3.2 Modeling Electromagnetic Propagation
3.2.5 Physical Optics
An efficient assay is derived from a series of test data that give an accurate description of petroleum quality and allow an indication of its behavior during refining. The first step is, of course, to assure adequate (correct) sampling by the use of the prescribed protocols (ASTM D4057).
Thus, analyses are performed to determine whether each batch of crude oil received at the refin-ery is suitable for refining purposes. The tests are also applied to determine if there has been any contamination during wellhead recovery, storage, or transportation that may increase the processing difficulty (cost). The information required is generally crude oil dependent or specific to a particular refinery and is also a function of refinery operations and desired product slate. To obtain the neces-sary information, two different analytical schemes are commonly used and these are as follows:
(1) an inspection assay and (2) a comprehensive assay (Table 2.1).
Inspection assays usually involve determination of several key bulk properties of petroleum (e.g., API gravity, sulfur content, pour point, and distillation range) as a means of determining if
TABLE 2.1
Recommended Inspection Data Required for Petroleum and Heavy Feedstocks, Which Include Heavy Oil, Extra Heavy Oil, and Tar Sand Bitumen
Petroleum Heavy Feedstocks
Density, specific gravity Density, specific gravity
API gravity API gravity
Carbon, wt% Carbon, wt%
Hydrogen, wt% Hydrogen, wt%
Nitrogen, wt% Nitrogen, wt%
Sulfur, wt% Sulfur, wt%
Nickel, ppm Vanadium, ppm Iron, ppm
Pour point Pour point
Wax content
Wax appearance temperature
Viscosity (various temperatures) Viscosity (various temperatures) Carbon residue of residuum Carbon residue
Ash, wt%
Distillation profile: Fractional composition:
All fractions plus vacuum residue Asphaltenes, wt%
Resin constituents, wt%
Aromatics, wt%
Saturates, wt%
major changes in characteristics have occurred since the last comprehensive assay was performed.
For example, a more detailed inspection assay might consist of the following tests: API gravity (or density or relative density), sulfur content, pour point, viscosity, salt content, water and sediment content, trace metals (or organic halides). The results from these tests with the archived data from a comprehensive assay provide an estimate of any changes that have occurred in the crude oil that may be critical to refinery operations. Inspection assays are performed routinely on all crude oils received at a refinery.
On the other hand, the comprehensive (or full) assay is more complex (as well as time-consuming and costly), and is usually only performed when a new field comes onstream or when the inspection assay indicates that significant changes in the composition of the crude oil have occurred. Except for these circumstances, a comprehensive assay of a particular crude oil stream may not (unfortunately) be updated for several years. A full petroleum assay may involve at least determinations of (1) carbon residue yield, (2) density (specific gravity), (3) sulfur content, (4) distillation profile (volatility), (5) metallic constituents, (6) viscosity, and (7) pour point, as well as any tests designated necessary to understand the properties and behavior of the crude oil under examination.
The inspection assay tests discussed earlier are not exhaustive but are the ones most commonly used and provide data on the impurities that are present, as well as a general idea of the products that may be recoverable. Other properties that are determined on an as-needed basis include, but are not limited to, the following: (1) vapor pressure (Reid method) (ASTM D323), (2) total acid number (ASTM D664), and (3) the aniline point (or mixed aniline point) (ASTM D611).
The Reid vapor pressure test method (ASTM D323) measures the vapor pressure of volatile petroleum. The Reid vapor pressure differs from the true vapor pressure of the sample due to some small sample vaporization and the presence of water vapor and air in the confined space. The acid number is the quantity of base, expressed in milligrams of potassium hydroxide per gram of sample that is required to titrate a sample in this solvent to a green/green-brown end point, using p-naph-tholbenzein indicator solution. The strong acid number is the quantity of base, expressed as mil-ligrams of potassium hydroxide per gram of sample, required to titrate a sample in the solvent from its initial meter reading to a meter reading corresponding to a freshly prepared nonaqueous acidic buffer solution or a well-defined inflection point as specified in the test method (ASTM D664).
The aniline point (or mixed aniline point) (ASTM D611) has been used for the characterization of crude oil, although it is more applicable to pure hydrocarbons and in their mixtures and is used to estimate the aromatic content of mixtures. Aromatic mixtures exhibit the lowest aniline points, and paraffin mixtures have the highest aniline points. Cycloparaffin derivatives and olefin derivatives exhibit values between these two extremes. In any hydrocarbon homologous series, the aniline point increases with increasing molecular weight.
