AHMED QASIM JABER

FIRST OPERATION ORGANISM

THIRD DRILLING AND WORKOVER SECTION
next
(ROLLER CONE BITS)
 TABLE OF SUBJECT
End
show
ROTARY
DRILLING
BIT

ROLLER FIXED

MILLED DIAMOND PDC

INSERT
TOOTH

IADC ROLLER BIT IADC DULL BIT GRADING BIT HYDRAULIC

 CONTENT:

1-(A)-MILLED TOOTH BITS

2-(B)-INSERT TOOTH BITS
3-IADC BIT CLASSIFICATION FOR ROLLER CONE BITS
4-IADC DULL BIT GRADING
5-Bit Hydraulics

‫السابق‬ ‫التالي‬ First

 1-ROLLER CONE BIT End
show

A-MILLED TOOTH BIT

AND
B-INSERT BIT (TCI TUNGSTEN CARBIDE )

1-ROLLER BIT 1-ROLLER BIT

‫السابق‬ ‫التالي‬ First
Tooth bit Insert
 End
Rolling Cutter Bits )‫(سؤال على تسميه الدقاقات الدوارة‬ show

Rolling cutter bits, which some may also call ROLLER CONE BITS or TRI-CONE BITS, have THREE
cones. Each cone can be rotated individually when the drill string rotates the body of the bit. ‫هو عن أنواع تسميه‬
‫الدقاقات الدواره‬
The cones have roller bearings fitted at the time of assembly. The rolling cutting bits can be
used to drill any formations if the proper cutter, bearing, and nozzle are selected.
There are two types of rolling cutter bits which are milled-tooth bits and tungsten carbide
inserts (insert bits). These bits are classified by how the teeth are manufactured:
‫هو عن مقدره الدقاقه في‬
‫حفر أي طبقه في حال توفر‬
‫المقومات األساسية لها‬

‫سؤال‬
‫ما هو معاني الرموز‬
‫تكتب بشكل كامل وترجمتها‬
‫باللغة العربية‬

‫هو طريقه تصنيف نوع‬

‫الدقاقات على ماذا نعتمد ؟‬

‫السابق‬ ‫التالي‬
 ROLLER CONE BIT

Geometry
Cutting Elements

Bearings

‫السابق‬ ‫التالي‬
 Geometry
The shape and profile of a bit depends partly on hole-size constraints and
partly on the type of cutting action desired.
Constraints
The one unalterable constraint on overall bit design is the diameter of the ‫التقيد‬
hole to be drilled. Desired
‫المطلوب‬.
Bit components must be of the proper sizes and proportions to fit within this Unalterable
limited space. ‫غير قابل للتغيير‬
Proportions
Hole size determines which design variations are possible, and sometimes ‫متناسب‬
makes it necessary to enhance one design element at the expense of Variations
another. ‫اختالف‬
The larger the hole size, the more flexible designers can be in developing a
well-balanced, optimum-performing bit.

‫السابق‬ ‫التالي‬
Cone Profile Angle
Because it is not possible to fit three true rolling cones into the confined diameter of the
borehole, designers must be align them at an angle.
‫س‬

Cone profile angle is a design concession to hole-size restrictions. There are normally
three types of cone profile angles on tri-cone bits: ‫س‬

 İNNER CONE PROFİLE ANGLE, in which the front part of the cone is trying to roll around an axis
which is normally past the center of the bit;
 İNTERMEDİATE CONE PROFİLE ANGLE, in which the intermediate section of the
cone rotates around an axis that is generally in the area just outside the bit diameter; Confined
OUTER CONE ANGLE, OR GAUGE, in which the apex of the outer cone is trying to ‫محدود‬
revolve around a point considerably outside the bit's outside diameter. Align
‫تراصف‬
The result of these cone angles is that the gauge (outer) rows produce a trailing/skidding action, the
Concession
inner rows are in approximately a true roll and the intermediate cone angle is a major area of bit wear. ‫تنازل‬
Restrictions
‫تقييد‬
Apex
‫قمه‬
Revolve
‫تدور حول‬

‫السابق‬ ‫التالي‬
 Journal Angle and Offset
Portion
The geometric design features that determine cutting action are the journal angle
‫جزء من‬
(where the journal is the bearing portion of the bit leg, as shown in Figure 1 ),
Formed
and the offset.
‫مكون من‬
The journal angle, by definition, is the angle formed by the
intersection of a line perpendicular to the axis (or center line) İntersection
of the journal and the center line of the bit. ‫تقاطع‬
Perpendicular
‫العمودي‬

‫السابق‬ ‫التالي‬
 Soft formation bits have smaller journal angles than hard formation bits
( Figure 2 and Figure 3 ).

