07.Politecnico Di Torino.bits SELECTION 2011

8/9/2019 07.Politecnico Di Torino.bits SELECTION 2011

1/141

07. DRILLING BITS TECHNOLOGY

1

CHAPTER 7 BITS TECHNOLOGY


2/141


2

BIT SELECTION

The selection of the proper bits for a well is an important decision that has a bigimpact on costs. Many factors need to be considered and evaluated:

Method of dr!!"#$rot%r&' t(r)"e' do*"ho!e +otor' %r,

-or+%to" t&e %"d roerte/

M(d /&/te+

R# o/t

Bt o/t

Drilling bit optimization is based on three main phases:

a) Selection of the proper bit as a function of drilling conditions.

b) Monitoring of the drilling performance and conditions on the wellunder evaluation so that the performance is eual to or better than theaverage in the area.

c) !mplementation of bit weight" rotary speed and hydraulic programmebased on theoretical calculations that will improve the performanceabove the previous best performances in the area. This phase isdifficult to be implemented in one or two wells" but is valuable indevelopment drilling.


3/141


BIT DE-INITION

#its can be divided into two main categories:

Ro!!er Co"e Bt/

$Milled Tooth #its

$!nsert #its

-ed C(tter Bt/

$%atural Diamond #its$Synthetic Diamond #its &'D( #its" TS' #its"

!mpregnated #its)

$ Drag bits &usually employed to drill water wells)


4/141


3

ROLLER CONE BITS


5/141

07. DRILLING BITS TECHNOLOGY4

Ro!!er Co"e Str(t(re

'! 'in

*eg

(one

%ozzle

%ozzle #oss

Shirttail

Tungsten (arbide

+ardfacing

*ubricant ,eservoir

(over

-uter ,ow &age)

(utting Structure!nner ,ow

(utting Structure


6/141


The main mechanisms according to which a bit wor/s are the following:/r%"# or #o(#"#

!o(#h"# %"d #r"d"#h"# %"d r(/h"#/he%r"#ero/o" $fro+ the dr!!"# f!(d,

!n some cases" a bit can wor/ according to some of these mechanisms at the same

time" though" very often" one mechanism prevails on the others depending on the type

and characteristics of the bit in use.

Ro!!er o"e )t/wor/:$with the mechanisms of gouging and scraping when drilling /oft for+%to"/0$with the mechanisms of chipping and crushing &crater mechanism) when drilling h%rd

for+%to"/.

D%+o"d )t/wor/:$with the mechanism of ploughing and grinding.

PDC )t/wor/:

$ with the mechanism of shear

Ho* Bt/ Dr!!


7/141


Ro!!er Co"e Bt C(tt"# Ato"6 Soft -or+%to"/

Scraping 1 ouging

2 !ndentation 1 3racture

2 Tooth Displacement


8/141


1. Tooth I+%t

2. 8ed#e -or+%to"

. -r%t(re

3. Po/t9-r%t(re

Ro!!er Co"e Bt C(tt"# Ato"6 H%rd -or+%to"/

(hipping 1 (rushing


9/141

07. DRILLING BITS TECHNOLOGY:

Geo+etr E!e+e"t/ of Bt De/#"

Dret!& "f!(e"e the t&e of C(tt"# Ato"

. -ffset

#. 4ournal ngle

(. (one 'rofile ngles


10/141


A. Bt Off/et

Def"to" of Off/et6

2 5..the horizontal distance of the cone a6is from the centre of thewellbore7 or as 5the angle of which is necessary to rotate the

cone a6is to ma/e it pass through the centre of the wellbore7.

Off/et +e%/(red " "he/

2 8ery Soft formations typically 3/8 or up to 4o

2 8ery +ard formations typically 1/32 or down to 0o


11/141


A. Bt Off/et


12/141


B. ;o(r"%! A"#!e

Def"to"2 5..is the angle formed

by a line perpendicular

to the a6is &or

centerline) of the

9ournal and the a6is &or

centerline) of the bit.7

#it 6is

4ournal ngle

4ournal 6is


13/141


B. Soft


14/141


C. Co"e Prof!e A"#!e/

I""er Co"e Prof!e A"#!e

I"ter+ed%te Co"e Prof!e A"#!e

O(ter Co"e Prof!e A"#!e


15/141


C. Co"e Prof!e A"#!e/

-uter (one ngle

&age ,ow)

!ntermediate (one ngle

&Middle ,ow)

!nner (one ngle

&%ose ,ow)


16/141


#earings and Seals


17/141


M%=or Be%r"# T&e/

%. Ro!!er Be%r"#/

2 Typically used in large

bit sizes

2lso referred to as

5nti$3riction7 bearings

). -rto" Be%r"#/

2 Typically used in small

bit sizes

2lso referred to as

54ournal7 bearings


18/141


%. Ro!!er Be%r"#

,ollers


19/141

07. DRILLING BITS TECHNOLOGY1:

%. Ro!!er Be%r"# > E!oded ?e*

Seals&s)

,ollers

#all #earings

Thrust ?asher

#earing

,ollers

Thrust 'lug


20/141


). -rto" Be%r"#

#earing Sleeve


21/141


). -rto" Be%r"# > E!oded ?e*

Seals&s)

#earing Sleeve

#all #earings

Thrust ?asher

#earing

Thrust (ap


22/141


). -rto" Be%r"#


23/141


. Se%!/

(one lubrication is an essential factor in determining a bit life. Two types of

bearing are adopted for ensuring an adeuate lubrication:oe" )e%r"#

/e%!ed )e%r"#

!n the oe" )e%r"# t&e )t/" the lubrication is ensured by the drilling fluiditself0 but because of the presence in the mud of abrasive solids" this type oflubrication is used only in large size bits &above @A


24/141


Oe" Be%r"#

(-%B

-#(re 20

(-%B

-#(re 20


25/141


). -rto" Be%r"#

'ressure

(ompensator

*ubricant

,eservoir

(onnecting

+ole

Seal

-#(re 21

'ressure

(ompensator

*ubricant

,eservoir

(onnecting

+ole

Seal

-#(re 21


26/141


. Se%!/

Se%!/ +(/t )e o+%t)!e *th do*"ho!e e"


27/141


(utting Structures


28/141


C(tt"# Str(t(re

The cutting structure determines the distinction of the roller cone bits

into:

$milled tooth bits

$tungsten carbide insert bits.


