EVALUATION OF CRUDE OIL QUALITY
ABSTRACT Fourteen type crude oils originated from USA, Mexico, Africa, Middle East, Russia, Canada,Colombia, Ecuador, and Venezuela having density and sulfur in the range API = 12.1 ÷ 40.8; S =0.4 ÷ 3.3% and total acid number varying in the range TAN = 0.1 ÷ 3.72 mg KOH/g oil havebeen investigated. The studied crude oils have been classified into four groups: I group – light,low sulfur one (30 - 400 API; S ≤ 0.5 % mass); ІІ group – light, sulfur one (30-400API; S= 0, 5 -1.5 % mass); ІІІ group – heavy, high sulfur one (15-300API; S=1.5 ÷ 3.1% mass); ІV group –extra-heavy, high sulfur one (150API, S ≥3 % mass). It has been established that extra-heavycrude oils (IV group) are characterized by light fraction low content, diesel fractions low cetaneindex, vacuum gas oil fractions low K-factor and vacuum residue fractions high Conradson carboncontent. It also has been found on the base of crude oil averaged prices for June 2009 (Brentcrude oil price = 69 US $/ barrel) that the difference of the Ist and IVth group crude oil prices wasabout 9 US $/ barrel. This difference amounts up to 22 US $/ barrel, as the crude oil price rises upto 140 US $/ barrel. The high acid crude oil price (such having TAN > 0.5 mg KOH/g oil) may beapproximately 9 US $/ barrel lower than one determined on the base of density and sulfur contentfor the corresponding group.
- SourceAvailable from: Will Meredith[show abstract] [hide abstract]
ABSTRACT: Quantitative analysis of separated carboxylic acid fractions of 33 crude oils from the UK, Italy and California, showed that the carboxylic acid fraction is a major factor responsible for the acidity in these oils. It was apparent that biodegradation is the main process that produces high concentrations of carboxylic acids in these crude oils with the extent of biodegradation, as measured from their hydrocarbon compositions, being clearly correlated with their total acid number (TAN). Although probably not important in influencing oil TAN, the distribution of C30–C32 hopanoic acids was also seen to be controlled by biodegradation, increasing in concentration for all but the most biodegraded oils. Hopanoic acids with the 17β(H),21β(H) stereochemistry were found in many of the biodegraded oils, and were thought to be mainly derived from the bacteria that were responsible for the biodegradation of the oil. This may have implications for the timing and mechanisms of the biodegradation involved. The role of C0–C3 alkylphenols in determining oil acidity was investigated and shown not to be a significant factor in the sample set studied. However, a number of undegraded oils, with low carboxylic acid contents were seen to have relatively high acidities, showing that factors other than biodegradation, possibly related to high sulphur content can control oil acidity in certain oil types.Organic Geochemistry. 01/2000;
- Processing opportunity crudes: A new strategy for crude selection” Proceedings ERTCCrude valuation for crude selection”, Petroleum Technology QuarterlyGravity and sulfur-based crude valuations more accurate than believed”, Oil & Gas journalIs your refinery model balanced?”, Hydrocarbon Processsing. 51-56..
Petroleum & Coal
Available online at w w w .vurup.sk/ pc
Petroleum & Coal 52 (1) 35-43, 2010
EVALUATION OF CRUDE OIL QUALITY
D. Stratiev1, R.Dinkov1, K. Petkov1, K. Stanulov2
1Lukoil Neftochim Bourgas, 8010 Bourgas, Bulgaria
2 University of Chemical Technology and Metallurgy - Sofia, 1756 Sofia,
Bulgaria, e-mail email@example.com
Received October 16, 2009, Accepted February 1, 2010
Fourteen type crude oils originated from USA, Mexico, Africa, Middle East, Russia, Canada,
Colombia, Ecuador, and Venezuela having density and sulfur in the range API = 12.1 ÷ 40.8; S =
0.4 ÷ 3.3% and total acid number varying in the range TAN = 0.1 ÷ 3.72 mg KOH/g oil have
been investigated. The studied crude oils have been classified into four groups: I group – light,
low sulfur one (30 - 400 API; S ≤ 0.5 % mass); ІІ group – light, sulfur one (30-400API; S= 0, 5 -
1.5 % mass); ІІІ group – heavy, high sulfur one (15-300API; S=1.5 ÷ 3.1% mass); ІV group –
extra-heavy, high sulfur one (150API, S ≥3 % mass). It has been established that extra-heavy
crude oils (IV group) are characterized by light fraction low content, diesel fractions low cetane
index, vacuum gas oil fractions low K-factor and vacuum residue fractions high Conradson carbon
content. It also has been found on the base of crude oil averaged prices for June 2009 (Brent
crude oil price = 69 US $/ barrel) that the difference of the Ist and IVth group crude oil prices was
about 9 US $/ barrel. This difference amounts up to 22 US $/ barrel, as the crude oil price rises up
to 140 US $/ barrel. The high acid crude oil price (such having TAN > 0.5 mg KOH/g oil) may be
approximately 9 US $/ barrel lower than one determined on the base of density and sulfur content
for the corresponding group.
