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MINISTRY OF ENERGY

MYANMAR OIL AND GAS ENTERPRISE

DRILLING DEPARTMENT

16 th September’ 2024.
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CONTENT

Page No

1. Preface 3

2. History of drill bit 3

3 Kinds of bit 3
- Drag bit
- Roller cone bit
- Fixed cutter bit
4 Parts of bit (Tri cone) 4
- Tooth
- Gage
- Bearing
5 Formation Characteristics 6

- Soft formation
- Medium hard formation
- Hard formation

6 Basic Bit Design 7

- Tooth

- Journal angle

- Cone and Bearing

-Fixed cutter bit { PDC bit, Impregnate bit, Hybrid bit}

7 IADC Dull grading charts 11

8 API Casing- Bit size and Clearance 16

9 Factors affecting penetrating rate 18

10 Bit Handling tool accessories 20

11 Causes due very slow ROP ( no progress) 20

12 Conclusion 20
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(1)Preface

There are two terms of drilling usage.

1. Drill stem – Swivel to the bit including Kelly is called drill stem.
2. Drill string – Drill pipe, Drill collar and bit is called drill string.

The bit is represented as heart of drill string. We need the proper bit selection for economic
drilling. The bit crushes the rocks by the two forces, one is vertical force (WOB) and another
one is horizontal force (Rotary RPM).Then chippings or cuttings flushed out away with mud.
This process result is drilling a hole.

(2) History of bit

(Bit innovation history )

No Description Year Remarks

1 First rotary rock bit – Sharp Hughes tool company 1909
2 Introduction to tri - cone drill bit design 1933
3 Christensen diamond product, co-founded salt lake city 1944
4 Introduction of Synthetic PDC bit 1976
5 Baker Hughes form Hughes Christensen 1990
6 Introduction of bit measurement 1997
7 Introduction of Hybrid drill bit 2010
8 Introduction of Adaptive drill bit 2017
9 Introduction of Anti-walk technology 2018
(Ref: Baker Hughes Company)

(3) Kinds of bit (တူးရ�င်းအမျးအစားများ)

ိ

Drill Bit
Fixed cutter Roller cone
PDC Diamond Milled tooth Insert
Natural diamond TSP Impregnated Roller bearing Friction bearing

Drag bit :- First bits used in rotary drilling for soft formation and unconsolidated formation.
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(Drag bit )

Roller cone bits :- Drilled by compression and crushing action.

Roller cone bit types –

(a) Steel tooth type

(b) Tungsten carbide insert
(c) First roller – two cone bit (balling with formation)
(d) Cones are mounted on bearing
(e) Bearing allow cones to rotate around own axis.

Natural diamond bit (Fixed cutter bit) –

(a) Cuts by plough and grinding.

(b) Hard rock and long section.
(c) Diamonds are bonded on surface of material.
(d) Sensitive to shock and vibration.
(e) Very costly (10-times more expensive)
-Slower ROP than roller cones
- Last longer than roller cones since no moving parts.

(4) Parts of bit

Parts of tri cone bit

Tooth Bearing Gage

1 Spear point Roller bearing Gage surface
2 Nose row Ball bearing Shirt tail
3 Middle row Friction bearing Shank shoulder
4 Heel row - Shank
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Tooth design- Soft formation; long, thin, widely spread – no bit balling

-Moderate hard formation; shorter, wide teeth, heavy WOB.

- Hard formation; shortest, stubbier.

(Teeth are covered with tungsten carbide to increase wear resistance.)

Bearing design- Roller bearing, journal bearing; with two thrust faces, ball locked cone,
[thrust face – friction reduction alloy + abrasion resistance + seizure resistance.]

Roller bearing – supports radial load (WOB).

Ball bearing - Resist longitudinal or thrust load.

Friction bearing- Support radial load.

Bearings must be made from toughened steel by heat treatment. Most important is space
availability. Bearing should be large to support applied load.

Bearing size is balanced with strength of the journal (journal diameter) and strength of
cone shell (shell thickness).