For example, a soft or medium formation bit may have a journal angle of 32 °, while a medium hard
or hard formation bit may have a journal angle of 36°. Some specialty bits have a 39° journal angle.

‫السابق‬ ‫التالي‬
Offset is the horizontal distance between the center line of the bit and a vertical plane
through the center-line of the journal. Figure 4 shows this offset as a positive displacement
in the direction of rotation.

‫السابق‬ ‫التالي‬
In general, the greater the offset distance on a bit, the higher the degree of gouging/scraping
cutting action it has. Soft formation bits generally have offsets that are considerably larger than
those of hard formation bits ( Figure 5 ).

‫السابق‬ ‫التالي‬
 A. MILLED-TOOTH BITS
Milled-tooth bits have STEEL TOOTH CUTTERS, which are fabricated as parts of the bit
cone. The bits cut or gouge formations out when they are being rotated. The teeth vary
in size and shape, depending on the formation. Teeth of the bits are different ‫سؤال‬
‫ما هو مبدأ‬
depending on formations as follows: ‫عمل هذا‬
‫النوع من‬
‫الدقاقات‬
1- : The teeth should be long, slender and widely spaced. These teeth
will produce freshly broken cuttings from soft formations.
2- : The teeth should be short and closely spaced. These teeth will ‫سؤال‬
‫االختالف في حجم االسنان‬
produce smaller, more rounded, crushed, and ground cuttings from hard formations. ‫وشكلها على ماذا يعتمد‬

Gouge
‫قلع‬
Slender
‫نحيل‬
Vary
‫تختلف فرق عن‬ ‫ما هو شكل السن وتوزيعه على‬
very ‫جيد والتي هي‬ ‫المخروط للطبقات الرخوة‬
Widely spaced
‫السابق‬ ‫التالي‬ First ‫متباعدة على نطاق واسع‬
 A-MILLED TOOTH BIT
Definition - What does Milled-Tooth Bit mean?
A Milled-Tooth Bit is a type of a rolling cutter bit that has tooth cutters made up of steel which
have been assembled as the parts of bit cone.
This bit is rotated to gouge or cut out the formations.
Every bit has a different kind of teeth based on the rock formation.
It may use inserts build-up of diamond or tungsten carbide on its gauge.
The Milled-Tooth Bit is used for enhancing durability, increasing the rate of penetration and for Durability
excellent drilling performance.
‫تحمل‬
Each Milled-Tooth Bit is different from the other as they are manufactured based on their Tiny
drilling applications, There are two types of formations for these bits:
‫صغيره الحجم‬
Hard Formation: In this type of formation, the teeth are short and closely placed. They are used Crumbs
to produce tiny, more rounded, smashed or crushed ground cuttings from the hard formations.
‫فتات‬
Soft Formation: In this type of formation, the teeth are slender, long and widely placed. They
are used for producing cuttings which are freshly broken from the soft formations.
These teeth are crafted with a wear-resistant material composed of tungsten carbide crumbs
which are dispersed in the steel matrix.
The performance of these bits is based on the material and toughness of their hard facing
materials. The performance also depends on the bond between the hard facing and steel tooth.

‫السابق‬ ‫التالي‬
MILLED TOOTH
bit design depends on the geometry of the cones &the bit body &geometry
and composition of the cutting elements (teeth).

