cge 654_lect 8_material selection.pdf

Material Selection

Faculty of Chemical Engineering

CGE 654

Well

Completion


Outlines

Materials for well completion equipment

Engineering standards

Material selection requirements and criteria

Types of materials

Materials failure

Corrosion management and methods of prevention


Material Selection

Introduction

Proper selection of completion materials is a key

factor in ensuring completion longevity.

Selection of material is particularly critical where

tubing, casing and other well-completion

components are exposed to corrosive conditions.

Several specifications and standards have been

developed for material description and selection for

well completions.


Material Selection

Materials for well completion equipment

TubularsCarbon steel

Stainless steel (13Cr, 22Cr, Inconel)

Special alloys

Composite materials (GRE, Fiber glass)

Elastomer and Rubber ElementsNitrile compound

Proprietary Elastomer (Aflas, Viton, Chemrez, Kalrez etc.)

Thermoplastic (Ryton, Teflon etc.)

Ceramic


Material Selection

Materials selection requirements Materials selection should be optimized and provide acceptable

safety and reliability.

Requirements??


Material Selection

Requirements

Corrosivity

During start up and shut-down conditions

Design life and system

availability requirements

Failure probabilities,

failure modes and failure

consequencesResistance to

brittle fracture

Inspection and corrosion

monitoring

Access for maintenance

and repair


Material Selection

Material selection criteria

Material selection criteria for oilfield equipment:

Mechanical properties (function)

Operating environment

Cost

Availability

Stock size and shape

These categories relate to the

selection of metals,

elastomers and plastics used

in construction of downhole

tools and equipment.


Material Selection

Standards for Materials

AISI classifications (American Iron and Steel Institute)

API Standard (American Petroleum Institute)

ASTM Standard (American Society for Testing and

Materials)

ASME Code Specifications (American Society of

Mechanical Engineers)

NACE Publications (National Association of Corrosion

Engineers)


Material Selection Materials Standards and Specifications

AISI (American Iron and Steel Institute)

system using 4 or 5 digits

first two digit -----> metallic alloy or alloy

last two digits ----> percentage of carbon

e.g: AISI 1040 = plain carbon steel with carbon content of 0.37 0.44%

AISI 4340 = 1.8% nickel, 0.80% chromium with carbon 0.375 0.44%

API (American Petroleum Institute)

the standard number "5" in titles refers to tubular goods (5A, 5AX, 5AC)

'5L' covers various grades of pipeline (5L, 5LX, 5LS)


Material Selection

Materials Standards and specifications(cont)

ASTM (American Society for Testing and Materials)

cover all metals and alloys include specifications, methods of tests, recommended practices

NACE (National Association of Corrosion Engineers)

guide in selecting corrosion resistant metallic materials for oilfield applications


Material Selection


The equipment for standard use - usually complies with API L-80 regulation.

The API L-80 also applies to corrosive or acidic environments, but does not take temperature into account.

Temperature has a great influence on the behaviour of non-metallic materials such as, for example, elastomers.


Material Selection


Elastomers materials deteriorate over time at temperatures above 275C, and lose all sealing capacity.

Special steels that do not come under the API categories are used in hostile environments that require high mechanical resistance or resistance to hydrogen sulphide.

Tubular


CGE 654

Well

Completion


Material Selection

Metals

Nearly all metals and alloys exhibit a crystalline structure

Strength - they are rarely used in engineering application

Alloys, a combination of several elemental metals are stronger

with more engineering usefulness.


Material Selection

Steels

Is an alloy consisting mostly of iron, with a carbon content

between 0.2% and 2.04% by weight, depending on grade.

Carbon is the most cost-effective alloying material for iron,

but various other alloying elements are used such as

manganese, chromium, vanadium, and tungsten.

Carbon and other elements act as a hardening agent,

preventing dislocations in the iron atom crystal lattice from

sliding past one another.


Material Selection


Material Selection

Cast Iron

Alloys of iron and carbon with a percentage of carbon over 2% are known as cast iron.

These alloys also have higher silicon content than steel.

Commonly used grades of cast iron in packers and accessories are gray iron (i.e. class 40 with tensile strength of 40,000 psi) and ductile iron.

Ductile iron is used in applications in which higher strength and ductility are required (e.g., grade 80-55-6 will have a 80,000 psi tensile strength, 55,000 psi yield strength and 6% elongation).


Material Selection

Stainless Steel

Steel will quickly rust in the presence of moisture and oxygen. The addition of chromium gives steel the stainless quality.

Stainless steel must contain approximately 12% chromium or more.

Stainless steel is classified by AISI based on its microstructure.

The 200 and 300 series stainless steels are austenitic, while the 400 series are ferritic or martensitic.

There are several grades in each class.

Stainless steel is often used due to its resistance to weight loss corrosion in a CO2 environment.


Material Selection


Material Selection

Nickle Based Alloy

Monel consists of approximately 70% nickel and 30% copper

and exhibits good resistance against H2S (except at high

temperatures), CO2, O2, and chloride corrosion while

maintaining a high degree of ductility and strength.

