Biodegradation Of Crude Oil Research Articles

Long-term biodegradation of crude oil in high-arctic backshore sediments: The Baffin Island Oil Spill (BIOS) after nearly four decades

With an on-going disproportional warming of the Arctic Ocean and the reduction of the sea ice cover, the risk of an accidental oil spill from ships or future oil exploration is increasing. It is hence important to know how crude oil weathers in this environment and what factors affect oil biodegradation in the Arctic. However, this topic is currently poorly studied. In the 1980s, the Baffin Island Oil Spill (BIOS) project carried out a series of simulated oil spills in the backshore zone of beaches located on Baffin Island in the Canadian High Arctic. In this study two BIOS sites were re-visited, offering the unique opportunity to study the long-term weathering of crude oil under Arctic conditions. Here we show that residual oil remains present at these sites even after almost four decades since the original oiling. Oil at both BIOS sites appears to have attenuated very slowly with estimated loss rates of 1.8–2.7% per year. The presence of residual oil continues to significantly affect sediment microbial communities at the sites as manifested by a significantly decreased diversity, differences in the abundance of microorganisms and an enrichment of putative oil-degrading bacteria in oiled sediments. Reconstructed genomes of putative oil degraders suggest that only a subset is specifically adapted for growth under psychrothermic conditions, further reducing the time for biodegradation during the already short Arctic summers. Altogether, this study shows that crude oil spilled in the Arctic can persist and significantly affect the Arctic ecosystem for a long time, in the order of several decades.

Retraction: Evaluation of crude oil biodegradation using mixed fungal cultures.

Retraction: Evaluation of crude oil biodegradation using mixed fungal cultures.

Efficacy of bioadmendments in reducing the influence of salinity on the bioremediation of oil-contaminated soil

This study aimed to investigate the potential of three bioamendments (rice husk biochar, wheat straw biochar, and spent mushroom compost) to enhance microbial degradation of crude oil in saline soil. A soil microcosm experiment was conducted, comparing the response of soil microorganisms to crude oil under saline (1 % NaCl) and non-saline conditions. The soils were amended with different bioamendments at varying concentrations (2.5 % or 5 %), and degradation rates were monitored over a 120-day period at 20 °C. The results showed that the bioamendments significantly influenced the degradation of total petroleum hydrocarbons (TPH) in both non-saline and saline soils by 67 % and 18 % respectively. Non-saline soils exhibited approximately four times higher TPH biodegradation compared to saline soils. Among the bioamendments, rice husk biochar and spent mushroom compost had the greatest impact on biodegradation in saline soil, while wheat straw and rice husk biochar combined with spent mushroom compost showed the most significant effects in non-saline soil. The study also revealed that the bioamendments facilitated changes in the microbial community structure, particularly in the treatments with rice husk biochar and wheat straw biochar. Actinomycetes and fungi were found to be more tolerant to soil salinity, especially in the treatments with rice husk biochar and wheat straw biochar. Additionally, the production of CO2, indicating microbial activity, was highest (56 % and 60 %) in the treatments combining rice husk biochar or wheat straw biochar with spent mushroom compost in non-saline soil, while in saline soil rice husk biochar treatment (50 %) was the highest. Overall, this research demonstrates that the application of bioamendments, particularly rice husk biochar and wheat straw biochar combined with spent mushroom compost, can effectively enhance the biodegradation of crude oil in saline soil. These findings highlight the potential of such bioamendments as green and sustainable solutions for soil pollution, especially in the context of climate change-induced impacts on high-salinity soils, including coastal soils.

Degradation of crude oil in a co-culture system of Bacillus subtilis and Pseudomonas aeruginosa.

Microbial remediation has been regarded as one of the most promising decontamination techniques for crude oil pollution. However, there are few studies on the interaction of bacteria in the microbial community during bioremediation. The aim of this work was to research the promotion of defined co-culture of Bacillus subtilis SL and Pseudomonas aeruginosa WJ-1 for biodegradation of crude oil. After 7 days of incubation, the analysis of residual oil, saturated and aromatic fraction in the samples showed that the degradation efficiency of them was significantly improved. The degradation efficiency of crude oil was enhanced from 32.61% and 54.35% in individual culture to 63.05% by the defined co-culture of strains SL and WJ-1. Furthermore, it was found that the defined co-culture system represented relatively excellent performance in bacterial growth, cell surface hydrophobicity (CSH) and emulsification activity. These results indicated that the combination of Bacillus subtilis and Pseudomonas aeruginosa can effectively promote the degradation and utilization of crude oil, which may provide a new idea for the improvement of bioremediation strategies. GRAPHICAL ABSTRACT.