29/141


Ro!!er Co"e Bt/6 Co"/tr(to"

The manufacturing of drilling bits is done in accordance with strict

metallurgical standards:

cones are manufactured with a nic/el$steel &C@E$+) alloy0 the bit legs are made from a special nic/el chrome steel &A;F$+)

alloy0

the bearings are made from a high$resistance steel capable of

sustaining high shoc/ loads.

#it cones and 9ournals are carburized" a process which includes the

addition of carbon to the steel surface and heating to a temperature of

G;Eo( for a minimum of @G hours.

M!!ed Tooth Bt/6 C(tt"# Str(t(re


30/141



Milled tooth bits for soft and hard formations are visually recognizableon account of the height and number of their cutters:

#its for soft formations have long and sparse cutters.

#its for hard formations have short and closely arranged cutters.

nother feature of roller$cone bits is the cuttersH location on the cones0

this is arranged so that each cutter row of each cone stri/es its own

roc/ portion on its circumferential path. This feature allows the entire

borehole surface area to be sub9ect to the bit action.


31/141


N(+)er 2 Co"e

N(+)er 1 Co"e

N(+)er Co"e

'artially Deleted

Tooth

Spearpoint

!ntermesh rea

or roove

+eel ,ow

'itch #rea/

Tooth +ardfacing

&*eading flan/)

G%#e Ro*

Mdd!e Ro*

No/e Ro*



32/141


Soft -or+%to" Bt/

soft formation bit is characterized bya limited number of teeth" the way they

are relatively spaced from one another

and their considerable length.

Soft formation bits mainly wor/

through:

scraping

gouging

-perations are carried out with !#ht

*e#ht/ &appro6imately ; tIin ofdiameter) and a high rotational speed

&@FF$;FF ,'M) of the drill string.



33/141


H%rd -or+%to" Bt/

+ard formation bits have a high numberof teeth and a high density of short

cutters.

+ard formation bits mainly wor/ through:

crushing

chipping

-peration are carried out with he% tIin of

diameter)" because formations oppose

considerable resistance to penetration"

and a /!o* rot%to"%! /eed of

appro6imately EF$>F ,'M.



34/141


-ffsetF.AE7

&I7)

F.;@7

&GI;7)

F.;@7

&GI;7)

F.@>7

&I@>7)

Total ,ows A G @;

Total Teeth >E A @FG @>F

12 Bt/


?er& Soft Soft Med(+9Soft Med(+


35/141


Ro!!er Co"e Bt/ H%rdf%"#

+ardfacing is the application of

tungsten$carbide on the gauge

and teeth to provide increased

resistance to abrasion. ?ithout

hard$facing a bit would lose

gauge and the teeth would dull

uic/ly.

+ardfacing provides wear

resistance to the teeth and

resistance to fracture.



36/141


Stee! Tooth Bt/

Ad


37/141


T("#/te" C%r)de I"/ert Bt/

!n these three$cone bits the cutting structure is formed by t("#/te"

%r)de INSERTS pressed into appropriate holes bored in the cones.

Designations of cones &@$;$) and insert rows are the same as withtooth bits.

!nserts have different lengths and shapes in function of the bit

hardness:soft formations reuire long and sparse inserts0hard formations reuire short and closely arranged inserts0small and round inserts are placed on the shoulders of the bit.

-#(re 7-#(re 7


38/141


I"/ert Sh%e6 I""er Ro*/

Soft

Soft

to Medium+ard

Medium

to +ard


39/141

07. DRILLING BITS TECHNOLOGY:

I"/ert Sh%e6 G%#e Ro*/


40/141


!nner ,ow

(hisel (rest !nsert

!ntermesh rea

or roove

N(+)er 2 Co"e

N(+)er 1 Co"e

N(+)er Co"e

age ,ow !nsert

Teeth ,ows

'itch #rea/



41/141


T("#/te" C%r)de $8C, ro


42/141


@F rows I G; inserts

@A rows I @F inserts

@@ rows I @@C inserts @; rows I @;F inserts

@; rows I @;E inserts @C rows I @CC inserts

AAI7 #its


8ery Soft Soft Medium$Soft

Medium$+ard +ard 8ery +ard


43/141



Ad


44/141


8%tero(r/e/

n important part of a roc/ bit is the

watercourse" without which the bit

could not function as intended.

The design of the passageways and

nozzles that direct the fluid when

coming out from the bit differentiates

between two types of watercourses:

@. (onventional watercourse that

directs the fluid onto the cutters

;. 4et watercourses that direct the

fluid onto the bottom of the hole&central nozzle and e6tended nozzles)

Ro!!er Co"e Bt/

3igure ;:3igure ;:


45/141


De/#" -%tor/ S(++%r&

-or+%to" Stre"#thSoft Med. Soft Med. Hard Hard Very Hard


46/141


47/141


IADC Bt C!%//f%to"

wide range of bits is available in the mar/etplace. There are many

different /inds of bits with different features.

3or this reason" the !nternational ssociation of Drilling (ontractors"

!D(" approved a standard classification system to compare bits

having similar features through the use of a numeric code.

This standardization" which has been introduced in @GA; and revised in@GG;" is e6tremely useful" because it allows engineers to rapidly find

bits with similar features" even if they are built by different

manufacturers.


