optimum parameters to

drill thru sand and shale and then try to see what

another bit will do for you.

Best of luck.

BJ



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Mehran,

I agree with what 'Rebel Tool' has just said, and I'm

beginning to think that you may well have a

hole-cleaning problem, if it's not the bits themselves

to blame.

Certainly your flowrate is low. But also I find it

curious that the mud PV should be at such a low

value if you're drilling through clays.

Also, at 900 GPM, I'd expect to be running with

shaker screens with a far finer mesh than 40/40/60

without them clogging up.

So I'm starting to suspect you should look closely at

the mud, or more particularly your solids control.You don't mention your sand / solids percentages.

Maybe they're high. If you're drilling intercalated

sandstone beds, some of that stuff might be getting

recycled, and it will eat up your bit, amongst other

things. Are you encountering frequent mud pump

problems such as premature liner/piston wear? If so,

this might tend to confirm such a hypothesis.

AK



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sk rMember

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Re: b i t pe r fo r mance

Reply #10 on Dec 15, 2011, 17:12

Solids content would be 4%, with an 8.9ppg mud

weight, assuming solids SG is 2.6. That's not too bad

I think for a gel mud (bearing in mind I don't have

any experience outside of western Canada and the


r 15 11/01/2012 00:17


8/15

Joined: Nov2011Gender: MalePosts: 16Location: Canada

garbage bit, and maybe some bit balling. I can't say

anything about the pump rate because I don't think

I've ever been on a rig capable of pumping 900gpm.

I know I've never seen it done. So I don't think I can

comment on things I can't comprehend.

Again, I don't have the global experience so I might

be wrong, but I'd never drill into soft clays with a pHhigher than 8. I don't know what other implications

that would have on your mud. Maybe you wouldn't

be able to get your properties in line without a little

caustic. But I personally make sure that my mud can

be drilled with first, and then optimize it. Mud that

would win a medal doesn't mean anything if you

can't drill a hole with it.

I would like to see a sand content, solids content

and MBT.

Last Edit: Dec 15, 2011,17:13 by skr

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skr,

Obviously we work on different rigs, in different

parts of the world, but also with a different mindset.I'm used to the sort of kit where I can get at least

1200 GPM on 17 1/2" hole. But running a low ph

mud in clays? I don't understand that.

AK


r 15 11/01/2012 00:17


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sk rMember

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Posts: 16Location: Canada


Our clays that we drill through here will cause or

mud to turn into a solid with the pH over 9. I don't

know what would happen if we got it over 11,

because that's the environmental cutoff for disposal.

A 12 pH might be a better answer, but then we're

left with a bunch of mud that we can't cheaply get

rid of.

If we keep a low pH we're able to get through the

clays without much trouble, but it comes with the

cost of not running "good" mud. That is, mud with all

the same properties as the program says it should

have. We can run a higher pH but then we have to

run a truckload if inhibitors, and even then it's a

time-sensitive mud that will go to hell in a few days

anyway. If we're going to do that we might as well

just use OBM and have a system we can take with

us from hole to hole.

The alternative is to drill with "floc water": A clear

water system, with calcium at 600-1000mg/l, and

an anionic flocculant added at the flow line or

injected into the centrifuge. The "mud" comes over

the shaker dirty, and into a settling tank to allow

the solids to flocculate and settle out before goingback downhole clean. There's no rheology, and the

hole is cleaned with AV (usually 80-120m/min), and

drilled at 75-150m/hr.

This is what works for us, and it would be the first

thing I'd suggest if I was somewhere else in the

world and dealing with the same problem.


s h o r t b i t sLeading Member

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A drill bit (of any kind) will only transfer energy...itwon't create any.

I agree with others that you may not have reached

your optimum energy transfer level (mechanical and

hydraulic) to dril l as fast as is possible in your

situation. Any simple drilling hydraulic program will

give you a bell curve for your bit hydraulics, and

then you just have to match up jet sizes accordingly.

Whether it is HSI, HIF, or a percentage of your total

hydraulics, you need to increase your hydraulics,

but not blindly. You can do it with high volume and

moderate velocity in the bit nozzles or lower GPM

and higher velocity in the nozzles.

Have you run any drill-off tests that vary mechanical

imput with a hydraulic constant and then that best

mechanical as a constant with varying hydraulic

levels? Benchmark.



r 15 11/01/2012 00:17


10/15


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skr,

That's really interesting, and an approach I didn't

really know about. And obviously in Canada the

environmental concerns are very probably higherthan in Sudan, where Mehran is drilling. And

certainly it wouldn't matter where in the world I

found myself, if I found I needed a ph over 10.5 I'd

be wondering if I had the right mud.

But maybe what you've said could help him

narrowing down whether he's actually got a mud

problem or not, and whether it's affecting his ROP

situation. Other than flowrate, of course.