Microbial responses to increased salinity in oiled upper tidal shorelines

The microbial degradation of crude oil stranded on seashores is usually much slower than that of dispersed oil at sea. This is usually attributed to nutrient limitation and higher oil concentrations on beaches than in dispersed plumes, in addition to the low moisture content and transient hypersaline conditions of the upper intertidal and supratidal zones. Here, we investigated the effect of hypersaline conditions, oil concentration, and nutrient limitation on the hydrocarbonoclastic activity. Beach sand, with oil concentrations of 1 and 10 mL/kg, was infiltrated with seawater at salinities of 30, 90, and 160 g/L to 20% saturation, with and without the addition of nutrients. Oil chemistry, 16 S rRNA gene amplicon, and metagenomic sequencing analyses were conducted every 30 days for 180 days. The biodegradation of aromatic hydrocarbons was much slower at higher salinities, while that of alkanes was not noticeably affected, and the addition of nutrients only marginally enhanced the biodegradation of hydrocarbons. The relative abundance and diversity of genera varied substantially with the increase in pore water salinity, whereby halophilic hydrocarbon-degrading microorganisms, particularly in the Marinobacter genus, were significantly abundant only under hypersaline conditions. The enzymes were considerably less abundant at high salinities, mainly for those associated to aromatic hydrocarbon degradation pathways. Consequently, occasional inundation of the upper parts of oiled sandy beaches with seawater to decrease the pore water salinity and reseed the contaminated region with indigenous hydrocarbon degraders, along with the concomitant addition of fertilizers, could be a suitable, non-destructive, and inexpensive response tool for enhancing the biodegradation of beached crude oil, particularly that of the aromatic fraction.

New biodegradation degree proxies based on acids and neutral nitrogen- and oxygen-containing compounds characterized by high resolution mass spectrometry

Heavy oil is one of the most significant unconventional petroleum resources and one of its formation mechanisms is biodegradation. The characterization of the molecular compositions of petroleum is crucial for determining the various degrees of biodegradation. In this work, detailed investigations of acids and polar NSO compounds in different levels of biodegraded oils from the Bongor Basin (Chad) were carried out by negative ion electrospray ionization (-ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The present findings show that the heteroatomic compounds of biodegraded crude oils are predominantly composed of N1, N1O1, O1, O2, O3 and O4 species. The relative content of N1, N1O1 and O1 species tend to decrease and those of O2, O3 and O4 species appear to increase with the increasing of biodegradation. The ratio of acyclic and cyclic acids (A/C ratio) of the O2 species increase with an increase of biodegradation, indicating the increasing of O2 class during microbial alteration. A new parameter, i.e. the ratio of (O2 + O3 + O4)/(N1 + O1) species, is presented to quantificationally define biodegradation levels. This parameter is inversely proportional to API gravity and has a favorable positive correlation with total acid number (TAN), suggesting acidic compounds are formed by the microbial alteration of N1 and O1 class and are more presented in advanced biodegradation. A modified ternary diagram including N1, O1 and O2 + O3 + O4 species describe the detailed changes of nitrogen- and oxygen- containing compounds. Data points with a high level of biodegradation tend to shift to O2 + O3 + O4 species end-member and retreat from N1 species end-member, showing the relative content of O2 + O3 + O4 species increase and those of N1 species decrease with increasing biodegradation which may due to the formation of organic acids in degradation oil. The ratio of (O2 + O3 + O4)/(N1 + O1) species and the modified ternary diagram provide new parameters to estimate the biodegradation degree and TAN in crude oil.