48/141


IADC Bt C!%//f%to"

ROLLER CONE BITS CLASSI-ICATION ACCORDING TO SER?ICE COMPANIES


49/141


39Ch%r%ter De/#"A!%to" Code

2 3irst (haracters are %KMB,!(

2 Cth (haracter is *'+#BT!(

E%+!e/14M 337 57Y

IADC ROLLER CONE BIT C!%//f%to"


50/141


N(+er Ch%r%ter/ def"e62 Series @st

2 Type ;nd

2 #earing 1 age rd

A!h%)et Ch%r%ter def"e/6

2 3eatures vailable Cth

IADC Bt C!%//f%to"


51/141

C!%//f%to" Ch%rt6 Sere/


52/141


C!%//f%to" Ch%rt6 Sere/

14M

337


53/141


T&%! -or+%to"/ H%rd"e//

H%rd"e// CS $/, E%+!e/

Kltra Soft L @"FFF gumbo" clay

8ery Soft @"FFF $ C"FFFunconsolidated sands" chal/"

salt" claystone

Soft C"FFF $ "FFF coal" siltstone" schist" sands

Medium "FFF $ @A"FFFsandstone" slate" shale"

limestone" dolomite

+ard @A"FFF $ ;A"FFFuartzite" basalt" gabbro"

limestone" dolomite

8ery +ard ;A"FFF marble" granite" gneiss

UC ! Unia"ial Uncon#ined Co$pressie trengt&

T


54/141


T&e

2. Seo"d Ch%r%ter6 T&e

De#ree of -or+%to" H%rd"e//

E%h Sere/ / d


55/141


C!%//f%to" Ch%rt6 T&e

14M

337

Be%r"# G%#e


56/141


Be%r"# G%#e

. Thrd Ch%r%ter6 Be%r"# G%#e

Be%r"# De/#" %"d G%#e Proteto"

Se


57/141


C!%//f%to" Ch%rt6 Be%r"# G%#e

14M

337


58/141


E%+!e 9 M!!ed Tooth

MSDGH IADC 14


59/141


E%+!e 9 TCI

-2 IADC 417

- A ! )!


60/141


-e%t(re/ A) lphabetic (haracters

2 Most Significant 3eature or pplication *isted

IADC - t A ! )!


61/141


IADC -e%t(re/ A


62/141


C!%//f%to" Ch%rt6 -e%t(re/ A


63/141


-IED CTTER BITS
http://marketing.corp.smithbits.com/vault/web/photos/PN8801.jpghttp://marketing.corp.smithbits.com/vault/web/photos/PN8801.jpg


64/141


T&e/

-ed C(tter Bt St&!e/ Drag #its

%atural Diamond #its

Synthetic Diamond #its &'D(: 'olycrystalline Diamond(ompact #its" TS': Thermally Stable 'olycrystalline

Diamond #its" !mpregnated #its)

T&e/


65/141


T&e/

Dr%# Bt/

drag bit is a drill bit usually designedfor use in soft formations such as sand"clay or some soft roc/. They do notwor/ well in coarse gravel or hard roc/formations.

Kses include water wells drilling" mining"geothermal" environmental ande6ploration drilling. ?henever possible"they should be used to drill pilot holesbecause they produce cuttings that arevery easy to log.

They are not in current use and are

mentioned here only for their historicalimportance.

-#(re 27 Drag #its


66/141


N%t(r%! D%+o"d Bt/

%atural diamond bits are constructed with diamonds embedded into a

matri6 and are used in conventional rotary" turbine and coringoperations. Diamond bits can provide improved drilling rates over roller

bits in some particular formations and all the diamond bit suppliers

provide comparison tables between roller bit and diamond bit

performance to aid users in bit selection based on economic evaluation.

Some of the most important benefits of diamond bits over roller bits are:

#it failure potential is reduced because there are no moving parts.

*ess drilling energy is reuired by their shearing cutting action

compared to the crac/ing and grinding action of the roller bit.

#it weight is reduced" therefore deviation control is improved.

The low weights reuired and lac/ of moving parts ma/e them wellsuited for turbine drilling.


67/141


N%t(r%! D%+o"d Bt/

%atural Diamond #its are made by three main components:

the cutters0the body or blan/0

the shan/.

The (tter/are natural diamonds placed on the surface of the bit" from

the nose to the gage" according to well$defined configurations or plots.

They are immersed in a matri6 composed by a mi6ture of tungsten

carbide and a metallic binder.

During the construction process" diamonds are included in the matri6by fusing it &each natural diamond bit is hand$built according to the

instructions received from the oil company that placed the order).


68/141


N%t(r%! D%+o"d Bt/

D%+o"d Bt Ter+"o!o#& -e%t(re/


69/141

D%+o"d Bt Ter+"o!o#& -e%t(re/

4un/ Slot

#rea/er Slot

'! 'in

(onnection

Diamond auge

Shan/

(rown (utters

N t ! D d Bt
http://marketing.corp.smithbits.com/vault/web/photos/PN8812.jpg


70/141


N%t(r%! D%+o"d Bt/

Diamond #it can have different profiles depending on the formation to

be drilled:a 5/"#!e9o"e rof!e7 presents a rounded shape" which determines

a limited load on each cutter. The bit is sub9ected to a slow wear and

long life0

the 5do()!e9o"e rof!e7 has a narrower attac/ front and is very

aggressive in its central part. The tapered zone maintains the hole ingauge. The bits with this profile ensure higher ,-'" but also a more

rapid wear0

the 5%r%)o! rof!e7 has a front more rounded than the previous

type0 it represents a compromise between the two previous profiles0

the 5o"%


71/141


N%t(r%! D%+o"d Bt/

-#(re 30 Prof!e/ of N%t(r%! D%+o"d Bt/-#(re 30 Prof!e/ of N%t(r%! D%+o"d Bt/

N t ! D d Bt


72/141


This type of bits is not euipped with nozzles. +ydraulics has the main

purpose of cooling the bit face and removing drilled cuttings.

