alexa Characterisation of Oil Properties from a Niger Delta Crude

ISSN: 2161-0525

Journal of Environmental & Analytical Toxicology

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Characterisation of Oil Properties from a Niger Delta Crude

Ofodile SE, Boisa N, Obunwo CC and Frank OM*
Department of Chemistry, Rivers State University, Port Harcourt, Nigeria
*Corresponding Author: Frank OM, Department of Chemistry, Rivers State University, Port Harcourt, Nigeria, Tel: +2347095415002, Email: [email protected]

Received Date: Apr 09, 2018 / Accepted Date: Apr 21, 2018 / Published Date: Apr 28, 2018

Abstract

The characterization of crude being physical, elemental, compositional and bulk parameter analyses is an investigative approach into the properties of crude oil. This study shows the properties of Afiesere crude oil in the Niger Delta area of Nigeria. The parameters investigated are density, specific gravity, API gravity, vapour pressure, kinematic viscosity, moisture content, gum content, cloud point, pour point, flash point, metallic constituents (V, Ni), elemental (N2,O2,S2) and compositional (aliphatic and heavier) hydrocarbons using ASTM/IP procedural methods. The results show density (0.9440 g/cm3), specific gravity (0.9450), API gravity (18.2°), vapour pressure (7 kPa), kinematic viscosity (80.4 cSt), moisture (3175 ppm), gum content (71,000 ppm), cloud point (-2°C), pour point (-10°C), flash point (95°C), Vanadium (0.05 ppm), Nickel (0.39 ppm), N2 (0.11%), O2 (<0.5%), S2 (1.25%), aliphatic hydrocarbons (0.032-2.804%), heavier hydrocarbons (0.210-1.737%). The outcome of these results can be used effectively to predict the transportation, storage and/or refining of the crude oil being analysed.

Keywords: Characterization; Niger delta; Afiesere; Crude oil; Properties

Introduction

Crude oil is a naturally occurring flammable liquid consisting of a complex of hydrocarbons and heteroatomic organic compounds of various molecular weights [1]. Crude oil exhibits wide variations in composition and properties and these occur not only in crude oil from different fields but also in oil taken from different production depths in the same well [2]. According to history, physical properties like boiling point, viscosity, odour and density (specific gravity) have been used to describe oils; however, because of the molecular complexity of crude oil and bitumen, there is more to analysis identification and characterization than the four properties mentioned above would indicate [2]. The mixture of hydrocarbon is highly complex and elemental analysis of petroleum shows mainly carbon and hydrogen, smaller amounts of nitrogen, oxygen and sulphur as well as trace metals like vanadium, nickel, etc. the refiner is concerned with methods of analysis that would provide information concrete enough to assess the potential quality of the oil, supply preliminary engineering data and indicate if any difficulty would arise in handling, transporting and/or refining crude oil and its products [2]. The end product of crude oil analysis is a series of data that allows the production analyst/ chemist to specify the character and quality of the material being analysed or investigated. Therefore, a series of specifications are determined for crude oil and its products [2].

Worthy of note is the interest of the refiner, marketer and consumer to make sure that the specifications are efficient. The efficiency of the specifications should be able to predict the feedstock behavior and product quality, measure independent properties and with adequate precision as well as render rapid response to refinery and laboratory demands [2]. Hence, crude oil characterization (analysis) is a complex task that needs a multidimensional approach and an explanation of the data obtained needs adequate interpretation. There are different analyses carried out on heavy oil including organic, chemical and elemental characterization. The characterization of heavy oil gives a valuable and detailed insight on the best method of production, cost of refining, environmental impact and the specification regarding the upgrading of heavy conventional oil [3,4]. The aim of the research work is to investigate the characterization of crude oil properties from Afiesere oil field and correlate the findings to the quality of the crude in terms of transporting, storing and/or refining of the crude oil.