Seal and lubrication- The bearing seal is adapting the high quality HNBR O-ring. The
best seal compression and the radial seal structure can enhance the seal performance. The
compensation system adopts the high quality bit grease and greatly increases the
lubricating reliability.

Formation and journal angles are designed as follow;-

Formation Soft Medium Hard

journal angle 33˚ 34˚ -36˚ 39˚
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Gage;-

Multiple heel position with gage trimmer on the heel, tungsten carbide and hard
facing on the shirt tail, strengthen spear point and will enhance gage protection.

(5) Formation characteristics-

Soft formation;- Unconsolidated clay and sand

Low WOB (3000-5000) lb/ in; of bit dia; with High RPM (120-250)

Medium hard formation;- Shale, Gypsum, Sand, Siltstone

Low WOB (3000-6000) lb/ in; of bit dia; with high RPM (120-250)

Hard formation;- Limestone, Andryte, Hard sand stone, Dolomite

High WOB (6000-10,000)lb/in; of bit dia; with slow RPM

“Engineering Classification for Rock Hardness”

Understanding the engineering classification for rock hardness is pivotal for selecting the right
drill bit tailored to the geological formation’s compressive strength. This classification
categorizes rock hardness based on compressive strength, spanning from very low to very high
strength formations, enabling drillers to align their tools with the specific demands of the drilling
environment.

(1) or (2) Soft and soft sticky – Highly drillable formations such as clay, marl, gumbo, and
unconsolidated sands.
(3) Soft-medium – Low compressive strength sands, shales, and anhydrite with hard layers
intermixed.
(4) Medium – Moderate compressive strength sand, chalk, anhydrite and shale.
(6) Medium hard – Higher compressive strength with non or semi-sharp sand, shale, lime, and
anhydrite.
(7) Hard – High compressive strength with sharp layers of sand or siltstone.
(8) Extremely hard – Dense and sharp formations such as quartzite and volcanic rock.

Classification Compressive Strength

Very Low Strength <4,000

Low Strength 4,000-8,000
Medium Strength 8,000-16,000
High Strength 16,000-32,000
Very High Strength >32,000
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(6)“Basic bit design”

1. How fast are the bits considered?

2. How durable are the bits considered?
3. How steerable are the bits considered?

Fixed cutter Bit, PDC bit, impregnated bit and Hybrid bit

Major components of PDC bit design are;

1. Bit body material

2. Bit profile
3. Cutting materials
4. Cutter rake
5. Cutter density
6. Cutter exposure
7. Cutter size
8. Fluid circulation

Cutter material PDC-

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Polycrystalline diamond – Synthetic material with (90-95)% pure diamond and manufactured into
compacts.

PCD is formed in two stage ;- HPHT process-

1. Manufactured artificial diamond crystals by exposing graphite to high pressures (600,000

psi) in presence of other chemicals.
2. Sintering of diamond powder with catalyst/ binder in >1400˚C , 750,000 psi.

Disc cutter and studded cutters ( Cutter material TSP)

- PDC cutters were chipped while drilling due to interval stresses caused by
differential expansion of diamond and binder material (cobalt)
- Thermal coefficient of expansion of binder 1.2x10-5
- Thermal coefficient of expansion of diamond 2.7x10-6
- Cobalt expands faster, stresses develop due to different rate of expansion.
- In TSP cutters binder material is removed by leaching with acid to improve
stability at higher temperatures.
- Absence of binder material make is impossible to bond TSP to tungsten carbide
substrate.
- Strength of PCD material and substrate is weaker.
- TSP are smaller size and should be set in matrix of the bit.

