Petroleum Potential Research Articles

Exploring for the Future geomechanics: breaking down barriers to exploration

Exploring for the Future (EFTF) is an Australian Government initiative focused on gathering new data and information about potential mineral, energy and groundwater resources across Australia. The energy component of EFTF, initially focussed on northern Australia, aims to improve our understanding of the petroleum potential of frontier Australian basins. Building an understanding of geomechanical rock properties is key to understanding both conventional and unconventional petroleum systems as well as carbon storage and sedimentary geothermal systems. Under EFTF, Geoscience Australia has undertaken geomechanical work including stress modelling, shale brittleness studies and the acquisition of new rock property data through extensive testing on samples from the Paleo- to Mesoproterozoic South Nicholson region of Queensland and the Northern Territory, and the Paleozoic Kidson Sub-basin of Western Australia. Work in these regions demonstrates regional stress orientations in broad agreement with previously modelled, continent-scale stress orientations and stress magnitudes that vary through the basin with depth and by lithology. Rock testing highlights potentially brittle shales and demonstrates variable rock properties in line with lithology. These analyses are summarised herein. Providing baseline geomechanical data in frontier basins is essential as legacy data coverage can often be inadequate for making investment decisions, particularly where unconventional plays are a primary exploration target. As EFTF increases in scope, Geoscience Australia anticipates expanding these studies to encompass further underexplored regions throughout Australia, lowering the barrier to entry and encouraging greenfield exploration.

GEOCHEMICAL CHARACTERISTIC OF THE SILURIAN ROCKS FROM THE EASTERN PART OF MOLDAVIAN PLATFORM (ROMANIA)

The scope of this paper is to assess the hydrocarbon potential of Silurian, respectively, the maturity of this stratigraphical interval, based, especially, of the geological and geophysical data derived from eight boreholes located in the north-eastern part of Moldavian Platform - Romania. The main conclusion is that the organic matter contents measured in the core and cutting samples of the different wells are low with the Organic Carbon (TOC) (residual) mainly clearly lower than 1%. Due to the poorness of the sample and the high maturity the petroleum potential and organic matter cannot be assessed. Estimation of the initial TOC allows to differentiate a richer interval at 24 – 27m thick below the top of Silurian. It shows higher TOC with estimated initial TOC reaching 3.6 % weight at the most. The maturity is high and shows a rapid increase with depth between around 2% at 200m and 4% eq. VRr at 1100m. An estimation of the eroded cap-rock is of around 3000m. Mineral carbon content obtained from Rock Eval permits to separate two lithological intervals: carbonated in the upper part (thickness of 250-300m), argillaceous in the lower part.

The Bamaga Basin: a frontier play in a non-frontier location

The undrilled, offshore Bamaga Basin (pre-Jurassic) is overlain by two previously explored sedimentary basins: Carpentaria (Jurassic–Cretaceous) and Karumba (Tertiary). In 1984, Duyken-1, the only well in the Gulf of Carpentaria, 120km southwest of the Bamaga Basin, tested the Carpentaria and Karumba successions but not the deeper Bamaga Basin, which at the time was unrecognised. 2D regional seismic data acquired in 2012, and a second infill seismic survey in 2014, confirmed the presence of a sedimentary succession in the Bamaga, probably of early–middle/late Paleozoic age, and identified an intriguing, complex structural history and large potential petroleum traps. Basin modelling in the centre of the Bamaga Basin where the sedimentary section is deepest shows that the sediments are mature for petroleum generation with the hydrocarbon phase being either oil or gas, although gas is more likely, especially below 2000m. Analysis of the available data indicates that in the oil generation zone there are six targets with the potential to hold prospective resources (3U) of more than 250 million stock barrels (MMstb) of oil each, the largest of which could hold as much as 663 MMstb of oil. In the gas generation zone, there are nine targets with the potential to hold prospective resources (3U) of 1 trillion cubic feet (Tcf) or more gas each, the largest of which could hold as much as 2.5 Tcf gas. The water depth (60m) and closeness to shore (150km) make it operationally and commercially attractive.

