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QUALITY, SPECIFICATIONS AND YIELD OF CRUDE OIL
FROM THE WELL TO THE REFINERY
Scott Blakely
Laboratory Services Manager
Central & West Coast Regions, Intertek
ENERGY CONFERENCE
Miami Beach
October 2014
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Many Various Crude Oil Types
Conventional Crudes
Altamont, Utah
42° API
• Virgin Crudes
• Blended Crudes
Ninian, North Sea
36° API
Arabian Light
33° API
Barrow Island,
Australia
38° API
Sumatran Light
35° API
Unconventional Crudes
• Shale Oils
• Oil Sands
Boscan, Venezuela
10° API
Nigerian Light
37° API
Empire Mix, Louisiana
Gulf
30° API
Offshore
California
18° API
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The three benchmark oil products:
•
North America's West Texas Intermediate crude (WTI)
•
North Sea Brent Crude
•
UAE Dubai Crude
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Bakken crude is described as a light sweet crude oil
similar to West Texas Intermediate (WTI).
What does that mean?
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The first quality characterization of crude oil is:
API Gravity
API gravity is a standard unit of density compared to water.
If a product’s API gravity is greater than 10, it is lighter and floats on water.
If a product’s API gravity is less than 10, it is heavier and sinks.
Quantities of crude oil are often measured in metric tons.
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API Gravity is determined by test methods:
ASTM D1298 or D287, Hydrometer
ASTM D5002, Densitometer
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The API gravity is used to classify oils as light, medium, heavy, or extra heavy:
• Light – API > 31.1
• Medium – API between 22.3 and 31.1
• Heavy – API < 22.3
• Extra Heavy – API < 10.0
WTI has an API Gravity around 40
Bakken has an API Gravity around 42
API Gravity of an oil is the largest determinant of its market value.
Less dense oil or “light oil” is preferable to more dense oil as it contains greater
quantities of hydrocarbons that can be converted to gasoline and diesel fuel.
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The second quality characterization of crude oil is:
Sulfur Content
The Sulfur content is used to classify oils as sweet or sour:
• Sweet < 0.5 %mass
• Sour
>= 0.5 %mass
Sour crude oil needs the sulfur to be removed before it can be refined,
thereby increasing the cost of processing.
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Sulfur is determined by test method:
ASTM D4294, X-ray Fluorescence
The sample is placed in an X-ray beam and
resultant excited X radiation is measured.
Water and Sediment can be a significant interference as they can settle out on
the cell membrane thus obscuring the X-Ray and giving falsely lower sulfur
value.
Centrifuging sample to remove water and sediment will remove this
interference.
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The next quality characteristics of crude oil are:
Water and Sediment
When extracted from formations, crude oil will contain some amount of
water and solids.
Most water and sediment is separated at the field.
Crude oil is typically sold under certain water and sediment specification.
Refiners may also have initial dehydration and desalting process units.
Obviously, at $100 per barrel, nobody wants to purchase water and sediment.
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Water and Sediment are determined by various test
methods:
ASTM D4007, Water & Sediment by Centrifuge
ASTM D4006, Water by Distillation
ASTM D473, Sediment by Extraction
ASTM D4807, Sediment by Membrane Filtration
ASTM D4928, Water by Coulometric
Karl Fischer Titration
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There are various specifications for Water & Sediment.
The industry has always been wary of setting specs for these
contaminants for fear that parties will determine it is acceptable
to “blend” these in, up to those limits.
These contaminants are much more expensive to remove at the
refinery than disposed properly at the oilfield.
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Who sets Crude Oil Specifications?
Refiners
Terminals
Transportation: Pipelines, Rail, Barges, & Ship
Government agencies: EPA, DOT/PHMSA
Contracts: Buyers, Commodity Exchanges such as NYMEX
Wellhead
Truck
Rail Freight
Pipeline
Storage
Barge
Refinery
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Vapor Pressure
EPA requirements for floating roof tank limits at terminals
DOT/PHMSA limits for transportation by pipeline, rail, and truck
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Vapor Pressure by test methods:
ASTM D323, manual cylinder
ASTM D6377, automated instrument
EPA has stated that D6377 result of
VPCR4(100ºF) is accepted alternative to
D2879.
ASTM D2879, Isoteniscope
ASTM Dxxxx, pending cylinder field test
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Critical Concerns of Vapor Pressure Sampling:
Live crude oil must be sampled into Floating Piston Cylinders
(FPC)
FPC are current industry recommendation, but they have drawbacks.
They are expensive.
Cylinders are reactive to hydrogen sulfide unless treated.