Biodegradation of Crude Oil Contaminated Soil in Sudan Using Sudanese Plant Acacia seyal Del

Phytoremediation is an environmental technology in which plants are used for decontamination of organic and inorganic pollutants from soils and water. Acacia seyal Delile was tested for it is ability to degrade crude oil contaminated soil in four concentrations 0.5, 1, 1.5 and 2% (w/w) of crude oil. Plant parameters, degradation percentage, retention time and bacterial count were calculated. Results showed that at the end of the growth period of A. seyal Del no such adverse effect was observed on the shoot length and it is better than that of the control at the 2% concentration by the end of the growth period. This result highlights the ability of A. seyal Del to grow under stress of oil contamination. A. seyal root length has substantially increased at two and four month’s interval and no significant difference was observed at these two intervals. A. seyal Del shoot biomass was significantly (p<0.05) negatively affected by crude oil at four month intervals, Root weight of A. seyal Del have decreased steadily. Degradation percentage was found to be in the range between 49-54%. Penadecane is the first compound appear in most cases and the retention time was between 13.7-32.9 min. Number of compounds detected in the rhizosphere those were 57, 70 and 167 compound after two, four and six month of growth respectively. Viable count of the dominant bacteria showed that there is no significant different between concentrations (P=0.699), also there is no significant difference between intervals (P=0.08) in bacterial number. This study reveals the visibility of using tropical plant Acacia seyal in crude oil degradation.

Isolation of indole biodegrading bacterial species from petroleum contaminated site of northeast India: Growth kinetics and crude oil biodegradation assessment

Petroleum industrial activities such as crude oil spillage, sludge generation, and effluent wastewater adversely affects the surrounding ecosystem. Several biological processes have been developed so far to remediate the petroleum contaminants. This article is focused on the remediation of petroleum waste using novel bacterial isolates from petroleum-contaminated sites. The indole biodegradation was studied in bioreactor wherein 84.86 % COD removal was observed using consortium of Alcaligenes faecalis RB-10, Pseudomonas guariconensis RB-12 and Pseudomonas monteilii RB-29. The residual analysis of biodegraded samples were performed using various analytical techniques. The maximum specific growth rate (μmax) and half-saturation rate constant (ks) were evaluated individually for Alcaligenes faecalis RB-10, Pseudomonas guariconensis RB-12 and Pseudomonas monteilii RB-29 species using Monod model. The crude oil degrading potential of isolated bacterial consortium was also investigated.

The Biodegradation for Two Kinds of Crude Oils by the Action of Fusarium moniliforme and Aspergillus flavus

The results showed that two fungi used in this research had positive and effective role in biodegradation of Kirkuk mid crude oil and Al-Qayarah heavy crude oil. Synergism between F.moniliforme and A.flavus was able to biodegrade hydrocarbons of Kirkuk mid crude oil by percent 86.6% then A.flavus could biodegrade the same crude oil by percent 85.3% where's F.moniliforme at third stage by percent 68.6%.
 But the percent of biodegradation of Al-Qayarah heavy crude oil, showed that synergim could biodegrade by percent 81.05%. A.flavus by percent 78.9% but F. moniliforme by percent 65.4%.
 From the results of viable counts for the two grown fungi on the two kinds of crude oil showed adaptation for new ecology and increase in 1st and 2nd weeks from growth but decrease the viable counts for two fungi in the 3rd., 4th. weeks of growth, analysis by gas-chromatography improved biodegradation the hydrocarbons of two kinds of crude oil by the action of two fungi used in this research.
 These two techniques produced another type for measured the profile oil hydrocarbons and disappeared many of peaks include components of crude oil which cleared through hydrocarbons profile before and after using two fungi as biotic analyzed factors, to affirmative results which cleared by weight as percent's in this research.

Origin of Mesozoic Biodegraded Crude Oils from the Eastern Chepaizi Uplift (Junggar Basin) Constrained by the Biomarker Recovery Method

