FORM-2
THE PATENT ACT,1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
(As Amended)
COMPLETE SPECIFICATION
(See section 10;rule 13)
"Novel Method for Measurement of Asphaltenes in Crude Oils and Petroleum Products"
NAYARA ENERGY LIMITED, a corporation organized and existing under the laws of India, of 39 KM Jamnagar-
Okha Highway, Vadinar, Dist Devbhoomi Dwarka, Gujarat, India.
The following specification particularly describes the invention and the manner in which it is to be performed:
2
Title of Invention: Novel Method for Measurement of Asphaltenes in Crude Oils and
Petroleum Products
Field of the invention:
The present invention is related to crude 5 petroleum oil exploration and refining, more
specifically testing of crude oil samples and petroleum products samples. More
particularly, the present invention relates to a novel method for measurement of
asphaltenes in crude oils and petroleum products like vacuum residue, heavy vacuum gas
oil, heavy coker gas oil, mixture of vacuum residue and furnace oil samples.
10
Background of the invention:
Crude oil is natural product and sometime synthetic materials are also mixed. Crude oil
is mainly consisted of variety of hydrocarbon molecules, which mainly having carbon and
hydrogen elements, it also contains some concentration of Sulphur, nitrogen, nickel,
15 vanadium, iron, sodium, arsenic, mercury etc. The concentrations of elements are vary
based on origin of crude oil.
Hydrocarbon molecules of crude oils are mainly consisted of four groups of chemical
structure a) Saturates b) Aromatics c) Resins and d) Asphaltenes. The mixture of a, b
20 and c are also called maltenes. Solubility of constituents depends on concentration of
these four groups, imbalance can result into precipitation of asphaltenes.
Asphaltenes is one of the key chemical compositions of crude oil which has various
adverse effects on petroleum refining processes. For example, asphaltenes precipitation
25 and deposition can occur on surfaces viz tank, pipeline, exchanger etc. and is undesirable
because it affects refining processes. Asphaltenes has very crucial role in many refining
process like hydro treating and delayed coking, hence it become critical parameter for
crude oil price justification, procurement, and processing. The measurement of
asphaltenes at every stage from crude oil exploration to refinery processing is highly
30 useful and become essential.
Asphaltenes is known as n-heptane insoluble and toluene soluble hydrocarbon molecules.
The measurement of asphaltenes in crude oils and petroleum products viz atmospheric
residue, vacuum residue and heavy vacuum gas oil is being done by mostly gravimetric
35 methods since long time. The auto instrumental methods currently known to us are ASTM
D 7996 and Japan Petroleum institute 5S-45-95.
3
Often the asphaltenes content in crude oil and petroleum products sample are measuring
to support the refining process using gravimetric method. Following are the
disadvantages experienced while testing asphaltenes using gravimetric test method
ASTM D 6560 or IS 1448,Part 22,
5 1) Poor precision (Repeatability: 10% and Reproducibility: 20%).
2) Very long testing time (up to 24 hrs.).
3) Very high chemical consumption (above 500 ml per sample).
4) High chemical HSEF (Heath, Safety, Environment and Fire) risk.
5) Release high chemical vapour into environment.
10 6) Repeat or duplicate analysis is not easy due to long testing time.
7) The chance of error is very high, if wax content or solvent not removed properly.
8) Required highly skilled manpower to get accurate test results.
While referring auto instrumental methods, it was has been identified that the auto
15 instrumental methods are not using exactly same matrix as sample blank as well as using
different asphaltenes molecules for calibration, hence it may affect the test results or
correlation to gravimetric method. Also auto methods are using costly patented
technology hence may be not widely used in Indian refineries.
20 Hence, need arise to develop measurement method for asphaltenes in crude oils and
petroleum products, which is better in accuracy, provide test results quickly, consume
less chemicals, having less chemical HSEF risk, cost effective and having close correlation
to gravimetric test method.
25 Description of Prior Art:
From the literature study, it is found that, ASTM D 7996 and Japan Petroleum institute
5S-45-95 test methods are there for measurement of asphaltenes using patented
instrument for crude oil and petroleum product sample using spectrophotometry
technique. Both the instrumental methods are not using exactly same sample matrix as
30 sample blank viz ASTM D 7996 using toluene matrix for sample spectral response and
heptane matrix for blank spectral response, while JPI-5S-45-95 using only heptane as
blank sample matrix (without using maltenes and toluene in balnk).
In the spectroscopic technique, blank (reference cell) sample has crucial role and is
35 directly impacting on measurement, hence it should be exactly same to the sample matrix
to produce correct test results.
4
Additionally, during experimental study work, the inventors found that response of
asphaltenes mass of crude oil and residue samples are different hence it will not correlate
with gravimetric method while using single calibration, in short the inventors must have
to use separate calibration graph for crude oil and residue samples to get correct results.
5 This is not specify in any of above test methods.
The inventors have verified 26 different crude oil which covering wide range of
asphaltenes concentration start from 0.01 to 14.7 % and all types of residues samples
asphaltenes concentration start from 1.9 to 20 % are tested in petroleum refinery
10 laboratory, hence our method will be more accurate compared to above spectroscopy
methods.
Inventors of the present invention have also analysed more than 150 samples by both
technique and correlation data tabulated and test results are highly correlate with
15 gravimetric results.
Japan Petroleum institute 5S-45-95 method working range is start from 0.5 to 15 % wt.
asphaltenes and ASTM D 7996 has mentioned < 15 % wt. Invented test method is
verified for asphaltenes concentration start from 0.01 to 20%, however calibration done
20 up to 34 mg asphaltenes will be useful to measure 34 wt. % asphaltenes using 0.10 gm
sample weight. The inventors can measure higher or lower concentration by increasing
or reducing weight of analysis sample.
Inventors are also working for heavy distillate samples (Heavy vacuum gas oil, Heavy
25 coker gas oil etc.) having <0.1% asphaltene and will be included in scope of method
shortly). This will be a wider scope of measurement by single technique and none of
exiting test method having this capability.
Therefore, it would be great benefit to provide a measurement method for asphaltenes
30 in crude oils and petroleum products, which having exactly same blank matrix as well as
better than gravimetric method with respect to precision, testing time, chemicals
consumption, chemical HSEF risk, cost effective. Also have close correlation with
gravimetric test results.
35 Therefore, the gravimetric test method is poor in accuracy, time consuming, consume
more quantity of chemicals, having more chemical HSEF (Health, Safety and Environment
and Fire) risk and difficult to verify test results due to its very long testing time. The auto
5
instrumental methods are not using exactly same matrix as sample blank as well as using
different asphaltenes molecules for calibration, hence it may affect the test results or
correlation to gravimetric method. Also auto methods are using costly patented
technology hence may be not widely used in Indian refineries.
5
Therefore, there is a need in the art to develop measurement method for asphaltenes in
crude oils and petroleum products, which is better in accuracy, provide test results
quickly, consume less chemicals, having less chemical HSEF risk, cost effective and having
close correlation to gravimetric test method. Also covering wider measurement range.
10
Objective of the invention:
The primary object of present invention is to develop a measurement method for
asphaltenes mass percent in crude oils.
