Umitek - Inhibitor Selection Deployment

8/13/2019 Umitek - Inhibitor Selection Deployment

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I P S A

Corrosion Inhibition

Issues associated with selection and deployment of

corrosion inhibitors


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2

Organic Film Forming Inhibitor

Mechanism

H

Inhibitor molecule

dispersed in processstream

Metal

Process Stream

HC

N

H H

HH

HHH H H H H H H H H H H HC C C C C C C C

N N

N

NNNNNN

Chemisorption & physicaladsorption by polar amine group

HydrocarbonOil molecule

Hydrocarbonchain “ R”


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3

Adsorption

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60

Concentration

c o v e r a g e , c o

r r o s i o n r a t e

coverage

corrosion rate


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4

Oil Field Corrosion Inhibitors

Primary Amine

Amide

Imidazoline

Quaternary

Ammonium Ion

Polyethoxylated

Amines

R CH 2 NH 2

R1 CH2 C NH R

O

N

NCH2 CH2 CH2 NH2R

NCH2

CH3

CH3

R N

O CH2 CH2 OHn

O CH2 CH2 OHn


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5

Typical Composition

1/3 Active

Ingredients

2/3 Solvents

or additives

Inhibitor Package

6 I hibit


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6 Inhibitor

Selection

Strategies

Decision

Process

leading to

Corrosion

Inhibitor

Selection

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Inhibitor Selection Strategies

Planning – define the objectives of the inhibition programme.

Corrosivity and Hydrodynamic Assessments – use of field

chemical data, corrosion prediction models, hydrodynamicmodelling, guidelines and field experience.

Inhibition Risks – need to address issues concerned with highCO2 / H2S concentrations, high temperatures and unusual

brines. Inhibitor Selection Process – aim is to choose the best

inhibitor, in terms of performance, economics, business needs,etc.

Inhibitor System Design – this includes design of the injectionsystem, including secondary containment, identification of themonitoring needs and selection of the monitoring method(s).

Operation and Maintenance Issues – identification of

personnel with responsibility for day-to-day operation of theinhibition system, training of personnel.

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Corrosivity Assessments

Typical desktop studies aim to clarify major

corrosion issues:

Fluid Chemistries

Hydrodynamic Considerations

Predictive Models

Inhibition Risks

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Operating Information needed for Facility

Design DecisionsParameter Common Units or Comments

Total pressure BarTemperature

maximum, range

°C

Flow rates:OilGasWater

m3/day

m3/day

m3/day

Sand production: Kg/dayGas composition

CO2, H2S, O2 mole %Water composition:

Full cation and anion AnalysisPHVolatile organic acids

mg/L

Type and concentration

Hydrocarbon phaseoil or condensateviscosity

ASTM boiling point

CP or ° APIEquipment to be protected Downhole, surface, pipelines, onshore, offshore Age and condition New-old, clean-dirtyCorrosion allowance Proposed or remaining (mm)Estimated corrosion rate mm/yr.

Environmental concerns Regulations, HSE policy Accessibility to area Possibility of repairs and monitoringPigging capabilities Only for pipelines and some gathering lines / flowlines

Business risk Conse uences of failure to business strate

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Hydrodynamic Considerations

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Typical Inhibitor Selection Process

Start

reviewcorrosivity

screening tests

final tests

select

candidates for

testing

past

experience

identify

candidates

final selection

suppliers

recommended

compatibility

Data base

Suppliers

Lab data

commercial,business

issues

pressure,

temperature flowother factors

determine testrequirements

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Vendor Recommendations

Expected uninhibited and inhibited corrosion rate inthe proposed application

Recommended concentration and application method

Laboratory test data

Practical method for quantitative determination of the

inhibitor in field fluids if required Physical and chemical properties of the product(s)

Information on environmental acceptability, toxicity

and biodegradability Oil/water partitioning data if appropriate

Compatibility with non-metallic components such as

elastomers

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Physical Property Tests

Main physical / chemical properties:

Solubility of corrosion inhibitor in the carrier media(oil, water, glycol)

Partitioning / phase distribution between aqueous

and hydrocarbon phasesEmulsion tendency

Foaming tendency

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Oil / Water Partitioning

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

water cut %

I n h i b i t o r C o n c ( p p m

)Conc in water

Conc in oil

Theoretical effect of water cut on inhibitor partitioning for a

preferentially water soluble inhibitor (partitioning coefficient = 2)added at 28ppm on total fluids.

