The Structural Characterization of Saturate,Aromatic, Resin,and Asphaltene Fractions of Batiraman Crude Oil

Abstract

The structural characterization of fractions of Batiraman crude oil, which is the heavy crude oil from a field in the southeastern part of Turkey, was investigated. Batiraman crude oil and its saturate, aromatic, resin, and asphaltene (SARA) fractions were seperated. Treatment of crude oil with n-heptane provided the separation of asphaltene. Maltene was collected by evaporating the n-heptane from the filtrate. Then, maltene was separeted into saturates, aromatics, and resins by SARA technique. Maltene was separated into saturate, aromatic, and resin fractions using column chromatography. SARA fractions were quantified on a weight percent basis. Fractions of Batiraman crude oil were characterized by elemental analysis, proton nuclear magnetic resonance (¹H NMR) analysis, electrospray ionization mass spectrometry (ESI-MS), and Fourier transform infrared (FTIR) spectroscopy techniques.     

Spectroscopic characterization of the maltene fraction of Nigerian bitumen for potential health-risk assessment

This study was carried out on maltene fraction of Nigerian bitumen to infer the environmental and health implications of its uses and also to characterize the fossil fuel. Bitumen was extracted from the oil sands obtained from six locations in Southwestern Nigeria using toluene via Soxhlet extraction and then deasphalted using n-pentane. The organic components of the maltenes were investigated using Fourier transform infrared spectroscopy, while the elemental content was determined using inductively coupled plasma-optical emission spectrometry (ICP-OES) and the radioactivity levels were measured using a sodium iodide (NaI)-based Gamma Spectrometry Detector System. The IR spectra of the maltene indicated the presence of various organics and heteroatoms, corroborating the fact that maltene is composed of high molecular weight polycyclic constituents comprising nitrogen, sulfur, and oxygen heteroatoms. The result of the elemental concentrations revealed that sulfur with the mean value of 2.155 μg/g comparatively has the highest concentration in the samples, followed by Fe (1.25μg/g), while Mn has the least value (0.075) μg/g. The values of the analyzed elements were comparatively lower in the maltene fraction than in the bitumen and higher molecular weight fractions of Nigerian bitumen, but higher than the maltene fraction of Nigerian crude oil (except Cr and Ni). The result of the cross-plot analysis between maltene and bitumen using their elemental mean concentrations as variables indicated significant strong and positive correlation (R² = 0.81) between them, indicating very strong inter-element and geochemical relationships between them. The elements showed close clustering, indicating similar sources or similar chemical affinity. The average activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K determined with a view to ascertaining the radiological health consequences associated with the burning of this maltene fraction were 1.66 ± 1.07, 0.72 ± 0.49, and 15.93 ± 3.37 Bqkg^?1, respectively. These values are below the standard values in radiation protection. The radiological health consequences associated with the burning of maltene fraction of Nigerian bitumen were insignificant with no radiological hazard to the general public, but long exposure may pose an intrinsic health hazard.     

Estimation of thermal maturity status of petroleum asphaltenes and maltenes

Asphaltenes from various bituminous sand, heavy oil and conventional oil reservoirs and maltenes from various conventional oil reservoirs have been pyrolysed at 130 °C (for the asphaltenes), and at 50 °C (for the maltenes) in the presence of hydrated aluminium chloride crystals as catalyst for the decomposition. The rates of production of gases were appreciable and measurable. Asphaltenes from bituminous sands from the same geographical location showed a clear correlation between the rate of gas production and the depth of burial. The trend indicates that the thermal maturity of the oil increases with increase in the depth of burial. For conventional oils, a correlation was also observed between the rate of the gaseous product yields and the geological age. Maltenes from the conventional oils gave similar results: here the trend indicates that the thermal maturity of the oils increases with increase in geological age. From the derived correlation curve, the geological age of unknown crude oil was determined (525 × 10⁶ years: middle Ordovician age).