His posts mention clays/shale bands, where ROP

decreases. I'm wondering if by 'clays' his

mud-loggers might not actually be referring to

claystone, which can actually be difficult stuff todrill, and medium/hard. Especially where there is a

limitation to flowrate, and hence a possibility of

redrilled cuttings. And shows up at the shakers

looking like a clay.

Maybe my reference to ph was completely wrong,

though I have to admit that when it's below 9, I

start to get worried, wherever I am. Unless it's in

Djibouti doing geothermal, where acidity helps, just

so long as the drillpipe will stand up to it.

Not sure I like the concept of 'no rheology', but keep

the discussion up. This old dog likes learning new

tricks!

Mehran,

Maybe as a pointer: when you get bottoms-up across

the shakers after the clay/shale sections, are the

cuttings sticky, clagged-up, clean and separate, or

what?

AK



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adoub leuk

Leading Member

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Dec 15 , 2011 , 22 :02 , s h o r t b i t s w r o t e :

A drill bit (of any kind) will only transfer energy...it won't create any.I agree with others that you may not have reached your optimum energytransfer level (mechanical and hydraulic) to drill as fast as is possible inyour situation. Any simple drilling hydraulic program will give you a bellcurve for your bit hydraulics, and then you just have to match up jet sizesaccordingly. Whether it is HSI, HIF, or a percentage of your totalhydraulics, you need to increase your hydraulics, but not blindly. You cando it with high volume and moderate velocity in the bit nozzles or lowerGPM and higher velocity in the nozzles.

Have you run any drill-off tests that vary mechanical imput with ahydraulic constant and then that best mechanical as a constant withvarying hydraulic levels? Benchmark.

Wouch!

'Shortbits', you've opened a whole can of worms

here! I hope this won't become a digression that will


ur 15 11/01/2012 00:17


11/15

Can you think of any occasion since the mid-eighties

where anyone wasted their rig time performing

'drill-off tests' as such? I certainly can't. You simply

find the 'sweet spot' and then go with it.

And although I agree with you regarding optimum

bit hydraulics vs available flowrate and annularvelocity, that is also being slowly consigned to the

wastebin where it belongs, being 1970's thinking,

when bits were crude, mud was rubbish, and people

thought oilwell drilling was rocket-science.

Our initial questioner, Mehran, came up with a

genuine problem. Rotten ROP, and a startling bit

grading after only 300m of 17 1/2" hole drilled.

Admittedly with a low flowrate. But if that's what his

rig is limited to, changing the bit hydraulics by a

change in nozzle size isn't going to aid him at all. It

may in fact help him to lose a cone, or something

like that.

We may be all going down the wrong track here. A17 1/2" bit should be able to go more than 300m (+

1000 ft before being Pooh graded 4-3. It's possible

that the client is correct, and the bits are no good.

3000ft, maybe, but 1000? No way.

AK


Rebel Too lLeading Member

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Mehran,

I realise that it is a really long shot, but you haven'tgot access to a sonic log for your well or any offset

wells do you? Failing that, presumably there has

been some seismic work done in the area which

means that someone must have worked out (or

guessed) a sonic velocity for your formations. Sonic

velocity is very closely related to compressive

strength. I'm sure that if you were using one of the

big international bit suppliers they would be able to

analyse the drilling parameters and log data that

you have and translate it into a bit recommendation.

Do the Chinese bit manufacturers provide that kind

of support?

It may just be that you are drilling formation thatjust cannot be drilled much quicker, on the other

hand it might well be that the bit is totally unsuited

or just badly engineered.

I notice that you talk about shales and sands tones

which implies that they are consolidated, cemented

formations rather than soft, unconsolidated clays

and sands.


t h e m u d 1Full Member

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Hi Mehran,Just a matter of interest regarding the bit wear....

How is your water return from the well? any losses

encountered?

TM1


ur 15 11/01/2012 00:17


12/15

Location:Queensland,Australia

s h o r t b i t sLeading Member

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Joined: Mar 2003Gender: MalePosts: 230Location:Garland, Texas


Well, UK, you found me out. Most of my rig

experiences were before the 80's and I haven't evenbeen to a rig since 2006, but if a guy is lost you

gotta find out where he is first before you guide him

out of the jungle. I didn't suggest that he should do

any drill-off tests...I simply asked him if he had.

Do you think Mehran has found his sweet spots in

WOB/RPM/ and hydraulic horsepower? Is the

formation weight sensitive or RPM sensitive or both?

What jets is he running? 700 to 900 GPM is a pretty

wide range...where is the sweet spot there? Is any

of his bit wear caused from re-drilling of cuttings?

I have never been to the Sudan, but my guess is the

situation there may be a little more primitive thanmost are used to. I guess I better stay out of this

discussion...sorry if I interrupted.



member isoffline



"I guess I better stay out of this discussion...sorry if

I interrupted. "

'shortbits'

I certainly didn't want to sound 'holier than thou',

and I apologise if that's the impression I gave.