Using the data derived from the test assay, it is possible to assess petroleum quality acquire a degree of predictability of performance during refining. However, knowledge of the basic con-cepts of refining will help the analyst understand the production and, to a large extent, the antici-pated properties of the product, which in turn is related to storage, sampling, and handling of the products.
Therefore, the judicious choice of a crude oil to produce any given product is just as important as the selection of the product for any given purpose. Thus, initial inspection of petroleum using properties such as API gravity and sulfur (Tables 2.2 and 2.3) will provide information relative to the most logical means of refining or correlation of various properties to structural types present and hence attempted classification of the petroleum (Speight, 2014; Ghashghaee, 2015). Indeed, careful evaluation of petroleum from physical property data is a major part of the initial study of any petroleum destined as a refinery feedstock. Proper interpretation of the data resulting from the inspection of crude oil requires an understanding of their significance. In the following section, an indication of the physical properties that may be applied to petroleum, or even petroleum product, evaluation will be presented.
TABLE 2.2
API Gravity and Sulfur Content of Selected Crude Oils
Country Crude Oil API Sulfur % w/w
Abu Dhabi (UAE) Abu Al Bu Khoosh 31.6 2.00
Abu Dhabi (UAE) Abu Mubarras 38.1 0.93
Abu Dhabi (UAE) El Bunduq 38.5 1.12
Abu Dhabi (UAE) Murban 40.5 0.78
Abu Dhabi (UAE) Umm Shaif 37.4 1.51
Abu Dhabi (UAE) Zakum (Lower) 40.6 1.05
Abu Dhabi (UAE) Zakum (Upper) 33.1 2.00
Algeria Zarzaitine 43.0 0.07
Angola Cabinda 31.7 0.17
Angola Palanca 40.1 0.11
Angola Takula 32.4 0.09
Australia Airlie 44.7 0.01
Australia Barrow Island 37.3 0.05
Australia Challis 39.5 0.070
Australia Cooper Basin 45.2 0.02
Australia Gippsland 47.0 0.09
Australia Griffin 55.0 0.03
Australia Harriet 37.9 0.05
Australia Jabiru 42.3 0.05
Australia Jackson 43.8 0.03
Australia Saladin 48.2 0.02
Australia Skua 41.9 0.06
Brazil Garoupa 30.0 0.68
Brazil Sergipano Platforma 38.4 0.19
Brazil Sergipano Terra 24.1 0.41
Brunei Champion Export 23.9 0.12
Brunei Seria 40.5 0.06
Cameroon Kole Marine 32.6 0.33
Cameroon Lokele 20.7 0.46
Canada (Alberta) Bow River Heavy 26.7 2.10
Canada (Alberta) Pembina 38.8 0.20
Canada (Alberta) Rainbow 40.7 0.50
Canada (Alberta) Rangeland South 39.5 0.75
Canada (Alberta) Wainwright-Kinsella 23.1 2.58
China Daqing (Taching) 32.6 0.09
China Nanhai Light 40.6 0.06
China Shengli 24.2 1.00
China Weizhou 39.7 0.08
Colombia Cano Limon 29.3 0.51
Congo (Brazzaville) Emeraude 23.6 0.600
Dubai (UAE) Fateh 31.1 2.000
Dubai (UAE) Margham Light 50.3 0.040
Ecuador Oriente 29.2 0.880
Egypt Belayim 27.5 2.200
Egypt Gulf of Suez 31.9 1.520
Egypt Ras Gharib 21.5 3.640
Gabon Gamba 31.4 0.090
(Continued )
TABLE 2.2 (continued )
API Gravity and Sulfur Content of Selected Crude Oils
Country Crude Oil API Sulfur % w/w
Gabon Rabi-Kounga 33.5 0.070
Ghana Salt Pond 37.4 0.097
India Bombay High 39.2 0.150