The e6it holes of the drilling fluid are positioned in the centre of the bit.

3luid is then directed into grooves carved out of the bit face.

rooves are designed according to two main configurations:

,adial flow

(ross$pad flowor feeder$collector flow.

!n both configurations" the outflow of drilling fluid from the bit centre

ta/es place through a 5crowfoot7 that distributes the flow into three

branches.

N%t(r%! D%+o"d Bt/

N t ! D d Bt


73/141


(ollector3eeder

(rowfoot

?aterways

'ad I ,ib

(rowfoot

Cro//9P%d -!o* R%d%! -!o*

N%t(r%! D%+o"d Bt/

N t ! D d Bt
http://marketing.corp.smithbits.com/vault/web/photos/PN8801.jpghttp://marketing.corp.smithbits.com/vault/web/photos/PN8801.jpghttp://marketing.corp.smithbits.com/vault/web/photos/PN3731.jpghttp://marketing.corp.smithbits.com/vault/web/photos/PN3731.jpghttp://marketing.corp.smithbits.com/vault/web/photos/PN3731.jpghttp://marketing.corp.smithbits.com/vault/web/photos/PN8801.jpg


74/141


%atural diamond bits wor/ by ploughing" hence with low weights &a few

tons) and a high rotation speed.

3or this reason" they are almost always employed in association with

turbines.

These bits are very e6pensive. Their use is limited to special situations

andIor needs. They are employed to drill directional wells" in side$trac/

operations" or in homogeneous medium$hard to hard roc/s" in

association with turbines.

N%t(r%! D%+o"d Bt/

N%t(r%! D%+o"d Meh%"/


75/141


74

N%t(r%! D%+o"d Meh%"/

%atural Diamond #its drillby ploughing and grinding

the roc/

%ormally reuire higher,'M for better

performance &e.g. high

speed motor or turbine)


76/141

S&"thet D%+o"d Bt/


77/141


77

S&"thet D%+o"d Bt/

Prod(to" Proe// of S&"thet D%+o"d/

The process is basically the following:

thin circular layers of %r)o"are alternated with a +et%!! /o!


78/141


7

TSP Bt/

!f uses in high temperature environments are predicted" it is possible to employ

construction techniues capable of producing industrial diamonds with a higherdegree of thermal stability" namely the TSP diamonds or ther+%!!& /t%)!e

o!&r&/t%!!"e d%+o"d/.

There are two main construction techniues: a techniue is based on the acid treatment of the synthetic diamonds

produced by the method described above" in order to dissolve cobalt0the second techniue reuires the use of silicon carbideas a bonding agent

for the diamond particles.

#oth these techniues allow the realization of industrial diamonds with a

thermal stability of about @@EFo(. The disadvantage is that TS' diamonds can

not be welded onto any substrate" differently from 'D( bits" but they must beincluded in the bit matri6. TS' bits are produced by means of techniues similar

to those described about natural diamond bits. !n general terms" they are

suitable to drill hard and abrasive formations.

Po!&r&/t%!!"e D%+o"d Co+%t PDC Bt/


79/141


7:

Prod(to" Proe// of % FCo+%t

PDC (tterconsists of a thin layer &@ mm usually) of polycrystalline diamondcompletely welded onto a tungsten carbide substrate. This structure is called a5o+%t7.

The production process is as follows: a layer of d%+o"d r&/t%!/ of predetermined granulometry is placed in acontainer made of refractory metal &zirconium or molybdenum). The container

shape is going to determine the final shape of the 5compact70a layer of t("#/te" %r)deis then placed on top of the diamond crystals0the container is then brought to a pressure of @"FFF"FFF psi and heated at atemperature of @CFFo(. #onding between diamond crystals ta/es place as aneffect of the catalyzing action of cobalt" that migrates from the tungsten carbidesubstrate &where it acts as a bonding agent)" thus creating a strong bondbetween the substrate and the polycrystalline diamond layer.

The presence of cobalt ma/es the 'D( unstable at temperatures higher thanAFFQ(0 at this temperature cobalt e6pands so much that it begins to brea/ thebonding between the diamond crystals" actually causing the brea/ of the5compact7 &this is why TS' bits are used in +T conditions)..

& &



80/141


0



81/141



82/141


2


'D( cutters are built in standard dimensions ranging from mm to ;C mm:?er& /+%!! cutters & mm wide) are used in hard formations.S+%!! cutters &@ mm wide) are used in medium to medium hard formations.L%r#e cutters &@G mm wide) are suitable for soft to medium formations.?er& !%r#e cutters &;C mm wide) are used in soft formations. (utters as wide

as C mm have also been used sporadically.

1:7 1:75 1:5 1:5Ye%r/ "tod(ted

D%+eter $++,

1 1: 23

-#(re 1 D+e"/o"/ of PDC CTTERS

1:7 1:75 1:5 1:5Ye%r/ "tod(ted

D%+eter $++,

1 1: 23

-#(re 1 D+e"/o"/ of PDC CTTERS



83/141


'D( bits can be manufactured as:/tee! )od& )t/+%tr )od& )t/

Stee! )od& )t/ consist of a single steel bloc/ and are characterized by a high

structural resistance" in terms of both impact and torue. 'roduction ta/es place by

means of computer$controlled euipment" hence manufacturing is particularly

accurate with high uality and repeatability standards. The main disadvantage of

this /ind of bit is low resistance to erosion" that ma/es it susceptible to the damage

caused by abrasive drilling fluids. To solve this problem" reinforcements made of

anti$abrasion material &hard$facing) are applied onto certain areas of the bit.