15 Another object is to develop a measurement method for asphaltenes mass percent in
petroleum products viz atmospheric residue, vacuum residue, heavy vacuum gas oil,
heavy coker gas oil and furnace oil.
Yet another object is to develop a quick measurement method compared to gravimetric
20 method.
Yet another object is to develop measurement method with better accuracy compared to
gravimetric method.
25 Further object is that the measured test results should be closely correlate with
gravimetric test results.
Further object is to reduce chemical HSEF risk compared to gravimetric method.
30 Further object is to cover wider measurement range.
Further object is to use exact sample matrix blank for better accuracy.
Further object is to develop single method for all refinery samples like Crude oils, vacuum
35 residue, heavy vacuum gas oil and heavy coker gas oil samples.
6
Further another objective is to develop a measurement method using simple and
affordable technology.
Summary of the invention:
In order to overcome the limitations 5 of the prior art and achieve the afore-said objectives
the present invention provides a novel/improved method for measurement of asphaltenes
mass percent in crude oils and petroleum products, which is based on simple
spectroscopic technique.
10 Currently available techniques are gravimetric and/or required patented costly auto
equipment, while the present invention provides a method using simple visible
spectroscopy technique which is very simple in use & cost effective, more accurate, lower
detection limit, improve repeatability up to 50%, reduce 90% testing time, reduce 80%
chemical consumption, and reduce chemical HSEF risk compared to the gravimetric
15 method. The precision of the present method is better and test results are closely
correlate with gravimetric method. Retest or repeat test easily possible within very short
time (two hours) which is highly useful for process unit.
Description of the drawings:
20 The foregoing and further objects, features and advantages of the present subject matter
will become apparent from the following description of exemplary embodiments with
reference to the accompanying drawings, wherein like numerals are used to represent
like elements.
25 It is to be noted, however, that the appended drawings illustrate only typical
embodiments of the present subject matter, and are therefore, not to be considered for
limiting of its scope, for the subject matter may admit to other equally effective
embodiments.
30 Figure 1 illustrates the measurement method for asphaltenes in crude oils and petroleum
products.
Figure 2 illustrates the graphical presentation of visible spectral response.
35 Figure 3 illustrates the calibration graph of asphaltenes mg vs spectral response at 755
nm for crude oil.
7
Figure 4 illustrates the calibration graph of asphaltenes mg vs spectral response at 795
nm for crude oil.
Figure 5 illustrates the calibration graph of asphaltenes mg vs spectral response at 755
5 nm for residue samples.
Figure 6 illustrates the calibration graph of asphaltenes mg vs spectral response at 795
nm for residue samples.
10 Detailed Description of the invention:
The following presents a detailed description of various embodiments of the present
subject matter with reference to the accompanying drawings.
15 The embodiments of the present subject matter are described in detail with reference to
the accompanying drawings. However, the present subject matter is not limited to these
embodiments which are only provided to explain more clearly the present subject matter
to a person skilled in the art of the present disclosure. In the accompanying drawings,
like reference numerals are used to indicate like components.
20
The specification may refer to “an”, “one”, “different” or “some” embodiment(s) in several
locations. This does not necessarily imply that each such reference is to the same
embodiment(s), or that the feature only applies to a single embodiment. Single features
of different embodiments may also be combined to provide other embodiments.
25
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural
forms as well, unless expressly stated otherwise. It will be further understood that the
terms “includes”, “comprises”, “including” and/or “comprising” when used in this
specification, specify the presence of stated features, integers, steps, operations,
30 elements, and/or components, but do not preclude the presence or addition of one or
more other features, integers, steps, operations, elements, components, and/or groups
thereof. It will be understood that when an element is referred to as being “attached” or
“connected” or “coupled” or “mounted” to another element, it can be directly attached or
connected or coupled to the other element or intervening elements may be present. As
35 used herein, the term “and/or” includes any and all combinations and arrangements of
one or more of the associated listed items.
8
The figures depict a simplified structure only showing some elements and functional
entities, all being logical units whose implementation may differ from what is shown.
According to an aspect of the present invention, the measurement method for
asphaltenes i 5 n crude oils and petroleum products explained in Figure 1.
As per the present method for measurement of asphaltenes, appropriate sample mass
(crude oil or petroleum product sample) in volumetric glass flask [1] is taken, adding
toluene to dissolve the mass and diluted with hot n-heptane up to the mark. Allowing the
10 diluted analysis sample [2] to precipitate the asphaltene molecules. Filtering the part
volume (one tenth volume) of analysis sample [2] to prepare sample blank [3], which
also called maltenes fraction (de-asphalted sample blank). Scanning the absorbance of
analysis sample [2] and using sample blank [3] by visible spectrophotometer [4] at
specified wavelengths. Calculating the concentration of asphaltenes mass% [5] using
15 absorbance, response factor of calibration graph and weight of sample.
Test method for measurement of asphaltenes mass percent in crude oils and
petroleum products sample by spectroscopic technique.
20 Scope: The test method is applicable to measurement of asphaltenes mass percent in
crude oils and petroleum products viz vacuum residue, heavy vacuum gas oil, heave
coker gas oil, blend of residue samples and furnace oil etc. The test method is capable
to measure asphaltenes mass concentration in the range of 0.0 mass % to 34.0 mass %.
The higher mass % samples can be measure using less sample weight and lower mass
25 % sample can be measure by higher sample weight. User has to verify performance of
spectroscopy method with gravimetric method as and when required.
Basic principle of present method: The determination of asphaltenes content using
vis-spectrophotometer is based on analysis sample dissolved in toluene and diluted with
30 heptane, after asphaltenes precipitation, spectral response measured at 755 & 795 nm
for analysis sample using maltenes fraction (de-asphalted) of same sample with solvents
(toluene and heptane) as blank. The asphaltenes mass percent calculated using average
spectral response, calibration factor and weight of sample.
35 Significance and Use: Asphaltenes are the organic molecules with higher molecular
mass. Their chemical compositions are quite complicated. They may give problem during
storage, handling and processing if the suspension of asphaltenes molecule disturb due
9
to excess stress or incompatibility. This test method is highly useful to quantifying
asphaltenes in crude oil and petroleum products
Equipment and chemicals requirements:
1) Visible spectrophotometer: Capable 5 to scan and measure in the region of 500 to
900 nm with resolution of 0.1 nm and digital display. It should have operating
software.
2) Sample Cell: pair of 10 mm cell made of quartz
3) Balance for sample weight: capable to take 0.0001 gm sample
10 4) Glassware for sample preparation: 100 ml volumetric flask, 2 ml pipette
5) Solvent for sample preparation: AR grade Toluene and n-Heptane
6) Filtering Device: 0.2 micron nylon filter paper with 10 ml syringe device
Preparation of Analysis Sample [2] - Asphaltenes + Maltenes + Solvents :
15 According to present measurement method, take a sample (crude oil or petroleum
products) weight in the range of 0.1 to 3.0 gm in tared 100 ml glass volumetric flask [1]
and record weight up to 0.0001gm. Add 2 ml of AR grade toluene to dissolve the sample
material mass, shake well and heat it up to 60 deg. C in water bath, if required. Further
added approximately 80 º C heated hot AR grade n-heptane, shake well, and make up
20 to the mark. Mixed thoroughly and allowed to stand for 75 minute in dark place at room
temperature for precipitation of asphaltenes molecules. Mix the sample periodically
during precipitation time. Further, make up the volume up to the mark with n-heptane.