Combined High-Resolution Solid-State 1H/13C NMR Spectroscopy and 1H NMR Relaxometry for the Characterization of Kerogen Thermal Maturation

A key factor for the petroleum potential of source rock is the degree of chemical and physical structure evolution of its kerogen fraction through a range of maturation processes. In this study, various high-field, solid-state NMR methods have been applied to a series of kerogen isolates (type I) over a defined maturity range (vitrinite reflectance R₀ from 0.98 to 1.86%). Results obtained from ¹³C MAS NMR show that the sp²/sp³-hybridized carbon ratio of kerogen, here defined as the aromatic/aliphatic ratio, increases with increasing maturity. ¹H MAS NMR spectra contain partly overlapping aliphatic and aromatic resonances with distinct transverse relaxation behavior. In Hahn-echo experiments, the aromatic signal decays more slowly than the aliphatic signal, indicating that for these systems, transverse ¹H relaxation is rather controlled by local distances between hydrogen atoms than by molecular mobility. Similar relaxation differences are also found in static (nonspinning) ¹H Hahn-echo NMR experiments, here used to discriminate between phases with different proton mobilities and/or densities in the kerogen samples and, ultimately, between aromatic and aliphatic fractions. The distributions of the static transverse relaxation time (T₂), extracted from the Hahn-echo decays, are characterized by a short-T₂ peak (∼10 μs) and a long-T₂ peak (∼100 μs). The ratio between these two peaks correlates well with the aliphatic-to-aromatic signal intensity ratios in MAS NMR spectra of the corresponding kerogen samples, suggesting that a net decrease in kerogen proton density—occurring during maturation—is also reflected by ¹H NMR relaxation. For the investigated kerogen isolates, the long-T₂ peak in the T₂ distribution can be considered an indicator of aromatic content, which can be directly detected by measuring ¹H T₂ relaxation.

Source rock characterization of the upper Barremian, Albian and Cenomanian–Turonian organic-rich strata outcropping in Oued Bazina area, NE of Thibar diapir: Northern Tunisia

Rock-Eval pyrolysis, total organic carbon (TOC) determination and gas chromatography-mass spectrometry (GC-MS) analysis were performed on samples from outcrop sections of the upper Barremian (M’Cherga Formation), Albian (Fahdene Formation) and Cenomanian–Turonian (Bahloul Formation) in the Oued Bazina area located in the NE of the diapiric structure of Thibar, northern Tunisia. The upper Barremian and Cenomanian–Turonian organic-rich strata display high TOC values with a mean of 3.39% and 2.82%, respectively, while the Albian succession deposits exhibit TOC values lesser than 2%. The half-graben structures developed at these epochs have acted as restricted mini-basins favouring the water stagnation, the accumulation and the preservation of the organic matter and consequently the development of locally euxinic conditions in the bottom waters. The generative petroleum potential (S1 + S2) of the upper Barremian and Cenomanian–Turonian studied organic-rich strata is good to very good and appears to be moderate for the Albian organic-rich deposits. The n-alkane distributions of the Cretaceous source rocks are typical for a marine planktonic origin. The Pristane/Phytane ratio indicates a sub-oxic depositional environment for the upper Barremian and Albian successions and a sub-oxic to anoxic environment for the Cenomanian–Turonian organic-rich strata. Regarding the maturity degree of the three studied organic-rich strata, only the upper Barremian source rock presents a high maturity level with Tmax values ranging from 441 °C to 448 °C, which indicates that the deposits have been deeply buried and consequently have generated hydrocarbons that have been recognized in the studied oil seep. The integration of our results with available data of Tmax values on other outcrops in the salt dome zone allowed drafting a maturity trend of the studied source rocks. A general northeast–southwest trend of maturity increase is observed with Tmax values varying from 436 to 446 °C.