PDC cutter sizes-

No Cutter size (mm) Formation

1 8, 11 Hard rock
2 13, 16 Medium hard
3 19, 22 High ROP, less durable
4 13 Most common

Cutter types-

No Manufactured company Cutter type

1 Reed Hycalog T-Rex and Raptor
2 Smith Geo Max, Sonic Max, Grid Max, Tec
Max Quick cutter, Arrow cutter
3 Hughes Christensen Zenith, Z plus
4 Security DBS, ERC, ESDRC, CRC, Z3
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Impregnated bit- Impregnated core bit-

Hybrid bit-

Innovation of PDC bit and tri cone bit to hybrid bit

Adaptive drill bits absorb shock and help prevent damage to the bit and bottom
hole assembly (BHA). Then extended tool life, significantly reduced nonproductive time
(NPT) and invisible lost time (ILT), optimized performance, and a step change in drilling
efficiency.
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Anti-Walk technology reduce slide time to increase rate of penetration (ROP), lower
overall drilling time, and improve wellbore placement. It also optimizes wellbore quality
and enables greater flexibility in BHA design.
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(7) IADC Dull Grading-

တူးရ�င်းမ,သည့်အခါများတွင် Bit record တွင် Bit ၏အေြခအေန(Tooth, Bearing, Gage) စသည်တို

ကို စနစ်တကျ ေဖာ်ြပြခင်းှင့်၊ပိုက်မ,ရသည့်အေကာင်းများ(Reason pull) ေဖာ်ြပြခင်းတိုကို
အေထာက်အကူြပေစပါသည်။

(Dull Grading For Tri-cone bit)

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(Dull Grading for PDC Bit)

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(8) Factors affecting penetrating rate-

1. Bit type

2. Formation characteristics

3. Drilling fluid properties (Mud weight, viscosity, Gel, water loss, ..etc)

4. Bit operating conditions (WOB, RPM )

5. Bit tooth wear / bearing life

6. Bit hydraulics (Annular Velocity, nozzle velocity)

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To get effective drilling, need more ROP, therefore require right bit selection. In this case bit
type is very important.

Cost per foot calculation and consideration should know for right bit selection.

We can calculate cost per foot as the following-

𝐶𝑏(𝑅𝑡+𝑇𝑡)𝐶𝑟
∁= $/ft
𝐹

Where;

C= Over cost per foot ($/ft)

Cb = Cost of bit ($)

Rt = Rotating time with bit on bottom (Hrs)

Tt = Round trip time (Hrs)

Cr = Cost of operating rig ($/hr)

Comparison of Mill tooth bit, Insert bit and PDC bit

No Kind of Bit Advantages Disadvantages

1 Mill tooth bit Cheap Limited cutting structure life
Steerable Life limited by bearing
Fast in correct application
2 Insert bit Durable Generally slower than mill tooth and
Steerable PDC bit.
Able to drill hard formation Life can be limited by bearing
3 PDC and Able to drill various formation Price
Impregnated bit Durable (no bearing) Parameter sensitive
High ROP (if corrected applied) Hydraulic sensitive
High RPM
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(9) Bit handling tools and accessories-

1. Adaptor plate

2. Bit breaker (especially PDC bit)

3. Jet identifier

4. Jet plier and Jet nozzle handle tool … etc

5. Hole cover (The lid for riser)

(10) “Causes due to very poor ROP while drilling”;-

(တူးေဖာ်ေနစဉ်ေပမသွားရြခင်းအေကာင်းရင်းများ)