M%tr )od& )t/are built by pouring a mi6ture of tungsten carbide powder and a

bonding agent over a steel body &called blan/). #esides 9oining carbide particles to

one another" the bonding agent allows a good association between the e6ternal

matri6 and the internal steel body. second steel body &called shan/) is then

welded onto the blan/. The bit connection is carved out of the shan/. The matri6 is

resistant to erosion but more brittle than steel.

PDC Bt/


84/141

PDC Bt/

M%tr Bod&Stee! Bod&

http://marketing.corp.smithbits.com/vault/web/photos/PS10482.jpg


85/141


4

'rofiles of 'D( #its

'D( bits have three basic profiles:&a) -!%t rof!e" used to drill hard but not abrasive formation

&b) Do()!e o"e rof!eoffers a larger wor/ surface and is thus suitable

to drill harder formations.

&c) P%r%)o! rof!e" used in combination with a turbine to drill soft but

abrasive formations

-#(re 179 PDC BIT PRO-ILES

% )0

-#(re 179 PDC BIT PRO-ILES

% )0



86/141


5

further discriminating construction feature is the number of blades" that

have the following main functions:

S(ort"# the (tt"# /tr(t(re. The positioning of cutters on

blades creates an adeuate support structure capable of absorbing the

forces engendered on the cutter itself. enerally spea/ing" when

moderately hard formations reuire a bit with many cutters" the tool will

also be euipped with many blades.

Deter+""# the h&dr%(! f!o* rof!e.#lades are set according to

well defined paths" so that the drilling fluid flows optimizing both cutting

removal from the bit surfaces and its cooling.

I"re%/"# the fro"t%! eo/(re of the (tter.

PDC Meh%"/


87/141

'D( cutters cut theformation in shear.

The shearing action is the

most efficient cuttingaction when operating

under identical

conditions.

PDC Bt 9 She%r"#

PDC Meh%"/


88/141

Knli/e %atural Diamonds and

,oller cone teeth" 'D( cutters

e6hibit self$sharpening wear.

The Tungsten (arbide carrier

wears faster than Diamond table

forming a sharp Diamond lip.

s cutting elements wear" the

specific energy reuirement

increases reducing the drilling

efficiency.

The self sharpening mechanism of

'D( cutters improves drilling

efficiency.

PDC Bt 9 Se!f Sh%re""#

PDC Meh%"/


89/141

-ne important feature of 'D( bits is their )% r%e %"#!e.

ngle at which a 'D( cutter attac/s a formation. +igher bac/ ra/e angles improve impact and wear

resistance.

*ower bac/ ra/es increase ,-'.

#ac/ ra/es can be varied to achieve ma6imum ,-' anddurability.

B.R+

PDC Meh%"/


90/141


:0

B% R%e A"#!e

2 EQ to @FQ

2 @EQ

2 ;FQ

2 FQ

-or+%to" H%rd"e//

2 8ery soft claysIshales.

2 *ow angle produces highest,-'s

2 ll formations.

2 #est in soft formations &e.g. shale)

2 ll formations.

2 !mproves cutter life.

2 #est in abrasiveIsand formations

2 +arder formations

2 Typically used on gage

IADC -IED CTTER BITS CLASSI-ICATION


91/141


:1

To ta/e into account the wide range of fi6ed cutter bits including natural

diamond and 'D(" !D( introduced a classification system consisting of a

fo(r h%r%ter ode:

(ode @ $ (utter Type and #ody Material &D" M" T" S" -)

(ode ; $ #it 'rofile &@$G)

(ode $ +ydraulic Design &@$G)

(ode C $ (utter Size and Density &@$G).



92/141


:2

Code 16 C(tter T&e %"d Bod& M%ter%!

The subgroup classification is simply a five letter designation categorizing the

type of cutter and body material.



93/141


:

Code 26 Bt Prof!e

The code numbers &@$G) categorize the bit profile by shape.



94/141


:3

Code 6 H&dr%(! De/#"

The code numbers &@$G) describe the hydraulic features.



95/141


:4

Code 36 C(tter Se %"d De"/t&

The code numbers &@$G) categorize the cutter size and cutter material.

EAMPLE O- CLASSI-ICATION fi6ed cutter bit with the code MCC; corresponds to a 'D( bit with matri6

body" medium taper$deep cone" changeable 9ets$ribbed design with large size

cutter of medium density.

E" Coror%te "


96/141


:5

E?ALATION O- ROLLER CONEBIT DLLNESS

3 d illi ll ffi i tl d i ll ibl thi

DLL BIT GRADING


97/141


:7

3or drilling wells as efficiently and as economically as possible" some things

are mandatory:

$best drilling information

$e6perienced crews

$correctly selected bits.

-ne way for obtaining timely and accurate drilling information is grading thed(!!"e//of roc/ bits. ?hen the dull bit comes out of the hole" an evaluation of

its cutting structure and bearing conditions can provide fundamental

information for the optimization of the ne6t bit runs. n accurate dull grade

gives a good picture of how the hole was drilled and can allow to answer to

uestions li/e:

Did the bit perform to its full potentialR

!f not" what changes do we need to ma/e before we go bac/ into the hole

againR

DLL BIT GRADING


98/141


:

(areful inspection of the d(!! (tt"# /tr(t(re %"d )e%r"#/can give us a

good handle on the bitHs dull characteristics which can affect our ne6t bit

selection" brea/$in procedures and operating practices. rading a dull bit and

evaluating the conseuent findings is a simple operation that can increase

drilling efficiency while lowering drilling costs.

The !ndustry has developed a d(!! )t #r%d"# +ethod %"d /&+)o!/ that

simplify this important operation. The dull grading symbols indicated here can

be used to grade all types of bits" including:

4ournal bearing bits" carbide and steel toothSealed ball and roller bits of both types%on$sealed bearing bits%atural diamond bits

'olycrystalline diamond bitsThermally stable polycrystalline diamond bits.

