CanmetMATERIALS

Canada’s Natural Resources – Now and for the Future

Standard and Non-Standard Methodologies to Evaluate

Crude Oil Corrosivity Under Pipeline Operating

Conditions

Outline

Introduction

Internal Corrosion Control

Crude Oil Corrosivity under Pipeline

Transportation Conditions

Oil-Water Emulsion

Oil-Wet-Water-Wet Condition

Influence of Oil Phase on Water Phase

Recommendations for Consideration

Introduction

CANMET laboratories spread across Canada

CanmetMATERIALS is the largest research centre in Canada dedicated to metals and materials fabrication, processing and evaluation

CANMET laboratories have studied crude oil corrosivity under pipeline operating conditions since 1993

Over the past two decades about 100 crude oils have been used to understand their corrosivity under pipeline operating conditions

CanmetMATERIALS research contributed to the development of a new ASTM International Standard Guide (ASTM G205), which describes methodologies for determining the corrosivity of crude oil under pipeline operating conditions

Internal Corrosion Control Modeling

Prediction, mechanism, mechanistic models, and guidelines

Mitigation

Cleaning, corrosion inhibitors, biocides, and internal liners

Monitoring

Intrusive, non-intrusive, and inline Inspection

Maintenance

Equipment, workforce, data, and communication

Management

Risk

Most Corrosion Occurs by Electrochemical

Mechanism

Four things are needed

Anode: Sites where metal

is lost and electrons and

ions are produced

Cathode: Sites where

electrons are consumed

Metallic path: Conducts

electrons from anodes to

cathodes

Electrolytic path:

Conducts ions or source

for reactants

Metallic path

Ionic path

Electrolyte

Anode Cathode

Characteristics of Electrolyte

A liquid (sometimes a solid) that conducts

electricity by the flow of ions

The more ions the electrolyte has the higher its

conductivity and the higher the probability it

sustains corrosion

Seawater is conductive – sustains corrosion

Pure water is non-conductive – does not

sustain corrosion

Crude oil is non-conductive – does not sustain

corrosion

Internal Corrosion

Stage 3

Metal

Stage 4

Water

Stage 1 Stage 2

Metal

Oil Surface layer Repassivation

Oil Transmission Pipeline 99.5% Oil and 0.5% Water and Solid

Oil Phase Water droplets

Prediction of Corrosion in an Oil

Transmission Pipeline

Identification of locations susceptible to corrosion

Water accumulation

Oil phase – water phase interactions in those

locations

Locations for Water Accumulation

(Standard Methods)

NACE – SP0208 - Internal Corrosion Direct Assessment Methodology for Liquid Petroleum Pipelines

Lists several models to predict locations where water may accumulate

NACE TG 447

To develop a state-of-the-art report on flow and corrosion modeling and to provide guidelines for selecting appropriate

models

Locations for Water Accumulation

(Non-Standard Method)

Water deposition in heavy

oil transmission pipeline

modelled

Computational fluid

dynamics (CFD)

Near-wall velocity of flow

in heavy oil is significantly

lower than in light oil

(a) Light oil turbulence model

(b) Heavy oil turbulence model

(c) Heavy oil laminar model

(a)

(b)

(c)

X.Landry, A. Runstedler, S.Papavinasam, and T. Place,

Corrosion Journal (2012), “Computational Fluid Dynamics

Study of Solids Deposition in Heavy Oil Transmission

Pipeline” – Available online

Oil phase – water phase interactions

Emulsion

Liquid-liquid physical interaction

Wettability

Liquid-liquid-solid interaction

Corrosiveness of the Aqueous Phase

Liquid-liquid chemical interaction

Influence of oil phase on water

phase corrosivity

Emulsion Water Droplets

Oil-Phase

Water-in-Oil Emulsion Oil-in-Water Emulsion

Water-Phase

Oil Droplets

Low conductivity

(Non-corrosive

electrolyte)

High conductivity

(Corrosive

electrolyte)

Inversion Point

Emulsion Inversion Point Determination

Non-Standard Methods

Electrical

Microwave

Radiation Scattering

Spectroscopic

Ultrasonic

Density-based techniques

Viscosity-based techniques

Emulsion Inversion Point Determination (Standard Method: ASTM G205)

Electrical method

Emulsion Inversion Point

0

50

100

150

200

250

0% 10% 20% 30% 40% 50% 60% 70%

Water cut

Res

ista

nce

(K

-Oh

ms) 0

1

2

3

4

5

Inversion Point

Wettability – Contact Angle Method

(Standard Method: ASTM G205)

Wettability – Contact Angle Method

(ASTM G205)

Metal surface

Wettability – Spreading Method (ASTM G205)

Wettability – Spreading Method (ASTM G205)

Pins

exhibiting

high

conductivity

More than 15

of 20 pins

5 to 15 of 20

pins

Less than 5

of 20 pins

Wettability Water-wet Mixed-wet Oil-wet

Effect of Crude Oil on the

Corrosiveness of Aqueous Phase

What is the influence

of crude oil on this

water phase?

