PDC Bit Dull Grading

Dull Grading:

Prepared by: Mohd Zulkhairi M Z

[outlines] • PDC bit - overview • Dull Grading-overview • IADC Dull grading system chart • • • • •

Inner/outer row cutting structure Dull characteristics Location Gauge Reason pulled

• Dull grading: example • Field application: SMDK-A5/ SMDK-A7 • Conclusion

PDC Bit overview Profile Blade

PDC Cutters

Gauge Junk Slot TFA Design Bit Breaker Slot API Threaded Pin From DBS Bit

PDC Bit overview Blade 3

Blade 4

Junk slot

Nozzle

Blade 1 Blade 5 Blade 6

Dull Grading-overview • IADC fixed cutter dull grading system • Developed by IADC in 1987- revised 1991 • Applied for all fixed cutter bits – PDC – Natural Diamond – Impregnated Diamond

Bit record- in 1984

•Old dull grading system (before 1987) [example from Malong SG17.2 appraisal well] •Not descriptive

•T- teeth B- bearing G- gauge

Dull Grading-overview Why?? • To draw a “quick view” of bit condition by using visual inspection and measuring tool.

When?? • Primary- just after the bit was pulled out of hole • Before rerunning back the used bit

IADC Dull grading system chart

Inner Rows

Outer Rows

Dull

Other

characteristics

characteristics

Reason pulled

•Applied for both fixed cutter bits and roller cone bits •First 4 spaces describes cutting structure

•“B” is for bearing and “G” for gauge •Remarks – indicate other dull characteristics and reason pulled

Cutting Structure Inner Rows

Outer Rows

B

G

Remarks

Dull Location Bearing Gauge Other Reason CharactSeals (1/16”) Charact- Pulled eristics eristics

X 0-No lost of tooth height

“Grading numbers increase with amount of wear, with O representing no wear, and 8 meaning no usable cutters left. A grade of 4 indicates 50% wear.” [Brandon B.D.et al, IADC/SPE 23939]

-Round cutter - Oval cutter

8-Total lost of tooth height

Cutting Structure Inner Rows

Outer Rows

2

6

B

G

Remarks

Dull Location Bearing Gauge Other Reason CharactSeals (1/16”) Charact- Pulled eristics eristics

X Inner Rows

Outer Rows

(Does Not include gauge cutters)

Cutting Structure Inner Rows

Outer Rows

Dull Characteristics

B

G

Location Bearing Gauge Seals (1/16”)

Remarks Other Characteristics

Reason Pulled

X

• Typical IADC PDC WEAR GAUGE. 13mm @ ½ in Diameter

19 mm @ ¾ in Diameter

19 mm @ 1in Diameter

38mm @ 1 ½ in Diameter

• Available PDC cutting sizes – • 8,13,16,19,24 mm

Cutting Structure

Dull Characteristics

Inner Rows

Outer Rows

B

G

Remarks

Dull Location Bearing Gauge Other CharactSeals (1/16”) Characteristics eristics

X BF - Bond Failure BT - Broken Teeth/Cutters BU - Balled Up CR - Cored CT - Chipped Teeth/Cutters ER - Erosion HC - Heat Checking JD - Junk Damage LN - Lost Nozzle

NR - Not Rerunnable PN - Plugged Nozzle/Flow Area RO - Ring Out RR - Rerunnable WO - Wash Out on Bit WT - Worn teeth/Cutters LT - Lost Teeth/Cutters

NO - No Other Major Dull Characteristics

*Only PDC relevant code are shown

Reason Pulled

• Location of the primary DC

Cutting Structure Inner Rows

Outer Rows

B

G

Remarks

Dull Location Bearing Gauge Other CharactSeals (1/16”) Characteristics eristics

X G – gauge S – shoulder N – nose C – cone

T – taper A – all areas

Reason Pulled

Cutting Structure Inner Rows

Outer Rows

B

G

Remarks

Dull Location Bearing Gauge Other CharactSeals (1/16”) Characteristics eristics

Reason Pulled

X Code

Explanation

I

In Gauge

1

Undergauge up to 1/16”

2

Undergauge 1/16” to 1/8”

3

Undergauge 1/8” to 3/16”

4

Undergauge 3/16” to 1/4”

* Use ONLY PDC gauge ring!!