Sedimentary characteristics of the Lower to Middle Ordovician Calathium reefs in the northwestern Tarim Basin, NW China

Recently, geologists are paying more and more attention to the Ordovician reefs in the Tarim Basin of China for related petroleum potential. This work presents a systematic study on the sedimentary characteristics of two well-exposed Lower to Middle Ordovician reefs of the Tarim Basin, one in the Yingshan Formation and the other in the Yijianfang Formation. The organism types, petrography and its sedimentary characteristics were analyzed based on detailed field and thin-section observations. The reef in the Yingshan Formation is identified as a patch reef that developed in open-platform environment and was distinguished four units, including the base facies, reef-core facies, reef-flank facies and sealing facies. In contrast, the reef in the Yijianfang Formation is a platform margin reef and was distinguished three units, including the base facies, reef-core facies and sealing facies. Both reefs had experienced phases of colonization, vertical aggradation and capping. However, the sea-level trends are different: reefs in the Yingshan Formation appear to reflect the sea-level rise with the subsequent fall, whereas reefs in the Yijianfang Formation appear to have been formed in the reverse order. This study improves the understanding of the sedimentary environments where reefs develop and provides guidance for exploration potential petroleum reservoirs in the Tarim Basin.

Changes of sensitive microbial community in oil polluted soil in the coastal area in Shandong, China for ecorestoration

Oil spills have an important threat to the ecological security and human health, for example the important oil field and coastal wetland Yellow River Delta is facing the dual problems of oil pollution and salinization. Therefore, the purpose of this study was to analyze the changes of soil microbial community and physicochemical properties, including pH value, total organic carbon (TOC), total petroleum hydrocarbons (TPHs) and electrical conductivity under the combined effect of petroleum and salinization. The soil properties results showed that the petroleum addition promoted the increase of TOC from 2.31±0.59mg/kg to 7.04±0.42mg/kg (r>0.95, P<0.1, R2 >0.9), TPHs from 9.18±0.07mg/kg to 33.09±4.61mg/kg (r>0.9, P<0.05, R2 >0.9) significantly. At the initial stage hydrocarbons caused the increase of soil salt content and the decrease of pH. Salt addition increased soil salt from 2.46±0.13g/kg to 15.12±0.21g/kg (r>0.8, P>0.1, R2 >0.95), but it had no direct effect on other soil properties. It was found that the nitrate reducing bacteria Halorhodospiraceae with potential petroleum degradation ability and the anaerobic bacteria Lactobacilliceae appeared after adding crude oil. The salt tolerant bacteria Halobacilli and the stone oil degrading bacteria Immundisolidcharacter appeared in the high salt and low salt environments respectively. The aerobic bacteria Acidimicrobiaceae, Hyphomonas and the nonoil efficient Peptoccaceae disappeared in the process of salinization and oil pollution. Lactobacilliceae can ferment carbohydrate, fatty acid or ester to produce lactic acid, acetic acid and fumaric acid to provide metabolic substrate for other microorganisms. The above results showed that sensitive microorganisms were easy to be affected by pollution to indicate soil conditions, while tolerant microorganisms could potentially use oil to achieve bioremediation. The soil properties and microbial results provided data support and theoretical basis for further understanding the pollution mechanism of oil and salinization combined stress on soil.

Geochemical and palynological characteristics of the Paleogene source rocks in the Northeastern Laizhouwan Sag, Bohai Bay Basin, China: Hydrocarbon potential, depositional environment, and factors controlling organic matter enrichment