Key w ords: opportunity crudes, crude value, high acid crudes, crude oil quality
1. I ntroduction
Crude cost is the single most important determinant for the profitability of an oil
company. With crude costs accounting for around 80% of the refinery expenditures,
processing cheaper crudes can have a very positive impact on refinery margins .
For refineries that have freedom in crude choice, the selection of an optimum crude
package is of vital importance. This requires intense teamwork between the trader and
the supply/ manufacturing economist and typically linear-program (LP) models of
individual refineries are routinely used to determine the relative use values among
crudes [3-14]. To achieve optimal crude selection and processing decisions, a refiner must
have exact information refer to crude oil quality [15-35]. This includes: crude oil TBP-curve
as main data for correct operation of refinery crude oil atmospheric-vacuum distillation
plants ; the characteristics of crude oil fraction:
- density, naphthenes and arene content, octane number, sulfur and metal as lead and
arsenic content, affecting isomerization and reforming plants operation;
- density, sulfur, pour point, freezing point, arene content (for aviation fuel); cetane
index, low temperature properties (CFPP), pour point and diesel and fuel oil blending
- density, sulfur, arene content, cetane index, pour point, low temperature properties
(CFPP), diesel and fuel oil blending viscosity;
Heavy gas oil:
- UOP “К” factor or hydrogen content, nitrogen and Conradson carbon quality
characteristics of this fraction as feed for Fluid Catalytic Cracking and other conversion
Atmospheric residue and vacuum gas oils:
- density, pour point, sulfur, viscosity, metals for fuel oil blending;
-UOP “К” factor or content of hydrogen, nitrogen and Conradson carbon as suitability
criteria for conversion processing (Fluid Catalytic Cracking and Hydrocracking)
- density, pour point, sulfur, viscosity, metals for fuel oil blending; UOP “К” factor or
hydrogen, nitrogen and Conradson carbon content as suitability criteria for their
processing by the conversion processes (Catalytic cracking and Hydrocracking).
In practice, data is also needed for additional cuts in order to generate property
profiles as a basis for recutting to actual refinery straight-run products. For example: the
increase demand of diesel in Europe drives the European refiners to cut naphtha fractions
and in this way to increase diesel yield . This information may be obtained by use of
standard laboratory test methods normally API or ASTM. One extensive laboratory
analysis of crude oil may cost over 20 000 US $ and generally it takes two to four weeks
. In practice it is extraordinary difficult and very expensive to carry out full laboratory
analysis of every cargo crude oil received at the refinery. This has resulted in
development of a number computing methods that permit prediction of petroleum
fractions properties by routine laboratory analyses
information about petroleum fractions distillation characteristics, density, sulfur content,
viscosity and refraction. This information may be obtained only after crude oil TBP
distillation, analysis which duration is not less than 24 hours . Another important
information of crude oil quality is organic acid content since organic acid presence at high
concentration may generate number of problems at equipment operation and especially
at crude oil atmospheric-vacuum distillation plants via their acid high corrosion activity
[47-53]. The crude oil total acid number is an indicator of the organic acids content in the
crude oil. It is well known that problem crude oils are those which total acid number is
over 0.5 mg KOH/g oil . But not always low acid number of crude oil feed means that
it is not possible corrosion problem to occur due to the presence of naphthenic acids in
definite petroleum fractions . Such cases exist when definite fraction has very low
sulfur content and presence of organic acids. Sulfur presence result to formation of
protective layer of ferric sulfide that renders difficult organic acid attack of the metal and
by that manner the equipment accelerated corrosion is reduced. Because of lower prices
of high acid crude oil feeds (total acid number over 0.5 mg KOH/g crude oil) their
processing is one opportunity to increase crude oil processing profit after use of adequate
programs for minimizing the risk of accelerated corrosion and subsequent equipment
untimely, unplanned damage .
There are basically four types of crude available to refiners around the world. They are
light-sweet (30-400 API, <0,5 wt% S), light-sour (30-400 API, 0.5-1.5 wt% S ), heavy-
sour ( 15-300 API, 1.5-3.1 wt% S) and extra-heavy (<150 API and >3 wt% S ). High acid
crude oils (HACs) represent the fastest-growing segment of global oil production.