1. Formation ှင့် Bit type မကိုက်ညီြခင်း၊

2. Weight on bit and Rotary RPM မြဖစ်ြခင်း၊
3. Proper break-in( Bottom hole pattern) မေဖာ်ဘဲတူးြခင်း၊
4. Bit ball up (တူးရ�င်းရ�ံလုံးြခင်း)၊
5. Jet nozzle pressure ကျြခင်း၊
6. Jet nozzle ြပတ်ကျြခင်း၊
7. Mud cut at pipe body (ပိုက်ေပါက်ြခင်း)
8. Mud weight များြခင်း၊
9. Formation change (ေြမသားေြပာင်းလဲြခင်း)၊
10. Bit vibration ြဖစ်ြခင်း၊
- Bit bouncing (တူးရ�င်းခုန်ြခင်း)
- Whirling (ကိးခါြခင်း)
- Torque – stick, slip (စားပွဲေဆာင့်ုန်းြခင်း)
11. Worn teeth (အသွားတုန်းြခင်း)(အသွားသက်တမ်းကုန်ြခင်း)
12. Bearing jammed (ဘယ်ယာရင် ဂျမ်းြဖစ်ြခင်း)(သိုမဟုတ်)ဘယ်ယာရင်သက်တမ်းကုန်ြခင်း)
13. Under gage bit (တူးရ�င်းဂိတ်ေသးလာြခင်း)
14. Junk at bottom (bolt & nut အစရှိေသာသံတိုသံစများတူးရ�င်းေအာက်တွင်ေရာက်ေနြခင်း)
15. Mud Gel strength (ရ�ံများြပစ်ေနြခင်း)

(11) Conclusion
ေရနံတွင်းတူးေဖာ်ေရးလုပ်ငန်းတွင် တူးရ�င်း(Bit)သည် အနက်ေပရရှိရန်(Progress) အေရးပါေသာ
ေနရာတွင်ပါဝင်ပါသည်၊(Bit)အမျးအစားများစွ
ိ ာရှိသည့်အနက်မှန်ကန်ေသာတူးရ�င်းေရ�ချယ်မ(Correct
bit selection) ြဖစ်ရန်အေရးကီးပါသည်၊ ေရနံတူးေဖာ်ေရးဌာနတွင် တာဝန်ယူရသူများသည်
မှန်ကန်ေသာ(Correct bit selection) ြဖစ်ရန်အတွက် (Drill bit) ှင့် ပတ်သက်ေသာဗဟုသုတ၊
နည်းပညာများစွာတိုကို ေလ့လာဆည်းပူးထားရန် လိုအပ်ပါသည်၊ သိုမှသာ မှန်ကန်ေသာ တူးရ�င်း
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ေရ�းချယ်၍ ေရနံတွင်းတူးေဖာ်ရာတွင် သတ်မှတ်အနက်ေပ (Target Depth) သို အချန်ိ တိုအတွင်း

ေချာေမာ ေအာင်ြမင်စွာ ေရာက်ရှိိုင်မည် ြဖစ်ပါသည်။
ကန်ေတာ်သည် ြမန်မာ့ေရနံှင့်သဘာဝဓာတ်ေငွလုပ်ငန်း၊ ေရနံတူးေဖာ်ေရးဌာန တွင်
တာဝန်ယူေဆာင်ရ�က် ခဲ့ရသည့် အချန်ိ ကာလအတွင်း အချေသာလု
ိ ပ်ငန်းအေတွအ�ကံများှင့်
နည်းပညာ ဗဟုသုတများ ကို ရရှိခဲ့ပါသည်၊ အနာဂတ်ေရနံတူးေဖာ်မ လုပ်ငန်းများအတွက် ထိုအေတွ
အ�ကံများှင့် နည်းပညာဗဟုသုတများကို လက်ကမ်းြဖန�်ေဝြခင်းြဖင့် ဤဌာနကို ေကျးဇူးဆပ်ြခင်း
ြဖစ်သည် ဟုခံယူမိပါသည်။

ေလးစားစွာြဖင့-်

စိုးြမင့်
အဂျင်နီယာမှးကီး(ငိမ်း)
ေရနံတူးေဖာ်ေရးဌာန
ြမန်မာ့ေရနံှင့်သဘာဝဓာတ်ေငွလုပ်ငန်း၊

References;-

-Min Job Bottom hole assembly (Youtube )

-Baker hughes drill bits digital catalog
-PPT lesson of Sarwar Alan Ansri MS Petroleum University of Baku Azerbaijan
-Trascone bit
-Drilling Engineering drilling bit presentation
-Techfact of Baker oil tool

၂၀၂၄ ခုှစ်၊စက်တင်ဘာလ(၁၆)ရက်။