Recommended Sample Weight:
Asphaltenes Mass % Sample Wt. in gm
<0.5 1.0 to 3.0
0.5 to 5 0.5 ± 0.2
>5 0.2 ± 0.1
25
Preparation of Sample Blank (de-asphalted) [3] : Maltenes + Solvents: Filter
10 ml of sample solution [2] through 0.2 micron nylon filter paper to prepare blank (deasphalted)
sample. Discard initial 2 to 3 ml of filtrate and collect filtered blank solution in
spectroscopy cuvette or in 10 ml flash.
30
Scanning of Analysis Sample and Sample Blank: Start the visible
spectrophotometer according to manufacturer’s operating manual and keep ready for
10
analysis. According to present measurement method, fill the analysis sample [2] in 10
mm spectrophotometer cuvette and kept at analysis path and fill the blank sample [3] in
another cuvette and kept at reference path. Start the scanning of absorbance at 755 and
795 nm wavelength and record the absorbance up to 0.001 angstrom unit. The
absorbance of sample 5 should be less than 2 AU to get desire precision.
Spectrophotometer cuvettes and glassware used for analysis to be clean with toluene
first to remove the asphltenes molecule from glass surface.
Calculation of Response Factor:
10 Preparation of Reference Samples: Take 250 ml representative samples of crude oil
or petroleum products in aluminium bottle, make it homogeneous by shaking, and heat
the high pour sample at just above the pour point. Measure the asphaltenes mass content
three times by gravimetric test method viz IS 1448, part 22 or ASTM D 6560. Ensure that
all three results must be in repeatability limits of test method. Average the test results
15 and use average mass concentration of reference sample for calibration graph. The
asphaltenes values must be cover the entire range of mass concentration to be measure
in future samples. Prepare at least three such samples for calibration response factor
calculation.
20 Note 1: During laboratory experiments of present invention, it is experience that residue
samples are having higher response at same concentration at both wavelength than
crude oil, this is may be due to the inherent properties of asphaltenes and maltenes
molecules present in the crude oil and residue samples, hence recommend to prepare
separate response factor for crude oil and residue samples to get correct test results and
25 close correlation with gravimetric test methods viz IS 1448, part 22 or ASTM D 6560.
Preparation of Calibration Graph: Test all the reference samples as per measurement
method explained in current invention and record the weight of samples in mg, percent
mass concentration of asphaltenes obtained by gravimetric test method and absorbance
30 at 755 and 795 nm. Draw the calibration graph of mg asphaltenes in sample taken Vs
absorbance at 755 and 795 nm.
Calculate the mg asphaltenes in sample taken: (Sample taken in mg X Mass % of
Asphaltenes by Gravimetric Method) / 100
35 Response Factor Calculation [RF at 755]: mg of asphaltenes / abs at 755
Response Factor Calculation [RF at 795]: mg of asphaltenes / abs at 795
11
Note 2: Calibration and testing at single or multi wavelength will be choice of user
laboratory, two wavelengths will give more confident to analyst hence recommended.
User can also calibrate instrument at other suitable visible wavelength.
5 Calculation of Asphaltenes Mass Percent:
In-built software of spectrophotometer can directly calculate the asphaltenes
concentration or it can be calculated manually by using formula given below,
Asphaltenes Mass % at 755 nm [A]: (Sample Absorbance at 755 nm X Response
Factor [RF at 755] X 100) / Weight of Sample in mg.
10 Asphaltenes Mass % at 795 nm [B]: (Sample Absorbance at 795 nm X Response
Factor [RF at 795] X 100) / Weight of Sample in mg.
Reporting of Asphaltenes Mass %: (Asphaltenes Mass% [A] + Asphaltenes Mass%
[B])/ 2
15 Note 3: Various test results and calibration graph mentioned in laboratory experimental
data is for ready reference.
Precision: The precision statement for measurement of asphaltenes in crude oils and
petroleum products by spectroscopic technique is based on test results found from intra
20 laboratory (single) study. The study involved duplicate measurement by three analysts,
each using three different samples and two different make visible spectrophotometer.
The change of analyst and or instrument count as a Laboratory to calculate repeatability
and intermediate precision. The test results and calculation explained in laboratory
experimental work. The standard deviation multiply by 2.8 formula is used for calculation
25 of r and R’.
Repeatability: r
The difference between two successive test results obtained by the same operator with
the same apparatus under constant operating condition on identical test material would,
30 in the normal and correct operation of test method, exceed the value in only one in case
of 20.
r = 0.0369x + 0.0313
Where X is the average results, in mass %
35 Intermediate Precision: R’
The difference between two single and independent test results obtained by different
operator working in different station using different apparatus at a single laboratory on
12
identical test material would, in long run, in the normal and correct operation of test
method, exceed the following value in only one in case of 20.
R’= 0.0848x + 0.015
5 Reproducibility: R
There is insufficient data to calculate reproducibility of the test method at this time due
to newly developed test method.
Bias:
10 Unable to determine bias for this method because there are no acceptable reference
standards.
The following experiments are presented as illustrative embodiments but should not be
taken as limiting the scope of the invention. Many changes, variations, modifications, and
15 other uses and applications of this invention will be apparent to those skilled in the art.
Laboratory Experimental work:
To overcome the difficulties experience during measurement of asphaltenes in crude oil
and petroleum residue samples by gravimetric method, the invetors have conducted
20 various laboratory experiments using actual crude oil and petroleum products samples to
develop new measurement method.
Following aspects are considered while developing new measurement methods for
asphaltenes
1) Development of instrumental test method
25 2) Calibration coefficient / linearity of method
3) Precision of test results in terms of repeatability
4) Correlation test results with gravimetric method
5) Time needs to complete test
6) Chemical requirements per sample
30 7) HSEF risk while performing test
8) The chance of error due to matrix change viz wax content or solvent
9) Lower detection limit
10) Measurement range
11) Simple in use
35 12) Exact same sample matric blank
13) Cost effectiveness
13
14) Applicable to all refinery samples like crude oil, residue samples and Vacuum gas
oil samples
The inventors have conducted various trial and error base laboratory experiments to
conclude the performance 5 parameters of new measurement method for asphaltenes. Out
of many such laboratory experiments, some of important experiments are explained
below for evidence and reference of laboratory experimental work.
Experiment: 1
10 Aim: To identify the visible wavelength for measurement of asphaltenes.
Crude Oil sample with 10% asphaltenes is use for this experiment.
The analysis sample (asphaltenes + maltenes + solvents) and sample blank (maltenes +
15 solvents) were prepared as describe in the details description of present method. The
analysis sample and sample blank individually scan for spectral response in the visible
range of 500 to 900 nm. The observed spectral response at every 50 nm interval
recorded. Additionally, asphaltenes response calculated by subtracting spectral response
of sample blank from analysis sample. The data presented in graphical form in Figure 2.