Inconels consist of nickel and chromium and are very resistant

to corrosion. The 200 series are pure nickel alloys, 400 and 500

series are nickel-copper alloys such as monel. The 600 and 700

series are nickel chrome alloys such as Inconels, while 800 and

900 series are nickel iron alloys.


Material Selection

Miscellaneous Alloys and Coatings Due to the shortages and limitations of many H2S service alloys, various

other metal compounds are being used for equipment manufacture.

Hasteloy a nickel and molybdenum alloy.

Highly corrosion resistant.

Stellites cobalt, chromium and tungsten alloys.

For anti wear application.

Colomonoys nickel and boron alloys.

For anti wear coating.

Cemented carbides containing tungsten carbide.

For anti wear coating.

All of the above alloys are resistant to H2S corrosion


Material Selection

General comparison of materials used in downhole completion components

Elastomer and rubber elements


CGE 654

Well

Completion


Material Selection

Elastomer

Elastomer - polymer with the property of elasticity.

Derived from elastic polymer,

Often used interchangeably with the term rubber, and is preferred when referring to vulcanisates.

Each of the monomers which link to form the polymer is usually made of

carbon, hydrogen, oxygen and/or silicon.

At ambient temperatures rubbers are thus relatively soft and deformable.

Their primary uses are for seals, adhesives and molded flexible parts.

ASTM definition of 'elastomer'

" a polymer material which at room temperature can be stretched to at least twice its original length and upon immediate release of the stress will return quickly to

approximately its original length "


Material Selection

Elastomer

A is a schematic drawing of an unstressed polymer. The dots represent cross-links.

B is the same polymer under stress. When the stress is removed, it will return to the A configuration.


Material Selection

Examples of Elastomers Unsaturated rubbers that can be cured by sulfur vulcanization:

Natural Rubber (NR)

Synthetic Polyisoprene (IR)

Butyl Rubber(copolymer of isobutylene and isoprene, IIR)

Halogenated butyl rubbers (Chloro Butyl Rubber: CIIR; Bromo

Butyl Rubber: BIIR)

Polybutadiene (BR)

Styrene-butadiene Rubber (copolymer of polystyrene and polybutadiene, SBR)

Nitrile Rubber (copolymer of polybutadiene and acrylonitrile,

NBR), also called Buna N rubbers

Hydrogenated Nitrile Rubbers (HNBR) Therban and Zetpol

Chloroprene Rubber (CR), polychloroprene, Neoprene, Baypren, etc.


Material Selection

Examples of Elastomers(cont)

Saturated Rubbers that cannot be cured by sulfur vulcanization:

EPM (ethylene propylene rubber, a copolymer of ethylene and propylene) and EPDM rubber (ethylene propylene diene rubber, a terpolymer of ethylene, propylene and a diene-component)

Epichlorohydrin rubber (ECO)

Polyacrylic rubber (ACM, ABR)

Silicone rubber (SI, Q, VMQ)

Fluorosilicone Rubber (FVMQ)

Fluoroelastomers (FKM, and FEPM) Viton, Tecnoflon, Fluorel, Aflas and Dai-El

Perfluoroelastomers (FFKM) Tecnoflon PFR, Kalrez, Chemraz, Perlast

Polyether Block Amides (PEBA)

Chlorosulfonated Polyethylene (CSM), (Hypalon)

Ethylene-vinyl acetate (EVA)


Material Selection

Examples of Elastomers(cont)

Various other types of elastomers:

Thermoplastic elastomers (TPE), for example Elastron, etc.

Thermoplastic Vulcanizates (TPV), for example Santoprene TPV

Thermoplastic Polyurethane (TPU)

Thermoplastic Olefins (TPO)

The proteins resilin and elastin

Polysulfide Rubber


Material Selection

Elastomers

Highly saturated nitriles

Highly or Fully Saturated Nitrile Rubbers are designed specifically

for applications with H2S production or high temperatures.

Most elastomers are cured using a sulfur vulcanization process,

exposure to H2S downhole results in the further hardening and the

eventual failure of the elastomer.

Produced by selectively saturating (hydrogenating) most of the

butadiene portion of the acrylonitrile-butadiene polymer.

Corrosion


CGE 654

Well

Completion


Material Selection

Corrosion

Corrosion is defined as the destruction of a metal by a chemical or electrochemical reaction.

Corrosion occurs when a metal in contact with water forms a corrosion cell.

The corrosion cell has four components,

the aqueous phase (water) which acts as an electrolyte (through which ions migrate)

an anode on the metal surface (where the metal is oxidized and goes into solution as metal ions),

a cathode (where excess electrons are consumed) and

a metallic path connecting the cathode to the anode.


Material Selection

Corrosion


Material Selection

Corrosion

How??? Why???

Corrosion is the electromechanical reaction of metal or metal alloy due to reaction with its environment

Pure metals do not exist in nature, only as ores or oxides of metal; the most stable state

Corrosion is the reversion of the pure metal to its stable state (ore)

For iron/steel in seawater:

Anodic reaction : Fe Fe2+ + 2e

Cathodic reaction : O + 4e + 2H2O 4OH


Material Selection

Corrosion

How??? Why???

