HF 1000
Crushed tungsten carbide held in a nickel bronze matrix. The 3mm grain size ensures greater concentration of carbide which is ideal for soft formation drilling.

HF 2000
Trapezoidal tungsten carbide inserts held in a sintered carbide nickel bronze matrix. This will give a greater depth of carbide coverage – ideal for high deviation drilling in abrasive formations.

HF 3000
Tungsten carbide inserts set in a powder spray deposit ideal for abrasive formations. 97% bonding guaranteed, certified by ultrasonic report. Recommended for non-magnetic stabilizers.

HF 4000
Tungsten carbide inserts (button type). The inserts have been developed to allow cold insertion and maintain close fit. A greater concentration of inserts on the bottom third of the blade and leading edge will increase surface contact to reduce wear in highly abrasive formations.

HF 5000
This oxy-acetylene process applies tough molten carbide particles of varying sizes held in a nickel chrome matrix which provides excellent bonding properties and greater surface wear characteristics are achieved. Surface hardness levels over 40 HRC. Ideal for GEO-THERMAL applications over 350°.

Bottomhole Assembly,

Abbreviated as BHA, is a complex combination of several drilling tools including directional drilling assembly. It is one of the components of a drilling rig. It consists of a string below the drill pipe in a drill string. It is primary made up of drill collars (see "Drill Collars"), stabilizers and the drill bit.

The Bottomhole Assembly affects the trajectory of the bit and the wellbore.

The design objective of BHA for directional drilling is to provide the directional drilling tendency in-line with the planned trajectory of oil or gas well.

There are various factors that determine the BHA’s directional drilling tendency. 


A stabiliser is a piece of downhole equipment used in the bottom hole assembly (BHA) of a drill string. It mechanically stabilises the BHA in the borehole in order to avoid unintentional side-tracking, vibrations, and ensure the quality of the hole being drilled. 

Stabilisers are used to:

  • Control hole deviation.
  • Reduce the risk of differential sticking.
  • Ream out doglegs and keyseats.

A Stabiliser is composed of a hollow cylindrical body and stabilizing blades, both made of high-strength steel. The blades can be either straight or spiralled, and are generally hard-faced for wear resistance.

Several types of drilling stabilisers are used in the oilfield today.

While integral stabilisers (fully machined out of a single piece of steel) tend to be the norm, other types can be used, such as :

Replaceable sleeve stabiliser,

These consist of replaceable sleeves that are mounted on the stabiliser body.

They offer the advantage of changing out a sleeve with worn blades or replacing it with one of another gauge size. The blades can be dressed with tungsten carbide inserts for abrasive formations.

There are two main designs of sleeve-type stabiliser:

Two-piece stabiliser (mandrel and sleeve):
The sleeve is screwed onto the coarse threads on the outside of the mandrel and torqued up to the recommended value. 
Sleeve makeup torque is low. 
There is no pressure seal at the sleeve. 
It is convenient to change sleeves on the drill floor. 

Three-piece stabiliser (mandrel, sleeve and saver sub):
The sleeve is screwed onto the mandrel first, by hand. 
The saver sub is then screwed into the mandrel and this connection is torqued up

to the recommended value. In this case, there is a mud pressure seal at the mandrel/saver sub connection. Makeup torque of this connection is the full value for that size of API connection. Great care must be taken (clean and dope the shoulders properly, use correct makeup torque), otherwise downhole washouts etc.

will result. It can be quite difficult and time-consuming to change/service the sleeve. 

Welded blades stabiliser,

where blades are welded onto the body.

This type is usually not advised on oil wells due to the risks of losing blades, but is regularly used when drilling water wells or on low-cost oilfields.

Clamp-on Stabilisers

Clamp-on stabilisers allow more flexibility in BHA design. 
They can be positioned on NMDCs, MWD, PDMs etc. at the required spacing to maintain directional control however these are the least commonly used because of the danger of them moving position downhole.

Non-Rotating Stabilisers

These stabilisers are used to centralise the drill collars, but a rubber sleeve allows the string to rotate while the sleeve remains stationary. The wear on the blades is therefore much less than in other stabilisers and so they can be used in harder formations.

Usually 2 to 3 stabilisers are fitted into the BHA, including one just above the drill bit (near-bit stabiliser) and one or two among the drill collars (string stabilisers).

Near-bit stabilizers have BOX x BOX connections.
They are usually bored out to accept a float valve. 

String stabilizers have PIN x BOX connections. 
Most stabilizers have a right-hand spiral.

​​Rental Drill Stem Accessories

Drill Pipe Pup Joints.

Drill Pipe Pup Joints are short sections of well tubing made to API standards.

