Transcript
IADC D UL U LL G RA RA D I N G SYSTEM FO R FI X ED CUTTER BITS
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A Baker Hughes company
INTRODUCTION Information provided by dull grading bits can be very significant. This value w as recognized by th e IADC some 25 years ago when a worldwide dull grading system for roller cone bits w as established. For fixed cu tter bits - th at is, all non-roller cone bits - this d ull grading system could not be applied, and a n ew system had to be established. The fixed cutter du ll grading system w as developed by the IADC Drill Bits Sub-Comm ittee in 1987 and revised in 1991. The fixed cutter d ull grading system can be used for all non-roller cone bits, including natur al diamond , polycrystalline diamond compacts (PDC), thermally stable polycrystalline (TSP) diamonds, impregnated bits, core bits and n onroller cone bits which d o not em ploy diamon d m aterial as a cutting element. The system does not d istingu ish between d rilling and coring bits. This guide will only show examp les of PDC, TSP, natural diamond and impregnated or sintered dr ill bits.
SYSTEM STRUCTURE The Dull Grading System Ch art adop ted by IADC includes all codes necessary to dull grade roller cone bits and fixed cutter bits. The chart d escribes eight factors on d rill bits. The first four sp aces describe the “Cutting Structure”. The fifth space (“B”) refers to “Bearing Seals” and does n ot app ly to fixed cutter bits. This space is alway s marked with an “X” wh en fixed cutter bits are grad ed. The sixth space (“G”) refers to “Gauge Measurement” w hile the last two “Remarks” spaces indicate “Other Dull Characteristics” (or secondary dull characteristics) and “Reason Pulled”.
IADC DULL GRADING SYSTEM CHART Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
Remark s Other Characteristics
X FIGURE 1
INNER AREA 2/3 RADIUS
OUTER AREA 1/3 RADIUS
Inner/Outer Rows Using a linear scale from zero to eight, a value is given to cutters in the inner and outer row s of surfaceset bits to ind icate the am ount of wear. Grading num bers increase with am ount of wear, with “zero” representing no wear and “eight” meaning no u sable cutter left. Accordingly, “four” ind icates 50% wear. PDC cutter wear is measured in a linear scale from o ne to eight a cross the d iamond table, regardless of the cutter shape, size, type or exposure. Figure 1 illustrates the cutter wear grading system schematically.
W hen grading a dull bit, the average amount of wear for each area should be recorded. A s shown above, 2/3 of the radius represents t he “inn er rows”. The five cutt ers in this area would be graded “two”. This is calculated by averaging the individual grades for each cutter in the area: (4 + 3 + 2 + 1 + 0) = 2 50000 The average wear for the “outer” area is calculated in the same manner: (5 + 6 + 7) = 6 3000 “Six” would be the average wear gradient for the outer area. This information can now be transferred to the IADC Dull Grading System Chart above. N OT E: For a core bit, the cent erline in Figure 1 would be the inside of the core bit ID.
Reason Pu lled
Dull Charact eristi cs / Other Characteristics The third an d seventh spaces are for use in noting dull characteristics of the bit, i.e., the m ost prom inent ph ysical changes from its new condition. Cod es for these characteristics are listed below in Tab le 1. In general, four different wear characteristics can be distinguished for fixed cutter bits, as shown in Figures 2A and 2B.
TABLE 1. DULL/OTHER CHARACTERISTICS *BC BF BT BU *C C *C D CI CR CT ER FC HC JD *LC LN LT NO
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NR OC PB PN
-
RG RO RR SD SS TR
-
WO WT
Broken Cone Bond Failure Broken Teeth/ Cutters Ba lle d U p C ra ck ed C o n e C on e Dr a gg ed Cone Interference Cored C h ip p e d Te et h / C u tt er s Er os io n Flat Crested Wear Heat Checking Ju n k D am a g e Lo st Co n e Lo st N o z zle Lost Teeth/ Cutters N o Ma jo r/ O th e r D u ll Characteristics N o t Re ru n n a ble Off-Center Wear Pinched Bit P lu g g ed N o z zle / Flow Passage Ro u nd e d G au g e Rin g O u t Re ru n n a ble Shirttail Damage Self Sharp ening Wear Tracking Washed Out Bit Worn Teeth/ Cutters
*Show cone number(s) under “Location”. N OT E: If no “Du ll Characteristic” is visible, mark this space “N o”. If no “Ot her Characteristic” is visible, mark this space “N o”.
IADC DULL GRADING SYSTEM CHART Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
Remark s Other Characteristics
Reason Pu lled
X
FIGURE 2A. STUD CUTTERS
FIGURE 2B. CYLINDER CUTTERS
Dull grading characteristics are based on PDC or stud wear, but also apply for TS P or Natu ral Diamond material. See photographs on the followin g pages.