DLL BIT GRADING6 SYSTEM STRCTRE -OR ROLLER CONE BITS


99/141


::

SYSTEM STRCTRE -OR ROLLER CONE BITS

The dull grading method described herein follows the IADC Gr%d"# S&/te+.Bight columns of information are used for reporting dull bit conditions on bit

records.

! n n e r, o w s

& ! )

- u t e r , o w s

& - )

D u l l( h a r .

& D )

* o c a $t i o n& * )

# r n g .S e a l& # )

a g e@ I @ >& )

- t h e r D u l l& - )

R e a s o n

' u l l e d& , )

C T T I N G S T R C T R E B G R E M A R J S

BT G R E M A R J S

1 2 3 4 5 7



100/141


100

1.Co!(+" 1 $I9I""er,: is used to report the condition of the

cutting elements not touching the wall of the hole &inner).

2. Co!(+" 2 $O9O(ter,: is used to report the condition of

the cutting elements that touch the wall of the hole &outer).

!n (olumns @ and ; % !"e%r /%!e fro+ 09 / (/ed to

de/r)e the o"dto" of the (tt"# /tr(t(refor:

$ Steel tooth bits

$ !nsert bits.



101/141


101

Stee! Tooth Bt/

The numbers from F to give a measure of lost tooth height" meaning:

F no loss of tooth height

total loss of tooth height.

0 1 2 3 4 5 7



102/141


102

I"/ert Bt/

The numbers from F to give a measure of

combined cutting structure reduction due to

lost" worn andIor bro/en insert" meaning:F no loss of cutting structure

total loss of cutting structure.

Example:

bit missing half of the insertsIteeth on the

inner rows of the bit" due to loss or brea/age"with the remaining insertsIteeth on the inner

rows having a EFJ reduction in height due to

wear should be graded a > in (olumn @.

!f the insertsIteeth on the outer row of the bit

were all intact but were reduced by wear to

half of their original height" the proper gradefor (olumn ; would be C.



103/141


10

. Co!(+" $D9D(!! Ch%r%ter/t/ > C(tt"# Str(t(re,:uses a two$letter

code to indicate the ma9or dull characteristic of the cutting structure. Table @ lists

the two$letter codes for the dull characteristics to be used in this (olumn .



104/141


103

3. Co!(+" 3 $L9Lo%to",: uses a letter or number code to indicate the

location on the face of the bit where the cutting structure dulling characteristics

occurs. Table ; lists the codes to be used for describing location on roller conebits.

Lo%to" / def"ed %/ fo!!o*/:auge: those cutting elements which touch the hole wall%ose: the centermost cutting element&s) of the bitMiddle: cutting elements between the nose and the gaugell: all rows

Co"e "(+)er/ %re de"tfed %/ fo!!o*/:The number @ cone contains the centermost cutting element(ones ; and follow in a cloc/wise orientation loo/ing down at the cutting

structure with the bit sitting on the pin.

Ge"er%! Co"e Ide"tf%to" R(!e


105/141


104

(entermost (utting Blement

&Spearpoint)

K1

K K2

K1

K K2



106/141


105

4. Co!(+" 4 $B9Be%r"#Se%!/,: uses a letter or a number code" depending

on bearing types" to indicate bearing condition of roller cone bits.

3or "o"9/e%!ed )e%r"# ro!!er o"e )t/" a linear scale from F$ is used toindicate the amount of bearing life that has been used. zero &F) indicated that

no bearing life &a new bearing) has been used and an indicated that all of the

bearing life has been used &loc/ed or lost).

3or /e%!ed )e%r"#/&9ournal or roller) bits" a letter code is used to indicate the

condition of the seal:

$5B7 indicates an effective seal

$537 indicates a failed seal

$5%7 is used when sealIbearing conditions cannot be determined.



107/141


107

5. Co!(+" 5 $G9G%(#e,: is used to report on the gauge of the bit:$the letter 5!7 &!%) indicated no gauge reduction$if the bit does have a reduction in gauge it is to be recorded in @I@>7 of an

inch.

.

A+o("t o(t of #%#e

Me%/(red d/t%"e

A+o("t o(t of #%#e

Me%/(red d/t%"e

A+o("t "der#%#e

" 15th/

IN I" G%#e

1 1152 215

15

Et..

A+o("t "der#%#e

" 15th/

IN I" G%#e

1 1

152 215

15

Et..


108/141

7 Co!(+" 7 $O Other D(!! Ch%r%ter/t/,: is used to report any dulling



109/141


10:

7. Co!(+" 7 $O9Other D(!! Ch%r%ter/t/,: is used to report any dulling

characteristic of the bit in addition to the cutting structure dulling characteristics

listed in (olumn &D). %ote that this (olumn is not restricted to only cutting

structure dulling characteristics. Table @ lists the two$letter codes to be used inthis (olumn.

Co!(+" $R Re%/o" P(!!ed,: is used to report the reason for terminating



110/141


110

. Co!(+" $R9Re%/o" P(!!ed,: is used to report the reason for terminating

the bit run. Table shows the two$letter or three$letter codes to be used in this

(olumn.


111/141

GRADED DLL E%+!e No 2



112/141


112

GRADED DLL E%+!e No. 2

This bit was graded 4''8T'A''2'-C'HRS.

This dull grade indicates proper bit selection and

application. There is not a great deal more tooth wear

&?T) on the outer cutters than on the inner cutters" which

suggests proper rpm and weight on bit.