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Partitioning Tests

Equilibrium

Allow HC and aqueous phase to equilibrate – testin aqueous phase

DynamicStudy rate of inhibitor transfer from HC to aqueous

phase

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Eff f P C i i


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Effects of Parameters on Corrosivity

and Inhibitor Efficiency

Parameter Corrosivity Inhibition

pp CO2 Large MediumTemperature Large Large

Flow Medium Small - Large

pH Medium Large

Oxygen Small LargeH2S Large Large

Calcium, Mg etc Small Possibly Large

Organic Acids Possibly Large Small ?

Brine components Small Possibly Large

Metallurgy Small ? Possibly LargePre-corrosion Small / Medium Possibly Large

Hydrocarbon Medium Possibly Large

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Test Environments

As close to real as possible

Brine composition

pp gases

Temperature

Flow rateMetallurgy

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Bubble Tests

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Standard Rotating Cylinder Cell

Thermocouple

pocket

Glass

vessel

Specimen

Counter

electrode

Luggin

Gas out

Shaft

Gas in

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Jet Impingement

Pt

Electrode

Luggin

capillary

QVF

Flange

QVF

Flange

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Inhibitor Persistency

What happens if inhibitor supply isinterrupted?

How quickly does rate return to uninhibited

rate?

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Loss of Performance after Depletion

Quaternary Amine at 20 ppm

1.000Inhibitor

Addition

Depletion

0.100

C o r r o s i o n r

a t e ( m m / y )

0.010

0 5 10 15 20 25 30 35

Time (h)

40 45 50 55 60 65

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Example of Good Persistency

Carboxylate - Amine at 20 ppm

1.0000

C o r r o s i o n r a t e ( m m / y ) Inhibitor

Addition

Depletion

0.1000

0.0100

0.00100 10 20 30 40 50 60 70 80 90

Time (h)

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Preferential Weld Corrosion (PWC)

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Cause of Preferential Weld Corrosion

Complex issue influenced by many factors

Differences in weld / parent material composition.

Weld procedure

Microstructure

Corrosion product film formationFlow

Environment conductivity

Inhibitors

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Effect of Inhibitor on PWC

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Weldment Sectioning

10mm

3mm

Flange

or pipeFlange

or pipe

HAZ

PipePipe

HAZWeld

metal

10mm

P2P1 H2H1W

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Consequences of Inadequate Dosing

-0.1

0.4

0.9

1.4

1.9

0 10 25 50

Inhibitor Concentr ation

C o r r o s i o n r a t e ( m m / y e a r )

P1

H1

W

H2

P2

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Inhibitor Deployment re PWC

Early deployment of CI is essential where

there is a risk of PWC Overdosing in the early weeks of operation is recommended

For systems already suffering PWC:

Increased dose rates recommended Inhibitor availability extremely important

Inhibitor optimisation should be carried out

using a weldment probe ER probe with weld metal element

Segmented probe with appropriate measurement technique

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Compatibility

Compatibility of the corrosion inhibitor with:

The production fluidsOther chemicals

Downstream processing of produced fluids (e.g.

oil/water separation) All materials in the injection and production

systems (such as elastomers, seals, liners)

The environment (environmental "friendliness" ondisposal/export)

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Key Points Testing

Lab tests tend to use simulated brine but it is

important to use ‘real’ hydrocarbon samples.

Use representative grade of steel

Use two corrosion rate methods, typically

linear polarisation or impedance

Use CO2 / N2 or CO2 / H2S / N2 mixtures to

simulate the gas phase

Use wall shear stress to simulate flow

conditions

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K P i S l i


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Key Points Selection

Develop a clearly defined inhibitor selection

strategy for use in various production

environments.

Test protocols for screening should address

the required key performance parameters.Check on compatibility with components and

other chemicals / fluids.

Optimise dose rates in the field


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I P S A

Deployment of Inhibitors

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Typical Field Concentrations of


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Typical Field Concentrations of

Corrosion Inhibitor

Location Corrosion inhibitor dose

based on total Fluids (ppm)

Oil Well 20 –50

Gas production 10- 20 l/m3 of gas

(100 based on total water)

Infield oil line 20 – 50 (100/300 in high vel water)

Short oil transport line 15Long oil transport line 30

Long gas transport line 2 pint/MMSCF

Extreme Cases

Hot, deep gas well 2000

50% H2S gas line 1000

V high velocity, high water oil line >300

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C i Ri k C t (BP)


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Corrosion Risk Category (BP)

RiskCategory

MaximumRequired

Availabi li ty

Max.ExpectedUninihb.Corr. Rate(mm/yr)

Comment

ProposedCategory

Name

1 0% 0.4 Benign fluids, corrosion inhibitor use notanticipated. Predicted metal loss may beaccommodated by corrosion allowance.