The geometry of the cones and of the bit body depend on:
• Journal Angle roller cone bit ‫تم شرحها بموضوع‬
• Cone Profile
• Offset Angle
The geometry and composition of the teeth depend on:
• Journal Angle
• Angle of Teeth
• Length of Teeth
• Number of Teeth
• Spacing of Teeth
• Shape of Teeth
• Tooth Hardfacing

‫السابق‬ ‫التالي‬
 TOOTH ANGLE AND LENGTH
As shown in Figure 9.5,
drill bits can have
{slender and long teeth (figure a) or short and stubby teeth (figure b)}.
1‫س‬
The long teeth are designed to drill soft formations with low compressive strength where the rock is
more yielding and easily penetrated.
Penetration is achieved by applying weight on bit (WOB) which forces the teeth into the rock by ‫ اليه االختراق‬2‫س‬
overcoming the rock compressive strength Rotation of the bit helps to remove the broken chips. ‫للصخره بواسطه‬
Slender
‫الدقاقه‬

Harder rocks have high compressive strength and can not be easily penetrated using typical field
‫ضعيف‬
WOB values. Stubby
Hard rock bits therefore have much shorter (and more) teeth with a larger bearing area ‫سميك‬
therefore the short teeth will be less likely to break when they are subjected to drilling Intended
loadings. ‫مجهز‬- ‫معد ل‬
‫ل‬
The teeth apply load over a much larger area and break the rock by a combination of crushing,
creation of fractures and chipping.

The teeth are not intended to penetrate the rock, 3‫س‬

but simply to fracture it by the application of high compressive loads.

‫السابق‬ ‫التالي‬
 TOOTH NUMBER AND SPACING
As discussed above,
a soft rock requires long and a few teeth allowing the WOB to be
distributed over fewer teeth. The teeth are widely spaced to reduce the risk of the bit being balled up when drilling
water sensitive clays and shales.
Wider spacing also allows the rows of teeth from one cone to engage into the space of equivalent row of the
adjacent cone and thereby help to self clean the cutting structure of any build up of drilled cuttings.

For hard formations, the teeth are made shorter, heavier and more closely spaced to
withstand the high compressive loads required to break the rock.

‫السابق‬ ‫التالي‬
 TOOTH SHAPE
Viewed from the side most teeth appear like an A without the crosspiece 1.
There are other design such as the T-,U-, or W-shape which are more durable and
are usually found at the gauge area of the bit. Figure 9.6 shows this. Crosspiece
‫اجزاء متقاطعه‬

Figure 9.6 Tooth Shape, Courtesy of Reed Hycalog

‫السابق‬ ‫التالي‬
TOOTH HARDFACING
To increase the life of the cutting tooth, hard metal facing (usually tungsten carbide) was
initially applied to one side of the tooth to encourage preferential wear of the tooth. As the bit
drills away, the tooth wears on one side (the uncovered steel side) thereby always leaving a Sustained
sharp cutting edge on the metal faced side. This style is known as self-sharpening ‫اسناد‬
hardfacing.
Nowadays 1, most toothed bits use Full Coverage Hardfacing, in which the entire tooth is
covered with hard metal. This practice provides greater durability of the tooth and offers
sustained ROP’s.

‫السابق‬ ‫التالي‬
 BIT STYLES
Illustrated
The previous bit design features1 can now be seen in the three bits illustrated in Figure
9.7,below, ranging from ‫موضح‬
an aggressive 1-1 cutting structure, ‫بالرسوم‬
through a 1-3, to a durable 2-1 cutting structure. 1‫س‬ distinguish
The numbers 1-1 etc. are actually IADC bit coding designed to distinguish
various bit types. For example, soft bits designed to drill very soft rocks are given the
‫تصنيف‬
number one for the cutting structure. Various
The IADC code is further subdivided to reflect the ‫مختلف او تنوع‬
varying rock strength with each category. 2‫س‬
Varying
Hence code of 1-1 reflects long teeth designed to
drill very soft rocks, see “IADC Bit Classification For Roller Cone Bits” on page 284 for more details on IADC coding ‫تباين‬
from book doctor Husain Rabia (WELL ENGINEERING & CONSTRUCTION) Category
‫فئه‬

‫السابق‬ First Figure 9.7 Various Bit Styles, Courtesy of Reed Hycalog
 B-INSERT BIT
Tungsten Carbide Insert (TCI) or Insert bits generally have
tungsten carbide inserts (teeth) that are pressed into the bit cones.
The inserts have several shapes such as long-extension shapes,
round shaped inserts, etc. Teeth of the bits are different 1‫س‬
depending on the formation as follows:
Soft formation: Long-extension, chisel shape inserts
Hard formation: Short-extension, rounded inserts 2‫س‬