Materials And Methods

Description of study area

Afiesere Oil Field is located at Afiesere community in Ethiope Local government area of Delta State, Nigeria on OML 30 of the NPDC FIELD as shown in the map in Figure 1. The licence covers 1,095 sq. km and the field was discovered between 1961 to 1966.

environmental-analytical-toxicology-circled

Figure 1: Map of OML 30 showing sample location circled in black.

Sample collection and analyses

The crude oil sample was collected from the Research & Development Division of the Nigerian National Petroleum Corporation (NNPC). The analyses were carried out at the Water/oil Laboratory of the Eleme Petrochemicals Company Limited, Rivers State and Laser Engineering Laboratory, Port Harcourt. The characterization of the crude oil was done by analysing the physical properties as well as elemental by using modified ASTM/IP Methods. Colour /appearance; Density, specific gravity, API Gravity; Moisture content (IP 831 KF Coulometer); Gum content; Cloud point; Pour point; Flash point; Kinematic and Dynamic viscosities; Reid vapour pressure; Metallic constituents (Operational Manual of Perkin Elmer AAnalyst 200 model) and compositional analysis (GC-FID) [5-12].

Results And Discussion

The crude oil analysis results are presented in Tables 1-3. The specific gravity values of petroleum products are close to density values and ranges from about 0.80-0.88 for light crude oils to about 0.94-0.98 for heavy oils and about 1.00-1.03 for bitumen [2]. The crude being studied falls under the group of heavy oil (Table 1). Earlier, petroleum refining companies, used density and specific gravity data to indicate crude oil quality and correlate it with the aromatic character and saturate (paraffin and naphthene) character that the specific gravity is highest for aromatics and lowest for saturates. The reverse of this analogy is the API gravity. The API gravity of the Afiesere crude oil (Table 1) which is 18.2° (≤ 20°) implied that, it contains a lesser proportion of lower boiling fractions and higher amounts of the higher boiling asphaltic constituents. This crude oil is heavy crude oil because it does not flow easily and its density /specific gravity are higher than that of light crude oil. Heavy oil is asphaltic (contain asphaltenes and resins). According to Dusseault et al., this type of crude is heavy, dense and viscous due to the high ratio of aromatics and naphthenes to paraffins and high amounts of nitrogen, sulphur, oxygen and heavy metals. The kinematic and dynamic viscosities have particular role in assessing the producibility of a reservoir (rate and amount of oil production from a reservoir) as well as determining the amount of diluent that will permit pipeline transportation of the crude oil i.e., it is used in calculating the flow of liquids through nozzles, orifices and pipelines. The kinematic viscosity of petroleum products is important for flow of fuel through pipelines, injection nozzles and lubricants for bearings, gears, compressor cylinders and hydraulic equipment. Also, for designing proper temperature ranges for the proper operation of the fuel in burners. The lower the viscosity of a fluid, the more easily it flows. Like density, viscosity is affected by temperature. As temperature decreases, viscosity increases. “Thin” liquids, like water or gasoline, have low viscosities; “thick” liquids, like Lubricating oils have higher viscosities. Fuels outside the required range may cause power loss or improper atomization of the fuel in a diesel engine. Lubrications assist in removing the frictional forces between two moving bodies. Moisture (water) can easily find its way into crude oil and its products (fuels) as a result of breathing in moisture laden air in storage facilities. When sudden drop in atmospheric temperature takes place, condensation of moisture occurs. Also, leakages of rain into fuel transportation and storage facilities; leakages of water during shipment of tanker. The presence of water accumulated in tanks used for storage and handling can cause contamination (adverse effect on product quality). The moisture content present in crude oil can also lead to difficulties in refining operations for instance; it corrodes equipment and blocks heat exchangers. Cloud point helps to determine the temperature at which paraffin crystals will begin to block fuel filters and lines and cause starting and stalling problems for diesel engines. The significance of cloud point is that, under low-temperature conditions, paraffinic constituents of a fuel may be precipitated as a wax. The wax settles out and blocks the fuel system lines and filters causing malfunctioning of the engine. Cloud point is one of the main guides to evaluate the wax precipitation of a fluid. Oil products are mixtures of many different components, and those properties of oil products which restrict their usability are often dependent on the properties of the individual components. The pour point of oil indicates the lowest temperature at which oil may be used in some applications. High pour points usually occur in oil that has significant paraffin content. Paraffin (or waxes) will start to precipitate as the temperature decreases. As some point, the precipitate accumulates to the point where the fluids can no longer flow. The lower the pour point, the more useful the oil is in cold temperatures. Afiesere crude oil has very minute percentage of paraffin (Table 1 and Figures 2a and 2b).