I haven't worked in Sudan either, but I havein

various nearby Central / East African countries. But

the tophole formations didn't really resemble each

other much, unlike the general case in North Africa,

where you can encounter tophole sections with very

similar characteristics extending over hundreds of

miles.

The point you made about the '700-900 GPM' you

noticed aroused my curiousity, as well. Why is it not

a fixed figure, preferably at the top end of that

window? Are Mehran's pumps maxed out, or his

surface equipment such as the solids control?

As mentioned earlier, some of us feel that 900 GPM

is way low for 17 1/2" hole, especially in the

absence of a motor or MWD. So all my comments

implied is that in such circumstances, optimising or

finding a hydraulics 'sweet spot' is probably difficult,

if not impossible to do.

It would be interesting to know what sort of rig

Mehran is operating, and its limitations.

AK


sk rMember

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ur 15 11/01/2012 00:17


13/15

Joined: Nov2011Gender: MalePosts: 16Location: Canada

This old dog likes learning new tricks!

In North Dakota and Montana they drill 6000+m

(~20,000ft) with 9-10ppg NaCl water. They use

beads or liquid lubricants, and viscosified sweeps

maybe every 1000'. There probably is some

rheology to it, but you'll never see it with a regular6 speed viscometer. You just can't get the

measurements precise enough.

For a mud man, it doesn't get much better than a

clear water system. A mud check takes 5 minutes

and as long as the weight's right and it's not dirty,

it's probably good. But this a discussion that should

probably go on in its own thread.



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skr,

Somehow I doubt that high-end products like beads

and quality lubricants are available in Sudan.

However, your comment has jogged my memory. I

wonder if Mehran's client has considered the

feasability of air/foam drilling the top and

intermediate hole sections? Now that is really a way

to make fast hole! Though of course if his bits are

getting so quickly worn with mud as the circulating

medium, I very much doubt they'd last more than a

few hours with foam.

AK

PS There ar eair/foam contractors present in

East/Central Africa. Air drilling has a great

advantage in such countries, that being once the

equipment is in place, the logistical requirements

regarding products, and even water supply, are

greatly reduced: not a negligible factor in that part

of the world.



member isoffline



Thanks everybody for your comments;

We do encounter partial to complete losses for the

first 200-250 m of the hole, and quite often we have

pump breakdowns. Bit balling is indeed an issue and

my options as you probably have noticed are quite

limited.

I tend to agree strongly with the observation that

the bit is crap, also if I could increase the GPM the

ROP would probably increase but I still have the

matter of lost circulation to contend with. The

shakers are definitely worth looking into and so are

the mud properties but I am out of my league here

since I am not a mud person.

What I am contemplating doing is to work on the

RPM and see if it is going to work on the next well. I

am planning to use a motor in conjunction with thesame bit and see if I can get anywhere but to be

frank I am not that confident.

BTW, regarding the matter of the drill-off test we

don't do one here and we tend to go with the 'sweet

spot' approach.


ur 15 11/01/2012 00:17


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Mehran



member isoffline



Dec 20 , 2011 , 9 :16 , m e h r a n w r o t e :

Thanks everybody for your comments;We do encounter partial to complete losses for the first 200-250 m of thehole, and quite often we have pump breakdowns. Bit balling is indeed anissue and my options as you probably have noticed are quite limited.I tend to agree strongly with the observation that the bit is crap, also if Icould increase the GPM the ROP would probably increase but I s till havethe matter of lost circulation to contend with. The shakers are definitelyworth looking into and so are the mud properties but I am out of myleague here since I am not a mud person.What I am contemplating doing is to work on the RPM and see if it isgoing to work on the next well. I am planning to use a motor inconjunction with the same bit and see if I can get anywhere but to befrank I am not that confident.BTW, regarding the matter of the drill-off test we don't do one here andwe tend to go with the 'sweet spot' approach.Thanks again for all the supportCheers;Mehran

Mehran,

More and more interesting!

Running a motor in top-hole is often a good idea. It

also acts in some way as a shocksub, though motor

manufacturers don't like to advertise that. But your

dull grades may imply a certain amount of bit

bounce, degrading your inner cutters faster than the

outer.

My advice when using such a setup would be to

ensure that the actual bit RPM (ie surface + motor)doesn't exceed that on your previous wells. This will

certainly involve some hydraulics calculations, given

that some of your power will be eaten up by the

motor, but you still want decent bottom-hole

cleaning, and the same annular velocity, which is

already sounding low. Not easy, but not impossible,

either!

By not changing bit RPM, but supplying it partially

by the motor, you'll have some constant factors in

play. Obviously, you'll be able to see immediately if

the motor improves your ROP. But otherwise, only

one change at a time is the best way to go.

Keep us posted...

AK


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