Benign

2 50% 0.7 Corrosion inhibitor probably required but withexpected corrosion rates there will be time toreview the need for inhibition based on inspectiondata.

Low

3 90% 3 Corrosion inhibition required for majority of fieldlife but inhibitor facilities need not be availablefrom day one.

Medium

4 95% 6 High reliance on inhibition for operational lifetime.Inhibitor facilities must be available from day oneto ensure success.

High

5 >95% >6 Carbon steel and inhibition is unlikely to provideintegrity for full field life. Select corrosion resistantmaterials or plan for repairs and replacements.

Unacceptable

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Summary of Monitoring & Inspection Requirements for Pipelines


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Corrosion

Inhibition

Risk

Overall System

Requirements

Inhibitor Injection

System

First

Inspection

Schedule

Monitoring of

Subsea lines

Category 1 Does not rely oncorrosion inhibition.

No requirement Inspection

determined by

previous

operation of

similar systems.

Process monitoring of

fluids.

Category 2 Inhibition not used inearly life but is available

when conditions change,

i.e. increased water cuts

Commissioning without

shutdown

As category 1 Standard inspection

techniques at accessible

points.

Category 3 Inhibition not availabledue to logistics problems

but must be operated as

soon as possible.

Commissioned as soonas practical and

incorporate level device

and flow monitor into

injection system.

Early inspectionas determined

by anticipated

corrosion rates.

As category 1 plusweight loss coupons,

ER / LPR probes and

occasional intelligent pig

runs.

Category 4 Corrosion control workingon day one. Inhibitor anddose rate pre-selected

As category 3 As category 3 As category 2 plus FSMor UT mats system.

Continual logging for all

monitoring devices.

Category 5 Assumes technical, SHE

& financial factorsanswered satisfactorily

Requirements as

category 4

As category 3 As category 3 As category 3 plus

increased inspectionfrequency.

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Inhibitor Efficiency and Availability


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Inhibitor Efficiency and Availability

Target acceptable corrosion rate to giverequired system life

Inhibitor “availability” must also be taken intoaccount

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Availability Approach


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Availability Approach

Assume a certain corrosion rate when

inhibitor added (e.g. 0.1 or 0.05 mm/y)

Assume uninhibited rate when inhibitor not

added

Emphasises that inhibitor downtime is critical

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Deployment Considerations


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Deployment Considerations

Injection System Requirements

Storage and Injection System

Monitoring and Data Acquisition

Analysis and Information System

Management of Inhibition Programmes

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Injection Location


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Injection Location

W E L L H E A D

F L O W L I N ES

M A N I F O L D

B

D

RESERVOIR

OIL

GAS

H2O

CO2

H2S

SAND

A

C

E2

E1

SEPARAT OR

SLUGCAT CHER

T ANKAGE

TRUNKLINE/

PIPELINE

TRUNKLINE/

PIPELINE

water disposal

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Continuous InjectionContinuous Injection


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Continuous InjectionContinuous Injection

Injectionpump

Chemicalreservoir

Pipeline

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Main Disadvantages of Continuous


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Injection Downhole

Slugging of inhibitor

Plugging of the valves

Large inhibitor inventory

Long residence time

Risk of killing the well

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Squeeze Treatment


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Squeeze Treatment

Casing

Displacing

Fluid

Tubing

Inhibitor

mixture

Packer

Perforations

Inhibitor

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Tubing Displacement Treating


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Method

Displacing

fluid or nitrogen

Inhibitor

mixture

Oil

Perforations

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Injection systems typically comprise:

Storage tank

Mixing tank, if product is to be diluted

Injection pumps and connecting lines

Injection ports, quills, valves

Control equipment – valves, gauges, instrumentation

Secondary containment to capture leaks and spills

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Storage TankStorage Tank


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Storage TankStorage Tank

Injectionpump

Chemicalreservoir

Pipeline

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Corrosion Inhibitor Pumping Problems


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Corrosion inhibitor fluid problems:

inhibitor viscosity

compatibility of inhibitor with pump materials

line blockages inhibitor storage tank empty

abrasive particles in inhibitor

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Pump and hardware problems :

wrong dose rate

pump wrongly sized

air lockspoor delivery system design/installation

dosing downhole

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Quality Control of

Corrosion Inhibitor


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Supplies

Comparison of

NMR Spectra

for TwoSamples of a

Corrosion

Inhibitor

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Injection Quill in a Pipeline