environmental-analytical-toxicology-Chromatogram

Figure 2: (a) GC Chromatogram of Afiesere crude showing heaviers (b) GC Chromatogram of Afiesere crude showing C1 to C40.

S/NO. Parameter Unit Result
1 Appearance/colour - Dark brownish liquid
2 [email protected]°C g/cm3 0.944
3 Specific [email protected] - 0.945
4 API gravity ° 18.2
5 Reid vapour pressure kPa 7
6 Kinematic viscosity cSt 80.4
7 Dynamic viscosity - 75.9
8 Moisture ppm 3175
9 Gum content mg/100 ml 71,000
10 Cloud point °C -2
11 Pour point °C -10
12 Flash point °C 95

Table 1: Physical and chemical characteristics of the crude oil.

S/no. Parameter Symbol Unit Result
1 Nickel Ni ppm 0.393
2 Vanadium V ppm 0.052
3 Nitrogen N2 % 0.111
4 Oxygen O2 % <0.5
5 Sulphur S ppm 1.253

Table 2: Metallic and Elemental constituents of the crude oil.

S/no. Parameter Symbol Raw Data (%) Normalized Result (%)
1 n-heptane C7 0.059 0.032
2 n-octane C8 0.205 0.11
3 n-nonane C9 1.501 0.809
4 n-decane C10 2.452 1.322
5 n-undecane C11 1.164 0.627
6 n-dodecane C12 1.991 1.073
7 n-tridecane C13 1.43 0.771
8 n-tetradecane C14 2.936 1.583
9 n-pentadecane C15 3.806 2.051
10 n-hexadecane (cetane) C16 3.793 2.044
11 n-heptadecane C17 3.41 1.838
12 Pristane Pr 3.452 1.861
13 n-octadecane C18 1.047 0.564
14 Phytane Ph 1.185 0.639
15 n-nonadecane C19 2.479 1.336
16 n-icosane (eicosane) C20 4.595 2.477
17 n-henicosane C21 4.54 2.447
18 n-docosane C22 3.353 1.807
19 n-tricosane C23 3.138 1.691
20 n-tetracosane C24 4.466 2.407
21 n-pentacosane C25 2.633 1.419
22 n-hexacosane (cerane) C26 2.079 1.121
23 n-heptacosane C27 3.174 1.711
24 n-octacosane C28 2.573 1.387
25 n-nonacosane C29 3.374 1.819
26 n-triacontane C30 4.826 2.601
27 n-hentriacontane C31 5.168 2.786
28 n-dotriacontane C32 5.203 2.804
29 n-tritriacontane C33 4.616 2.488
30 n-tetratriacontane C34 2.252 1.214
31 n-pentatriacontane C35 2.753 1.484
32 n-hexatriacontane C36 3.787 2.041
33 n-heptatriacontane C37 3.019 1.627
34 n-octatriacontane C38 1.36 0.733
35 n-nonatriacontane C39 1.532 0.826
36 n-tetracontane C40 0.652 0.351
37 cyclohexane   0.513 0.277
38 1,1'-methylene bis-cyclohexane   0.39 0.21
39 9,12-octadecadienoic acid (z,z)-2H-inden-2-one   0.916 0.494
40 5-eicosyne   0.535 0.288
41 Trans, cis-1,9-dimethylspiro[4.5] decane   0.452 0.244
42 Isocamphane cyclohexane   0.446 0.24
43 Iridomyrmecin   0 0
44 Bicycle [2.2.1] heptane,2,2,3-trimethyl-endo-amorphane-B   0.613 0.33