They usually require 30psi pressure to fill.
FPC only pull spot samples which may not be representative of whole tank.
Dead crude oil (stabilized to remove C1-C3 hydrocarbons)
can be sampled in 1L bottles filled 70% – 80%.
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Hydrogen Sulfide
Concentration (ppm)
Symptoms/Effects
0.01-1.5
Odor threshold (rotten egg smell)
2-5
100
500-700
700-1000
1000-2000
Prolonged exposure may cause nausea, tearing of the
eyes, headaches or loss of sleep. Airway problems
(bronchial constriction) in some asthma patients.
Coughing, eye irritation, loss of smell after 2-15 minutes.
Altered breathing, drowsiness after 15-30 minutes.
Death may occur after 48 hours.
Staggering, collapse in 5 minutes. Serious damage to the
eyes in 30 minutes. Death after 30-60 minutes.
Rapid unconsciousness, "knockdown" or immediate
collapse within 1 to 2 breaths, breathing stops, death
within minutes.
Nearly instant death
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Hydrogen Sulfide by test methods:
UOP163, H2S in Liquid Phase
by Potentiometric Titration
ASTM D7621 / IP 570, H2S in Liquid Phase
by Analyzer
ASTM D5707 Modified, H2S in Vapor Phase
by Drager Tube
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Critical Concerns of Hydrogen Sulfide:
Bakken crude oil and many other types typically contain
more than 2000ppm Hydrogen Sulfide in vapor phase.
Hydrogen Sulfide kills and creates a major transportation
and handling danger.
Crude Oil containing high amounts of Hydrogen Sulfide must be additized
with scavenger to remove this danger.
Too much scavenger is also a concern for the refiner.
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Other tests required by DOT / PHMSA
for rail transport of Bakken Crude Oil:
Initial Boiling Point, ASTM D86
Flash Point, ASTM D56 manual preferred
It can be dangerous to perform a flash point on flammable product
with a theoretical flash point of -40ºC (-40ºF)
• If IBP <=95oF, then PG I classification and nothing further needs to be done.
• If IBP >95oF & Flash Point is <= 73oF then PG II classification
• If IBP >95oF & Flash Point is >73oF and <=140oF then PG III classification, which may
well still need to be transported under PG I or II requirements.
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Organic Chlorides
Organic chlorides are not known to be naturally present in crude oils.
Organic chlorides can be produced from hydrochloric acid in hydrotreating or
reforming reactors. The acid accumulates in condensing regions of the
refinery causing damaging corrosion.
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Organic Chlorides by test methods:
ASTM D4929,
Procedure A - Potentiometric Titration
Procedure B - Combustion Microcoulometry
ASTM D7536, X-ray Fluorescence
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Critical Concerns of Organic Chlorides:
Organic Chlorides have caused detrimental effects to
refiners numerous occasions.
The industry is fearful of setting specifications other than at the
lower detection limit of the methodologies (<1ppm) over
concerns that this contaminant might be blended into product.
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Crude Oil Characterization
NYMEX Specifications
API Gravity
Sulfur
Sediment & Water
Vapor Pressure
Pour Point, ASTM D97
Viscosity, ASTM D445
ASTM D7042
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Crude Oil Characterization
Other Typical Contract Specifications
Acid Number (TAN), ASTM D664
Ash Content, ASTM D482
Nickel, Vanadium, and Iron,
ASTM D5863 / D5708
Acidic constituents can cause corrosion.
Indicates amount of inorganic metals,
rust, or dirt present.
These elements can deactivate
refinery catalysts during processing
and also cause corrosion. Crude oil
value can be affected by high
concentrations.
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Crude Oil Characterization
Other Typical Specifications
Asphaltenes,
ASTM D3279, D6560 / IP143
Heptane insoluble, highest molecular
mass material. They may give problems
during storage and handling
Microcarbon Residue Test,
ASTM D4530
Indicates tendency to form
carbonaceous type deposits under
degradation conditions
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Crude Oil Characterization
Other Typical Refinery Requirements
Salt, ASTM 3230
Excessive chloride can result in
corrosion and has detrimental effects on
catalysts. Results indicate whether
crude oil requires desalting.
Nitrogen content, ASTM D5762
Nitrogen compounds can contaminate
refinery catalysts.