The Northeastern Laizhouwan Sag (NLS) is a marginal sag in the Bohai Bay Basin, China. Paleogene source rocks from 3 wells (K-a, K-b and K-c) in this region, i.e., the third to the first member of the Shahejie Formation (Es3, Es2, and Es1), and the third member of the Dongying Formation (Ed3) were investigated for their petroleum potentials and depositional environments using geochemical and palynological methods. Among these members, the Es3 and Es1 members hold considerable hydrocarbon potential, while the rest are relatively fair. Although there are variations between the wells, the organic matter (OM) in the Es3 member is primarily composed of low mature or mature type I-II1 kerogen, which were primarily contributed by lower aquatic organisms and prokaryotes. During the Es3 stage, saline, stratified, and anoxic bottom water prevailed in the K-a well, while freshwater and weak reducing conditions dominated the K-b well. The OM in the Es1 member was contributed more by lower aquatic organisms than that in the Es2 member, but both are primarily composed of types II1-II2 kerogen; further, OM in the Es2 member is low mature, while that for the Es1 member ranges from immature to low mature, and higher maturity is expected in deeper buried places for the two members. Saline and anoxic bottom water prevailed during the both Es2 and Es1 members. Compared with other members, noticeable terrigenous OM was deposited during the Ed3 stage, which is dominated by immature type II2 kerogen. Lower salinity and weak reducing depositional conditions occurred in the Ed3 member. OM enrichment in the Es3 member was mainly determined by primary productivity, while that of the K-a well was also enhanced by the anoxic bottom water condition. The accumulations of OM in other members are speculated to have been controlled by the deposition rate.

Structure, stratigraphy, and petroleum potential of the deepwater Colombian Basin, offshore northern Colombia

We have defined the structure and stratigraphy of the central area of the Colombian Basin — offshore of the northern Caribbean coast of Colombia — using approximately 8400 line km of depth-converted 2D seismic data assembled from academic and industry sources. We integrate information from offset deep sea drilling program and ocean drilling program wells into a structural and stratigraphic model of the Colombian Basin, identifying the key elements of a petroleum system. These elements are (1) Upper Cretaceous marine shale source rock, (2) Middle to Upper Miocene (16–5.3 Ma) basin-floor fans associated with the Magdalena fan turbidite system, (3) structural traps and stratigraphic traps, and (4) sealing intervals formed by Miocene hemipelagic marine shale associated with sea-level high-stands. We extend a previously recognized trap type for the Colombian margin to include stratigraphic traps within the distal Miocene Magdalena fan section. We base our interpretations upon seismic observations of amplitude anomalies conformant with structures; fluid migration pathways along faults; and bright, laterally continuous, and low-impedance seismic reflectors. The primary risk for the exploration potential of the area is the presence of a laterally extensive Upper Cretaceous source rock within the main Colombian basin depocenter. The 1D burial history models and 3D basin modeling indicate that a source rock of this age and at this stratigraphic level would have expelled hydrocarbons during Middle to Late Miocene from the deepest part of the basin and may continue to expel hydrocarbons in the present day.

PETROLEUM POTENTIAL OF THE EDIACARAN SUCCESSION RELATED TO GEOLOGICAL AND GEOCHEMICAL CONDITIONS IN THE VOLYN-PODILIAN

This work is concerned with the studying of Ediacaran petroleum potential within Volyn-Podyllian. For the first time ever, the lithostratigraphycal, geological, geothermal, geochemical and paleohistorical analysis was provided for the whole Ediacaran section to determine its petroleum potential.The description of Precambrian succession in the world with its hydrocarbon occurrence was included. In addition to that, this work contains methodology and methods of the basin analysis study, which was perfomed. The potential source rocks, reservoirs and seals within the study area were defined and described.Based on the computer-integrated instruments, for the Neoproterozoic deposits were created: third-dimensional model of its succession, depth map, schematic map of katagenetic zones and concentration model of organic carbon. The paleoconditions of deposition and maturation processes of organic matter were reconstructed. Key words: Ediacaran deposits, Volyn-Podillian, oil-and-gas potential, computer modelling, basin analysis, sedimentary

Bioprospecting of potential petroleum hydrocarbon degraders using bacterial strains isolated from soils around transformer installation areas