45 Naphthalene   0.71 0.383
46 Adamantane   0.564 0.304
47 Tricycle [3.3.1.13.7] decane   1.16 0.625
48 Bicycle [4.1.0] heptane   0.509 0.274
49 Adamantane, 1,3-dimethyl adamantane   0.554 0.299
50 Bicycle [4.1.0] heptane, 3-methyl naphthalene   2.216 1.194
51 3,9-epoxy-p-mentha-1,8(10)-diene benzenemethanol   1.117 0.602
52 Adamantine,1,3-dimethyl-tricyclo[4.3.1.13,8] undecane   0.755 0.407
53 Trans,cis-1,8-dimethylspiro[4.5] decane   1.069 0.576
54 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole   0.406 0.219
55 Trans,trans-1,10-dimethylspiro[4.5]decane   1.073 0.578
56 Adamantine,1,3-dimethyl-1H-Indene   1.098 0.592
57 Benzoic acid   0 0
58 Bicycle[2.2.1]heptane   0 0
59 Trans,trans-1,8-dimethylspiro[4.5]decane   0 0
60 3-dodecyne   0.392 0.211
61 2H-benzocyclohepten-2-one   0.92 0.496
62 Muurolane-A   0.428 0.231
63 Cis,cis-2,10-dimethylspiro[5.5] undecane   0.589 0.317
64 Cis,trans-2,9-dimethylspiro[5.5]undecane   0.75 0.404
65 Bicycle[3.1.1] heptane-2-carboxalde   0.677 0.365
66 Neopentylidene cyclohexane   0.655 0.353
67 ([email protected],[email protected],[email protected])-5,9-dimethylspiro[3.5]nonan-1-one   0.853 0.46
68 3-dodecyne cyclohexane   0.404 0.218
69 3-cyclohexane-1-carboxaldehyde   1.874 1.01
70 cyclopentane   0 0
71 Decahydro-4,4,8,9,10-pentamethylnaphthalene bicyclo [2.2.1] heptane   3.222 1.737
72 Decahydro-4,4,8,9,10-pentamethylnaphthalene benzene acetonitrile   1.028 0.554
73 Isocamphane 3-cyclohexene-1-carboxaldehyde   0.462 0.249
74 2(1H)-naphthalenone   1.024 0.552
75 1-dodecyne   0.515 0.278
76 Benzene acetonitrile   2.488 1.341
77 Decahydro-4,4,8,9,10-pentamethylnaphthalene neopentylidene cyclohexane   0.712 0.384
78 3-cyclohexane-1-carboxaldehyde   0 0
79 Silane   0.78 0.42
80 Α-phenyl-decahydro-4,4,8,9,10-pentamethylnaphthalene 2(1H)-naphthalenone   0.967 0.521
81 3-cyclohexene-1-carboxaldehyde   0 0
82 Decahydro-9-ethyl-4,4,8,10-tetramethylnaphthalene neopentylidene cyclohexane cyclopropane   0 0
83 Bicycle [2.2.1] heptane   1.212 0.653
84 3,4-bis (1-methylethenyl)-1,1-dimethyl-cyclohexane   0 0
85 Diallyldivinylsilane   1.117 0.602
86 Neopentylidene cyclohexane naphthalene   3.009 1.622
87 Decahydro-9-ethyl-4,4,8,10-tetramethylnaphthalene   0 0
88 p-menth-8(10)-en-9-ol   0 0
89 2-dodecen-1-yl (-) succinic anhydride spiro [cyclobutane-1,3'-[7] oxabicyclo [4.1.0] heptan-2-one   0.685 0.369
