core laboratories (u.k.) limited analytical chemistry
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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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
Upon receipt of samples, they are booked into a database.
Prior to commencing any analysis, the radioactivity level is determined.
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
Corrosion Products(Mainly Iron)
Organic (Wax)
Proppant & NaCl
Calcium Carbonate
Corrosion Products(Mainly Iron)
Barium Sulphate & Strontium Sulphate
Calcium CarbonateCalcium Carbonate
DEPOSIT, SCALE & SLUDGE ANALYSIS
Before & After Cleaning Photos: Napthenate
Oily hard/brittle brown chunks
Hard/brittle brown chunks
DEPOSIT, SCALE & SLUDGE ANALYSIS
Before & After Cleaning Photos: Organics + Man-made Materials
Damp brittle brown large and small flakes
Pale brown fines. Extraneous fabric/rubber removed
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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”.
DEPOSIT, SCALE & SLUDGE ANALYSIS
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.
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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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cm-1
%T
1032.68cm-1
1083.50cm-1
860.47cm-1
881.64cm-1
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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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nC9
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nC16
nC17
nC18
nC19
nC20
nC21
nC22
nC23
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nC25 nC
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67 nC
68 nC
69 nC
70 nC
71 nC
72
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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).
DEPOSIT, SCALE & SLUDGE ANALYSIS
Example Scanning Electron Microscopy Images
Polymer Backing
Rust & Mercuric Sulphide
Ceramic Fibres
Pyrite Pyrite –– Iron (IIIron (II) Iron (II) Disulphide
DEPOSIT, SCALE & SLUDGE ANALYSIS
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.
DEPOSIT, SCALE & SLUDGE ANALYSIS
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).
DEPOSIT, SCALE & SLUDGE ANALYSIS
FTIR analyser compares the spectra with a database of thousands ofknown samples.
Fourier Transform Infra-Red (FTIR) Analysis
DEPOSIT, SCALE & SLUDGE ANALYSIS
HTGC can identify and quantify a n-alkane hydrocarbon wax distribution.
High Temperature Gas Chromatography Analysis
DEPOSIT, SCALE & SLUDGE 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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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.
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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.
DEPOSIT, SCALE & SLUDGE ANALYSIS
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
DEPOSIT, SCALE & SLUDGE ANALYSIS
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.
DEPOSIT, SCALE & SLUDGE ANALYSIS
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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