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Crude Oil Yield Structure Various Crudes
0%
Light Gases
20%
Naphtha
40%
Kerosene
60%
Distillate
Fuel –
Gas Oil
80%
Heavy
Products
100%
API
Sulfur Content
Wt.%
Eagle
Ford
WTI
Brent
Blend
ANS
Arab
Hvy
WCS
40.1
39.1
37.5
32.1
27.9
20.6
Light Gases
0.13
Naphtha
0.35
Kerosene
0.40
Distillate Fuel - Gas oil
0.93
2.85
Heavy Products
3.34
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Crude Assay
Laboratory
Atmospheric Crude
Oil Distillation Unit,
ASTM D2892
TBP 15 / 5 Tower
IBP to 752oF
(or 400oC)
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Crude Assay
Laboratory
Vacuum
Distillation Unit
ASTM D5236
Vacuum Potstill
752oF to 1050oF
(or 565oC)
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IBP
Laboratory Atmospheric
Crude Oil Distillation Unit,
ASTM D2892
TBP 15 / 5 Tower
IBP
to
752o F
(or 400o C)
700o F Range
Laboratory Vacuum
Distillation Unit
ASTM D5236
Vacuum Potstill
752o F
to
1050o F
(or 565o C)
1050o F
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Petroleum Fractions
Boiling Range (°C) / (°F)
Light gases
<15.5°C (60°F)
quantitative determination of individual C2 to C4 and total C5+
hydrocarbons by GC
Gasoline (light naphtha
15.5–149°C (60–300°F)
API Gravity, density or specific gravity, total sulfur, mercaptan
sulfur, hydrogen sulfide, octane number , quantitative
determination of PIAN by GC
149–232°C (300–450°F)
API Gravity, density or specific gravity, total sulfur, mercaptan
sulfur, hydrogen sulfide, aniline point , total acid, naphthalene
content, smoke point, total nitrogen, basic nitrogen, cold
properties (F/C/P), flash point
232–343°C (450–650°F)
API Gravity, density or specific gravity, total sulfur, aniline point,
total acid, naphthalene content, smoke point, total nitrogen,
basic nitrogen, cold properties (C/P), flash point, viscosity,
cetane index (calculated)
343–371°C (650–700°F)
API Gravity, density or specific gravity, total sulfur, aniline point,
total acid, total nitrogen, basic nitrogen, cold properties (C/P),
viscosity, refractive index
Kerosene (medium naphtha)
Distillate Fuel - Gas oil
Light vacuum gas oil
Heavy vacuum gas oil
Residuum
371–566°C (700–1050°F)
>566°C (1050°F)
Typical Analytical Parameters
API Gravity, density or specific gravity, total sulfur, aniline point,
total acid, total nitrogen, basic nitrogen, cold properties (Pour
Point), viscosity, trace metals, asphaltenes, carbon residue, wax
content, refractive index
API Gravity, density or specific gravity, total sulfur, total acid,
total nitrogen, basic nitrogen, cold properties (Pour Point),
viscosity, trace metals, asphaltenes, carbon residue , wax
content, penetration, softening point
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Pilot Plant Evaluations
P84-88, fixed bed hydroprocessing pilot plants
150 Still, 150 gallon batch distillation unit
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Intertek “Rapid Yield Assay”
ASTM D7169,
High Temperature Simulated Distillation
Gas Chromatography
ASTM D7900,
Light Hydrocarbons (C1-C9)
Gas Chromatography
Rapid Yield Assay is merged data from
ASTM D7169 & ASTM D7900
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Rapid Yield Crude Quality Monitoring
Comparison of TBP, HTSD and Merged GC Data for Asia Pacific Crude B
800
700
600
Temp (deg C)
500
400
Merged GC Data
TBP
HTSD
300
200
100
0
0
10
20
30
40
50
60
70
80
90
100
-100
Wt.%
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Intertek “Rapid Yield Assay” Benefits:
Limited sample size requirement (5mls)
Fast turnaround time for analysis – 24hrs
Cost is much less expensive.
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Conclusion
• Crude Quality is more than Gravity/Sulfur.
• Quality can affect transportation safety.
• It can be restricted by government regulations.
• There can be a direct effect of commodity value.
• It can give a good indication of refinery yields.
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This presentation has been prepared for the sole benefit of providing general
comparative type information on crude oil. Intertek assumes no responsibility for the
content, accuracy, or completeness of the data presented and does not in any way
endorse its use or fitness for a particular purpose.
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References
Contact Details:
Scott Blakely, Laboratory Services Manager
Central & West Coast Regions, Intertek
Email: [email protected]
References:
COQA.org “Crude Oil Quality Association”
CCQTA.com “Canadian Crude Quality Technical Association”
North Dakota Petroleum Council
American Society for Testing and Materials (ASTM)
www.osha.gov/SLTC/hydrogensulfide
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