90 Neopentylidene cyclohexane 3-cyclohexene-1-carboxaldehyde   2.101 1.132
91 Cis-2(1H)-naphthalenone   0.766 0.413
92 1,3,4-trimethyl-longifolenaldehyde   0 0
93 Cis-3,6-nonadien-5-one   1.08 0.582
94 2,10-dodecadien-1-ol   1.384 0.746
95 Bicycle[3.1.0] hexan-2-one   0 0
96 2-dodecen-1-yl(-)succinic anhydride I,3,5-trihydroxy-2,6-dinitrobenzole   1.379 0.743
97 4-hexenoic acid   1.266 0.682
98 2-butanone   1.445 0.779
99 2(1H)-naphthalenone   0 0
100 9-oxabicyclo[6.1.0] nonane   0 0
101 3-methyl-4-(methoxycarbonyl) hexa-2,4-dienoic acid   1.172 0.632
102 Acetamide   0.78 0.42
103 Cis-1-naphthalenol   0 0
104 Cis-6-octenal   1.161 0.626
105 1-(cyclohexylmethyl)-2-ethyl,-cis-cyclopentane   0.741 0.399
106 4-methyl-1-(1-methylethyl)-, (1α,4β,5α)-6-octenal   0.485 0.261
107 N-methyl-N-[4-[4-methoxy-1-hexahydropyridyl]-2-butynyi]-2H-bisoxireno[2,3:8,8a] azuleno [4,5-b]furan-7(3ah)-one   0.864 0.466
108 2-dodecen-1-yl (-) succinic anhydride 1H-indene   0.834 0.45
109 4-methyl-1-(1-methylethyl)-1α,4β,5α-amorphane-B   0.474 0.255
110 Oxirane   0 0
111 2-dodecen-1-yl(-) succinic anhydride decahydro-9-ethyl-4,4,8,10-tetramethylnaphthalen cyclopentane   0.663 0.357
112 2-dodecen-1-yl(-) succinic anhydride 3,5-decadiene   0.523 0.282
113 1-(1,5-dimethylhexyl)-4-(4-methylpentyl)-anthracene   0 0
114 Octadecane   1.086 0.585
115 3,5-decadiene   0.799 0.431
116 1H-indene   0 0
117 D-homoandrostrane   0 0
118 2-buten-1-one   0.61 0.329
119 5-butyl-6-hexyloctahydro-1H-indene   0.71 0.383
120 5-butyl-6-hexyloctahydro-amorphane B   0 0
121 5-butyl-6-hexyloctahydro-picrotoxinin   0.536 0.289
122 2H-Bisoxirano [2,3:8,8a] azuleno [4,5-b] furan-7(3ah)-one   2.276 1.227
123 2,6-dimethyl-6-(4-methyl-3-pentenyl) α-damascone   0.929 0.501
124 Tricyclo [4.3.0.07.9] nonane   1.123 0.605
125 15-isobutyl-(13-α.h)-isocopalane   1.318 0.71
126 4(1H)-Pteridinone   2.55 1.374
127 Cyclodeca[b] furan-2(3H)-one   1.893 1.02
128 Sesquirosefuran   2.331 1.256
129 Cis-1H-cycloprop[e] azulene   2.415 1.302
130 5α,13α-1H indene   0.774 0.417
131 5-butyl-6-hexyloctahydro-citenamide   2.137 1.152
132 9-cyclohexyltetradecahydro-2H-1,2,3-triazole-4-carboxaldehyde   3.029 1.633
133 Isoquinoline   2.544 1.371
134 2-(acetoxylmethyl)-3-(methoxycarbonyl) biphenylene   0.493 0.266
135 Anthracene   0.583 0.314
136 3,3-diethoxy-1,1,1,5,5,5-hexamethyl trisiloxane   0.41 0.221
  TOTAL   185.53 100