20
Observations:
The graphical data indicates that,
1) There is very minor response of sample blank (maltenes + solvents) in the
wavelength range 750 to 900 nm
25 2) The asphaltenes, maltenes and oil sample (asphaltenes+maltenes) response
increase toward lower wave number
Conclusions:
From the spectral response and observations, it is conclude that, asphaltenes
30 measurement can be possible in the wavelength range of 700 to 900 nm. The response
near 700 nm is higher hence it will help to detect lower concentration of asphaltenes.
Use of more than one wavelength will give further confidence to the chemist, hence
recommend measuring at two wavelength and reporting of average measurement
results. Asphaltenes measurement possible at other wavelength also but maltenes
35 interference will be more.
14
Laboratory Experiment: 2
Aim: To prepare calibration graph for crude oil samples and calculate linearity &
coefficient.
Since certified reference 5 material for asphaltenes are not available in the market, hence
crude oil reference samples were prepared in-house using gravimetric then these crude
oils sample are used for calibration of spectroscopic method. Mineral oil used for zero
asphaltenes concentration.
10 Crude oil reference Sample Preparation: Different crude oil samples having various range
of asphaltenes concentration tested thrice by gravimetric method and average
asphaltenes concentration used for calibration of visible spectrophotometer. Crude oil
sample selected for calibration based on its regular testing requirements.
15 Total 10 numbers of different crude oil samples are identified and used to prepare
calibration graph. The details of asphaltenes concentration tabulated in table-1 and
calibration graph of asphaltenes mg vs spectral response at 755 nm and 795 nm
presented in figure 3 and 4.
20 Table: 1
Sample
Sr. No.
Crude Oil Reference
Samples
Asphaltenes mg
in Calibration
Sample
Abs at
755 nm
Abs at
795 nm
1 RM-00, Mineral oil 0.00 0.000 0.000
2 RM-01, Mangala 0.25 0.003 0.002
3 RM-02, Oman export 1.66 0.062 0.051
4 RM-03, Ural 3.39 0.160 0.131
5 RM-04, Basrah Heavy 13.47 0.665 0.563
6 RM-05, Ras Gharib 13.90 0.688 0.577
7 RM-06,Merey-16 16.23 0.853 0.718
8 RM-07, DCO 17.55 0.847 0.715
9 RM-08, Oriente 19.57 0.963 0.814
10 RM-09, Maya 24.55 1.259 1.072
11 RM-10, Talam 34.19 1.751 1.509
Observations: From the calibration graph of different crude oils at 755 nm and 795 nm
indicate that,
15
1) All the different crude oils having asphaltenes concentration in the range 0.10 mass
% to 14.7 mass % are found linear response at both the wavelength
2) The calibration graph of asphaltenes mg Vs visible spectral response at 755 nm
having calibration coefficient R2 = 0.9983 and trend line passed through zero.
3) The calibration 5 graph of asphaltenes mg Vs visible spectral response at 755 nm
having calibration coefficient R2 = 0.9974 and trend line passed through zero.
4) Sample weight needs to be increase for lower asphaltenes mass to get repeatable
results.
5) Response factor @ 755nm found to be 19.776 and @ 795 found to be 23.193
10 6) Mineral oil used as blank sample found to be satisfactory.
Conclusions: From the calibration data and observation, it is conclude that,
1) All selected crude oils are giving spectral response according to presence of
asphaltenes concentration
15 2) Excellent calibration coefficient, which is quite close to ideal value (1.0000)
3) There is no interference of maltenes and solvent at 755 nm and 795 nm wavelength
used for measurement
4) Spectral response found linear to measure asphaltenes up to 0.0 mass percent,
however higher sample weight will produce more repeatable results.
20 5) User can measure asphaltenes at any wavelength close to above region
6) User can use single or multiple wavelength for measurement, however multiple
wavelength will give more confidence to the chemist, hence recommended the
same.
7) Calibration up to 34 mg will be useful for sample having 34% asphaltenes by using
25 0.10 gm sample weight of crude oils
Laboratory Experiments: 3
Aim: To verify the performance of new method calibration and calculate the correlation
data.
30
Crude oil samples: different crude oils samples are selected for testing including reference
crude oil sample which are part of calibration data.
Spectral response of individual crude oil sample, sample weight, and calibration factors
35 are used to calculate asphaltenes mass concentration as explained in details description
of present method. Total 55 test results of gravimetric method and spectroscopic method
tabulated in table 2.
16
Table: 2
Sr.
No
Crude Oil Sample
Details
Asphaltenes
mass % By
Spectroscopy
Asphaltenes
mass % By
Gravimetric
Diff.
Gravimetric -
VIS
%
Correlation
1 RM-00, Mineral oil 0.00 0.00 0.00 0
2 RM-01, Mangala 0.02 <0.1 NA NA
3 RM-02, Oman export 0.62 0.75 0.13 17.6
4 RM-03, Ural 1.37 1.50 0.13 8.4
5 RM-04, Basrah Heavy 6.23 6.40 0.17 2.7
6 RM-05, Ras Gharib 6.70 6.90 0.20 2.9
7 RM-06,Merey-16 7.85 7.60 -0.25 -3.2
8 RM-07, DCO 7.50 7.90 0.40 5.1
9 RM-08, Oriente 8.82 9.10 0.28 3.1
10 RM-09, Maya 12.26 12.10 -0.16 -1.3
11 RM-10, Talam 14.97 14.70 -0.27 -1.8
12 Ural 1.31 1.50 0.19 12.9
13 SRFO 6.21 5.90 -0.31 -5.2
14 SRFO 5.89 5.90 0.01 0.2
15 SRFO 6.18 5.90 -0.28 -4.7
16 SRFO 6.11 5.90 -0.21 -3.6
17 Dalia 0.35 0.40 0.05 11.8
18 Dalia 0.37 0.40 0.03 7.9
19 Dalia 0.37 0.40 0.03 7.9
20 Merey-16 7.85 7.60 -0.25 -3.2
21 Merey-16 7.54 7.60 0.06 0.7
22 Merey-16 7.79 7.60 -0.19 -2.5
23 Molo 1.73 1.80 0.07 3.7
24 Molo 1.50 1.80 0.30 16.5
25 Molo 1.68 1.80 0.12 6.8
26 AWB 6.18 6.50 0.32 4.9
27 AWB 6.29 6.50 0.21 3.3
28 AWB 6.12 6.50 0.38 5.9
29 Kuwait Export 2.91 2.90 -0.01 -0.4
30 Basrah light 2.80 3.20 0.40 12.5
31 Tubarao Martelo 5.05 5.40 0.35 6.4
32 Napo 12.26 11.00 -1.26 -11.4
33 Bonga 0.04 <0.10 NA NA
34 Bonga 0.01 <0.10 NA NA
35 Maya 12.26 12.10 -0.16 -1.3
36 CPC 0.02 <0.10 NA NA
17
37 Kearl 5.18 5.20 0.02 0.5
38 Merey-16 8.20 7.60 -0.60 -8.0
39 Merey-16 8.03 7.60 -0.43 -5.7
40 Merey-16 7.87 7.60 -0.27 -3.6
41 Merey-16 8.20 7.60 -0.60 -7.9
42 Merey-16 7.91 7.60 -0.31 -4.1
43 Merey-16 7.46 7.60 0.14 1.8
44 Ural 1.34 1.45 0.11 7.7
45 Ural 1.34 1.45 0.11 7.5
46 Ural 1.29 1.45 0.16 11.2
47 Ural 1.26 1.45 0.19 13.2
48 Ural 1.30 1.45 0.15 10.6
49 Ural 1.21 1.45 0.24 16.6
50 Talam 15.06 14.70 -0.36 -2.4
51 Talam 15.32 14.70 -0.62 -4.2
52 Talam 14.02 14.70 0.68 4.6
53 Talam 14.88 14.70 -0.18 -1.2
54 Talam 14.77 14.70 -0.07 -0.5
55 Talam 14.64 14.70 0.06 0.4
NA: Not applicable due to lower mass reported as less than (<) by gravimetric method
Observations: From the observed test results and comparison data,
1) All the tested crude oil samples test results are found within reproducibility limit of
gravimetric method
2) Approximately 82 % test results are 5 found within repeatability limit of gravimetric
method
3) Test results are closely correlate with gravimetric test results
4) Very low asphaltenes (<0.1%) also found satisfactory results.