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Injection Quill in a Pipeline

PUMP

ACCESS

FITTING

PIPE

QUILL

FLOW

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Monitoring and Data Acquisition


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o o g a d a a cqu s o

Data collected to aid system performance evaluation:

Inhibitor injection data

Corrosion monitoring data Inhibitor residuals

Condition monitoring

Production rates and conditions System upsets

Financial data

Maintenance data Water chemistry

Inspection data

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Corrosion Inhibitor Dose Record


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Failure to meet target of injection rate limited the pipelinelife

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Typical Monitored Process Parameters


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yp

Parameter Effect Action

Flow rates

(oil/gas/water)

+ or - Alter corrosion inhibitor delivery rate to

maintain concentration

Water cut + or - Could increase or decrease inhibitor

delivery depending on the oil/water

partitioning properties

Temperature + Increase [CI] but scope to reduce [CI] if

protective carbonate films occur

pH + or - Scope to reduce [CI] or increase [CI],may need to reselect

Sand + Reselect CI and/or increase [CI], reduce

velocity, install downhole sand screen

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Inhibition System - Data Storage,



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Inhibited corrosion rates – on-line data is compared withoperational data on fluid chemistry/bio-chemistry, inhibitor residualsand inspection data (check out initial predictions of corrosion rates and

changes with time)

Changes in wall thickness – obtained through inspectionrecords

Inhibitor consumption – obtained through injection data

Impact on operations – obtained through feedback fromoperations and downstream experience

Mechanical/maintenance performance – obtained through

maintenance feedback of records/costs On-line availability – obtained through on-line monitoring and

maintenance inspection records


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Monitoring methods used in

corrosion inhibition


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corrosion inhibition

Iron counts (regular chemical analysis to provide trends)

Coupons (weight loss & detection of pitting/scales/bio-films)

Insert probes electrical resistance/modern versions

electrochemical - linear polarisation resistance / electrochemical

impedance / electrochemical noise / galvanic coupling)

Hydrogen patches/probes (electrochemical, beta foils)

FSM (field signature method)

Ultrasonic strips (UT Mats)

Erosion/sand probes Radiochemical

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Data Storage, Analysis and Information System


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Inhibited corrosion ratesChanges in wall thickness

Inhibitor consumption

Impact on operations

Mechanical/maintenance performance

On-line availability Human factors

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Effective Management for Corrosion

Inhibition Programmes


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Inhibition Programmes

Stated aims to include:

Agreed strategies/policies

Procedures for activities from design to abandonment

Assessments of risks & management of mitigation procedures

Agreement of responsibilities and identification of personnelauthorised to carryout actions

Development of appropriate organisational structures, teams and

reporting routes Effective deployment of resources, including budgets, in-

house/alliance personnel and contractors

Procedures for the management of change - change in process

conditions and personnel Use of key performance indicators for all activities

Defined and regular updates based on reviews and audits and

Personnel to be nominated as procedure owners

59 Independent AuditScheme that Ensures

I tGetting it

Health &Safety,

Integrity &C i


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Improvement

No leaks or emissions20% annual reductionsReduce/elimivate emissions

Assess skills and competenceDefine roles & responsibilitiesEnsure co-operation & communication

Identify hazards & assess risks Agree targets, processes & systemsSet standards for measuring performance

Review activities & trendsCheck for complianceLearn from experience & make changes

Clear Polic ies& Objectives

Getting itRight

OrganisationalStructure &

Responsibilities

Planning, Procedures &

Implementation

Yes No

Review of Data& Performance

CorrosionIssues

Meetingthe control

criteria?

Independent Audi t

Proactive

Reactive

measurement using regular checks to show controls are working

measurement identifies whyperformance was substandard

MeasurePerformance

Reports

used to achieveimprovements

Reviewsused to provide

correction

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Inhibitor Review Meetings


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Information to be reviewed at Corrosion Team

meetings:

oil, water, gas production rates; inhibitor consumption and expenses;

inhibitor performance results;

inspection results, if available;

operational upsets, related to chemical usage;

safety and environmental incidents, concerns and results,

related to chemical usage;

maintenance and reliability issues;

ideas for improvements: how to reduce costs, improve HSE

performance.

Documents

Umitek - Inhibitor Selection Deployment