ABSTRACT The study assessed the contamination levels of the soils around transformer installation areas in Ile-Ife, which were contaminated with transformer oil. Contamination levels are determined by using some soil physicochemical properties (pH, electrical conductivity, and organic matter) and also identifying some hydrocarbon utilizing bacteria in the oil-contaminated soils. Soil samples were collected from transformer oil-contaminated and uncontaminated soils at 5−15-cm depth. Soil physicochemical properties were determined using standard methods. The soil samples were screened for hydrocarbon-degrading bacteria; the isolates were duly identified using the matrix-assisted laser desorption/ionization-time of flight/mass spectrometry technique. The growth rate of the bacterial isolates in the hydrocarbon medium was monitored. Thereafter, the residual oil was analyzed quantitatively and qualitatively using gravimetric and gas chromatography–mass spectrometry techniques, respectively. The results of the physiochemical parameters of the oil-contaminated soils showed that the soils had mean values of pH (5.01 ± 0.22), electrical conductivity (574.45 ± 63.35 µs/cm), and soil organic matter (50.53 ± 5.67 g/kg). The chromatogram of the residual oils from the biodegradation process showed the efficacy of Providencia stuartii and Bacillus pseudomycoides in degrading alkyl polycyclic aromatic hydrocarbons (PAHs), cycloalkanes, unsaturated alkanes, and unsaturated-branched alkanes, while Providencia rettgeri could adequately degrade cycloalkenes, cycloalkanes, unsaturated alkanes, and unsaturated-branched alkanes. In this study, novel hydrocarbon-degrading bacterial isolates were identified, and the extent of their hydrocarbon and complex organic compound utilization was shown, it suggests the need for further studies to explore their potentials in bioremediation programs.

An ABC-optimized fuzzy ELECTRE approach for assessing petroleum potential at the petroleum system level

AbstractAn inevitable aspect of modern petroleum exploration is the simultaneous consideration of large, complex, and disparate spatial data sets. In this context, the present article proposes the optimized fuzzy ELECTRE (OFE) approach based on combining the artificial bee colony (ABC) optimization algorithm, fuzzy logic, and an outranking method to assess petroleum potential at the petroleum system level in a spatial framework using experts’ knowledge and the information available in the discovered petroleum accumulations simultaneously. It uses the characteristics of the essential elements of a petroleum system as key criteria. To demonstrate the approach, a case study was conducted on the Red River petroleum system of the Williston Basin. Having completed the assorted preprocessing steps, eight spatial data sets associated with the criteria were integrated using the OFE to produce a map that makes it possible to delineate the areas with the highest petroleum potential and the lowest risk for further exploratory investigations. The success and prediction rate curves were used to measure the performance of the model. Both success and prediction accuracies lie in the range of 80–90%, indicating an excellent model performance. Considering the five-class petroleum potential, the proposed approach outperforms the spatial models used in the previous studies. In addition, comparing the results of the FE and OFE indicated that the optimization of the weights by the ABC algorithm has improved accuracy by approximately 15%, namely, a relatively higher success rate and lower risk in petroleum exploration.

Современное представление о тектонической неоднородности Восточного Устюрта в связи с перспективами нефтегазоносности палеозойских отложений

Современное представление о тектонической неоднородности Восточного Устюрта в связи с перспективами нефтегазоносности палеозойских отложений

Geological structures and potential petroleum exploration areas in the southwestern Sichuan fold-thrust belt, SW China

