Correlation of Metals with Hydrocarbons of Crude Oil in Maysan Province Southern Iraq

Correlation of Metals with Hydrocarbons of Crude Oil in Maysan Province Southern Iraq

Asaad Kadhim Eqal

Mechanics- Production Department

Southern Technical University Amarah Technical Institute, Amarah, Iraq

Abstract: It is known that Crude oil and its finished products contain mainly hydrocarbons, especially alkanes, naphthenic and aromatics. Hydrocarbons, which, composed mostly of carbon and hydrogen. Also, crude oil found to contain trace metal amounts of the element as well as oxygen and sulfur contained compounds. In order to clarify the relationship between hydrocarbons and trace metals in crude oil, separated samples of crude oil from four oil fields (Amarah field, Buzurgan field, Noor field, and Abogarab field) were collected and analyzed by Atomic Absorption spectrophotometer and Gas Chromatography to identify the trace metals, and hydrocarbons. The results revealed that the concentration of Mn ranged between (1385.1 to 1395.1) ppm, , Pb ranged between (62 to 87) ppm, Fe ( 14 to 30 ) ppm, Cu ( 6.9 to 29.1) ppm, Ni ( 17.1 to 27.3) ppm, Zn ( 10.6 to 21) ppm, Co (10.8 to 15.1 ) ppm, V ( 2.97 to 1.03) ppm, while the concentration of hydrocarbons from (C1 to C31) ranged from (0.02 to 3.46) wt% and other hydrocarbons (C32+) ranged (55.31 to 69.59) wt% in all field crude oil positions. In conclusion, there is a different amounts of trace metals found in crude oil, however, these metals shows a positive and negative correlation with oil hydrocarbons.

Keywords: Trace Metals, hydrocarbons, compounds, Crude Oil, Concentration, Element. Petroleum, Aromatics, organometallic

1. INTRODUCTION

   Crude oil and its finished products (Petroleum Products) contain mainly hydrocarbons, especially alkanes (paraffins), naphthenic, aromatics hydrocarbons, organometallic compounds and inorganic salts (metallic compounds). Hydrocarbons are mostly based on two elements carbon and hydrogen ranges from 84-87% carbon and (11-15%) hydrogen (ASTM D-4175). Fuel oil is a complex mixture of highly heterogeneous compounds of aliphatic (saturated), olefinic (unsaturated), aromatic and asphaltene hydrocarbons with significant amounts of additional elements, such as sulfur, oxygen, nitrogen and compounds containing metallic constituents, particularly; Vanadium, Nickel, Iron and Copper [1, 2, 3, 4]. Since petroleum is generated from organic matter of fine grained rocks, it is possible to correlate crude oils having a common source but reservoir in different horizons [5]. One of such ways of doing this is by analyzing the hydrocarbon fractions, Petroleum hydrocarbons fingerprinting (Gas chromatography fingerprinting) analysis for quantitative and

   qualitative oil characterization which is often used for evaluating the range of hydrocarbons in crude oil or rock extract [6]. The distribution of n-alkanes in crude oils can be used to indicate the organic matter source. Generally, short and medium chain, odd carbon numbered compounds of aliphatic hydrocarbons with carbon numbers between n-C15 and n- C25 are associated with aquatic sources, whereas shorter derivatives originate from lacustrine in contrast to mainly microphysics plants as sources of the longer chain derivatives [7]. The instrumental techniques of chromatography, ultraviolet and infrared spectroscopy together with mass spectrometry facilitate knowledge of the detailed hydrocarbon type composition of crude. The metal contents are present in crude oil either as inorganic salts, such as sodium and magnesium chlorides, or in the form of organometallic compounds, such as those of nickel and vanadium (as in porphyrins) [8, 9]. The total hydrocarbon composition and concentration of trace metals in crude oil varying from one paper to another, due to the place of study. Several studies investigated the presence of metals and hydrocarbons in crude oil to evaluating its petroleum system independent of the higher hydrocarbon makers in order to provide a quick and inexpensive way of understanding its petroleum system and result were different [5, 10, 11, 12, 13, 14, 15]. The aim of this study is to investigate the correlation of metals with a type of hydrocarbons in crude oil in Amarah city Maysan province Iraq.

