Corrosion of Petroleum Industry[1]

8/20/2019 Corrosion of Petroleum Industry[1]

1/21

Corrosion in

Petrochemical

Industry

Group 1

Dong

Ji


2/21


3/21

Corrosion Accidents

• 1. Pollution by Oil Pipeline Releases

• 2. Critical

Pollution

by

Corroded

• 3. Corrosion in the Petroleum Extraction


4/21

Pollution by Oil Pipeline Releases

• According to

an

Environmental

Defense

Fund

(EDF)

engineer, the average amount of oil released from a

pipeline spill in 1998 was over 45,000 gallons.

• Since 1995, the overall amount of oil released to the

environment has increased each year.

•

An

average

of

tens

of

thousands

of

gallons

of

oil

was

released from pipelines approximately every other

day throughout the 1990s.

• Corrosion is

the

most

common

cause

of

pipeline spills.


5/21

Pollution by Corroded Pipeline

• In the winter, 2001, 92,000 gallons of

saltwater and

crude

oil

onto

Alaskan

tundra

from corroded pipeline.

•

The

spill

was

apparently

caused

by

corrosion

in a 10‐inch pipe.


6/21

Corrosion in

the

Petroleum

Extraction

• There could produce 300t oil and 100,000m3

national gas

in

the

No.

58

oil

well

in

Huabei

Oil‐field before.

•

3.1%

of

the

oil

was

water

and

42%

of

national

gas was CO2

• But after 18 months, it had to be closed

because of

the

corrosion

of

iron

pipe.


7/21

Corrosion Mechanisms

• 1. Electrochemical Corrosion

• 2. Chemical

Corrosion

• 3. Mechanical and Mechanical/Corrosive Effects


8/21

Electrochemical Corrosion

Crevice Corrosion

Much metal

loss

in oilfield casings is caused by

crevice corrosion.

In the crevice, metal is in

contact with

an

electrolyte, but does not have

ready access

to

ox en.


9/21

Chemical CorrosionHydrogen

Sulfide,

Polysulfide

and

Sulfur

Hydrogen sulfide

[H2S]

when dissolved in water,

is a weak acid and,

therefore, it

is

a source

of

hydrogen ions and is

corrosive.The corrosion products

are iron sulfides [FeSx]

and hydrogen.


10/21

Chemical Corrosion

Carbon Dioxide

Like H2S,

carbon

dioxide

[CO2]

is

a weakly

acidic

gas and becomes corrosive when dissolved in water. However , CO2 must hydrate to carbonic

acid [H2CO3]

—a

relatively

slow

Process—before

it becomes acidic.

The corrosion product is iron carbonate (siderite)

scale.

CO2 + H2O + Fe →FeCO3 + H2


11/21

Chemical Corrosion

Strong Acids

Strong acids

directly

chemical

attack

to

the

equipment.

Strong acids

are

often

pumped

into

the

wells

to

stimulate production by increasing formation

permeability in the near wellbore region.

For limestone

formations,

5 to

28%

hydrochloric

[HCl] acid is commonly used.


12/21

Chemical Corrosion

Biological Effects

The most

important

biological effect is the generation of H2S by

sulfate‐reducing

bacteria

(SRB). These anaerobic bacteria metabolize

sulfate ions

and

produce

hydrogen sulfide.


13/21

Chemical Corrosion

Oxygen

Oxygen can

enter the mud system at many

points.But oxygen is not normally

present in

oil

industry. It is only at the drilling stage.


14/21

Mechanical and Mechanical/Corrosive

Effects

Cavitation( 空腐蚀

This type

of

metal

loss

is

due

to

high

‐pressure

shock waves, generated from the collapse of

minute bubbles in high‐velocity fluids impinging

on nearby

metal

surfaces.

Cavitation

metal

loss

is usually found on pump impellers developing

too

low

a

suction

pressure.


15/21


Effects

Corrosion

Fatigue

This results

from

subjecting

a metal

to

alternating stresses in a corrosive environment.

Eventually this leads to crack initiation and crack

growth by

a combination

of

mechanical

and

corrosive action.

Because of this combined action, corrosion fatigue

is

greater

at

low

stress

cycles

that

allow

time for the corrosion process.


16/21


Effects

Sulfide

Stress

Corrosion

Production of

hydrogen

results from sulfide stress

cracking (SSC).

SSC occurs when a susceptible metal is under tensile stress

and exposed to water

containing hydrogen sulfide or

other sulfur compounds.


17/21


Effects

Stress

Corrosion

Cracking

(CSC)CSC is an example

of broad range of

stress‐corrosion

cracking, defined

as

corrosion

accelerated by

tensile stress.


18/21

Protection1. Mud remaining noncorrosive;

2. Maintaining

high pH

3. Oxygen scavengers

4. Corrosion control

of

CO2


19/21


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21/21

Thanks!

Documents

Corrosion of Petroleum Industry[1]