SYSTEM STRUCTURE IADC DULL GRADING SYSTEM CHART Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
Remark s Other Characteristics
Reason Pu lled
X
Worn Cutter (WT), Round TSP
Worn Cutter (WT), Mosaic
Worn Cutter (WT), Round TSP Broken Cut ter (BT), Round TSP
Broken Cutter (BT), Natural Diamond
Worn Cutter (WT), Triangular TSP Broken Cutter (BT), Triangular TSP
Broken Cutter (BT), Triangular TSP
IADC DULL GRADING SYSTEM CHART Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
Remark s Other Characteristics
Reason Pu lled
X
Cored PDC Bit (CR)
Ring Out (RO) on a PDC Bit
Junk Damage (JD), PDC Bit
Balled Up (BU), Impregnated Bit
Ring Out (RO) on a TSP Bit
Erosion (ER) on a PDC Bit
SYSTEM STRUCTURE IADC DULL GRADING SYSTEM CHART Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
Remark s Other Characteristics
X
Worn Cutter (WT), PDC
Chipped Cutt er (CT), PDC
Lost Cutter (LT), PDC
Chipped Cutt er (CT), PDC
Worn Cutter (WT), PDC Heat Checking (HC), PDC
Erosi on (ER), PDC
Reason Pu lled
Location The “Location” space is used to indicate the location of the p rimary “Dull Characteristics” noted in the third sp ace. Four possible fixed cutter bit profiles are shown in Figure 3, along w ith the codes used to identify commonly referred to locations on the bit. One or more of these codes are used to indicate the location of the dull characteristic(s) noted .
IADC DULL GRADING SYSTEM CHART Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
G
Bearing Seals
Gau ge 1 16” /
X
FIGURE 3. FIXED CUTTER BIT PROFILES
Bearing Seals This space is used on ly for roller cone bits. Therefore, it will alway s be marked “X” wh en grad ing fixed cutter bits.
Gauge The “Gauge (G)” space is used to record the condition of the bit gauge. Record an “ I” here if the bit is still in gauge. Otherw ise, the amou nt the bit is un dergaug e is recorded to the nearest 1 / 16”. For specific un derg au ge markings, see Figure 4.
Location
B
FIGURE 4. GAUGE CONDITION Cod e I 1/ 16 2/ 16
Exp lan ation In Gau ge Und ergau ge up to 1 / 16” Und ergau ge t o 1 / 8”
1 / 16”
3/ 16
Und ergau ge t o 3 / 16”
1 / 8”
4/ 16
Und ergau ge t o 1 / 4”
3 / 16”
Remark s Other Characteristics
Reason Pu lled
SYSTEM STRUCTURE Reasons Pulled The last space on the IADC Dull Grading System Chart is used to record th e reason the bit w as pu lled. A list of codes is shown below in Tab le 2.
IADC DULL GRADING SYSTEM CHART Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
X TABLE 2. REASONS FOR PULLING BIT BH A - C h an g e Bo tt om h o le Assembly DMF- Downhole Motor Failure D SF - D ril ls tr in g Fa ilu r e D ST - D ril l St em Te st D TF - D ow n h o le To ol Fa ilu r e LO G - Ru n Log s RIG - Rig Rep air CM - Con dition Mu d CP
- Core Point
DP
- Drill Plu g
FM
- Form ation Ch an ge
H P - H ole Problem s H R - H ou rs PP
- Pu m p Pressu re
PR
- Pen etration Rate
TD
- Tota l Dep th / CSG Dep th
TQ
- Torqu e
TW - Tw ist Off W C - Wea th er Co nd ition s W O - Wa sh o ut Dr ills tr in g
Remark s Other Characteristics
Reason Pu lled
DULL GRADING WORN BITS The following examples show how to app ly the IADC Fixed Cu tter Dull Grading System to worn bits.
IADC DULL GRADING SYSTEM CHART Cu ttin g Stru ctu re Inner Row s
Example 1
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
X
This S279 was u sed to d rill a very hard and abrasive sandstone formation in the Rotliegendes in N orthern Germ any. The special featur e on this bit is its C ore Ejector (CE). It drilled 100 meter s in 51 hou rs on a 4 3 / 4” Mach 2 dow nhole motor at an average ROP of 2.0 m/ hr, and was p ulled at 4750 meters to change the BHA . After p ulling the bit, a un iform wear pattern was observed with the exception of the beginning of a ring out on the bit should er. Eight waterways were plugged w ith formation, which did not slow d own the penetration rate. The bit was still in gauge.