2. MATERIALS AND METHODS

   1. Sample Collection and Preparation

      Four crude oil samples were collected from different fields, Noor field, Amarah field, Buzurgan field and Abogarab field in Maysan province south of Iraq. The determination of the metals in crude oil requires pretreatment to the sample before presentation to the instrument, hence our samples treated and digested in wet as seen in [16, 17].

   2. Trace Metal Concentrations

      Ten trace metal content in crude oil samples were measured by using Atomic Absorption Spectrometer (PgAA500) in Basra University Marine Science Centre.

   3. Total Hydrocarbon Contents

      Thirty two of the hydrocarbons content were measured by using Gas Chromatography Agilent (7890 A) in Maysan Oil Company Labs.

   4. Correlation of Trace Metal and Hydrocarbons Content

   The correlations between trace metal and hydrocarbons compounds in crude oil samples were done by using SPSS and EXCEL program.

3. RESULTS AND DISCUSSION

1. Trace Metals Concentration

   The results showed that Mn the most abundant metal followed by Pb, Fe, Cu, Ni, Zn, Co, and V in Amarah field, While, Mn is the most abundant followed by Pb, Ni, Zn, Co, Fe, Cu, and V and in Buzurgan field. In addition Noor

   field and Abogarab field was the most abundant Mn followed by Cu, Pb, Zn, Ni, Fe, Co, and V and Mn followed by Pb, Ni, Fe, Co, Zn, Cu, and V respectively seen in table

   1. These values are higher than the value which was reported by [18, 19, 20]. However the results of trace metal could be different due to the contact of crude oil with rocks contained this metal and the distribution of the metals is fairly homogenous in the samples. Also the difference in geological activity, and mineral accumulation during rock deposition. The relatively higher levels of Mn, Cu, Pb, Zn, Ni, Fe, Co, and V observed in the result except Cr, may explained by the fact that most soils associated with the areas of study are also associated with appreciable deposits of metal ores such as iron [20].

      TABLE 1 CONCENTRATION OF THE TRACE METALS ASSOCIATED WITH CRUDE OIL IN DIFFERENT FIELDS (PPM)

      Field Oil	Mn	Cu	Pb	Zn	Ni	Fe	Co	V	Cr
      Amarah	1395.1	29.1	87	21	27.3	30	14.9	2.71	0
      Buzurgan	1392.2	9.9	87	21	23	14	15.1	2.27	0
      Noor	1386.5	125	74.8	61	28	26.2	14.1	2.78	0
      Abogarab	1385.1	6.9	62	10.6	17.1	14.2	10.8	1.81	0

2. Hydrocarbons Content

   The results of gas chromatography of crude oil samples showed in Table 3. Methane and butane were found to be the most abundant gases in these samples. The percentages of gases as well as the total percentage of the other alkane and alkene components were used as indicators to characterize the nature of the hydrocarbon mixture emitted by each sample [27.] The results also revealed that concentrations of (C1 to C31) hydrocarbons ranged from (0.02 to 3.46) wt% in all field of crude oil samples. From the summation of these results we obtained total petroleum hydrocarbon (TPH) that ranged from (30.44 to 44.97) wt%

   in Abogarab field followed by Buzurgan, Amarah, and Noor fields while the high concentration of hydrocarbons (C32+) ranged from (55.31 to 69.56) wt% in Abogarab field followed by Buzurgan, Amarah, and Noor fields. The highest concentrations were found of total petroleum hydrocarbons showings that terrestrial vascular plants contributed to n-alkanes in the study area and n-alkanes indicating an input of mixed marine and terrestrial organic matter [24].

