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M

AY

2016

71

AR T I C L E

SMS Group

xx

Machinery and plants for the production

of oilfield tubulars

By Dr Ing Hansjörg Hoppe and Dr Ing Hans Pelster, SMS Group

The use of oilfield tubulars made from high-alloy materials is

always necessary when one of the following concentrations is

exceeded in the oil or gas stream:

pCO

2

concentration > 1,500psi

Cl- concentration > 250mg/l

pH

2

S concentration > 10psi

Temperature > 390°F

Commonly used high-alloy and corrosion-resistant materials

are duplex steels (22Cr-5Ni), super-duplex steels (25Cr-7Ni-N),

super-austenitic steels such as alloy 28 (28Cr-32Ni), nickel-

based alloys such as alloy 825 (42Cr-21Cr-3Mo) or titanium

alloys such as Ti Grade 5 (Ti-6Al-4V). The material to be

chosen for a particular application depends on the corrosion

conditions.

Currently most manufacturers are limited in the production

of large-diameter, high-alloy oilfield tubulars that have to be

cold worked in order to achieve the strengths necessary for

such deep wells. There is a growing demand for tubings and

casings up to outside diameters of 10

3

/

4

" (273.1mm) and

appropriate lengths from 30 to 40ft (9 to 12m).

The SMS group as a system supplier offers its customers

tailor-made solutions. Hot-finished, high-alloy oilfield tubulars

or mother tubes that still have to be cold-formed can be

produced in the diameter range 33.4 to 323.9mm (nominal 1

to 12") on extrusion press lines from the SMS group. Cold-

rolled tubes in the diameter range from 5 to 280mm can be

The rising worldwide demand for oil and gas is leading to

ever deeper well depths. Well depths of 25,000ft (7,620m)

and more are no longer unusual. Generally speaking,

increasing depths mean increasing temperatures and

pressures. Many high-pressure and high-temperature

(HPHT) wells with temperatures up to 400°F (204°C) and

pressures up to 20,000psi (138MPa) have already been

drilled. At the bottom of the well, the conditions become

even tougher.

The real challenges for the materials from which the

oilfield tubulars are produced arise during the oil and gas

extraction. Depending on the temperature, pressure, flow

velocity and corrosive constituents in the gas stream,

such as H

2

S and CO

2

, the use of low-alloy steel, high-

alloy stainless steel, nickel-based alloys or titanium

alloys is necessary.

produced on SMS group cold pilger mills. The SMS group also

offers complete hot and cold processing lines as a package

solution. These include, in addition to the core machines such

as extrusion press lines or cold pilger mills, machines for billet

preparation, pickling and degreasing facilities, finishing and

testing equipment – in some cases from subcontractors.

Production of high-alloy oilfield tubulars

Stainless steels or nickel-based alloys are melted in an electric

arc furnace melting process or in induction furnaces under the

exclusion of air, and are further processed in downline plants

by argon-oxygen decarburisation (AOD) or vacuum-oxygen

decarburisation (VOD).

If the batch size allows, continuous cast starting material

is used; otherwise chilled cast material is used. Simple

austenitic steels can be extruded directly without prior hot

forming. Higher alloy materials must first be forged or hot-

rolled in order to break down the linear casting structure and

achieve a homogeneous microstructure.

The product portfolio of the SMS group includes all the plants

for primary and secondary metallurgy for the melting of high-

purity stainless steels and nickel-based alloys as well as the

necessary casting plants. After casting, the round ingots are

rolled to the required billet size or forged on radial forging

machines from the SMS group.

In the final work step, the rolled or forged bars have to be

peeled in order to create the surface quality necessary for the

extrusion process. Peeling is performed on special machines

from the SMS group.

1 Rotary gas furnace

2 Induction furnaces

3 Glass lubrication

4 Piercing press

5 Hydraulic station

6 Final heating

7 Glass lubrication

8 Extrusion press

9 Water quenching

10 Cooling table

Figure 1: Layout of extrusion press line