Gas chromatographic analysis of whole oil samples: implications for biodegradation in the Niger Delta

Abstract

The levels of biodegradation of five whole oil samples from five oil fields in the Niger Delta were assessed using a high-resolution gas chromatography. The results show that all the samples are at different levels of degradation ranging from slight to heavy. The crude oils from Fs, Bs and Qe fields had undergone extensive to heavy degradation, while those from Ai and Ea fields had undergone slight to moderate degradation. The low paraffinic content values in the samples suggest that the nparaffins have been degraded and reduced consistently. The aromatic fractions (C 14 -C 18 ) have been reduced slightly, though the 3-Methylhexane component was observed to show strong resistance to the bacterial attack even at deeper fields. These levels of biodegradation show indications that they could be caused by the degrading anaerobic bacteria present in the deep reservoir and/or by the influx of meteoric water, especially for the Bs crude, which is from an onshore field. As this degradation continues to deplete the light hydrocarbon components, the residual heavy components such as sulfur and asphaltenes are gradually concentrated, while the API gravity is consequently lowered.

Heavy Oil Biodegradation by Mixed Bacterial Consortium of Biosurfactant-Producing and Heavy Oil-Degrading Bacteria

“…Pr and Ph are usually regarded as biomarkers and have been used to study the geochemical properties of crude oil for decades due to their complex structures and stable chemistry [24]. Recently, these compounds, due to their high resistance to microbial degradation, have been proposed by environmental chemists for use in oil spills fingerprinting and as conserved markers for evaluating the degradation extent of spilled oil [25,26]. Fig.…”

Meteoric-Water Incursion, Crude-Oil Degradation And Calcite Cementation In An Upper Cretaceous Carbonate Reservoir: Bekhme Formnation, Kurdistan Region, Iraq

“…Undersaturated meteoric waters preferentially remove water-soluble compounds from oil such as light aromatics (benzene and toluene; Pytlak et al 2017), which results in an increase of bitumen and heavy oil residues (Mason et al 1995;Bennet and Larter 2008). This process is known as water washing (Mode et al 2017).…”

Geochemical Characterization of Some Biodegraded Oils from the Niger Delta Basin, Nigeria

“…Meanwhile, Huang et al [1] suggests that biodegradation is entirely uncontrolled by present-day reservoir temperature, because not all low-temperature reservoirs contain degraded oil [2,9], and not all deep-seated reservoired petroleum are free of petroleum degraders. Consequently, residency time, together with temperature records, play significant role [1].…”

“…Biodegradation, water-washing, and fractionation are thought to be the most common petroleum alteration processes in the Niger Delta Basin [9,14,15]. These processes are considered to be widespread in the Niger Delta, a deltaic basin with complex structural/tectonic setting, amidst reports of secondary and tertiary migrations, meteoritic water incursions in shallow reservoirs [9,14,15]. Mode et al [9] and Abrakasa and Nwankwo [15] observed variable degrees of biodegradation among some crude oils sampled from different locations in the Niger Delta.…”

“…These processes are considered to be widespread in the Niger Delta, a deltaic basin with complex structural/tectonic setting, amidst reports of secondary and tertiary migrations, meteoritic water incursions in shallow reservoirs [9,14,15]. Mode et al [9] and Abrakasa and Nwankwo [15] observed variable degrees of biodegradation among some crude oils sampled from different locations in the Niger Delta. It was further stated that 'Niger Delta oils are predisposed to biodegradation because of the potential influx of water into their reservoirs, which provides nutrients to the microbes' [14], and that most reservoirs in the Niger Delta basin had been 'invaded by marine and meteoric waters, through faults, and extensive sand stringers' [15], creating favorable channel for in-reservoir biodegradation to take place.…”