basic production chemicals

8/2/2019 Basic Production Chemicals

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This Handout....

Chemicals are one of the tools that can be used atan oil production or treating installation to solve aproblem, increase the production, give better waterquality or give a better quality of the oil or gas.Chemicals are being used in many processsystems, among them:

Water Injection Oil & gas production Gas separating & dehydrating Utilities etc..

There is almost always a large stock of variouschemicals on the installations, each dedicated toa particular purpose. Therefore specialized productsare necessary to ensure that they

are optimally effective are being used in a safe way are being used in an economical way

This handout describes chemical treatmentof all types and gives a short description of typicalproperties for each chemical.


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Why Are Chemicals Needed?

Production of oil, gas and water:

The oil can contain wax, asphaltenes and other

solids.

Water can cause corrosion in process equipment and

pipe lines, precipitation of salts, and give emulsionwith oil.

Gas can cause foaming, and corrosion due to CO2 or

H2S.

These problems are

solved with correct

design or USE OF

CHEMICALS.


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This group of chemicals are used when theprocess equipment is not functioning properly,or there are problems such as scale, corrosion,foaming or emulsions.

Again, these chemicals are divided into watersoluble and oil soluble, depending upon inwhich phase they are to be used.

All chemicals that are supplied and used shallhave approved safety data sheets, and

complete environ- mental documentation.

Typically, topside process chemicals mayinclude:

Anti foam Emulsion Breaker Scale Inhibitor Corrosion Inhibitor Wax / Asphaltene inhibitor Flocculant Microbiocides

Process ofOil and Produced Water


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Where do problems occur inoil production ?

Perforating zone/

Production

tubing:Scale

Wax

Asphaltenes

Topside

Process:Emulsions

Foam

Scale

Corrosion

Utility:Scale

Corrosion

Water injection:Scale, Corrosion,

Bacteria growth

Water to sea/

Produced water:Scale

Corrosion

Oil content

Export:Wax

Water

Hydrates


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Scale dissolver:In production tubing / flow line, acids are normally used

to remove calcium carbonate. For barium sulphate,sequestrants (Scale Dissolvers) must be used.

Acids:Depending of the steel quality the acid and inhibitor that

effectively removes the carbonate scale, but at the

same time shows acceptable corrosivity against thesteel quality must be defined and blended.

Examples of acids are: hydrochloric acid, phosphoric acid,

nitric acid or citric acid. Process specific corrosion

inhibitors are required.

Sequestrants:Are normally used to remove/dissolve sulphate scale.

The chemicals are often based on EDTA or its homologs.

They do not release gas or give a noticeable exothermicreaction. These are more generic.

Well and flow line


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Hydrate Inhibition:Normally methanol is used to avoid hydrates inpipeline, or when starting or closing a well.

Methanol is toxic and flammable and must behandled with care.

To overcome the HSE issues of methanol neweasily handled chemicals are applied. Thesechemicals are specific for each type of process anddistribution system

Well and flow line


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Crude oil is a geographically unique and complexsubstance, that is formed under high pressure andtemperature. An infinite mixture of organic chemicalcomponents exist in light, paraffinic, or heavy oils.These include, waxes up to C60, esters, organic acids,asphaltenes and napthalenes.

Depending on the make up of the above components,

the crude oil has its own specific characteristics suchas, specific gravity, wax content, pour point, colour, etc.

The crude oil can cause a series of problems such as:-

Wax deposition Emulsion problems

Residual Oil in Water problems

North Sea oil Texas oil Utah oil

Oil Processing


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WaxWax is present in most crude oils at normally < 5%. In thePacific Rim wax content ranges from 10 to 60%. Wax isdetected by industry specific analytical methods (IP) andnormally represents that fraction of the oil with carbon

number C-18 to C-60.

Wax crystals are formed when the oil is cooled, inconnection with production from the wells.

. Subsea pipelines

Heat exchange

The wax crystals form at

specific temperatures(wax appearance point).