Table 3: Compositional content (components) of the crude oil.

The flash point provides a simple convenient index for assessing the flammability of a wide variety of materials. The flash point is often used as one descriptive characteristic of liquid fuel, but it is used to describe liquids that are not used intentionally as fuel. The flash point is just one flammability characteristics that is used to assess the hazardous nature of a material. Too low a flash point will cause fuel to be a fire hazard, subjecting to flashing, and possible continued ignition and explosion. A low flash point may indicate contamination by more volatile and explosive fuel such as gasoline. The values from flash point test can affect how the fluid may be shipped, stored and discarded. Flash point is used by manufacturers and marketers of petroleum products to detect contamination e.g., an abnormally low flash point on a sample of kerosene may indicate gasoline contamination. The flash point is also an aid in establishing the identity of a petroleum product. Another related flammability property of a fluid is its autoignition temperature. This is much higher than the flash point and it represents the temperature at which the sample will ignite from only the heat being applied and no external source of ignition. Vapour pressure is an important physical property of volatile liquids. It is the pressure that a vapour exerts on its surroundings. For volatile petroleum products, vapour pressure is used as an indirect measure of evaporation rate. High vapor pressures and a low distillation temperature for 10% evaporated both help cold starting. Under hotoperating conditions, high vapor pressure also contributes to vapor lock and increases vapor formation in fuel tanks. In cold weather, a gasoline that is not volatile enough may cause hard starting and poor warm-up. In the winter months, for example, your vehicle's engine is extremely cold before startup, and the gasoline must have a high enough volatility to be able to vaporize easily in a cold engine (Table 2).

Metallic constituents of the crude oil

Metallic trace components such as nickel, vanadium, lead and arsenic have an adverse effect on refining or processing operation. These metals are catalyst poisons, and some of them do additional harm. For example, vanadium compounds damage turbine blades and refractory furnaces but from Table 1, vanadium, Nickel, nitrogen, oxygen and sulphur in the analyzed crude were far below the specification as given by Speight et al., Vanadium 50-250 ppm; Nickel 20-100 ppm; Nitrogen 0.1-2.0%; Oxygen 0.05-1.5% and Sulphur 0.05-6.0%, thereby making the Afiesere crude one of the Nigerian crude that has minute quantities of metals and heteroatoms. The metallic and elemental constituents are found in every crude oil and hence, their concentrations must be reduced to enable the conversion of the crude oil to transportation fuel. The essence is that, if sulphur and nitrogen are present in the final fuel during combustion, sulphur oxides (SOx) and nitrogen oxides (NOx) may be formed respectively [13]. Since numerous laboratory techniques are available to analyse a crude oil for metallic contaminants, the one used is a matter of individual preference or availability of analytical tools. However, metallic contaminants are often determined using the Atomic Absorption method.

Aliphatic components present in the crude oil

The components present in the crude oil indicated a very low paraffinic nature (lighters), higher amounts of heaviers and about 120 carbon atoms (Table 3, Figures 2a and 2b). This is in line with that heavy crude oil has a higher percentage of compounds with over 60 carbons atoms and hence a high boiling point and molecular weight. nC7 and nC8 were the least n-alkane hydrocarbon obtained on the chromatogram with no traces of nC5 and nC6 on it [14-19].

Conclusion

The investigation showed that, Afiesere crude oil is a heavy one that contains very little amounts of paraffin (saturates) and high level of higher asphaltic components (aromatics, resins and asphaltenes). This crude oil when distilled, due to its physical and chemical properties, the petroleum products can be conveniently used in cold temperature regions and as a non-fire hazard; maintains vapour formation in fuel tanks and can help in the conversion of crude oil to transportation fuel as the concentration level of metals present in the crude is minimal.

References

Citation: Ofodile SE, Boisa N, Obunwo CC, Frank OM (2018) Characterisation of Oil Properties from a Niger Delta Crude. J Environ Anal Toxicol 8: 563. DOI: 10.4172/2161-0525.1000563

Copyright: © 2018 Ofodile SE, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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