FORMATIONS IADC BIT CLASSIFICATION
CHARACTERISTICS TYPE 1st CHARACTER ROCK
BITS
The table above correlates formation characteristics against bit type based on the IADC bit classification system. Although this is fairly straight forward for rock bits, it is more nebulous for fixed cutter bits (in particular, the PDC variety). PDC usage has only come into its own in the last few years; compared to rock bits this technology is still in the "toddler stage". Consequently, a good, compressive, clear-cut classification system has not yet been developed. To classify the fixed cutters, the World Oil's 1995 Drill Bit Classification Tables were reviewed to determine which bit types were recommended by manufactures for a particular formation. The bold characters indicate
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The bit classification which appears most often under a particular formation. The relative size is secondary indication of how often a particular bit type is recommended. A comprehensive discussion of the IADC classification system follows.
5.3 IADC BIT CLASSIFICATION SYSTEM IADC Bit Classification
The IADC Bit Classification System identifies bits using a numbering system. For roller cone bits, these numbers identify the formation/tooth type, degree of hardness within the basic formation and bearing type. For fixed cutter bits, the characters identify body material, PDC cutter density or Diamond size, PDC size or Diamond type, and bit profile.
The IADC Bit Classification System is described below.
Roller Cone Bits
For example, a typical IADC classification for a roller cone bit is 1-1-1.
First Character: Cutting Structure Series (1-8). Refers to formation characteristics. Within the steel tooth and insert groups, the formations become harder and more abrasive as the series number increases.
Mill Tooth Bits (1-3) 1 - Soft
2 - Medium to Medium Hard 3 - Hard, Semi-Abrasive / Abrasive Insert Bits (4-8)
4 - Soft
5 - Soft to Medium
6 - Medium to Hard, Semi-Abrasive 7 - Hard, Semi-Abrasive/Abrasive 8 - Extremely Hard, Abrasive
Second Character: Cutting Structure Types (1-4). Refers to the degree of hardness within a formation type.
1 - Softest formations => 4 - Hardest formations Third Character: Type of Bearing / Gage Protection (1-9).
1 = Standard Roller Bearing 2 = Roller Bearing, Air Cooled 3 = Roller Bearing, Gage Protected 4 = Sealed Roller Bearing
5 = Sealed Roller Bearing, Gage Protected 6 = Sealed Friction Bearing
7 = Sealed Friction Bearing, Gauge Protected
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8 = Directional
9 = Other, Reserved For Future Use
Fourth Character: Special Features (Alpha characters). Defines additional features of roller cone bits with regard to cutting structures, bearings, seals, hydraulics, and specific applications.
A = Air Application (Journal bearing with air nozzles) B = Special Bearing Seal
C = Center Jet
D = Deviation Control
E = Extended Jets (Full length) G = Extra Gage / Body Protection H = Horizontal / Steering Application J = Jet Deflection
L = Lug Pads
M = Motor Application
S = Standard Steel Tooth Model T = Two Cone
W = Enhanced Cutting Structure
X = Predominantly Chisel Tooth Inserts Y = Predominantly Conical Inserts Z = Other Shape Inserts
Fixed Cutter Bits:
New (Current) IADC Classification:
For example, a typical IADC classification for a fixed cutter bit is M-1-2-1.
First Character: Body Material (Alpha Character). Refers to the type of body construction.
M = Matrix or S = Steel (only two designations)
Second Character: Cutter Density. For PDC bits this refers to total cutter count, including standard gage cutters. For Diamond bits this refers to diamond size. As with rock bits, the larger the number the more suited for harder more abrasive applications.
PDC Bits (1- 4) Designation of 1 represents a light set while 4 represents a heavy set. Cutter count is based on 1/2" cutter size, cutter (larger/smaller) sizes are projected as 1/2" cutter densities.
1 = 30 or fewer 1/2" cutters 2 = 30 to 40, 1/2" cutters 3 = 40 to 50, 1/2" cutters 4 = 50 or greater 1/2" cutters
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Diamond Bits (6 - 8) A designation of 6 represents larger diamonds while 8 represents smaller diamonds
6 = < 3 stones per carat 7 = 3 to 7 stones per carat 8 = > 7 stones per carat
Note: (0, 5, & 9) are undesignated and reserved for future use.
Special designs using additional gage cutters, such as sidetrack bits, or bits for horizontal drilling, are not considered for the purpose of classification.
Third Character: Size or Type of Cutter. For PDC bits, the third character refers the size of the cutter while for Diamond bits, it refers to the type diamonds.
PDC Bits (1- 4) Size
1 = > 24mm in diameter
2 = 14mm to 24mm in diameter 3 = 9mm to 13mm in diameter 4 = < 8mm in diameter
Diamond Bits (1- 4) Type 1 = Natural Diamonds
2 = TSP (Thermally Stable Polycrystalline) Diamonds 3= Combination Cutters (such as natural diamond and TSP)
4 = Impregnated Diamond Bit (Applies only the highest density Bits)
Fourth Character Profile or Body Style. Gives an idea of the basic appearance of the bit, based on overall length of the cutting face of the bit.
PDC Bits (1- 4) 1 = Fishtail 2 = Flat Face
3 = Long bit profiles
4 = Increasingly longer bit profiles Diamond Bits (1- 4)
1 = Flat Face TSP and Natural Diamond 2 = Long
3= Longer
4 = Increasingly Longer Old IADC Classification:
For example, a typical IADC classification for a fixed cutter bit is D-2-1-2.
Letter: Cutter Type and Body Material
D = Natural Diamond M = Matrix Body PDC
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S = Steel Body PDC T = Thermally Stable Polycrystalline
O = Other (TSP)
First Number: Bit Profile (Gauge Point to Cone)
1 = Long Taper, Deep Cone 2 = Long Taper, Medium Cone 3 = Long Taper, Shallow Cone 4 = Medium Taper, Deep Cone 5 = Medium Taper, Medium Cone 6 = Medium Taper, Shallow Cone 7 = Short Taper, Deep Cone 8 = Short Taper, Medium Cone 9 = Short Taper, Shallow Cone
Second Number: Hydraulic Design
Type Body Changeable Jets Fixed Ports Open Throat
Bladed 1 2 3
Ribbed 4 5 6
Open Faced 7 8 9
Alternate designations: R = Radial Flow, X = Cross Flow, O = Other Third Number: Cutter Size and Density
Cutter Size Light Density Med. Density Heavy Density
Large 1 2 3
Medium 4 5 6
Small 7 8 9
Impregnated 0 0 0
Note Size Distribution Definitions
Small Þ Greater than 7 stones/carat for natural Diamond.
Þ Less than 3/8" diameter of usable height for PDC bit.
Medium Þ 3 to 7 stones/carat for natural diamond.
Þ 3/8" to 5/8" diameter of usable height for PDC bit.
Large Þ Less than 3 stones/carat for natural diamond.
Þ Greater than 5/8" diameter of usable height for PDC bit.
5.4 IADC BIT GRADING SYSTEM