10 Conclusions: From the test results, correlation data and above observations, it is
conclude that, test results are closely correlate with gravimetric test results. Test method
performance verified between 0.0 to 14.7 % Wt. asphaltenes in crude oil samples.
15
Laboratory Experiments: 4
Aim: To prepare calibration graph for petroleum residue samples and calculate linearity
& coefficient.
18
Since certified reference material for asphaltenes are not available in the market, hence
petroleum products viz vacuum reside, heavy vacuum residue and blend of residues
reference samples were prepared in-house using gravimetric method, then these sample
are used for calibration of spectroscopic method. Mineral oil used for zero asphaltenes
5 concentration.
The primary laboratory experimental data indicate that, the response of residue sample
is approximately 20% higher than crude oil at same concentration at both wavelength,
hence to get correct test results as well as close correlation with gravimetric method,
10 separate calibration graph is prepared.
Petroleum Residue Reference Sample Preparation: Different petroleum residue
samples viz atmospheric residue, vacuum reside, heavy heavy vacuum residue and blend
of residues having various range of asphaltenes concentration tested thrice by gravimetric
15 method and average asphaltenes concentration used for calibration of visible
spectrophotometer. Petroleum residue samples selected for calibration based on its
regular testing requirements.
Total four numbers of different petroleum residue samples are identified and used to
20 prepare calibration graph and mineral oil used as zero asphaltenes concentration sample.
The details of asphaltenes concentration tabulated in table-3 and calibration graph of
asphaltenes mg vs spectral response at 755 nm and 795 nm presented in figure 5 and 6.
Table: 3
Sr. No.
Details of Petroleum Residue
Samples
Asphaltenes
mg in
Calibration
Sample
Abs at
755 nm
Abs at
795 nm
RRF-00 Mineral oil 0.00 0.000 0.000
RRF-01 CDU2-VR-161219 11.75 0.719 0.598
RRF-02 CDU1-VR-230919 23.91 1.496 1.276
RRF-03 HHVGO-300919 27.08 1.683 1.459
RRF-05 DCU-VR Feed-140919 31.97 1.964 1.712
25
Observations: From the calibration graph of different petroleum residue samples at 755
nm and 795 nm indicate that,
19
1) All the different petroleum residue samples having asphaltenes concentration in
the range 5.1 mass % to 16.8 mass % are found linear response at both the
wavelength
2) The calibration graph of asphaltenes mg Vs visible spectral response at 755 nm
5 having calibration coefficient R2 = 0.9998
3) The calibration graph of asphaltenes mg Vs visible spectral response at 795 nm
having calibration coefficient R2 = 0.9995
4) Response factor @ 755 found to be 16.155 and @ 795 found to be 18.704
10 Conclusions: From the calibration data and observations, it is conclude that,
1) All selected petroleum residue samples are giving spectral response according to
presence of asphaltenes concentration
2) Excellent calibration coefficient, which is quite close to ideal value (1.0000)
3) There is no interference of maltenes and solvent at 755 nm and 795 nm wavelength
15 used for measurement
4) Spectral response is sufficient to measure asphaltenes lower mass percent
5) User can measure asphaltenes at any wavelength close to above region
6) User can use single or multiple wavelength for measurement, however multiple
wavelength will give more confidence to the chemist, hence recommended.
20 7) Response factor found to be different at both wavelength compared to crude oil
calibration, hence separate calibration will give accurate results.
8) Calibration up to 32 mg will be useful for sample having 32% asphaltenes by using
0.10 gm sample weight of residue samples.
25 Laboratory Experiments: 5
Aim: To verify the performance of residue sample calibration and calculate the correlation
data.
Petroleum Residue samples: all residue reference samples as well as different petroleum
30 residue samples are tested using response factor found in graph 4 and 5.
Spectral response of individual petroleum residue sample, sample weight and calibration
response factors are used to calculate asphaltenes mass concentration as explained in
details description of present method. Total 27 test results of gravimetric method and
spectroscopic method tabulated in table-4.
35
Table: 4
20
Sr.
No.
Petroleum Products
Sample Details
Asphaltenes
mass % By
Spectroscopy
Asphaltenes
mass % By
Gravimetric
Diff.
Gravimetric
-VIS
%
Correlation
1 RRF-00, Mineral oil 0.00 0.00 0.00 0
2 RRF-01, CDU2-VR-161219 4.95 5.10 0.15 3.0
3 RRF-02, CDU1-VR-230919 16.88 16.80 -0.08 -0.5
4 RRF-03, HHVGO-300919 11.06 11.00 -0.06 -0.6
5 RRF-04, DCU-VR Feed-140919 14.66 14.70 0.04 0.3
6 DCU VR-23.02.2020 13.44 13.60 0.16 1.2
7 CDU 1 HHVGO-24.02.2020 7.86 8.50 0.64 7.5
8 DCU VR-240220 12.06 12.80 0.74 5.8
10 DCU VR 270220 13.28 12.80 -0.48 -3.8
11 TBP VR(Atlanta) 03.03.20 1.94 2.00 0.06 3.2
12 CDU1 HHVGO 02.03.2020 8.66 9.10 0.44 4.8
13 DCU VR 02.03.2020 14.15 14.80 0.65 4.4
14 CDU1 VR 02.03.2020 16.38 15.30 -1.08 -7.1
15 STD DCU VR 16.09.2019 14.58 14.00 -0.58 -4.1
16 STD DCU VR 18.09.2019 14.38 14.00 -0.38 -2.7
17 DCU VR 03.03.2020 13.75 14.20 0.45 3.2
18 CDU1 VR 04.03.2020 14.36 15.3 0.94 6.1
19 CDU1 HHVGO 04.03.2020 8.41 9.3 0.89 9.6
21 CDU 1 VR 18.03.2020 15.59 15.3 -0.29 -1.9
22 DCU VR 18.03.2020 14.21 14.5 0.29 2.0
23 TBP-VR-Ural MT Nordic Tellus 6.42 7.00 0.58 8.3
24 TBP-VR-Ural MT Tartan 7.38 7.00 -0.38 -5.4
25 TBP-VR-BCF 21.9 20.28 21.30 1.02 4.8
26 TBP-VR-Arab Heavy 14.68 14.00 -0.68 -4.8
27 TBP-VR-Merey-16 16.90 17.30 0.40 2.3
Observations: From the observed test results and comparison data,
1) All the tested petroleum products (residue) samples test results are found within
repeatability limit of gravimetric method
5 2) Test results are closely correlate with gravimetric test results
3) Test results
Conclusions: From the test results, correlation data and above observations, it is
concluded that, test results of all petroleum residue sample are closely correlate with
gravimetric method. The test method performance has been verified between 1.9 to 20
10 % wt. asphaltenes in residue samples and test results found to be satisfactory.