?orn teeth is a normal dull characteristic in the harder

tungsten carbide insert bits" as opposed to chipped or

bro/en teeth" both of which could indicate e6cessive rpm

or weight. ?hen pulled" the bit was still drilling well as

indicated by listing +,S as reason pulled. The bit"however" was slightly under gauge &;I@>7) at this point

and may well have rapidly lost more gauge if left in the

hole. This supports the decision to pull the bit based on

hours.

bearing condition 57 on the air bearings suggests

adeuate bearing life still remaining. Since there are no

harder bits available and the dull grade indicates a softerbit would not be appropriate" th/ /ee+/ to h%


113/141

IADC DLL GRADING SYSTEM -OR -IED CTTER BITS

DLL BIT GRADING6 SYSTEM STRCTRE -OR -IED CTTER BITS


114/141


113


!nformation provided by dull grading bits can be very significant for an effective

drilling optimization. This value was recognized by !D( over ;E years agowith the introduction of the dull grading system for roller cone bits.

3or fed (tter )t/2 that is all non$roller cone bits 2 this dull grading system

could not be applied and a new system had to be established. The fi6ed cutter

dull grading system was developed by the !D( Drill #its Sub$(ommittee in

@GA and revised in @GG@.

The fi6ed cutter dull grading system can be used for all non$roller cone bits"

including natural diamond" polycrystalline diamond compact &'D()" thermally

stable polycrystalline &TS') diamonds" impregnated bits" core bits and non$

roller cone bits which do not employ diamond material as a cutting element.

The system does not distinguish between drilling and coring bits. This guide

will only show e6amples of 'D(" TS'" natural diamond and impregnated or

sintered drill bits.




115/141


114


The Dull rading System (hart adopted by !D( includes all codes necessary

to dull grade roller cone bits and fi6ed cutter bits.

The (hart describes factors on drill bits as follows:

The first C spaces describe the 5(utting Structure70 the Eth space refers to

5#earing Seals7 and does not apply to fi6ed cutter bits0 this space is always

mar/ed with an 5N7 when fi6ed cutter bits are graded. The >th space &57)

refers to 5auge Measurement7" while the last ; 5,emar/s7 spaces indicate

5-ther Dull (haracteristics7 and 5,eason 'ulled7.

1. COLMNS 126 INNEROTER RO8S



116/141


115

Ksing a linear scale from F to " a value is given to cutters in the inner and

outer rows of surface$set bits to indicate the amount of wear. rading numbers

increase with amount of wear with 5F7 representing 5no wear7 and 57 meaningno usable cutter left. ccordingly" 5C7 indicates EFJ wear.

'D( cutter wear is measured in a linear scale from F to across the diamond

scale" regardless of the cutter shape" size" type or e6posure. The following

figure schematically shows the cutter wear grading system.




117/141


117

The following figure schematically shows the

cutter wear grading system. s shown here" ;I

of the radius represents the 5inner rows7: the

five cutters in this area would be graded 5;7.This is calculated by averaging the individuals

grades for each cutter in the area:

The average wear for the 5outer7 area is

calculated in the same manner:

5>7 would be the average wear gradient for the outer area. The information can now betransferred to the !D( Dull rading System (hart above.




118/141


11

2 COLMNS 76 DLL CHARACTERISTICSOTHER CHARACTERISTICS



119/141


11:

2. COLMNS 76 DLL CHARACTERISTICSOTHER CHARACTERISTICS

The rd and Ath columns are for use in noting dull characteristics of the bit" i.e.

the most evident physical changes from its conditions as new.

(odes for these characteristics are listed in the Table of the following page.

!n general four different wear characteristics can be distinguished for fi6ed cutter

bits.


120/141

COLMN 36 LOCATION



121/141


121

. COLMN 36 LOCATION

The 5*ocation7 space is used to indicate the location of the primary 5Dull

(haracteristics7 noted in the third space. 3our possible fi6ed cutter bit profiles

are shown in -#(re" along with the codes used to identify locations on the bit.-ne or more of these codes are used to indicate the location of the dull

characteristics noted.

3 COLMN 46 BEARING SEALS



122/141


122

3. COLMN 46 BEARING SEALS

This space is used only for roller cone bits. Therefore" it will always be mar/ed

5N7 when grading fi6ed cutter bits.

4 COLMN 56 GAGE



123/141


12

4. COLMN 56 GAGE

The 5auge &)7 space is used to record the condition of the bit gauge. ,ecord

an 5!7 here if the bit is still in gauge. -therwise" the amount the bit is undergaugeis recorded to the nearest @I@>7" as shown below.

5 COLMN 6 REASONS -OR PLLING OT



124/141


123

5. COLMN 6 REASONS -OR PLLING OT

5 COLMN 6 REASONS -OR PLLING OT



125/141


124

5. COLMN 6 REASONS -OR PLLING OT

EAMPLE No 1



126/141


125

EAMPLE No.1

This ,CA% was run in a horizontal well to

drill brittle to plastic shale and sandstone. !t

drilled A meters in ;G.E hours with anaverage ,-' of @.@ mIhr on a Mach @

d9ustable ic/ -ff Motor.

The bit was pulled at @;F meters because

of slow penetration rates. Kpon pulling out"

the bit resulted to be cored out and without

all four nozzles. The remaining cuttersdid not show any significant wear.

PRACTICAL APPLICATIONS



127/141


127

The !D( Dull grading System can be used for multiple purposes.

Manufacturers evaluate the bit design and bit application. -perators evaluateand improve their drilling programs. The system can also be computerized to

build up a worldwide database to coordinate bit applications.

The ma9or target of the dull grading system is to draw a 5standardized picture7

of a bit regardless of where or under which conditions the bit may have been

used. This standardization is e6pected to lead to further improvements in bitapplication and design.

The/e /!de/ %re o)t%"ed )& H(#he/ Chr/te"/e" )oo!et/ FIADC D(!!

Gr%d"# S&/te+ for Ro!!er Co"e Bt/ %"d FIADC D(!! Gr%d"# S&/te+ for

-ed C(tter/ Bt/.