Based on the latest geological, seismic, drilling and outcrop data, we studied the geological structure, tectonic evolution history and deformation process of the southwestern Sichuan fold-thrust belt to find out the potential hydrocarbon exploration areas in deep layers. During key tectonic periods, the southwestern Sichuan fold-thrust belt developed some characteristic strata and structural deformation features, including the Pre-Sinian multi-row N-S strike rifts, step-shaped platform-margin structures of Sinian Dengying Formation, the western paleo-uplift in the early stage of Late Paleozoic, the Late Paleozoic–Middle Triassic carbonate platform, foreland slope and forebulge during Late Triassic to Cretaceous, and Cenozoic multi-strike rejuvenated fold-thrusting structures. The fold-thrust belt vertically shows a double-layer structural deformation controlled by the salt layer in the Middle Triassic Leikoupo Formation and the base detachment layer at present. The upper deformation layer develops the NE-SW strike thrusts propagating toward basin in long distance, while the deeper deformation layer had near north-south strike basement-involved folds, which deformed the detachment and thrusting structures formed earlier in the upper layer, with the deformation strength high in south part and weak in north part. The southern part of the fold-thrust belt is characterized by basement-involved fold-thrusts formed late, while the central-northern part is dominated by thin-skin thrusts in the shallow layer. The Wuzhongshan anticlinal belt near piedmont is characterized by over-thrust structure above the salt detachment, where the upper over-thrusting nappe consists of a complicated fold core and front limb of a fault-bend fold, while the deep layer has stable subtle in-situ structures. Favorable exploration strata and areas have been identified both in the upper and deeper deformation layers separated by regional salt detachment, wherein multiple anticlinal structures are targets for exploration. Other potential exploration strata and areas in southwestern Sichuan fold-thrust belt include the deep Sinian and Permian in the Wuzhongshan structure, pre-Sinian rifting sequences and related structures, platform-margin belt of Sinian Dengying Formation, and Indosinian paleo-uplift in the east of the Longquanshan structure.

The relationship between oil generation, expulsion and retention of lacustrine shales: Based on pyrolysis simulation experiments

The oil expulsion efficiency of shales is restricted by quite a few geological and geochemical factors, resulting in a great challenge to be evaluated quantitatively. In this paper, a semi-open pyrolysis simulation experiment based on a gold tube system was applied to simulate the oil generation and expulsion of seven lacustrine shale core samples with low maturities (Ro between 0.54% and 0.68%) and different kerogen types (types I and II) taken from the Shengli Oilfield, eastern China, and the corresponding seven suits of artificially matured sub-samples with a Ro range of 0.70–1.35% were obtained. The evolution of oil generation and oil expulsion, and their coupling relationships with oil retention for these samples with increasing maturity were investigated. The results show that the main stage of oil expulsion of these shales lags significantly behind the main stages of both oil generation and oil retention, with a corresponding Ro range of 0.80–0.90%, 0.70–0.85% and 0.65–0.82%, respectively. The oil expulsion efficiencies of these shales are not only constrained by their maturities, but also affected by their kerogen types and TOC contents. The shales with greater petroleum potentials and/or greater TOC contents have greater oil expulsion efficiencies. There is a good positive correlation between the retained oil and the total oil (i.e., the generated oil) for these shales as their Ro ≤ 0.98%, and this relationship is not significantly influenced by their kerogen types and maturities. The results may provide an alternative way for predicting the oil expulsion efficiency of natural shales according to their retained oil.

Groundwater in the Mesozoic hydrogeological basin of the Middle Ob (a case study of the Ust-Balykskoye oil field)

Despite the fact that there is the large amount of accumulated factual material, formation of hydrogeochemical conditions of deep oil and gas horizons in the Middle Ob and the West Siberian megabasin still contains many questions. This is due to numerous hydrogeodynamic and hydrogeochemical anomalies that don't have an unambiguous explanation. The presence of inversion hydrogeochemical zoning in the Lower Cretaceous and Upper Jurassic deposits and the presence of low-mineralized reservoir water of a sodium-bicarbonate composition are the peculiarity of groundwater in the considered territory. A change in the genetic type of water, a decrease in mineralization, a decrease in the content of calcium ion, and an increase in the amount of bicarbonate ion in the Mesozoic hydrogeological basin are associated with the transformation of mineral and organic matter in sedimentary rocks, when they are immersed, at the water expelling stage. The determination of the origin of low-mineralized reservoir water of a sodium-bicarbonate lying at significant depths is of great practical importance, since the relationship between the inversion of groundwater and oil content has been revealed, so this fact can be considered a search criterion for petroleum potential.