21
Laboratory Experiments: 6
Aim: To determine precision statement for present measurement method of asphaltenes
by spectrophotometric.
5
Since present method is newly developed, hence within laboratory precision data
generated using two different make spectrophotometers, three analyst, three test
samples of different crude oils and twelve test results of each samples are used for
calculation of repeatability and intermediate precision. The samples selected for precision
10 data are considering to cover wider working range of asphaltenes concentration like 1.3
8.0 and 14.6% wt. The precision data tabulated in below table 5 and 6.
Repeatability: r
The difference between two successive test results obtained by the same operator with
15 the same apparatus under constant operating condition on identical test material, in the
normal and correct operation of test method.
Table: 5, Repeatability Test Data
Instrument Analyst Test
Sample-1 Sample-2 Sample-3
Test
Results
STDDEV
Test
Results
STDDEV
Test
Results
STDDEV
1 1 1 1.34
0
8.2
0.085
15.06
0.13
1 1 2 1.34 8.03 15.32
1 2 1 1.29
0.015
7.87
0.165
14.02
0.43
1 2 2 1.26 8.2 14.88
1 3 1 1.3
0.045
7.91
0.225
14.77
0.065
1 3 2 1.21 7.46 14.64
2 4 1 1.41
0.005
8.12
0.155
14.6
0.1
2 4 2 1.42 7.81 14.8
2 5 1 1.29
0.01
7.91
0.17
13.48
0.385
2 5 2 1.31 8.25 14.25
2 6 1 1.4
0.025
7.98
0.055
14.53
0.025
2 6 2 1.45 7.87 14.48
Average 1.34 0.017 7.97 0.143 14.57 0.189
Allowable Limit (Avg STDDEV*2.8) 0.047 0.399 0.530
Repeatability Precision % 3.5 5.0 3.6
Repeatability Equation Y= 0.0369x + 0.0313
22
Precision statement for repeatability: The difference between two successive test results
obtained by the same operator with the same apparatus under constant operating
condition on identical test material would, in the normal and correct operation of test
5 method, exceed the value in only one in case of 20.
Repeatability: r = 0.0369x + 0.0313
Where X is the average results, in mass %
Intermediate Precision: R’
10 The difference between two single and independent test results obtained by different
operator working in different station using different apparatus at a single laboratory on
identical test material, in long run, in the normal and correct operation of test method.
Table: 6, Intermediate Precision (R’) Test Data
Instrument Analyst Test Sample-1 Sample-2 Sample-3
1 1 1 1.34 8.2 15.06
1 1 2 1.34 8.03 15.32
1 2 1 1.29 7.87 14.02
1 2 2 1.26 8.2 14.88
1 3 1 1.3 7.91 14.77
1 3 2 1.21 7.46 14.64
2 4 1 1.41 8.12 14.6
2 4 2 1.42 7.81 14.8
2 5 1 1.29 7.91 13.48
2 5 2 1.31 8.25 14.25
2 6 1 1.4 7.98 14.53
2 6 2 1.45 7.87 14.48
Average
Test
Results
1.34 7.97 14.57
STDDEV 0.07 0.21 0.47
Allowable Limit (STDDEV*2.8) 0.19 0.58 1.30
Intermediate Precision % 13.4 7.4 9.0
Intermediate Precision Equation Y= 0.0848x + 0.015
15
Intermediate Precision (R’) statement:
The difference between two single and independent test results obtained by different
operator working in different station using different apparatus at a single laboratory on
23
identical test material would, in long run, in the normal and correct operation of test
method, exceed the following value in only one in case of 20.
R’= 0.0848x + 0.015
Reproducibility (R): There is insufficient data to calculate reproducibility of the test
5 method at this time due to newly developed test method.
Laboratory Experiments: 7
Aim of this experimental work is to preparation of quality control standards (QCS), since
certified standards are not know to us these standard material are useful for training and
10 day to day verification of calibration.
Following different refinery samples were collected and tested by gravimetric method and
used as quality control sample for training and verification of test method.
1) QC STD CDU-2 VR : 5.1 Wt % Asphaltenes
15 2) QC STD CDU-1 HHVGO : 12.2 % Wt. Asphalenes
4) QC STD DCU VR Feed : 14.0 % Wt. Asphaltenes
Laboratory Experiments: 8
Aim of this experiment is to verify precipitation time error on analytical results.
20
Following two asphaltenes QC standard samples are prepared as per procedure and
analysed at different precipitation time viz 30, 60, 75, 90 and 120 minutes, observed test
results of asphaltenes are tabulated in below table-7.
25 Table-7
Precipitation
Time in Min.
CDU 2 VR QC STD 5.1 % Wt. DCU VR QC STD 14.0 % Wt.
Result at
755 nm
Result at
795 nm
Avg. Test
Results Wt.%
Result at
755 nm
Result at
795 nm
Avg. Test
Results
Wt.%
30 Min. 4.95 4.97 4.96 13.68 13.60 13.64
60 min. 5.01 5.05 5.03 13.96 13.89 13.92
75 Min. 5.12 5.19 5.15 14.08 14.12 14.10
90 Min. 5.19 5.24 5.21 14.16 14.21 14.18
120 Min. 5.33 5.29 5.30 14.24 14.34 14.29
24
Observations : From the above test results, it is observed that test results are slightly
increased by increase in precipitation time, hence for better accuracy proposed to
maintained precipitation time closed to 75 minutes.
5 Laboratory Experiments: 9
Aim of this experimental work is to train the Nayara Laboratory chemists and validate the
method performance in wide group of people before implementation for in-house use.
Training was arranged and various routine refinery process samples along with quality
control standard have been tested by different chemist by both test methods. The test
10 results of 45 samples are tabulated in table 8.
Table 8
Asphaltenes test method training and validation data
Sr.
No.