3‫س‬

chisel ‫ازميل‬

‫التالي‬ First
 B-INSERT TOOTH BITS
THE DESIGN FACTORS RELATING TO CONE OFFSET, BIT PROFILE AND CONE PROFILE
DISCUSSED ABOVE FOR
MILLED TOOTH BITS APPLY EQUALLY TO INSERT BITS.
The cutting structure of insert bit relies on using tungsten carbide inserts which are pressed 1‫س‬ Relies
into pre-drilled holes in the cones of the bit. ‫تعتمد على‬
The following relates to the various design features of inserts which are designed to suit pressed
various rock types. ‫محشوره او‬
2‫س‬ ‫مضغوطه‬

‫السابق‬ ‫التالي‬
 INSERT PROTRUSION
INSERT PROTRUSION REFERS TO the amount of insert protruding from the 1‫س‬
cone and is always less than the total length of the insert, Figure 9.8
.
Inserts with large protrusions are suitable for soft rocks as would be seen on a 4-3 type
cutting structure and to a limited protrusion as on the insert as on an 8-3 cutting structure.

PROTRUSION
‫نتوء‬, ‫تجسيم‬
Protruding
‫بارز‬

Figure 9.8 Insert Protrusion, Courtesy of Reed Hycalog

‫السابق‬ ‫التالي‬
 INSERT NUMBER, DIAMETER AND SPACING
The same argument used in milled tooth bits applies here.
Soft insert bits have fewer and longer inserts to provide aggressive penetration of the rock.
Durable, hard formation bits have many, small diameter inserts with limited protrusion,

see Figure 9.9.

1‫س‬

Figure 9.9 Insert Bit Styles

‫السابق‬ ‫التالي‬
 INSERT SHAPE
For soft formation bits, the inserts have chisel shapes to provide aggressive drilling 1‫س‬
action.
In soft, poorly consolidated formations the chisel shape is more efficient at penetrating
the formation than a
more rounded conical shape. Figure 9.10 a
shows five shapes for use on 5-1 type inserts, the longer, chisel shape is for soft rocks The Consolidated
conical rounded ‫معزز ب‬, ‫مقسى‬
shape is for hard rocks, Figure 9.10 B.

‫السابق‬ ‫التالي‬
 INSERT COMPOSITION
The composition of the inserts 1can be varied by altering grain size or cobalt
concentration.
In general changes that increase the wear resistance of the insert will make it more COMPOSITION
likely to ‫تركيب‬
break, while tougher inserts, less prone to breakage, may wear more rapidly Varied
‫متنوع‬,‫متعدد‬
Altering
‫تغير‬
prone
‫س‬ ‫ميال او مستعد ل‬
1,2

‫السابق‬ ‫التالي‬
 Abrasive
‫خشن‬
1‫س‬
ADDITIONAL FEATURES Ribs
‫اجنحه او اضلع‬
Heel
Additional enhancing features (Figure 9.11) include: READ the words in the
‫كعب او قاعده‬
figure 9.11 its required Enhance
• Gauge trimmers to assist in cutting a gauge hole ‫تحسين ادائيه‬
• Shirttail compacts to reduce leg wear in abrasive formations

2‫س‬

4‫س‬

‫من ماذا تتكون هذه‬:‫س‬

‫البروزات في المخروط‬
3‫س‬ ‫؟‬

‫السابق‬ ‫التالي‬
 Gauge Retention
2‫و‬1‫س‬

The majority of the drill bit work is spent around

the heel and gauge area and therefore this part
suffers the greatest amount of wear. Maintain
Gauge trimmers are USED TO maintain bit gauge ‫يحافظ على‬
(diameter). Achieved
‫تحققه ب‬
this achieved by the USE OF T-shaped
teeth on milled tooth bits and very short inserts in
the gauge row.
The gauge inserts may be d i a m o n d
coated.

‫السابق‬ ‫التالي‬
 Worn
Shirttail Protection ‫تردي او تهرئ‬
Expose
‫انكشاف‬
All drill bits 1 may have tungsten carbide inserts
Margin
placed in the heel area of the bit. A worn shirttail 1
‫حاشيه‬
(Figure 9.12) may expose the seal, ,1‫س‬
leading to seal wear and bearing failure. ,2
Various devices may be used to limit or delay 3
shirttail wear.
1-Tungsten Carbide Inserts may be placed in the shirttail
itself.
2-Lug pads may be added to the upper part of the
shirttail.
3-A band of hard metal can be added to the margin of the
shirttail.