Indonesia Anoa 45.2 0.040
Indonesia Ardjuna 35.2 0.105
Indonesia Attaka 43.3 0.040
Indonesia Badak 49.5 0.032
Indonesia Bekapai 41.2 0.080
Indonesia Belida 45.1 0.020
Indonesia Bima 21.1 0.250
Indonesia Cinta 33.4 0.080
Indonesia Duri (Sumatran Heavy) 21.3 0.180
Indonesia Ikan Pari 48.0 0.020
Indonesia Kakap 51.5 0.050
Indonesia Katapa 50.8 0.060
Indonesia Lalang (Malacca Straits) 39.7 0.050
Indonesia Minas (Sumatran Light) 34.5 0.081
Indonesia Udang 38.0 0.050
Iran Aboozar (Ardeshir) 26.9 2.480
Iran Bahrgansar/Nowruz 27.1 2.450
Iran Dorrood (Darius) 33.6 2.350
Iran Foroozan (Fereidoon) 31.3 2.500
Iran Iranian Heavy 30.9 1.730
Iran Iranian Light 33.8 1.350
Iran Rostam 35.9 1.550
Iran Salmon (Sassan) 33.9 1.910
Iraq Basrah Heavy 24.7 3.500
Iraq Basrah Light 33.7 1.950
Iraq Basrah Medium 31.1 2.580
Iraq North Rumaila 33.7 1.980
Ivory Coast Espoir 32.3 0.340
Kazakhstan Kumkol 42.5 0.07
Kuwait Kuwait Export 31.4 2.52
Libya Amna 36.0 0.15
Libya Brega 40.4 0.21
Libya Bu Attifel 43.3 0.04
Libya Buri 26.2 1.76
Libya Es Sider 37.0 0.45
Libya Sarir 38.4 0.16
Libya Sirtica 41.3 0.45
Libya Zueitina 41.3 0.28
Malaysia Bintulu 28.1 0.08
Malaysia Dulang 39.0 0.12
Malaysia Labuan 32.2 0.07
Malaysia Miri Light 32.6 0.04
Malaysia Tembungo 37.4 0.04
Mexico Isthmus 33.3 1.49
(Continued )
TABLE 2.2 (continued )
API Gravity and Sulfur Content of Selected Crude Oils
Country Crude Oil API Sulfur % w/w
Mexico Maya 22.2 3.30
Mexico Olmeca 39.8 0.80
Neutral Zone Burgan 23.3 3.37
Neutral Zone Eocene 18.6 4.55
Neutral Zone Hout 32.8 1.91
Neutral Zone Khafji 28.5 2.85
Neutral Zone Ratawi 23.5 4.07
Nigeria Antan 32.1 0.32
Nigeria Bonny Light 33.9 0.14
Nigeria Bonny Medium 25.2 0.23
Nigeria Brass River 42.8 0.06
Nigeria Escravos 36.4 0.12
Nigeria Forcados 29.6 0.18
Nigeria Pennington 36.6 0.07
Nigeria Qua Iboe 35.8 0.12
North Sea (Denmark) Danish North Sea 34.5 0.260
North Sea (Norway) Ekofisk 39.2 0.169
North Sea (Norway) Emerald 22.0 0.750
North Sea (Norway) Oseberg 33.7 0.310
North Sea (United Kingdom) Alba 20.0 1.330
North Sea (United Kingdom) Duncan 38.5 0.180
North Sea (United Kingdom) Forties Blend 40.5 0.350
North Sea (United Kingdom) Innes 45.7 0.130
North Sea (United Kingdom) Kittiwake 37.0 0.65
North Yemen Alif 40.3 0.10
Oman Oman Export 34.7 0.94
Papua New Guinea Kubutu 44.0 0.04
Peru Loreto Peruvian 33.1 0.23
Qatar Dukhan (Qatar Land) 40.9 1.27
Qatar Qatar Marine 36.0 1.42
Ras Al Khaiman (UAE) Ras Al Khaiman 44.3 0.15
Russia Siberian Light 37.8 0.42
Saudi Arabia Arab Extra Light (Berri) 37.2 1.15
Saudi Arabia Arab Heavy (Safaniya) 27.4 2.80
Saudi Arabia Arab Light 33.4 1.77
Saudi Arabia Arab Medium (Zuluf 28.8 2.49
Sharjah (UAE) Mubarek 37.0 0.62
Sumatra Duri 20.3 0.21
Syria Souedie 24.9 3.82
Timor Sea (Indonesia) Hydra 37.5 0.08
Trinidad Tobago Galeota Mix 32.8 0.27
Tunisia Ashtart 30.0 0.99
United States (Alaska) Alaskan North Slope 27.5 1.11
United States (Alaska) Cook Inlet 35.0 0.10
United States (Alaska) Drift River 35.3 0.09
United States (Alaska) Nikiski Terminal 34.6 0.10 United States (California) Hondo Sandstone 35.2 0.21
(Continued )