Drill Pipe Pup Joints are often machined from bored steel bars rather than manufactured along with the drill pipe in the mill, although this is not exclusive. Drill Pipe Pup joints are available in various lengths, the most common being, 5 feet, 10 feet, 15 feet and 20 feet.

5ft Drill Pipe Pup Joints are often substituted for 6ft pup joints as, during handling on the rig, it is easier to set slips and elevator on a 6ft pup than on a 5ft pup. 

 The primary use of the pup joint is to adjust the overall length of the drill string to land at a specific depth whilst staying within the working area of the kelly valve.

PST Energy Ltd

Drill Stem Valves

​PST Energy Ltd holds rental stock of certain types of Drill Stem Valve

Inside BOP (Gray) Valves 

Inside Blowout Preventer (Inside BOP / IBOP)

is a valve which is used to prevent wells from unconditionally flowing up the drill string.

It is held with a dart in an open position to allow stabbing.

The flow is shut off on turning the release handle after stabbing.

The stabbed body can be removed and the drill string can be connected again

to re-establish the pressure stabilisation.

Then the valve can be removed

and returned to a ready state

or left in the drill string

to ensure downward flow only.

Kelly Valves (One and Two Piece)

Kelly valves are used as safety valves for drill pipe and there are various types and pressure ratings

Upper Kelly Valve:

An Upper Kelly Cock, also known as Upper Kelly Valve,

is a full-opening valve installed just between the Kelly and the Kelly swivel

with its outside diameter equal to the outside diameter of the drill pipe tool joint.

The upper Kelly valve acts like a check valve when it is in engaged position.

The valve can be used to shut off the flow in the drill string and act as a safety valve

to control the blowout pressures

Lower Kelly Valve:

A Lower Kelly Valve is a full-opening safety valve (FOSV) installed in the drill string with an outside diameter equal to the outside diameter of the drill pipe tool joint. The valve provides a closure to stop mud loss when the Kelly is removed from the drill string. It is required to close the valve before the Kelly is disconnected so that the hoses and mud in the Kelly stay there. The valve can be used to shut off the flow in the drill string and act as a safety valve to control the blowout pressure

Some valves, generally 2 piece construction, have the ball directly fitted to the crank

There are different "Classes" of Kelly Valve:

Class 1 - surface only
Class 2 - surface & down hole valves
In some High Pressure, High Temperature (HPHT) wells valves are also placed in

the string that is down hole. This usually involves placing a valve in each stand of

drillpipe so the driller can operate valves whilst tripping out.

Drop-in Check Valves

Drop-in Check Valves (DICV / Dart Sub / Check Guard) are used to provide protection

from backflow during periods when the drill string is left open or kicks are frequent.

The landing sub is installed just above the bit sub.

The valve may either be installed with the landing sub or placed in the drill string at the

top and pumped down to the landing sub.

Once seated it allows downward mudflow only.

Casing Scraper.

Casing Scrapers are used to clean cement, mud, embeded bullets, rust, mill scale, paraffin, perforation burrs and other substances from the inside walls of casing. 

Drill Stem Subs

Lifting Subs, Kelly Saver Subs, Bit Subs, Float Subs, Drill Stem Crossover Subs etc are short subassemblies used for connecting drill stem components, often of different thread types or sizes, during drilling applications.

A sub is a special short length of threaded pipe used to connect drill pipes to drill collars, with a drill pipe connection on one end and a drill collar connection on the other.

When a sub is used to convert connectors of different types or sizes, it is generally called a crossover sub.

The sub that connects the drill bit to the last drill collar is the bit sub.

There is a wide range of subs available, including:

Straight (slick) Crossover Sub 
Bottleneck (reduced section) Sub 
Crossover Sub with Float Bore 
Bit Sub with Float Bore 
Bit Sub without Float Bore 
Top Drive Saver Sub 
Kelly Saver Sub 
Kelly Saver Sub with a stretched on rubber protector 
Lift Sub (18 deg taper) 
Lift Plug 

Lift Nubbin (dial head with square shoulders)

Lift Cap

Pad Eye Lift Sub

Options to consider with subs:

API Pin Stress Relief Groove and Box Boreback
Cold Rolling
Phosphate Coating
Proprietary Connections of Leading Manufacturers
Rubber Sleeve Protectors (For Kelly Saver Subs only)
Third Party Inspection

Safe Working Load of Lift Subs/Caps/Nubbins

Shank Size of Lift Subs/Nubbins

​Liability Disclaimer:

PST Energy Ltd has made every effort to ensure the reliability and accuracy of the data presented.

However, PST Energy Ltd makes no representation or warranty (whether expressed or implied) and shall have no liability whatsoever for the accuracy or completeness of the material contained in this presentation (or any part thereo)

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