The Mesozoic (Jurassic and Cretaceous) sandstone reservoirs in the eastern Chepaizi Uplift of the Junggar Basin (NW China) have become hot targets in recent years for their substantial amounts of oils discovered. However, the oil origin has been a controversial issue due to biodegradation. In this study, hierarchical cluster analysis and principal component analysis show that the Mesozoic crude oils can be divided into three oil families (A1, A2, and A3). Meanwhile, the biodegradation level of the three oil families (PM 6 to 9+) was evaluated based on the PM scale and the parameter-stripping method of strongly resistant parameters. Allowing for this extremely high biodegradation case, this study adopted a biomarker recovery method to recover the original appearances of the three oil families. Here, eight parameters related to hopane (H), tricyclic terpane (TT), and C24-tetracyclic terpane (C24 Tet) were recovered, the dispersion of eight parameter sets is significantly reduced, and the geochemical characteristics are more obvious, especially for TT. Thus, this reliability and robustness, as well as the similarity between the source rock and the biodegraded crude oils, encourage us to perform oil–source correlation. The oil–source correlation revealed that family A1 was derived from the Permian source rocks in the Shawan Sag, family A2 was mainly derived from the Permian source rocks in the Shawan Sag and mixed with a small amount of oils generated by the Jurassic source rocks in the Sikeshu Sag and the Carboniferous source rocks in the Chepaizi Uplift, and family A3 mainly originated from the Permian source rocks in the Shawan Sag mixed with a small amount of oil produced by the Carboniferous source rocks in the Chepaizi Uplift. This conclusion is also further supported by effective biomarker parameters and a stable carbon isotope (δ13C), discriminant analysis, hydrocarbon migration, and restored paleogeomorphology. The parameter recovery is evidenced as one of the most useful methods and showed higher resolution than the conventional oil–source correlation to identify the origins of biodegraded oils.

Reconstruction of microbiome and functionality accelerated crude oil biodegradation of 2,4-DCP-oil-contaminated soil systems using composite microbial agent B-Cl

Biodegradation is one of the safest and most economical methods for the elimination of toxic chlorophenols and crude oil from the environment. In this study, aerobic degradation of the aforementioned compounds by composite microbial agent B-Cl, which consisted of Bacillus B1 and B2 in a 3:2 ratio, was analyzed. The biodegradation mechanism of B-Cl was assessed based on whole genome sequencing, Fourier transform infrared spectroscopy and gas chromatographic analyses. B-Cl was most effective at reducing Cl– concentrations (65.17%) and crude oil biodegradation (59.18%) at 7 d, which was when the content of alkanes ≤ C30 showed the greatest decrease. Furthermore, adding B-Cl solution to soil significantly decreased the 2,4-DCP and oil content to below the detection limit and by 80.68%, respectively, and reconstructed of the soil microbial into a system containing more CPs-degrading (exaA, frmA, L-2-HAD, dehH, ALDH, catABE), aromatic compounds-degrading (pcaGH, catAE, benA-xylX, paaHF) and alkane- and fatty acid-degrading (alkB, atoB, fadANJ) microorganisms. Moreover, the presence of 2,4-DCP was the main hinder of the observed effects. This study demonstrates the importance of adding B-Cl solution to determine the interplay of CPs with microbes and accelerating oil degradation, which can be used for in-situ bioremediation of CPs and oil-contaminated soil.

Phytoremediation of Crude Oil Polluted Soil Using Dried Yam Peels (Discorea sp) as a Case Study in Niger Delta Environment of Southern Nigeria

This study aimed at enhancing the remediation of crude oil polluted soil using yam peels. 2kg of the soil samples were polluted crude oil at different concentrations ranging from 5%, 10% and 15%. There were three amended and un-amended samples each labeled A-F. The amended samples were A, C and E which contained the following respectively, 5% polluted soil + 150g yam peels, 10% polluted soil + 150g of yam peels and 15% polluted soil + 150g yam peels. The un-amended samples were B, D and F which were called the control samples with 5%, 10% and 15% concentration of crude pollutant. Parameters such as soil moisture content, total organic carbon, pH and total hydrocarbon content were analyzed before and after remediation. The result showed that yam peels enhanced remediation of the soil especially in treatment A. The reduction in Total Hydrocarbon Content was highest in the 5% crude oil polluted soil sample resulting 57.4% and least at 15% polluted control sample resulting 44.2%. The higher the concentration of crude oil in the soil the lower the percentage degraded. Yam peels which are agro waste can enhance biodegradation of crude oil in polluted soil and therefore can act as remediating agent.