128/141


12

BIT SELECTION

AND

OPTIMIATION

BIT SELECTION

The bit selection process is comple60 however there are still simple


129/141


12:

The bit selection process is comple60 however there are still simple

guidelines that can be used to increase drill rates and hence reduce drilling

costs.

#elow" are listed some indications about bit selection.

-or+%to" H%rd"e//A)r%/


130/141


10

M(d T&e/

-il based muds often reduce the drilling rates with roller cone bits.

-il based mud is actually believed to enhance the performance of 'D(

bits since they inhibit clay hydration and stic/iness.

ir drilling almost certainly reuires the use of roller cone bits as air can

not provide sufficient cooling as liuids do" therefore causing bit failure.

BIT SELECTION

Dreto"%! Co"tro!


131/141


11

Dreto"%! Co"tro!

,otary drillingoperations are inclined to right$hand wal/. This tendency is

increased when roller bits are used and as cone offset from the bit centreincreases. The advantage of increased drilling rate when using cones with

higher offsets must be balanced with the difficulty in maintaining directional

control.

Turbine drillingmay have a tendency to left$hand wal/. This is controlled

by the type of turbine used" bit gauge length and #+ stabilization.

+igh bit weights" ?-#" tend to increase directional control problems"

while" vice versa" low bit weights help maintain straight holes but with

reduced drilling rates.

BIT SELECTION

Dr!!"# Method


132/141


12

Dr!!"# Method

Due to turbine drillingefficiency" bits with long life e6pectancies should be

used such as 'D(" diamond and 9ournal bearing insert bits.

!n deep wells" 'D( bits are preferred when using surface rotary systems

as reduced weight on bit reduces torue due to bit and wall friction which

can be significant.

BIT OPTIMIATION

CALCLATION O- THE COSTMETER O- A BIT


133/141


1


To ma/e an evaluation of the cost per meter of a bit" the following

parameters have to be considered:

time the bit remains on bottom0

time reuired to run in hole and pull out of hole the bit0

rig cost per hourta/ing into account also all ancillary costs such as: rig

cost per hour" mud logging unit cost" mud engineering cost" etc.0

meters drilledby the bit0

cost of the bit.

BIT OPTIMIATION



134/141


13


@) The euation used to calculate the costImeter of a bit is as follows:

J1 A $C @ E, @ B

D

where:

$@ costImeter

$ rig costIhour

$# bit cost

$( bit drilling hours

$D meters drilled by the bit

$B trip hours

BIT OPTIMIATION



135/141


14

;) To have an idea if the costImeter of a given bit is acceptable or not" it is

necessary to build a comparison curve" called the eo"o+t& (r


136/141


15

where:

$@ average costImeter calculated on the bits ta/en as comparison" UIm

$ rig costIhour" UIh

$# average cost of the bits ta/en as reference" U

$( average drilling time of the bits ta/en as reference" h

$D average footage drilled by the bits ta/en as reference" m

$B average tripping time of the bits ta/en as reference" h

$3 cost of the bit under evaluation" U

BIT OPTIMIATION



137/141


17

) To build the economicity curve of the bit" it is necessary to calculate the

meters" which are necessary to drill" Di

" and the corresponding rates of

penetration" 8i" which is necessary to achieve" in order to obtain an

economic bit run. To do this" it is made the hypothesis that the bit under

consideration will drill a certain number of hours" for instance: h@ @F h" h;

;F h" h F h" V. hn FF h with the constants" @" ;and eual to

those of the bit runs ta/en as reference" and then the pairs D iand 8i" the bit

under evaluation has to satisfy" are calculated using the following euations:

D h J2@ J

? Dh

where:

$ Di meters drilled" m

$ 8i rate of penetration" mIh

BIT OPTIMIATION



138/141


1

C) These values Diand 8iare plotted obtaining a graph which represents

the economicity curve the bit under evaluation has to satisfy.

E) -n this graph" the actual performance of the bit under evaluation is

plotted0 the bit will result economic when its points &meter drilled vs rate of

penetration) are above the comparison curve. ?hen the points go below

the comparison curve" the bit has to be pulled out of the hole.

Cost/MeterCost/Meter

F"FF

;"FF

C"FF

>"FF

"FF

@F"FF

F"F EFF @FFF @EFF ;FFF

ROP'+Ch

Meter/ Dr!!ed +

Eo"o+t& C(r


139/141


1:

D%t%6,ig costIhour" : E@> WIhverage reference bits cost" #: ;EF Wverage drilled hours by the reference bits" ( F hverage meters drilled by the reference bits" D @F mverage tripping hours of the reference bits" B @;"EF h

(ost of the bit under evaluation" 3 AAEF W

E(%to"/6

@ X 6 &( Y B) Y #ZID

; I@ X& 6 B) Y 3ZI@Di hi6 ;Y 8i DiIhi

BIT OPTIMIATION EAMPLE

h D ? J1 J2 J


140/141


130

10 5:' 5': 27:'4 1'4 40'0

20 7' 3':

0 105' '43

30 123' '12

40 13' 2'7

50 151' 2'70

70 10' 2'4

0 1:' 2'3:

:0 217' 2'31

100 24' 2'5

140 2' 2'1:

200 320' 2'10

240 41' 2'0400 504' 2'02

40 5:' 2'00

300 7:0' 1':

BIT OPTIMIATION EAMPLE

h D ? J1 J2 J


141/141

340 ' 1':5 27:'4 1'4 40'0

400 :74' 1':4

440 105' 1':3

500 1150' 1':

540 124' 1':

700 134' 1':2

740 13' 1':2

00 140' 1':1

40 152' 1':1

07.Politecnico Di Torino.bits SELECTION 2011

Documents

Transcript of 07.Politecnico Di Torino.bits SELECTION 2011