   TABLE 3 CONCENTRATIONS OF THE HYDROCARBONS ASSOCIATED WITH CRUDE OIL IN DIFFERENT FIELDS

   Component	AMARAH Field Concentration WT%	Buzurgan Field Concentration WT%	NOOR Field Concentration WT%	ABOGARAB Field Concentration WT%
   C1	0	0	0	0
   C2	0.02	0.06	0.03	0.04
   C3	0.15	0.2	0.12	0.12
   *I-C4	0.11	0.2	0.13	0.1
   **N-C4	0.44	0.5	0.37	0.28
   I-C5	0.45	0.45	0.43	0.3
   N-C5	0.74	0.67	0.57	0.4
   C6	1.78	1.76	3.46	1.08
   C7	2.46	2.25	2.02	1.49
   C8	2.17	2.03	1.93	1.38
   C9	2.23	2.06	2.05	1.38
   C10	2.41	2.2	2.16	1.51
   C11	2.07	1.97	1.94	1.35
   C12	2.05	1.98	1.95	1.42
   C13	1.95	1.89	1.87	1.4
   C14	2.35	2.19	2.18	1.63
   C15	2.36	2.2	2.21	1.65
   C16	2.23	2.11	2.11	1.6
   C17	2	1.89	1.88	1.42
   C18	1.34	1.33	1.33	1.01
   C19	1.9	1.8	1.8	1.35
   C20	1.15	1.78	1.69	0.99

   C21	1.36	1.14	1.16	1.03
   C22	1.33	1.62	1.34	1.19
   C23	1.45	1.34	1.44	1.04
   C24	1.31	1.25	1.26	0.87
   C25	1.3	1.25	1.28	0.78
   C26	1.01	1.32	1.27	0.93
   C27	1.22	1.13	1.23	0.74
   C28	1.21	1.19	1.19	0.79
   C29	1.12	1.09	1.19	0.77
   C30	0.86	0.9	1	0.33
   C31	0.16	0.34	0.38	0.07
   Summation of C1 to C31	44.69	44.09	44.97	30.44
   C32+	55.31	55.91	55.03	69.56
   TOTAL	100%	%100	%100	%100

   Note: sample density = 0.9744 g/cm3 with 15.6 c

   * I= ISO-

   **N= NORMAL-

3. Correlation of Trace Metal and Hydrocarbons Content Figures 1 and 2 shows the relationships between Mn, with hydrocarbons compounds in different field of crude oil. In this study Mn metals observed to increase in content with increasing of (C1 to C31) hydrocarbons while decrease with decreasing of ( C32+ ) hydrocarbons. Figure 3 and 4 shows the metals Cu, Ni and Zn increase with the increasing of (C1 to C31) hydrocarbons while decrease with decreasing of ( C32+ ) hydrocarbons. Figures 5 and 6 shows the metals Fe, Co, Pb, and V decrease with decreasing of (C1 to C31) hydrocarbons and increase in content with increasing of content ( C32+ ) hydrocarbons increase. The difference of these results may be because metal as ion ( +2 ) associated with hydrocarbons as porphyrins in crude oil. The porphyrin

   ring system is composed of four pyrrole rings joined by (=CH-) groups. Many metal ions can replace the pyrrole hydrogens and form chelates that have abundance of electrons to obtain orginometallic compound more regular chains and saturated. The chelate is planar around the metal ion and resonance results in four equivalent bonds from the nitrogen atoms to the metal to obtain hydrocarbons compounds. In addition, some metals have negative correlation with hydrocarbons (C32+) these hydrocarbons may not tend to form chelate sand more saturated and regularly, in addition due to different proportions of the various molecular types, sizes of hydrocarbons and other elemental constituents in the crude mix [21]

   Fig 1 Correlation of Mn content with Hydrocarbons C1 to C31 in all fields Fig 2 Correlation of Mn content with Hydrocarbons C32+ in all fields

   Fig 3 Correlation of metals content with Hydrocarbons C1 to C31 in all fields Fig 4 Correlation of Metals content with Hydrocarbons C32+ in all fields.

   Fig 5 Correlation of metals content with Hydrocarbons C1 to C31 in all fields Fig 6 Correlation of Metals content with Hydrocarbons C32+ in all fields.

   CONCLUSION

   The current study determined a correlation between hydrocarbon content and metals such as correlation may result from. Also, this study found a different concentration of metals in crude oil samples that differ field to field, where showed higher concentrations of Mn followed by, Pb, Fe, Cu, Ni, Zn, Co, and V except Cr equal. The hydrocarbons content and organometallic compound were measured by using Gas Chromatography that shows the hydrocarbons from (C1 to C32+). Some of metal observed have correlations with hydrocarbons content, where increase with the increasing of (C1 to C31) hydrocarbons and decrease with decreasing of (C32+) hydrocarbons in samples of crude oil from four oil fields (Amarah field, Buzurgan field, Noor field, and Abogarab field) in Maysan province.

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