‫السابق‬ ‫التالي‬
BEARINGS AND SEALS
BIT BEARINGS ARE USED TO PERFORM THE FOLLOWING
FUNCTIONS: Perform
‫انجاز‬
• support radial loads

• support thrust or axial loads

• secure the cones on the legs

The bearings must take the loads generated as the bit cutting structure
(and gauge area) engage with the formation as weight (on bit) is applied.

These loads can be resolved into radial and axial forces.

The principal radial load is taken by the main journal and the axial
load by the thrust face and, in some cases, the ball bearings.

‫السابق‬ ‫التالي‬
There are two bearing types, roller and friction Races
(or journal). ‫جيل‬
Roller bearings may be sealed or unsealed Distinguishes
Whilst ‫تصنيفات‬
Friction Bearings are always sealed. Whilst
In Roller Bearings, the loads applied to the cutting structure is
‫بينما‬
transmitted to the journal through a series of rollers,
see Figure 9.13.
hence the
There may be one, two or three of these roller RACES name.
depending upon the size of the bit. ‫ومن هنا جاءت‬
‫التسميه‬
The main feature of the friction or journal bearing Contrast
(Figure 9.13) that distinguishes it from roller bearings is that ‫تناقض‬
the load placed on the cutting structure is transmitted fatigue.
directly to the journal over a wide surface area, hence the ‫اجهاد‬
name.
Friction bearing journal experiences a more even,
continuous load compared to roller bearings and can handle high
drilling loads.
In contrast, the journal surface on a roller bearing bit is subjected to
cyclic loading as each roller passes over a given point. ‫لماذا سميت‬/‫س‬
journal ‫نوعيه‬
With time and at high loads, the roller bearings surface will ‫بهذا‬bearing
fail in fatigue. ‫االسم؟‬

‫السابق‬ ‫التالي‬
The even continuous load on journal bearings makes them suffer much higher sliding
velocities than roller bearings and consequently can with stand higher temperatures1
.
Small diameter friction bearing bits can handle relatively high RPM without suffering
the damaging high temperatures that would occur with the same RPM on a larger
diameter friction bearing bit Because of the above, ‫لماذا القطر الصغير‬/‫س‬
roller bearings 1 are the common bearing down to 12 ¼" diameter and friction bearings rpm ‫بامكانه تحمل‬
are the standard up to this size; 12 ¼" is the cross-over from friction to ‫عالي بينما القطر‬
roller. ‫الكبير اليتحمل بل‬
Friction bearing bits are always sealed: the close tolerances and the area contact lead ‫يعاني؟‬
to rapid wear IF solid contaminants,
such as cuttings or mud solids, get into the bearing.
Roller bearing bits can tolerate such contamination more readily and so may be left
unsealed.
Bearing life is affected by:
• Heavy Reaming Which Reduces Bearing Life Tolerate
• Directional Effects Which Produce High Side Loadings ‫تحمل‬
• Severe Drill String And Bit Vibrations such as
‫مثل‬
Readily
‫بسهوله‬

‫السابق‬ ‫التالي‬
BEARING LUBRICATION SYSTEM 1‫س‬
A sealed bearing system is lubricated by a sealed grease
reservoir as shown in Figure 9.13
(Journal Bearing). The pressure of grease within the
bearing must be the same as that outside
2‫س‬
in the mud.
THE LUBRICATION SYSTEM WORKS AS FOLLOWS :
An elastomer pressure diaphragm communicates annular
pressure to the grease in a grease
reservoir (inside the leg) and then, via grease passages to
the grease within the bearing itself.
Thus zero differential pressure is maintained across the seal at
all times. Some leakage of the
grease may occur due to rapid pressure changes resulting from
axial movement of the cone
on the journal. The grease reservoir has enough fluid to allow
for minor leakages.
/3‫س‬
‫هل يؤثر نضوح‬
‫قليل على تشحيم‬
‫الدقاقه ؟‬

