Classification Code Code

There are several letters used in IADC to represent these special features. They are not used very often. Most of the time the bit manufacturer will choose to identify the special feature in their nomenclature as opposed to the IADC code. Below is a list of these special features:

A = air application B = special bearing /seal C = center jet

D = deviation control E = extended jets

G = gauge or body protection

H = horizontal or steering application J = jet deflection

L = lug pads

M = motor application

S = standard steel tooth model T = a two-cone bit

W = enhanced cutting structure

X = predominantly chisel tooth inserts Y = conical tooth insert

Z = other shaped insert

The M letter is used most often to designate a bit is designed for motor application.

The IADC code for roller cone bits has several uses. It is a good starting place when trying to compare roller cone bits on offset bit records. In order to determine what bit is going to be run in a specific application, bit

performance has to be evaluated. By looking at offset bit records, the IADC code of the offset bits can be identified. Why would the IADC code be only a starting place? If a customer says, “I need a 12-1/4” IADC code 517,” sure, which one do they want? Within the industry there are probably 60+ 12 ¼” 517 type bits. The IADC code gives a general indication of what kind of cutting structure is needed. The features, or combination of features, will then be selected for the specific application.

Schlumberger Drill Bits – Roller Cone Nomenclature

Below is an example of two of Schlumberger’s roller cone bits: a 12-1/4” EHP51HDLK and a 17-1/2 EMS13GC.

The first set of numbers, the 12-1/4 and the 17-1/2, represent the size in inches. The size is also indicated in metric on Schlumberger’s box labels for those that work in the metric system.

The next set of prefixes in Schlumberger’s nomenclature represent the product line. In this case, EHP, Enhanced High Performance, and EMS, Enhanced Motor Series, are the product lines for these particular bits. The Schlumberger product lines will be discussed later.

The next two numbers are the first two numbers of the bit’s IADC code. Schlumberger Drill Bits is the only company that uses the first two numbers of the IADC code, to identify their cutting structure. All the rest of the competitors use different sets of nomenclature and different sets of numbers to identify their bit types. In the top example, the 12-1/4" EHP51, the 51 indicates that the first two numbers of the IADC code for this bit is a 517. In the bottom example, the 17-1/2" EMS13, the IADC code for this bit is 135. So the first two numbers of the IADC code is represented in our nomenclature as 13. In 2001, Schlumberger launched three product lines which do not use the first 2 numbers of the IADC code in it’s nomenclature. The numbers used in the FMJ, DJ, and DR product lines are not associated with the IADC code.

12 ¼”

EHP

51 H

DLK

17 ½”

EMS

13 G C

The next letter, if there is one, would represent the design variant. There are three different design variants frequently used by Schlumberger. They are designated by A, H, and X. Below are the design variants:

A = Chisel-Shaped Inserts. The application for this would be an aggressive insert shape typically for soft to medium formations. The downside to using the A variant is that an insert shape that is sharp chisel may not be durable enough. If the insert is not durable enough, the bit life could be limited.

H = Chisel-Shaped Inserts in IADC code 41 to 51 with 3° cutter skew. Typically insert bits in 41 to 51 range have 5° cutter skew. The application for the H designate is that it is a durable skew angle for any application where you need more durability. A 5° skew is for a more aggressive bit but it is less durable. A 3° skew is a little less aggressive but it is more durable. Durability could be needed in situations like running high RPM

(Revolutions Per Minute), a directional situation, motor bit runs, or any time there are streaky formations. The downside is that the more durable the bit, the slower the ROP. So a little bit of ROP is sacrificed in order to get durability. Schlumberger also builds bits that have faster ROP. So it depends on the customer's expectations, the application, and the objective for that bit run.

X = is a special cutting structure that might vary from type to type. When an X is in the suffix of Schlumberger’s nomenclature, the special cutting structure will be different from a normal bit. The applications for this type bit are formations such as medium-hard carbonates that suit an aggressive gauge design but does not lead to gauge breakage. The downside is that if you put a little longer gauge row inserts in for aggressive gauge design, there could be a tendency for the inserts to break.

Schlumberger Drill Bits has several options for added features.

With the example of the 12-1/4", DLK stands for diamond lug pad and K shirttail protection, and in the case of the 17-1/2" EMS13, G stands for gage protection on the bit and C stands for center jet.

