Core Laboratories (U.K.) Limited Analytical Chemistry ...

Core Laboratories (U.K.) LimitedAnalytical Chemistry Laboratory

DEPOSIT, SCALE & DEPOSIT, SCALE & SLUDGE ANALYSIS

DEPOSIT, SCALE & SLUDGE ANALYSIS

Why do we perform deposit analysis ?

From the deposit composition the mechanism for the formation may bederived.

It may also be possible to decide upon a chemical or mechanicalprocedure for removal of the deposit and prevent any reoccurrence.

Scaled Pipe Debris from Bailer Run Particles in Filter


Solids/sludges can be extremely varied and only through experience andby seeing the sample can the most appropriate analysis route be selected.

Analytical options include:

• Wet chemistry

• SEM/EDX

• XRD

• GC Fingerprint

• FTIR


Upon receipt of samples, they are booked into a database.

Prior to commencing any analysis, the radioactivity level is determined.


Initial Naturally Occurring Radioactive Material (NORM) Screening

Sample Received

NORM Check

Exceeds Safe Working Limit – No Analysis

Performed

Continue AnalysisWith Special NORM

Precautions

Continue AnalysisNo Special NORM

Precautions

Equal to Background (less than 3 cps)

cps = counts per second

3 to 500 cps

> 500 cps


If it is safe to proceed, then some rudimentary tests are performed.

• Check for Magnetic properties• Qualitative Carbonate test (adding drops of acid)• Qualitative Sulphide test (check for odour & moist lead acetate

paper on gas from acid addition)• Take digital photograph of sample “As Received”, prior to sample

preparations (see examples overleaf)• Record visual description:

Initial State Hardness Colour Sizes Extraneous MatterWet Hard Brown Wax Metal fragments

Moist Soft Dark Grey Flakes Paint flakes

Oily Sticky Black Fines Rubbery chunks

Dry etc Chunks etc


Corrosion Products(Mainly Iron)

Organic (Wax)

Proppant & NaCl

Calcium Carbonate

Corrosion Products(Mainly Iron)

Barium Sulphate & Strontium Sulphate

Calcium CarbonateCalcium Carbonate


Before & After Cleaning Photos: Napthenate

Oily hard/brittle brown chunks

Hard/brittle brown chunks


Before & After Cleaning Photos: Organics + Man-made Materials

Damp brittle brown large and small flakes

Pale brown fines. Extraneous fabric/rubber removed


Initial Screening

Sample Received

Low NORM

Is sample Water Wet ?

No Is SampleOil Wet ?

% Water content by Loss On Drying

Organic Testing: • FTIR spectroscopy• Wax content• Asphaltene content• GC analysis

% Oil content by Solvent Extraction

Yes

Deposit AnalysisNo

Yes

Optional Analyses


If the sample is “Water Wet”, it is weighed and placed in an oven set at105°C then cooled in a dessicator and re-weighed.

The moisture content of the sample is calculated based on the % weight“loss on drying”.


If the sample is “Oil Wet”, then quantification of the % oil contamination isdetermined by % weight loss after performing toluene and acetonesolvent washes on the sample followed by drying in a dessicator.


If the sample is “Oil Wet”, then - if necessary - some of the followingoptional organics tests may be performed:

• Wax content (n-alkanes C17+) measured using modified UOP 46

• n-C7 insoluble Asphaltene content measured by modified IP 143

• Fourier Transform Infra-Red (FTIR) spectroscopy

• Gas Chromatography Fingerprint Analysis by modified IP 318method utilising high resolution capillary gas chromatography


Fourier Transform Infra-Red (FTIR) Analysis

FTIR analysis is a technique looking at bond vibrations and is especiallygood at identifying chemicals and organic solids and liquids.

megName Description

4000 6503500 3000 2500 2000 1500 1000

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1032.68cm-1

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860.47cm-1

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3294.03cm-1

2937.17cm-1

2874.43cm-1

1411.81cm-1

1455.38cm-1

1331.86cm-1

1204.68cm-1

1257.36cm-1

Monoethylene Glycol


Gas Chromatography Fingerprint Analysis

GC analysis is good at determining a hydrocarbon distribution anddifferentiating crude oil and petroleum products.EOG Resources - Conwy Pig Wax (10,1) abz_htliq_1_testing,abz_htliq_1.041_blnk_ref s_sample,10,1,1

Acquired 05 December 2017 20:49:15 ACL 2017 04515

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72


Deposit Analysis Flowchart

Clean, DrySample

Loss on Ignition

Are Solids Organic ?