‫السابق‬ ‫التالي‬
 1‫س‬

SEALS ‫اين تستخدم‬

‫المحاور الغير‬
‫محميه ؟‬

Unsealed bearings are still used, generally

on large diameter bits where run length is
limited
and the bearings are of a size that can
endure substantial wear and high Endure
temperatures. ‫تحمل‬
Substantial
Most bits have their bearings sealed ‫اساسي‬, ‫كبير‬
(Figure 9.13) from the mud using a variety Abrasion
of designs ‫تأكل‬
including 1: Variety
2‫س‬ ‫تنوع‬
1- ‘O’ Ring and Radial,
2- V-Ramp Seal,
3-Wave Seal (shaped seal pushing pockets
of grease around the sealing area)
4-and Metal Face Seal. 3‫س‬
Seals should offer resistance to abrasion by
mud solids and cuttings and resistance to
Temperature.
‫السابق‬ First
 IADC BIT CLASSIFICATION FOR ROLLER CONE BITS 1‫س‬

In 1972, the International Association of Drilling Contractors (IADC) established a THREE

Established
CODE system for ROLLER CONE BITS. ‫أنشئت‬
2‫س‬
Respectively
THE FIRST CODE OR DIGIT defines : ‫على التوالي‬
Signifies
The Series Classification Relating To The Cutting Structure.
‫يدل على‬
The first code carries the numbers 1 to 8. Subdivision
‫قسم فرعي من‬
For MILLED TOOTH BITS, the first code carries the numbers 1 to 3, which describes soft, 3‫س‬
medium and hard (and semi-abrasive or abrasive) rocks respectively.
This number actually signifies the compressive strength of rock.
For INSERT BITS, the first code carries the numbers 4 to 8. 4‫س‬
THE SECOND CODE relates to the formation hardness subdivision within each group and
carries the numbers 1 to 4. 5‫س‬
These numbers signify formation hardness, from softest to hardest within each series.
The second code is a subdivision of the first code (1 to 8) 6‫س‬

‫التالي‬ First
THE THIRD CODE DEFINES
The Mechanical Features Of The Bit Such As Non-sealed Or
Sealed Bearing.
1‫س‬
Currently there are seven subdivisions within the third code:

1. Non-sealed roller bearing no sealed

2. Roller bearing air cooled
3. Sealed roller bearing
sealed
4. Sealed roller bearing with gauge protection
5. Sealed friction bearing
Friction
6. Sealed friction bearing with gauge protection
7. Special features - category now obsolete.
.‫ فئة عفا عليها الزمن اآلن‬- ‫ميزات خاصة‬
As an example, a code of 1-2-1 indicates (Figure 9.7):

Code 1: long, slim and widely spaced milled tooth bit

Code 2: medium soft formations (if this number was 4, then it is hard soft formation)
Code 3: non-sealed bearings Within
‫ضمن‬

‫السابق‬ ‫التالي‬ First

 End
show

9.0 IADC DULL BIT GRADING

‫التالي‬ First
9.0 IADC DULL BIT GRADING

This section applies to:

• Natural diamond, PDC and TSP bits(Thermally Stable Polycrystalline), otherwise known as ‘Fixed Cutter Bits’,
AND
• Roller Cone Bits.
The 1987 IADC dull grading system and subsequent revision can be used to accurately ‫س‬
describe dulled tungsten carbide insert and steel tooth roller cone bits as well as fixed cutter
bits.
It describes the 1-condition of the cutting structure, 2-the primary (with location) and ‫س‬
secondary dull characteristics, 3-the bearing condition (where applicable), the 4- gauge condition
and the reason the bit was pulled.

Figure 9.20 illustrates the formats and dull characteristics for all types of dull bit grading.

‫السابق‬ ‫التالي‬ First

9.1 THE IADC SYSTEM FOR ROLLER CONE BITS

The format of the dull grading system is shown in Figure 9.20. It contains all the codes
needed to dull grade roller cone bits, as described below :
1. Column 1(I) is used to report the condition of the cutting structure on the inner 2/3rds of the bit. ‫س‬
2. Column 2 (O) of Figure 9.20 is used to report the condition of the cutting structure on the outer 1/3rd of the bit.
In columns 1 and 2 a linear scale from 0-8 is used to describe the conditions of the cutting structure, based on the initial
usable cutter height.
Steel Tooth Bits ‫س‬
0 - indicates no loss of tooth height due to wear or breakage.
8 - indicates total loss of tooth height due to wear or breakage.
Insert Bits ‫س‬
0 - indicates no lost, worn and/or broken inserts ‫س‬
8 - indicates total reduction of cutting structure due to lost, worn and/or broken inserts.
3. Column 3 (D) uses a two-letter code to indicate the major dull characteristics of the ‫س‬
cutting structure. Figure 9.20 lists the two letter codes for the dull characteristics to be used in this column.
4. Column 4 (L) uses a letter code to indicate the location on the face of the bit where the major cutting structure
dulling characteristics occurs. ‫س‬
Figure 9.20 lists the codes to be used for describing locations on roller cone bits.