Biodegradación de petróleo crudo presente en aguas residuales: evaluación de la producción de biosurfactantes y actividad de catecol 2,3 dioxigenasa

Water demand is increasing because of demographic and urban development in the last decades. Crude oil is an essential energy resource for many anthropogenic activities. However, it is associated with the generation of environmental pollution. In the present work, a native microbial consortium was used to study hydrocarbon biodegradation of crude oil and its potential use to remove organic pollutants in wastewater. The kinetic degradation of crude oil was analyzed to determine the production of biosurfactants and the enzyme activity of catechol 2,3 dioxygenase. The degradation of the hydrocarbon was determined by aromatic-hydrocarbons (96.11%) and total-hydrocarbons (74.23%). The maximum values of the biosurfactant production were evaluated by oil displacement (206.95 mg/L) and emulsification capacity (DO600 0.2895). The kinetic analysis showed that the complex mixture of hydrocarbons was the main responsible for generating the stress to synthesize biosurfactants through a native microbial consortium. However, the decrease in catechol 2,3 dioxygenase activity and biosurfactant production was related to the degradation of aromatic hydrocarbons. The microbial consortium was capable to produce biosurfactants during crude oil degradation, and it has a great potential to remove aromatic hydrocarbons present in wastewater.

Heavy Crude Oil Biodegradation: Catechol Dioxygenase Gene Copy Number Variation Determination by Droplet Digital Polymerase Chain Reaction

The crude oil reserves in Oman mainly consist of heavy oil. Microbial enhanced heavy oil recovery (MEOR) has been proved to be an efficient technique in the tertiary heavy oil recovery. Five Bacillus species potential for enhanced heavy oil recovery (EHOR) were isolated and the biodegradation ability of these isolates was studied. As heavy crude oil comprises of aromatic hydrocarbons rather than aliphatic ones, the aromatic catabolism gene, catechol 2,3-dioxygenase (C23O) and catechol 1,2-dioxygenase (C12O) were the genes of interest in this study along with the reference gene, 16S rDNA. The copy number variation of these genes was determined using droplet digital PCR (ddPCR). The primers and probes for ddPCR assay were designed targeting these genes. It was observed that the heavy crude oil biodegradation potential of the isolates correlated with the copy number of C23O gene in the microbial genomes. The isolate, Paenibacillus ehimensis BS1 had the highest C23O gene copy number (1.057) followed by Bacillus firmus BG4 (0.895) and Bacillus halodurans BG5 (0.031) as demonstrated by their biodegradation potential. This is one of the few studies deploying ddPCR in the field of heavy crude oil biodegradation by spore forming bacteria.

Emergence of hydrocarbon-degrading bacteria in crude oil-contaminated soil in a hyperarid ecosystem: Effect of phosphate addition and augmentation with nitrogen-fixing cyanobacteria on oil bioremediation

Hyperarid hot deserts impose limiting conditions for microbial activity, thus delaying crude oil biodegradation resulting from accidental spills. This study examined the emergence of oil-degrading bacterial species in the soil of a hyperarid area in the southern Negev desert, Israel, which was exposed to a major oil spill. Amplicon sequencing of the 16S rRNA gene showed dominance of the phyla Proteobacteria and Actinobacteria in both contaminated and control soils. Significant differences were seen in the abundance of the phylum Firmicutes. Classes Actinobacteria, Gammaproteobacteria and Bacilli dominated the oil-contaminated soil. Bacterial species capable of degrading aromatic and aliphatic oil constituents were isolated from the contaminated soil. Contaminated soil microcosms were amended separately with nitrogen, phosphorus, or nitrogen-fixing cyanobacteria (NFC) biomass; the highest reduction in total petroleum hydrocarbons was observed in the phosphorus-supplemented soil. The abundance of alkB gene, encoding alkane monooxygenase, increased significantly in the control, NFC and phosphate treatments, but not in the nitrogen treatment. However, nahA abundance (coding for naphthalene dioxygenase) was only considerably increased with the phosphorus amendment. While nitrogen amendment via NFC bioaugmentation is a sustainable and novel biostimulation method, phosphorus amendment significantly accelerates the biodegradation of crude oil under extremely arid conditions.