Measure the gap between ring gauge and gauge cutter

• ¼” ( 4/16”) undergauge

Cutting Structure

Reason pulled

Inner Rows

Outer Rows

B

G

Remarks

Dull Location Bearing Gauge Other CharactSeals (1/16”) Characteristics eristics

Reason Pulled

X BHA - Change Bottomhole Assembly DMF - Downhole Motor Failure DSF - Drillstring Failure DST - Drill Stem Test DTF - Downhole Tool Failure LOG - Run Logs RIG - Rig Repair CM - Condition Mud CP - Core Point DP - Drill Plug

FM - Formation Change HP - Hole Problems PP - Pump Pressure PR - Penetration Rate TD - Total Depth/CSG Depth TQ - Torque TW - Twist Off WC - Weather Conditions WO - Washout Drillstring

Dull characteristics Bond Failure [ BF ] • Occur when cutter failing along the bond between two carbide substrates • Formation too hard for the selected bit • Bit may bouncing due to formation changes

Broken teeth [ BT ] • Cutting element is considered broken when 1/3 of the cutting element is broken to the substrate • Caused by lack of bit stability

Dull characteristics Balled up [BU] • A condition where formation attached to the blade and bit body/face of the cutters • May results in reducing ROP • Create physical damages to bit’s body • Rotary torque ↓ as the bit balls up

Washed out [ WO ] • Occur when drilling fluid eroded a passage from internal to external area • May results in twist off • Causes ↓Ppump and ↓ROP

Dull characteristics Cored [ CR ] • A bit is considered cored if its centermost cutting elements are worn, broken or lost • The cone area will show a significant wear from the formation

Heat checking [ HC ] • Normally seen as cracks intersecting cutting elements • Cracks initiated due to thermal shock/fatigue • Can be seen at all areas: nose, shoulder, gauge

Dull characteristics Ring out [ RO ] • A bit is said to have ring out when a circular band of cutting elements are worn, broken or lost. • The blade will show a significant wear from the formation. • Always associated in ↑Ppump &↓ROP

Plugged nozzle/waterway [ PN ] • A characteristics when one/more nozzles are obstructed • Always associated in ↑Ppump

Dull characteristics Worn Teeth [WT] • A condition where bit height reduces due to cutting action • Exhibit smooth wear characteristics

Lost Nozzle [ LN ] • Describes a bit that missing one or more jet nozzles. • Only stated at remarks column as “LN” • Caused by improper installation

Dull characteristics Lost Teeth [LT] • No portion of cutter remain • Graded as “8” in cutting structure • Caused by overload condition

Erosion [ ER ] • Usually occur around cutters • Caused by several factors: body material, nozzle orientation, mud properties • Often a secondary characteristics

Dull characteristics Junk Damage [JD] • Junk damage when contact with object other than formation • Caused by foreign object in the hole

Chipped Teeth/Cutters [ CT ] • Minor damage to diamond table and substrate • Caused by impact damage

Example A

• R437GN was run in horizontal well • 1st run: drilled 118 m in 8.5 hrs, ROP = 13.9 m/hr • 2nd run: drilled 218 m in 13.5 hrs, ROP = 16.2 m/hr • Formation type: n/a

Example B

• R437GN was run in horizontal well • Drilled 387 m in 30 hrs • ROP = 13.1 m/hr • Formation type: brittle to plastic shale/sandstone

Example C

• R435SG was run 4 times in North Sea • Total footage drilled =977m in 166 hrs • Formation type = salt / anhydrite

SMDK-A7 – 12 ¼” PDC Smith M75HKLSBPX

IR 0

OR 1

DC CT

L S

B/S X

G IN

O/C R/P NO TD

SMDK A5-8 ½” PDC Varel VB552-MG2

IR 0

OR DC 0

NO

L

B/S

G

O/C R/P

A

X

IN

NO TD

Conclusion/Recommendation • Dull grading is vital in drilling campaign in order to evaluate the overall bit performance • A thorough research should be conducted to optimize the bit performance • For your reading pleasure: • • • •

www.smithbits.com www.bakerhughes.com www.varelintl.com SPE/IADC papers 16142,16145 and 23939

DIMS-Bit record

Q&A

• Thank you