Schlumberger Drill Bits – Roller Cone Features

Below are the Schlumberger Drill Bits roller cone features:

C = Center Jets. There are 2 types of center jets. There is a single-port

center jet that is installed in the center of the bit to provide hydraulic fluid to the inner row and nose area. There is also a three-port center jet. The three- port center jet is fixed and is installed in the factory. For the single-port center jet, it is interchangeable and can be installed or changed

in the field.

There are several benefits to running center jets. They reduce bit balling and help keep the nose and inner rows of the cutting structure clean. The major disadvantage of center jets is that they can reduce the outer cutter cleaning. If a bit has three nozzles, and then a center jet is added, there will be less fluid exiting out of the 3 outside nozzles.

C - Center Jet

F - Flame Spray cutter shell coating

G - Heel Row Inserts on tooth bits

JA - Jet Air Drilling

K - Shirttail Inserts

KP - Shirttail Inserts - Premium Coverage

KPR - Shirttail Inserts Raised - Premium Coverage

L - Lug Stabilizing Pad

M - Mudpick II Hydraulics on HP Bits

T - GageGuard - shorter inserts in between the gauge row Inserts

Another disadvantage is the center jet can aggravate the nose area. With high flow rates through your center jet, there can be nose cone erosion in the center of the bit. The applications for center jets are basically in bits 12-1/4" and larger. It is available in 7-7/8" and larger, and on occasion, a center jet has been installed in a bit smaller than 7-7/8". Typically center jets are used in medium to very soft, very sticky, gumbo type formations, or where

cleaning around the center of the bit is most important. Generally, no more than 18% of the TFA (Total Flow Area) should be going through the center jet. If the center jet is more than 18% TFA, the outside nozzles could be starved for fluid and will not keep the gauge row of inserts cleaned.

D = Diamond PDC-coated inserts. PDC stands for Polycrystalline Diamond

Compact. The purpose of using PDC-coated inserts is to eliminate thermal fatigue and to eliminate abrasive wear. Almost any of the cutting structure or shirttail inserts can be replaced with the diamond PDC-coated inserts. In the Schlumberger nomenclature, it is very simple to identify what features have diamond PDC-coated inserts and which ones do not. When looking at the suffixes of Schlumberger nomenclature, everything to the right side of the D represents diamond PDC-coated inserts. Everything to the left side of the D represents non-diamond PDC-coated inserts. The competition uses the D repetitive when they indicate their diamond coated inserts.

The benefits of PDC-coated inserts, the D feature, are that it does eliminate abrasive wear and thermal fatigue. There are some downsides, however. It is costly. Some of the PDC-coated inserts could cost $25, $50, or $100 per insert. The application must be right for using these inserts because it does increase the cost of the bit. Another downside is it will not solve fracture due to overload. If the inserts are breaking due to overload, using diamond

The applications for the D feature would be any application where abrasive cutting structure wear or thermal fatigue limits bit life. It can also be used in directional applications where there would be excessive wear on the gauge row inserts. The diamond PDC-coated insert would be a good solution to that gauge wear problem.

F = Flame Spray. This is a tungsten carbide coating that is applied to the

finished cutter in a high-velocity oxygen-fuel environment. After the inserts are pressed into the cutter, the cutters are sent to an outside vendor for the Flame Spray to be applied. For Flame Spray, the steel cutter shell surface is bombarded with tungsten carbide pellets at high velocity and they are

embedded into the cutter shell.

The benefits of Flame Spray are that it reduces cutter shell erosion and eliminates cone wear. The downside is that the coating may flake due to differences in modulus of elasticity between the tungsten carbide pellets and the steel. The best applications for flame spray is directional, or any

application where there is off-center rotation, gyration, or cutter wear limits bit life due to erosion. Sometimes this happens with poor solids control or high solids in the mud. Flame spraying has to be done in the before the bit is assembled. It is not something that can be done in the field. It has to be requested while the bits are being built. If there is a very abrasive formation, the abrasive formation will erode the steel. The problem with cutter shell erosion is that when the cutter shell is eroded, there is no longer support for the inserts. Once the inserts fall out, the bit will not drill at an adequate ROP. The bit will have to pull out of the hole and be replaced.

Flame