Date of
Testing
Sample Details
Asphaltenes
% Wt. by
ASTM D-
6560
Asphaltene
% Wt. by
UV/VIS
( Avg of 755
& 795 )
Diff. =
ASTM D6560 –
UV/VIS
1 29.10.20 DCU VR 12.2 12.83 -0.6
2 30.10.20 HHVGO 9.2 10.2 -1
3 02.11.20 CDU VR 18.6 17 1.6
4 02.11.20 CDU VR 18.6 17.3 1.3
5 02.11.20 DCU VR 13.5 14.1 -0.6
6 02.11.20 CDU VR 18.6 18.8 -0.2
7
04.11.20
QC STD HHVGO 12.2
%
12.2 11.9 0.3
8 05.11.20 HHVGO 10.6 11.2 -0.6
9 05.11.20 CDU VR 18.5 17.2 1.3
10 05.11.20 DCU VR 14 14.2 -0.2
11 06.11.20
QC STD CDU-2 VR
5.1% 16.12.2019
5.1 5.3 -0.2
12 07.11.20
QC STD CDU-2 VR
5.1%
5.1 5.6 -0.5
13 07.11.20
QC STD CDU-2 VR
5.1%
5.1 5.3 -0.2
14 07.11.20
QC STD DCU VR 14.0
% 18.09.19
14 14.2 -0.2
15 10.11.20 CDU HHVGO 10.9 11.1 -0.2
16
10.11.20
QC STD CDU-2 VR
5.1%
5.1 5 0.1
17 10.11.20 CDU 1 VR 19.2 18.6 0.6
18 11.11.20 CDU 1 HHVGO 10.8 11.7 -0.9
19 11.11.20 DCU VR 13.2 13.7 -0.5
20 11.11.20 CDU 1 VR 21.6 20 1.6
21
12.11.20
QC STD DCU VR 14.0
%
14 14.3 -0.3
22 12.11.20 DUBAI CRUDE 2.2 2.1 0.1
25
23 18.11.20 BASRAH HEAVY CRUDE 5.5 5.9 -0.4
24 18.11.20 RAS GHARIB CRUDE 6.8 6.4 0.4
25 18.11.20 DUBAI VR 12.4 11.7 0.7
26
18.11.20
QC STD CDU-2 VR 5.1
%
5.1 5.8 -0.7
27
18.11.20
CDU 1 HHVGO
14.11.20
8.4 7.8 0.6
28
18.11.20
QC STD DCU VR 14.0
%
14 13.7 0.3
29
19.11.20
CDU 1 HHVGO
18.11.20
11 9.9 1.1
30
20.11.20
QC STD DCU VR 14.0
%
14 14.3 -0.3
31
20.11.20
QC STD CDU 2 VR 5.1
%
5.1 5.7 -0.6
32
20.11.20
CDU 1 HHVGO
18.09.19
10.6 9.7 0.9
33 23.11.20 DCU VR 14.11.2020 11.7 10.9 0.8
34 23.11.20 CPC Blend crude 0.95 0.6 0.4
35 23.11.20 DCU VR 30.01.2020 14.5 14.7 -0.2
36 23.11.20 CDU-1 VR 15 14.2 0.8
37 23.11.20 SANKOFA VR 0.77 0.8 0
38 23.02.2020 DCU VR-23.02.2020 13.60 13.44 0.16
39 24.02.2020 CDU 1 HHVGO 8.50 7.90 0.60
40 24.02.2020 DCU VR-240220 12.80 12.08 0.72
41 27.02.2020 DCU VR 270220 12.80 13.29 -0.49
42 03.03.2020 TBP VR(Atlanta) 2.00 1.98 0.02
43 02.03.2020 CDU1 HHVGO 9.10 8.69 0.41
44 02.03.2020 DCU VR 02.03.2020 14.80 14.14 0.66
45 02.03.2020 CDU1 VR 02.03.2020 15.30 16.36 -1.06
46 03.03.2020
QC STD DCU VR 14.0
%
14.00 14.57 -0.57
47 03.03.2020
QC STD DCU VR 14.0
%
14.00 14.37 -0.37
48 03.03.2020 DCU VR 03.03.2020 14.20 13.73 0.47
49 04.03.2020 CDU1 VR 04.03.2020 15.3 14.35 0.95
50 04.03.2020 CDU1 HHVGO 04.03.20 9.3 8.41 0.89
51 18.03.2020 CDU 1 VR 18.03.2020 15.3 15.59 -0.29
52 18.03.2020 DCU VR 18.03.2020 14.5 14.22 0.28
53 18.03.2020 Ural Crude Oil 1.5 1.53 -0.03
54 18.03.2020 AWB Crude oil 6.5 6.17 0.33
Laboratory Experiments: 10
Aim of this experimental work is to measure the lower level (<0.1%) asphaltenes mass
in heavy distillates petroleum product samples.
5
Preparation of reference standard sample:
26
Petroleum residue sample having 5.10 % mass asphaltenes tested three times by
gravimetric method which was earlier used for calibration of higher mass is further diluted
at lower concentration level viz 0.005, 0.010, 0.025 0.050 and 0.100 % mass and used
for calibration of spectrophotometer.
5
Preparation of stock standard solution [A]:
Take 2.0200 gm of 5.10 % mass asphaltenes sample in flask and dissolved into toluene
and make it 100gm with toluene. The diluted stock sample is having 0.103 % mass or
1030 ppm mass asphaltenes.
10
Preparation of lower-level working standard [B]:
Take 5, 10, 25 and 50 gm in separate flask and make it 100 gm using toluene as diluent.
The working standard preparation and calculated asphaltenes concentration data
tabulated in below table-9
15 Table: 9
Wt. of Stock
Std. soln. [A]
Wt. of Diluent
(Toluene)
Wt. of Working
Std. [B]
Concentration of
Working Std. in
ppm mass
Concentration
of Working Std.
in % mass
5 95 100 51 0.0051
10 90 100 103 0.0103
25 75 100 257 0.0257
50 50 100 515 0.0515
100 0 100 1030 0.1030
Calibration of Visible Spectrophotometer for lower concentration (<0.1%
mass):
20 Take 4 to 6 gm weight of above working standard in separate flask and make it 100 ml
as per SOP. The absorbance of sample minus blank recorded at 755 and 795 nm and
tabulated in below table-10
Table: 10
Working Std. in
ppm mass [C]
Wt. of Working
Std. [B] for
Calibration. In
gm
Asphaltenes in mg
in working std.
[(C X B)/1000]
Abs. at 755
nm
Abs at 795
nm
51 5.041 0.257 0.009 0.007
27
103 4.1125 0.424 0.016 0.014
257 4.9122 1.262 0.043 0.036
515 4.0821 2.102 0.078 0.066
1030 4.0112 4.132 0.148 0.127
Analysis of Vacuum Gas Oil samples:
Vacuum Gas Oil samples are collected from VGO unit and used for analysis. The sample
weight taken in the range of 9 to 10 gm and prepared 100 ml as per SOP. The observed
5 test results are tabulated in below table-11.
Table: 11
Date Sample Details Asphaltenes mass
ppm at 755 nm
Asphaltenes mass
ppm at 795 nm
27.07.21 VGO Product 73 77
29.07.21 VGO Product 65 64
02.08.21 VGO Product 64 66
02.08.21 VGO Product (24.07.21) 74 77
03.08.21 VGO Product (24.07.21) 76 80
04.08.21 VGO Product (24.07.21) 70 72
05.08.21 VGO Product (24.07.21) 65 67
06.08.21 VGO Product (24.07.21) 98 104
24.07.21 VGO Feed 153 153
25.07.21 VGO Feed 128 129
26.07.21 VGO Feed 143 145
27.07.21 VGO Feed 119 120
02.08.21 VGO Feed (25.07.21) 102 104
04.08.21 VGO Feed (25.07.21) 115 119
06.08.21 VGO Feed (25.07.21) 113 115
Observations:
1) Table-10, calibration data of lower level asphaltenes indicates that, lower level
10 asphaltenes calibration is possible up to 50 ppm concentration using approx. 5 gm of
working standard weight.