‫السابق‬ ‫التالي‬ First

 IADC DULL BIT GRADING

1-Cutting structure

Dull
Inner row Outer row Location
characteristics
0-8 0-8 (L)
Two-letter

Steel
tooth Insert bit CT- BT-
WT-
CHIPPED broken
WORN ROLLER
teeth
teeth
TEETH ,cutter
{0}no loss tooth height {0} no lost broken
{8} total loss height {8} lost broken

NO- no
LT-LOST dull
teeth charactr
istic N- M- G-
A-ALL
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ROW
MIDDLE
ROW
GAGE
ROW ROW
 Broken teeth chipped teeth Lost teeth

worn teeth
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 ‫س‬ ‫س‬
5. Column 5 (B) uses a letter or a number code, depending on bearing type, to indicate bearing condition on roller cone
bits.
For non-sealed bearing roller cone bits
a linear scale from 0-8 is used to indicate the amount of bearing life that has been used. ‫س‬
A ‘0’ indicates that no bearing life has been used (a new bearing), ‫س‬
and an ‘8’ indicates that all of the bearing life has been used (locked or lost).
For sealed bearing (journal or roller) bits
A letter code is used to indicate the condition of the seal. ‫س‬
An ‘E’ indicates an effective seal, and a ‘F’ indicates a failed seal(s). ‫س‬

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 IADC DULL BIT GRADING

2-BEARING /SEALS

NON
SEALED
SEALED
BEARING
0-8

8=LIFE HAS
0=NO LIFE E=EFFECTIVE
BEEN USED F=FAILED
BEEN USED
(LOCKED OR
(NEW)
LOST)

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 IADC DULL BIT GRADING

3-GAUGE

2/16”,1/8”= 4/16”,1/4”=
1/16”=OUT
I=IN GAUGE OUT OF OUT OF
OF GAUGE
GAUGE GAUGE

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6. Column 6 (G) is used to report on the gauge of the bit. The letter ‘I’ indicates no gauge reduction.
If the bit does not have a reduction in gauge it is recorded in 1/16th of an inch. The ‘2/3rds rule’ will be used for
three-cone bits.
Note :
The 2/3rds Rule, as used for three-cone bits, requires that the gauge ring be pulled so that it contacts two of the cones at their
outer most points. Then the distance between the outermost point of the third cone and the gauge ring is multiplied by 2/3rds
and rounded to the nearest 1/16th of an inch to give the correct diameter reduction.

7. Column 7 (O) is used to report any drilling characteristics of the bit, in addition to the major cutting structure dulling
characteristics listed in Column 3 (D). Note that this column is not restricted to only cutting structure dulling characteristics.
Use the two-letter codes in column 3 to report drilling characteristics for column 7.
8.Column 8 (R) is used to report the reason for pulling the bit out of the hole.
Figure 9.20 lists the two or three-letter codes to be used in this column.

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 IADC DULL BIT GRADING

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OTHER DULL
CHARACTERISTICS

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 IADC DULL BIT GRADING

4-REASON PULLED

BHA DMF DTF DSF DST LOG LIH RIG CM CP

DP FM HR PP TD TQ TW WC

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Bit Hydraulics
Hydraulic conditions at the bit are as important as its mechanical design features in
determining overall drilling performance.
The objective of a drilling hydraulics program is to maximize bit life and
penetration rate by efficiently removing cuttings as they are drilled, and by cleaning,
cooling and lubricating the bit and drill string.
To accomplish this, the hydraulics system must deliver the optimum amount of
energy to the bit.

Parameters that influence drilling hydraulics include formation characteristics,

mud properties, circulating rate and pressure, hole size and system pressure losses.

In general, the easiest, most practical method of optimizing hydraulics energy is to

utilize the system pressure losses by varying the size of the bit nozzles.

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