BIT INFORMATION Style: S279CE Size: 5.875” TFA: 0.5
BIT INFORMATION Pu lled Bit
Remark s Other Characteristics
Reason Pu lled
DULL GRADING WORN BITS IADC DULL GRADING SYSTEM CHART
Example 2 This R437GN w as run in a h orizontal dr illing operation. The first run was in shale on a 6 3 / 4” Mach 1 fixed angle-build motor. The bit d rilled 118 meters in 8.5 hours an d was p ulled at 1433 meters. The ROP was 13.9 m/ hr. After the bit was p ulled, no obvious w ear could be seen, resulting in the IADC grading show n above. The bit was re-run on another well in the same field in the same forma tion, dr illing 218 meter s in 13.5 hour s for an average ROP of 16.2 m/ hrs. The bit was pu lled w hen the bottomhole assembly had to be changed. When d ull grading the bit, little wear on th e cutting structure was seen, resulting in a d ull grading of 1 for “inner / outer rows”. Three cutters were lost du e to matrix erosion from a high flow rate, as shown in the “Dull” and “Oth er Char acteristics” column s. The bit was still in gau ge, as indicated by “I” in the “Gauge” colum n.
Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
Remark s Other Characteristics
Reason Pu lled
X Dull grading for the rerun bit. IADC DULL GRADING SYSTEM CHART Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
Remark s Other Characteristics
Reason Pu lled
X
BIT INFORMATION Style: R437GN Size: 8.5” TFA: 0.6
IADC DULL GRADING SYSTEM CHART
Example 3 This R437GN w as run in a h orizontal w ell to drill brittle to plastic shale and sandstone. It drilled 387 meters in 29.5 hours w ith an average ROP of 13.1 m/ hr on a Mach 1 Adjustable Kick Off Motor. The bit was pu lled at 1820 meter s because of slow penetration rates.
Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
X
Remark s Other Characteristics
Reason Pu lled
Upon pu lling th e bit, it became obvious wh y the bit had ceased d rilling — it was cored out an d h ad lost all four nozzles. The remaining cutters did not show any significant w ear. NO TE: Alt hough t he bit lost all four nozzles, the primary “Dull Characteristic” is “cored” because this is the main reason the nozzles were lost. Lost nozzles are recorded under “Other Characteristics”.
BIT INFORMATION Style: R437GN Size: 8.5” TFA: 0.6
IADC DULL GRADING SYSTEM CHART
Example 4 This S725 BallaSet bit with cylindrical TSPs was used to d rill claystone and sand in the medium hard and dense Rotliegendes formation in Ho lland. It dr illed 154 meter s in 57 hours, achieving an ROP of 2.7 m/ hr on a Mach 2 dow nhole motor in a d irectional well. The bit was pulled du e to a slow rate of penetration. Dull grading ind icated the cutters were w orn 75% and 100% on th e inner an d outer rows, respectively. In add ition, a ring ou t can be seen in the taper area. The bit was also 1 / 16” und ergauge d ue to abrasive sands in the formation.
Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
Location
B
G
Bearing Seals
Gau ge 1 16” /
X
BIT INFORMATION Style: S725GN Size: 8.38” TFA: 0.10
Remark s Other Characteristics
Reason Pu lled
DULL GRADING WORN BITS IADC DULL GRADING SYSTEM CHART
Example 5 This R435SG was ru n fou r tim es in the Nor th Sea area. The bit dr illed a tota l of 977 meters in 166.3 hours, mainly in salt/ anhydrite formations of the Zechstein. Three of the four run s were on a Mach 1 DTU motor with RPMs of 210 to 320. Dull grading of the first two ru ns shows n o visible cutting structure failure. The “Reason Pulled ” wa s Dow nh ole Tool Failur e (DTF) in both cases. After the third run (389 meter s in 89.5 hour s ), the bit was p ulled d ue to BHA prob-lems, and showed a uniform wear pattern of 20% w ear for the inner and ou ter rows. When pu lled after run four, the cutting structure wear was 50% and 60% for the inner and outer row s, respectively. After four ru ns, the bit also showed some severe erosion and lost cutters in the taper area. (See photo taken after run 4)
Cu ttin g Stru ctu re Inner Row s
Ou ter Row s
Du ll Characteristics
References: SPE/IA DC Papers 16142, 16145 and 23939.
G
Bearing Seals
Gau ge 1 16” /
X Run 2
X Run 3
X Run 4
X
Practical Applications. The IADC Dull Grading System can be used for multiple purp oses. Manu facturers evaluate bit design and bit application. Operators evaluate and improve their drilling programs. The system can be compu terized to build up a worldwide database in order to coordinate bit applications. The main objective of the dull grad ing system is to draw a “standardization picture” of a bit, regardless of wh ere, or und er what circum stances the bit may have been u sed. This standardization is expected to lead to better bit app lication an d design throughout the industry.
Location
B
BIT INFORMATION Style: R435SG Size: 12.25” TFA: 0.65 - 1.60
Remark s Other Characteristics
Reason Pu lled
©1996 Hughes Christensen Company. The emblems , and Hughes, Christensen, Eggbeater, Kingcutter and BallaSet are registered trademarks of Hughes Christensen Company. Black Ice, CSE, ECP, Mosaic, and SEC are trademarks of Hughes Christensen Company. ®
Printed in U.S.A.
WL / 6M US / 4M A4 / 6-96