2) Table-11, VGO product & feed samples analysis indicates that lower level asphaltenes
measurement also possible by visible spectroscopy method.
Conclusions:
15 Lower level asphaltenes measurement in heavy distillates type samples is possible using
lower-level calibration.
28
Laboratory Experiments: 11
Aim of this experimental work is to verify long term precision data as well as check the
stability of reference standard prepared in-house.
Two of in-house prepared asphaltenes reference standards were selected for this study
work and analysed on different dates during 5 Jan-21 to Oct-21. The observed asphaltenes
test results are tabulated in below tables- 12 and 13.
A) Asphaltenes reference sample having 5.1% mass was used regularly as QC check
sample during Jan-21 to Oct-21. The average test results of both wavelengths (755 &
10 795nm) are recorded and tabulated below table-12.
Table: 12
Date of Analysis Asphaltenes % mass
04.01.21 5.20
13.01.21 4.81
21.01.21 5.45
02.06.21 4.80
16.06.21 5.30
03.07.21 4.80
07.07.21 5.30
10.07.21 5.20
21.07.21 5.00
04.08.21 5.30
18.08.21 5.40
01.09.21 5.20
15.09.21 5.30
06.10.21 5.30
20.10.21 5.20
Avg. 5.17
STD Dev. 0.208
B) Asphaltenes reference sample having 14.0 % mass used for regularly as QC check
15 sample during Jan-21 to Oct-21. The average test results of both wavelengths (755 &
795nm) are recorded and tabulated below table -13.
Table: 13
Date of
Analysis
Asphaltenes % mass Date of Analysis Asphaltenes % mass
08.01.21 14.30 19.05.21 14.10
29
09.01.21 14.00 24.05.21 14.10
11.01.21 14.50 31.05.21 14.80
16.01.21 14.33 05.06.21 14.20
19.01.21 13.80 09.06.21 14.20
23.01.21 14.90 16.06.21 14.50
24.01.21 14.20 21.06.21 14.30
25.01.21 14.20 26.6.21 14.40
30.01.21 13.60 29.06.21 14.10
01.02.21 14.70 04.07.21 14.40
03.02.21 14.80 07.07.21 14.30
04.02.21 14.20 17.07.21 14.30
05.02.21 13.20 24.07.21 14.40
06.02.21 15.00 26.07.21 14.30
08.02.21 14.40 31.07.21 14.50
09.02.21 13.80 04.08.21 14.00
10.02.21 14.70 09.08.21 14.70
13.02.21 14.30 14.08.21 13.90
22.02.21 13.70 18.08.21 14.40
27.02.21 14.60 23.08.21 14.40
02.03.21 14.80 30.08.21 14.00
08.03.21 14.30 06.09.21 14.30
17.03.21 13.70 11.09.21 14.70
22.03.21 13.70 20.09.21 14.20
29.03.21 13.80 27.09.21 14.40
03.04.21 14.40 06.10.21 14.50
07.04.21 14.80 13.10.21 14.80
19.04.21 14.20 27.10.21 13.90
28.04.21 14.00 01.11.21 14.20
05.05.21 15.00 Avg. 14.29
12.05.21 14.00 STDDEV 0.37
Observations:
Observed test results of both reference standards indicates that, asphaltenes reference
standard prepared in-house are stable and produce repeatable results. Test results are
5 also in line with precision limit of method.
Conclusions:
Asphaltenes reference material prepared in-house found to be stable for long time and
produce precise results by visible spectroscopy method.
10
30
Advantages of the invention:
The present method for measurement of asphaltenes mass percent in crude oil and
petroleum residue samples and test results of various laboratory experiments &
observations, the inventors conclude as follow,
1) 5 The method has improved repeatability up to 50% than gravimetric method.
2) The method is having lower detection of asphaltenes from 0.01 % wt. in place of
0.5% by gravimetric method.
3) The method’s test results are closely correlate with gravimetric method.
4) The method has reduce 90% analysis time from 24 hours to 2 hours, which is very
10 quick compared to gravimetric method.
5) The method has reduce 80% chemicals consumption from 500 ml to 100 ml, which
is quite less than gravimetric method
6) The method is very simple in use than gravimetric method
7) The method has used latest and simple spectroscopic technique
15 8) The method has less HSEF risk compared to gravimetric method
9) The method has less impact on environment compared to gravimetric method
10) The method has reduce cost of analysis compared to gravimetric method
11) Retest and repeat test possible within short time by present method, which is very
difficult in case of gravimetric method
20 12) Asphaltenes molecules of crude oils and petroleum residue are having different
response at same wavelength hence separate calibration is recommend to get the
desire correlation with gravimetric method. This is advantage over existing
spectroscopic method.
13) Equipment cost will be lower compared to existing patented method.
25 14) Exactly same matrix blank used to produce more accurate results compared to
existing spectroscopic method.
15) Covering wider measurement range (0.0 to 34%) compared to existing methods.
16) Method also useful for measurement of asphaltenes in heavy petroleum distillates
sample like vacuum gas oil which is having very low level asphaltenes.
30 17) Stability of in-house prepared asphaltenes reference material verified for long time
and found stable.
Looking to the multiple benefits of present method, the method will be highly useful
globally for petroleum exploration & refining industries, testing laboratories, research
35 institutes, academic institutes, who are looking for simple, accurate, quick, safe and cost
effective asphaltenes measurement.
31
Although the invention has been described with reference to specific embodiments, this
description is not meant to be construed in a limiting sense. Various modifications of the
disclosed embodiments, as well as alternate embodiments of the invention, will become
apparent to persons skilled in the art upon reference to the description of the invention.
It is therefore contemplated that such 5 modifications can be made without departing from
the spirit or scope of the present invention as defined.
32
We claim:
1. A method for measurement of asphaltenes, comprising the steps of
A. taking appropriate sample mass (crude oil or petroleum product sample) in volumetric
5 glass flask [1];
B. adding toluene to dissolve the mass and diluting with hot n-heptane up to the mark;
C. allowing the diluted analysis sample [2] and precipitating the asphaltene molecules;
D. filtering the part volume (one tenth volume) of analysis sample [2] to prepare sample
blank [3], which also called maltenes fraction (de-asphalted sample blank);
10 E. scanning the absorbance of analysis sample [2] and using sample blank [3] by visible
spectrophotometer [4] at specified wavelengths;
F. calculating the concentration of asphaltenes mass% [5] using absorbance, response
factor of calibration graph and weight of sample.
15 2. The method as claimed in claim 1, wherein the crude oils and petroleum products are
selected from the group comprising of vacuum residue, heavy vacuum gas oil, heave coker
gas oil, blend of residue samples and furnace oil etc.
3. The method as claimed in claim 1, wherein the said method measures asphaltenes mass
20 concentration in the range of 0.0 mass % to 34.0 mass %.
4. The method as claimed in claim 1, wherein the said method measures higher mass % of
asphaltenes samples using less sample weight and lower mass % of asphaltenes sample
by higher sample weight.
25
5. The method as claimed in claim 1, wherein the spectral response measured at 755 & 795
nm for analysis sample using de-asphalted fraction of same sample with solvents as blank.
6. The method as claimed in claim 1, wherein the asphaltenes mass percent calculated using
30 average spectral response, calibration factor and weight of sample.