Methods to avoidwax precipitation

Heat

Solvents (e.g. xylene) Wax inhibitors

Mechanical equipment

No of CarbonAtoms

Melting point,Celsius

16 18

17 22

18 28

19 35

20 37

23 50

25



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Wax inhibitors modifies the structure on the growing crystal, eitherby co - crystallization or by absorption to the surface of the waxcrystal Further growth will then be stopped

Inhibit further3D growth

H3C-(CH2)N-CH3

Higher alkanes (n,iso,cyklo-)Deposit and forms tick, firm layerof wax at specific conditions

Depositions

treatment withwax inhibitors

Modifying ofwax crystals

treatment withdisperssents orsurfactants

Wax crystal

Wax particles

Keeps the waxparticles

dispersedin the oil phase

Wax inhibitors

Pipeline and Process


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AsphaltenesAsphaltenes are present in most oil, and is mainlyresponsible for the black colour of the oil. Chemically

asphaltenes can be described as very complex

hydrocarbons with a ring structure. They are charged

molecules, and therefore they can agglomerate due to

electrochemical binding mechanisms. Asphaltenes are

defined as the hydrocarbons that are not soluble inpentane - C5.

Asphaltenes deposit during production afterthe following process changes:-

Physical effects as pressure drop

Cooling Mixing of oil from several wells/formations.

Typical molecule -structure of anasphaltene molecule



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Emulsions

Emulsions are defined as one phase dispersed in another

Emulsions are dynamic, they change with operating conditions.There are two types of emulsions

Water in oil emulsions (WIO)Oil in water emulsions (OIW), or reverse emulsions

Oil will easily emulsify with water, when the followingconditions are present:

Energy - normally pressure loss over the choke orvalve and mixing in a high shear pump

Emulsifier - normally a chemical component in the

oil or other substances such as wax, solids etc.Separators are designed for separation of oil, gas, and water,

but if an emulsion is formed. To help the separation process,we use;

HeatChemicals (emulsion breaker)Chemicals (flocculants)

Typical example of thebreaking of an emulsion



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Mode ofoperation

Reduces the surface tension on the microwater droplets. These will then coagulate toform larger water droplets and fall out of theoil. They separate the water from the oil and

give a sharp clear interface

Typical injectionpoint(s)

Normally they are injected as early in thesystem as possible. If that's not possible,increased dosage rate may compensate forthis.

Typical dosagerate

Normal dosage rate for emulsion breakers isin the area 5 - 25 ppm based on total flowRate (oil + water). Some heavy crudesrequire much higher doses

Typical physicaldata

Flash point > 63 0CViscosity: 20 - 100 cP depending of the

temperature and solvent

Emulsion Breaker



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Emulsion breakers are used when the naturalseparation of oil / water is not satisfactory.

Water - in oilemulsion

Demulsifier

Treatment

Surface activepolymer

Separation ofoil and water

Emulsion breakers are formulated for each process.Because the process of oil changes with time (caused bynew wells, increased water cut, etc.) the system specificemulsion breakers must be optimised from time to time.Emulsion breakers are made up of three to four activecomponents in a solvent system.The active components normally consist of polymers, ofesters, polyols, block polymers and other surface activepolymers.Total active content of an emulsion breaker is usually 30- 40 %, but dosage rates are calculated as ppm ofproduct.

ProcessOil and Produced Water


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Gas Hydrates

1m3 of hydrate contains 150

m3 of methane. Hydrates canbe avoided by injection ofmethanol or glycol, and thesame chemicals can be usedto dissolve ice plugsMethanol is very toxic and

very flammable. Safehandling procedures must beimpressed upon the customer.Be careful!

Generally

Methanol is very flammable. Flash point -16 0C.

Neutralizing amines and alkanolamines are often irritatingTo skin and have a sharp smell

Most corrosion inhibitors are toxic to marine life

Hydrates start forming even at moderate pressure andtemperature below 10 0C. Hydrates are snow-like crystalsthat are build up of methane and water. This hydrocarbon icecan plug pipelines and destroy process equipment.


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