NSO-bearing compounds in severely–extremely biodegraded crude oil revealed by ESI(-) FT-ICR MS

The heavy oil is essentially comprised of asphaltene and nitrogen, sulphur, and oxygen-bearing (NSO) compounds, which records the alteration processes of aerobic biodegradation. In this study, six biodegraded oils were geochemically examined using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in negative-ion electrospray ionization (ESI(-)) mode to decipher the NSO heteroatom compounds molecular compositions. The results reveal that the NSO compounds, especially those strongly resistant to biodegradation, i.e., alcohol/phenols, carboxylic acids with various alkyl substitution, naphthenic acids with 2 to 5 naphthenic/aromatic rings, nitrogen- and sulphur-bearing carboxylic acids, and hydroxy acids (O3) and dibasic acids (O4) are enriched in biodegraded oils. The O1, N1O1, and O1S1 classes appear in trace amounts in severely to extremely biodegraded oils (PM > 7) but are abundant in moderately biodegraded oils (PM < 7), implying the alcohol group generated by biodegradation are further oxidized to form a carboxylic acid with the progressively biodegraded process. Abnormal enrichment of O2 and O4 classes was trapped in the severely–extremely biodegraded oils, implying the generation of additional monobasic acid/dibasic acids during microbial aerobic degradation of crude oils. Besides, the relative content of monocyclic naphthenic acid (DBE = 2) gradually decreased with biodegradation level, while those of the bicyclic-, tricyclic-, and tetracyclic–naphthenic acid (DBE = 3-5) showed an increasing trend. The newly developed proxies of NSO compounds (i.e., the ratios of biodegradation products with different numbers of oxygen atoms of the specified compound, and the O2, O3, O4, and O5 classes with various DBE values and/or various carbon numbers) agreed well with the existing biodegradation indicators (i.e., C2925-NH/C30H, C2117-NT/C23TT, C27DS/C27RS, and C28TAS/C21TAS), confirming the availability of ESI(-) FT-ICR MS to distinguish the biodegraded oils with high resolution.

Kinetics of Arab Light Crude Oil Degradation by Pseudomonas and Bacillus Strains

The biodegradation of crude oil is a consequence of the presence of a specific enzymatic system in the microorganisms selected: the alkane hydroxylase (AlkH). The enzymatic biodegradation has been described since 1994, when the enzyme was first isolated from P. putida (formerly P. oleovorans), but the kinetics of microbial degradation has been weakly considered. We studied and described in this work the kinetics of Arab Light biodegradation, a light crude oil used for gasoline production (46.4% C7–C12 n-alkanes), using two oleophilic strains (Bacillus licheniformis and Pseudomonas putida). Alkanes were extracted from aqueous solutions in the bioreactors by dichloromethane, with a high ratio aqueous:organic volumes (1:0.2 mL) for the amplification of the GC n-alkane signals, and GC spectra were monitored in time over 40 days. Petroleum emulsions were visualized using optical microscopy as a result of biosurfactant segregation, which is necessary for the enzymatic biodegradation of oil by microorganisms. Kinetic analysis in biodegradation of Arab Light (total petroleum hydrocarbons, TPH) exhibits first-order kinetics with 0.098 d−1 and 0.082 d−1 as kinetic coefficients for 8.6 g/L initial crude oil concentration (30 °C), which results in degradation rates of 843 mg/Ld and 705 mg/Ld in B. licheniformis and P. putida, respectively. These results can be applied for oil spill bioremediation, using these microorganisms with the objective of removing contamination by petroleum alkanes.

Improving mass transfer rates in microbial cell immobilization system for environmental applications: Synergistic interaction of cells on crude oil biodegradation

Among the various techniques used to clean up polluted environments, bioremediation is the most cost-effective and eco-friendly option. The diversity of microbial communities in a consortium can significantly affect the biodegradability of hazardous organic pollutants, particularly for in situ bioremediation processes. This is largely attributed to interactions between members of a consortium. In this study, the effect of internal diffusion limitations in substrate model biodegradation was firstly examined by immobilized bacterial cells at different particle sizes produced by the electrospray technique. According to the obtained results, for particles with large size, the effectiveness factors (η) were about 0.58–0.67, and the resistance to diffusive on the biodegradation rate was significant, while with decreasing the particle size, η increases and approaches about 1. After selection of suitable bead size, heavy crude oil biodegradation was investigated using a consortium consisting of three oil-degrading bacterial strains at different treatment systems. The removal rate in the suspended co-culture system stands at minimum value of 38% with all three strains which is an indicator of negative interactions among consortium members. Independent immobilization of microorganisms minimizes the competition and antagonistic interactions between strains and leads to more crude oil removal, so that, the biodegradation rate reached 60%.