Corrosion cells are created on metal surfaces in contact with an electrolyte because of energy differences between the metal and the electrolyte.

Different area on the metal surface could also have different potentials with respect to the electrolyte.

These variations could be due to i) metallurgical factors, i.e., differences in their composition, microstructure, fabrication, and field installations, and ii) environmental factors. Carbon and low alloy steels are the most widely used material in the oilfield.

Stainless steels (Fe-Cr-Ni), and nickel-base corrosion resistant alloys (CRA), such as Incoloys (Ni-Fe-Cr), Inconels (Ni-Cr), Hastelloys (Ni-Cr-Mo-Fe-Co) etc., are also used in highly corrosive environments.


Material Selection Types of corrosion

Uniform corrosion Uniform removal of metal from a surface

May be observed in tubing and sucker rods

Acidizing treatment

Galvanic corrosion Occurs when two dissimilar metals are connected electrically and are in contact with

an electrolyte solution

Eg: When a new section of pipe is added to an older section. The new pipe becomes anodic and corrodes preferentially.

Intergranular corrosion Localized corrosion along grain (metals&alloy) boundaries

Dealloying Occurs when one or more components of an alloy are more susceptible to corrosion

than the rest.

Eg: The removal of zinc from brass, known as dezincification.


Material Selection Types of corrosion(cont)

Crevice and pitting corrosion Crevice corrosion - occur in crevices (stagnant, shielded areas) such as those formed under

gaskets, washers, insulation material, fastener heads, surface deposits, disbonded coatings, threads, lap joints and clamps.

Pitting corrosion - "self nucleating" crevice corrosion, starting at occluded cells.

Environmentally induced cracking Occur when a susceptible alloy is under tensile stress in a corrosive environment.

Elements: tensile stress, corrosive environment, susceptible alloy

Hydrogen damage Brittle mechanical fracture caused by penetration and diffusion of atomic hydrogen into the

crystal structure of an alloy

Occurs in corrosive environment under constant tensile stress

Erosion corrosion Also known as flow-enhanced corrosion

Takes place in flowing systems where turbulence occurs, typically in pipe bends (elbows), tube constrictions, and other structures that alter flow direction or velocity.

Mechanism - The continual flow of water, which removes any protective film or metal oxide from the metal surface.


Material Selection

Types of corrosion(cont)

Crevice Corrosion of a Titanium Flange

Screws Showing Crevice Corrosion


Material Selection

Types of corrosion(cont)

Schematic of an actively growing pit in iron

Corrosion Product Accumulation

Pitting Corrosion of Tube Wall


Material Selection

Cost of corrosion

Plant Downtime

Loss of Product

Loss of Efficiency

Contamination

Over design

Environmental Issues

Health and Safety


Material Selection

Corrosion Management

Legislation (Legal Liability)

Ensure Asset Integrity

Manage production

Maintenance

Ensure Health and Safety

Prudent Operator


Material Selection

Methods of prevention

Coatings

Inhibitors

Cathodicprotection

Alloying (metallurgy).


Material Selection Coatings Inhibitors Cathodic Protection Alloying (metallurgy) Inorganic, organic or

metallic coatings alter the corrosion process by changing the nature of the metal solution interface.

Provide a temporary barrier to the solution / metal reaction interface.

It must be remembered that all these coatings are permeable to water, chlorides, hydrogen, and other gases such as CO2 and H2S.

Thus coating represent a temporary although often sufficient solution to corrosion problems.

Another method of corrosion control - any chemical that reduces the tendency for corrosion.

Eg: oxygen scavengers, passivators, biocides, etc., are all included.

Can alter the corrosion environment reacting with the corrodents, by forming a transient barrier or by changing the local potential of the metal surface to a more noble potential.

Organic and inorganic inhibitors (anodic, cathodic, anodic/cathodic, neutralising). Adsorption Inhibitors (Primary and Polysubstituted Mono Amines, Amides, Imidazolines, Quaternary Ammonium , Compounds)

Physical characteristics solubility, emulsion, foaming, compatibility, thermal stability.

Selection of inhibitors static corrosion test, wheel test, flow test, misc tests.

Cathodic protection is effective in many situations except for H2S corrosion and CO2 corrosion.

Cathodic protection of metals is simply the addition of direct current applied to a metal in reverse of the natural flow (the anode becomes the cathode, the cathode becomes the anode).

The resulting current (if sufficient) makes metal loss impossible.

The formation of hydrogen gas at the metal surfaces further protects them from chemical attack. The resulting anode is sacrificed to the system by migration into the surrounding soils.

Alloying is the processing of mix two or more kinds of metals together (at least one kind of metal needed) to get better characteristics than sole metal.

Substitute and alloy with greater corrosion resistance for the alloy that has corroded.

Alloying element (Metallic or non-metallic elements such as aluminum, boron, chromium, cobalt, copper, manganese, nickel, silicon, titanium, tungsten, vanadium, zirconium, added in specified or standard amounts to a basae-metal to make an alloy).

Alloying elements have the capability to block slip panes.


Material Selection Example: Material selection for well

(http://www.sveis.no)

cge 654_lect 8_material selection.pdf

Documents