ICP Analysis of Acid Extract

Optional FTIR,GC or HTGC Analysis

Yes

Optional SEM/EDX Analysis

No Acid Soluble Content

Silica Content

Optional XRD Analysis

Water Soluble Content

ICP Analysis of Water

Melt

Acid Insoluble Content

ICP Analysis of Acid

Melt

Acid Fusion


Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis

SEM is used to determine the morphology of any solid material. EDXanalysis is used in conjunction with SEM to produce a semi-quantitativeelemental composition of the same solid material.

It can also be used if only small amounts of solids are present (few mg).


Example Scanning Electron Microscopy Images

Polymer Backing

Rust & Mercuric Sulphide

Ceramic Fibres

Pyrite Pyrite –– Iron (IIIron (II) Iron (II) Disulphide


X-Ray Diffraction Analysis

XRD is used to determine the exact crystal structure of compounds anddifferentiates between different structural states of crystalline compoundsand minerals (e.g. different states of CaC03 for calcite and aragonite ordifferent oxidation states of iron for FeO, Fe2O3, Fe3O4, etc).

Non-crystalline (amorphous) material is not detected.


Loss On Ignition

A subsample is weighed in aplatinum crucible and ignited in aBunsen burner.

The ashing process completed bytransferring into a muffle furnacemaintained at 750°C, then cooled ina dessicator and re-weighed.

A high “Loss On Ignition” indicates the presence of Wax (hydrocarbons),Calcium Naphthenate, Sodium Polacrylate, Polymers, Chemical Residues &Biomass (bacteria).


FTIR analyser compares the spectra with a database of thousands ofknown samples.

Fourier Transform Infra-Red (FTIR) Analysis


HTGC can identify and quantify a n-alkane hydrocarbon wax distribution.

High Temperature Gas Chromatography Analysis


The acid soluble material is dissolved in hot 50% hydrochloric acid.

A high acid solubility indicates the presence of Salts (water soluble),Corrosion products (including iron sulphides), Calcium Carbonate, CalciumSulphate (partial solubility but predominantly acid soluble) and StrontiumSulphate (partial solubility).

Acid solubles tend to be salts such as MgCl and NaCl (e.g. often from gaswells in Southern North Sea where the gas strips out water from the highsalinity formation waters to leave salt residues).

Inorganics: Acid Soluble Content


Inductively Coupled Plasma Analysis

ICP is a technique which determines the concentrations of elementsrather than compounds. Therefore a factor must be used to determine theweight % of compounds based upon the elemental % and the most likelycompounds present.

For example:

Calcium x 2.5 = Calcium CarbonateSodium x 2.54 = Sodium ChlorideIron x ~1.4 = Iron oxide

An interpretation of the deposit results is always presented at the bottomof the report page.


The residue is boiled in 40% hydrofluoric acid on a hotplate until dry. Thecrucible is then heated with a Bunsen flame to ensure complete removalof the hydrofluoric acid and cooled in a dessicator.

This process is repeated until a constant weight is achieved.

The % weight loss corresponds to the Silica content.

A high Silica content indicates the presence of sand (quartz SiO2) & clay.

Inorganics: Silica Content


The residue is mixed with potassium carbonate and sodium carbonate andheated to 1000°C+. When allowed to fuse with a sample containingbarium sulphate or strontium sulphate (which is insoluble in hydrochloricacid), the reaction is as follows:

Na2CO3 + BaSO4 Na2SO4 + BaCO3=

K2CO3 + SrSO4 K2SO4 + SrCO3

The crucible is then heated over a Bunsen flame until the white fusionmixture melts into the sample. The mixture is kept in its melted state androlled around the crucible to ensure it reacts with all of the sample. Thecrucible is then cooled in a dessicator.

Inorganics: Acid Fusion


The cooled acid fusion is boiled in distilled water. The resulting slurry iscompletely washed into a volumetric flask through a filter, ensuring all ofthe slurry is removed from the crucible.