California, Brasil, North Sea, Russia, China, India and West Africa are known to supply
HACS. Over half of the world’s oil supply is heavy and sour. Hence, synthetic petroleum
feeds derived from bitumen sands are considered as high acid ones. Table 1 represents
comprehensive assay of fourteen crudes which belong to the four basic type petroleum
feeds. The crude comprehensive assay of all investigated crude oils was obtained in the
Lukoil Neftochim Research Laboratory. Price of the crudes was obtained from the Energy
Information Agency (EIA) and this price was related to June 2009 . These data show
that for June month 2009 the average prices of four type basic petroleum feeds are as
І group – light low sulfur ones (30-400 API; S ≤ 0.5 % mass) = 68.5 US $ / barrel
ІІ group – light sulfur ones (30-400 API ; S=0,5 1.5 % mass) = 67.5 US $ / barrel
ІІІ group – heavy, high sulfur (15-300 API S=1.5 ÷ 3.1% mass) = 66.8 US $ / barrel
ІV group – extra-heavy high sulfur (150API, S ≥3 % mass)= 60.0 US $ / barrel
Herein, it is seen that the price of light, low sulfur crude oil from Louisiana
nevertheless of its low sulfur content and low density (High API) according to which it
[38-45]. These methods require
D. Stratiev et al./Petroleum & Coal 52(1) 35-43, 2010 36
should be applied to first group crude oils, is equal to that of the lowest quality crude oils
of fourth group. This may be explained by the high acid number of the crude oil that in
combination with low sulfur content means high corrosion reactivity and so unfavorable
feed for processing . The price of EMERAUDE (origin – Congo) and TIA JUANA PESADO
(origin Venezuela) crude oils is not included in Table 1 as they are not available on the
market due to their extra high acid number. The crude oil light fraction (distilled up to
343oC) content decreases in the following order: I group > II group > III group > IV
group. Vacuum residue content decreases in reverse sequence. The average
characteristics of the fractions derived from crude oil groups included in Table 1 show
(Table 2) that IV group crude oil naphtha has the highest octane number and diesel
fractions of the same crude oils have the lowest cetane number that corresponds to the
conclusions drawn up by other authors .
Table 2 Average characteristics of the fractions derived from crude oils presented in
RON Cetane index К- factor Conradson
Fractions Fractions Fraction fraction
343-565 > 565
І 70.7 61.0 44.4 46.0 46.2 53.3 12.08 14.2
ІІ 71.1 58.3 42.0 45.0 45.0 50.2 11.84 21.8
ІІІ 66.8 50.9 32.8 50.0 49.8 51.2 11.78 21.9
ІV 75.5 64 53.6 37.0 37.4 41.4 11.56 23.1
Vacuum gas oil fraction from group IV has the lowest K-factor and due to this at
conversion processes from them will be produced the lowest yields of valuable products
like naphtha, diesel fraction and C3 and C4 alkenes. The IV group crude oil vacuum
residues have the highest Conradson carbon and so they are unfavorable feeds for
catalytic conversion processes. They are suitable for processes like cocking at which as
by product is produced low valuable coke. All of these characteristics show that from IV
group crude oils may be produced the lowest yields of high valuable transport fuels.
Similarly, they require higher costs for processing due to required high degree of
upgrading at hydrotreating processes and higher consumption of high prices hydrogen.
The difference in prices between group I and group IV crude oils has been 8.5 US $ /
barrel on June 2009, but as a whole this difference depends on the crude oil price. The
plot of Brent type crude oil price change for period 1997 – 2009 is shown on Figure 1. It
may be seen from it that difference of prices between high quality crude oils (low density
and low sulfur content) and low quality crude oils (high density and high sulfur content)
increases along with the increase of crude oil price. For example at crude oil price of
order 30 US $ / barrel the difference between Brent и Maya crude oils is about 30 US $ /
barrel and at 140 US $ / barrel it is already 20 US $ / barrel. Hence, as higher is the
crude oil price so more advantageous is to process low quality crude oils.
D. Stratiev et al./Petroleum & Coal 52(1) 35-43, 2010 37
03/01/1997 03/07/199703/01/1998 03/07/1998 03/01/199903/07/199903/01/2000 03/07/200003/01/2001 03/07/200103/01/2002 03/07/200203/01/200303/07/2003 03/01/2004 03/07/200403/01/2005 03/07/2005 03/01/200603/07/2006 03/01/200703/07/200703/01/2008
1997 - 2009
Brent и Maya crude price US $/barrel
Weekly Europe (UK) Brent Blend Spot Price FOB (Dollars per Barrel) Weekly Mexico Maya Spot Price FOB (Dollars per Barrel)
Figure 1 Crude Brent price and difference in prices of crudes Brent and Maya in the period
1997 - 2209 (Source: Energy Information Administration;
The following conclusions may be drawn up as a result of the carried out investigation:
1. The high quality crude oils (low density and low sulfur content) are characterized by
light fractions high content, diesel fractions high cetane index, vacuum gas oils high K-
factor and vacuum residue fractions low Conradson carbon content.
2. Low quality crude oils (high density and high sulfur content) are characterized by light
fractions low content, diesel fractions low cetane index, vacuum gas oils low K-factor
and vacuum residue fractions high Conradson carbon content.
3. The difference between the high quality and low quality crude oils increases with the
crude oils price growth.
4. At high crude oil prices the most profitable will be refineries having available heavy
petroleum residues conversion plants that allow them to process low quality crude oils
to high valuable transport fuels.
5. The high acid number and low sulfur content of crude oil results to its price decrease
by about 9 US $/ barrel at crude oil price about 69 US $/ barrel.
6. It is proved the conclusion drawn up by other authors that high acid crude oil diesel
fractions have low cetane index.
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