Geochemical characteristics and origin of crude oil from Carboniferous volcanic rocks in the Hongche Fault Zone of the Junggar Basin of China

In recent years, significant advances have been made in the exploration of Carboniferous volcanic reservoirs in the Hongche Fault Zone of the Junggar Basin of China, showing good prospects for further exploration. However, the large variation in the physical properties of crude oil and the complex distribution rule inhibit the one-step exploration. In this study, the PM scale of the biodegradation of crude oil and source of crude oil were studied using experimental methods that target the properties, bulk properties and biomarker compounds of crude oil. The exploration potential of crude oil in this area was analysed, and an accumulation model of crude oil was established. Based on the differences in biomarker compounds and the degree of biodegradation, crude oils were divided into four groups and seven subgroups. Additionally, the analysis of the biomarker compounds of crude oil combined with the hydrocarbon-generation history of source rocks showed that there were at least two periods of oil charging in this area. The first period was the late Triassic, with crude oil derived from the P1f source rock. Owing to the strong tectonic activity during the late Indosinian movement, the oil reservoirs were distributed in the footwall of the fault zone, and the oil in the reservoir exhibited different degrees of biodegradation, forming crude oils of subgroup I1, II and III1. The second period was Cretaceous, during which the P1f source rock was in the natural gas generation stage, and the P2w source rock was at a mature stage. A small part of the crude oil formed by the P2w source rock migrated to the Carboniferous reservoirs and mixed with the crude oil formed by the earlier P1f source rock, resulting in crude oils of subgroups I2, III2, and IV2. The crude oil in the studied area originated from the source rocks in the sag during the peak of oil generation. As tectonic activity approached stability in the latter period, it is speculated that there may be well-preserved primary oil and gas reservoirs in the footwall and slope areas of the fault, making these potential exploration sites.

Implications of groundwater flow on preservation of heavy and extra-heavy oil accumulations in Southern Llanos Basin, Colombia

The southern sector of the Llanos Basin in Colombia is a heavy and extra-heavy crude oil province where it has been hypothesized that hydrodynamic flow has influenced the potential of hydrocarbon storage and production. In this area, the hydrodynamic flow and the geochemical nature of the fluids are thought to decrease the potential for hydrocarbon retention. This work provides a comprehensive view on the impact of the regional hydrodynamic flow on the retention of the heavy oil accumulations present in the reservoirs that are part of the most important regional flow unit identified in the Southern Llanos Basin. The Basal Flow Unit (BFU) constitutes a basin-scale flow unit that hydraulically and laterally connects rocks from the Cretaceous (west) to the Oligocene (east) and extends from the basin's southwestern margin up to hundreds of kilometers within the Llanos foreland basin, and whose main water recharge zone has been identified towards the eastern flank of the Serranía de la Macarena. To understand the impact of the physicochemical properties of the fluids on hydrocarbon retention, we analyze the relationship between hydraulic data and the main characteristics of the fluids present in the BFU as well as their spatial distribution. This analysis integrated information from hydraulic heads, SARA analysis (Saturates, Aromatics, Resins, and Asphaltenes), Whole Oil Gas Chromatography analysis, API-gravity, and oil densities. In addition, hydrochemical analyses of the primary ions were performed in groundwater samples from the BFU, which was integrated with deep resistivity data measured in producing and exploratory oil wells in the area. The results allowed identifying the southwestern corner of the southern Llanos Basin as the area with the highest hydrodynamic flow impact, and therefore, the area with the least potential for hydrocarbon retention. We attribute the main causes to: 1) the proximity to recharge areas, and 2) the low contrast of fluids densities (freshwaters and highly biodegraded heavy crude oils), implying high Tilt Amplification Factor (TAF) values (10–100). In addition, the highest values of hydraulic heads (200–400 m), groundwater with the lowest ion concentrations (up to < 5 ppm Cl−), highly biodegraded crude oils, and the presence of poorly developed geological structures with low dip angles occur in this area, which allows us to interpret that the water washing process has decreased the hydrocarbon retention potential for this sector of the Llanos basin. Furthermore, gradual changes in resistivities (decreasing eastward) and ions concentration (increasing eastward) in groundwaters suggest the eastern flank of the Serranía de la Macarena as the main recharge zone of meteoric waters into the BFU. Finally, numerical simulation techniques were used to analyze the behavior of hydrocarbon drainage under hydrodynamic conditions, obtaining a first approximation to the average linear groundwater flow velocities between 10−3 and 10−4 ft/day.