The filtered “Water Melt” is made up to the mark on the volumetric flaskand analysed by ICP.

This test quantifies the sulphate present (Na2SO4 & K2SO4 from fusion).

Inorganics: Water Solubles from Water Melt


The filter paper from the Water Insolubles is transferred to anothervolumetric flask and washed with 50% hydrochloric acid. This is repeateduntil all of the slurry has been dissolved.

The filter paper is washed with warm distilled water up to the mark on thevolumetric flask. The “Acid Melt” is then analysed by ICP.

Acid insolubles include Barium Sulphate (BaCO3 from fusion) andStrontium Sulphate (SrCO3 from fusion).

Inorganics: Acid Solubles from Acid Melt


Deposit Analysis Flowchart Summary

NORM Checked.

Clean, DrySample

Loss on Ignition

Are Solids Organic ?

ICP Analysis of Acid Extract

Acid Soluble Content

Silica Content

Acid Insoluble Content

ICP Analysis of Acid

Insoluble Melts

Water Soluble Content

ICP Analysis of Water Soluble Extract


Optional Analysis – Total Mercury Content

Weighed sample is placed in a nickel boat and combusted in a stream ofultra-high purity oxygen. The released mercury vapour is concentrated onan internal amalgamator cooled trap.

The trapped mercury is thenrevapourised by heating to750°C and the mercurydetected by UV fluorescenceat Hg’s main signaturewavelength of 253.7 nm.


Optional Analysis – Laser Particle Size Distribution (0.01 to 3,000 microns)

A PSD can be performed if the solids are not in clumps. A stable, dispersedsuspension is created in toluene/IPA mix where each particle is wettedand separated by sonification & stirring. A He-Ne laser illuminates theparticles. The intensity & diffraction angles of the scattered light ismeasured by a series of detectors and used to calculate each particle size.

A stable, completely dispersed suspension is created in toluene/IPA mixwhere each particle is wetted and separated by sonification & stirring. AHe-Ne laser illuminates the particles and the intensity and diffractionangles of the scattered light is measured by a series of detectors and usedto calculate each particle size.

Size Low % In Size High % Below 0.00 0.89 1.00 0.91.00 10.69 5.00 11.65.00 8.88 10.0 20.510.0 6.74 20.0 27.220.0 8.25 45.0 35.545.0 4.26 63.0 39.763.0 7.24 90.0 47.090.0 10.17 125 57.1125 6.43 150 63.6150 9.31 200 72.9200 5.51 250 78.4250 3.36 300 81.7300 2.36 350 84.1350 1.92 400 86.0400 1.74 450 87.8450 1.64 500 89.4500 2.95 600 92.3600 2.44 700 94.8700 1.87 800 96.7800 1.35 900 98.0900 0.94 1000 98.9

1000 1.03 1250 100.01250 0.03 1500 100.01500 0.00 1750 100.01750 0.00 2000 100.0

D,10 D,50 D,904.40 μm 100 μm 520 μm

D [3,2] D [4,3]12.6 μm 177 μm

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Example Report 1

% In % Below


Technique Advantages Disadvantages

Wet chemistry Truly quantitative.Maximum information.

Organic samples require an additional technique.No mineral morphologies.

SEM/EDX Small sample size.Surface morphology.Particle identification.

Semi-quantitative.

XRD Mineral identification.Identifies different states of the same element

Semi-quantitative.Only detects crystalline material

GC/HTGC Carbon number distribution.Organic fingerprint identification of some chemicals.

Semi-quantitative.

FTIR Identification of chemicals and organic materials.Small sample size.

Not quantitative.Mixtures problematic.


High Loss on Ignition Acid Soluble Acid Insoluble

Wax (hydrocarbons) Salt (water soluble) Silica

Calcium NaphthenateSodium Polacrylate

Corrosion products Barium Sulphate

Polymers Calcium carbonate Clays

Chemical Residues Calcium Sulphate (partial, but predominantly acid soluble)

Calcium Sulphate (partial)

Biomass Strontium Sulphate (partial) Strontium Sulphate (partial, but predominantly acid insoluble)

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