Preventive Inhibitive Neutral Corrosive

99.5% Oil and 0.5% Water and Solid

Effect of Crude Oil on the

Corrosiveness of Aqueous Phase -

Non-standard methods

Chemical analysis of fluids Acid number and water content were found

irrelevant to corrosivity

Optical spectroscopy

Iron concentration

pH, viscosity, and density Could not be correlated with corrosivity

Electrochemical measurement Unreliable

Microelectrodes

Conducting polymer method

Electrochemical quartz crystal microbalance

No Correlation between physical properties and crude corrosivity

(Non-Standard Methods)

0

1000

2000

3000

4000

5000

0 10 20 30 40 50 60 70Crude Oil Number

Wate

r co

nte

nt,

pp

m

0

1

2

3

4

5

Water Content

Acid Number

Ac

id N

um

be

r, , m

g K

OH

/g

.001 mpy

.001 mpy

.001 mpy

.001 mpy

Only 4 crudes showed somewhat measurable corrosion rate

Effect of Crude Oil on the

Corrosiveness of Aqueous Phase -

Standard methods ASTM G170: Guide for evaluating and qualifying oilfield

and refinery corrosion inhibitors in the laboratory ASTM G184: Practice for evaluating and qualifying oilfield

and refinery corrosion inhibitors using rotating cage ASTM G185: Practice for evaluating and qualifying oilfield

and refinery corrosion inhibitors using rotating cylinder electrode

ASTM G202: Test method for using atmospheric pressure rotating cage

ASTM D665: Test method for rust-preventing characteristics of inhibited mineral oil in the presence of water

NACE TM0172: Standard Test Method of determining corrosive properties of cargoes in petroleum product pipelines

Hierarchy of ASTM Standards

Standard Guide Provides general guide (ASTM G170)

Standard Practice

Prescribes procedure (ASTM

G184, G185, and G188)

Standard Test Method Prescribes procedure and expected

results (ASTM G202)

Precision developed based on round

robin tests

Based on 225 data points produced by

10 different laboratories around the

world (Canada, India, USA, and

Venezuela)

Bench-mark aqueous phase corrosion

rate established by round robin tests:

23 + 2 mpy or 0.58 + 0.05 mm/y

Rotating Cage

Corrosivity of Aqueous Phase in the

Presence of Different Crude oils

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Crude Oil Identification Number

Co

rro

sio

n R

ate

(m

py)

Inhibitive Crude Oil

Neutral Crude Oil

Corrosive Crude Oil

23 + 2 mpy

ASTM G205: Standard Guide for Determining

Corrosivity of Crude Oils

Emulsion

W/O

O/W

No Corrosion

Wettability

Oil-Wet

Mixed-Wet

Water-Wet

No Corrosion

Corrosivity of Brine in

the Presence of

Hydrocarbon

Less then 0.01 mpy (Preventive

Hydrocarbon)

Lower then Absence of Hydrocarbons

(Inhibitive Hydrocarbon)

No Change (Neutral Hydrocarbon)

Higher then Absence of Hydrocarbons

(Corrosive Hydrocarbon)

Reduced Corrosion

Aqueous Corrosion

Accelerated Corrosion

No Corrosion

Summary

No crude oil can sustain corrosion under pipeline

operating conditions

Absence of conductive electrolyte phase

Conductive water phase is required for corrosion to

occur

In the presence of water and oil phases three

properties should be evaluated

Emulsion

Wettability

Change in corrosivity of Aqueous phase by oil

phase

Recommendations

Crude oils should be tested as per ASTM G205

at the point of entry into the pipeline

Unless test shows that it is “neutral” or

“corrosive”, no new action is required with

respect to Dil-bit

Preventive

crude oil

Inhibitive

crude oil

Neutral

crude oil

Corrosive

crude oil

Contributions from

Jennifer Collier

Heather Dettman

Alex Doiron

Wally Friesen

Jean-Philippe Gravel

Xavier Landry

Sankara Papavinasam

Parviz Rahimi

Allan Runstedtler

Winston Revie

Bill Santos

Chao Shi