The effect of volcanism to the source rock maturity in Gunung Endut area: Insight for subvolcanic hydrocarbon exploration

Banten region is known to have subvolcanic hydrocarbon system but no proven play despite oil seeps and the potential source rock have been identified in this area. A Geochemical analysis of source rock have been done on Gunung Endut, Banten Province. There are four coaly shale sample from Genteng Formation and Bojongmanik Formation collected and analysed in this study. The purpose of this study is to understand the influence of volcanic environment towards the quality, quantity and maturity of source rock based on TOC, pyrolysis, and vitrinite reflectance analyses. The result obtained showed TOC value between 8–18 wt% which indicated excellent petroleum potential from the source rock. In addition, Pyrolysis data showed S1 value between 0.05–0.19, S2 value between 1.52–11.53, S3 value between 4.10–7.57 and Tmax 414.8–523.2 °C. From both analyses, TOC and Pyrolysis, the source rock is categorized as Type 3 Kerogen producing gas and Type 4. Based on its maturity, three sample are categorized as immature while one specimen is categorized as postmature. Furthermore, Vitrinite Reflectance analysis result shows Ro value between 0.27–0.63 that support the result of pyrolysis analysis. Maturity anomaly found in the sample is presumed to be caused by intrusion that have been identified by the geological mapping in the same region. The condition on the surface may also reflect the source rock in the subsurface. A number of source rock in Banten region may be matured due to intrusion that related to volcanic activities. Subsurface zone with abundance igneous bodies will have different maturity compare to other area. Hence, it is important for petroleum exploration activities in Banten region or other volcanic area to properly identify the distribution of subsurface igneous body due to its effect to the source rock maturity.

English

Potential petroleum degrading bacteria, Pseudomonas aerogenosa and Micrococcus sp. was isolated from petroleum contaminated soil in petroleum microbiology laboratory, Department of Microbiology University of Nigeria, Nsukka. Hydrocarbon utilization in liquid media was assessed through time &ndash; course optical density measurement. Concentrations of the heavy metals ranging from 50 to 200 mg/L were introduced into 100 ml of mineral salt medium containing 10 ml of kerosene inoculated with P. aeruginosa or&nbsp; Micrococcus sp. and incubated at room temperature (25-30&deg;C) for 384 h. Control samples contained kerosene but no heavy metals. At low concentrations the heavy metals significantly (p &lt;0.05) improved the growth of the isolates as indicated by the highest OD600 obtained with 50 mg/L of the metals which was the lowest concentrations. This was confirmed by the bacterial cell number extrapolated from an OD standard curve. At higher concentrations of the heavy metals (150 to 200 mg/L) there was a decline in the growth rates of the isolates. The effects of the heavy metals on the hydrocarbonoclastic efficacy of the isolates were dose-dependent and their growth rates in the presence of the metals were in the following order: Lead &gt; Cadmium &gt; Mercury. Key words: Heavy metals, kerosene, bioremediation, bacteria. &nbsp;

Petroleum potential of the Riphean of the Siberian on hydrogeological data (on the example of the Kuyumbinskoe structure)

In the article, when considering the prospects of oil and gas potential of the Riphean strata in Siberia as indicators of oil content, special attention is paid to hydrocarbon gases in sorbed form. Sorbed hydrocarbon gases are still poorly used as indicators of oil content, although they have significant prerequisites for this. Some of them can be understood by reading this article.

ADVANCES ON THE GEOLOGY AND EVALUATION OF POTENTIAL PETROLEUM SYSTEMS OF THE SOKOTO BASIN IN NW NIGERIA

The stratigraphy of the Sokoto Basin has the Illo/Gundumi Formation at the bottom, followed successively upward by the Taloka, Dukamaje, Wurno, Dange, Kalambaina, Gamba and Gwandu Formations. Re-mapping of the basin carried out in this study shows that the geological framework remains largely as previously outlined except that some hitherto unreported tectonically controlled structures have been documented. The basin is generally shallower at the margin and deepens towards the centre such that the areas around the border with Niger Republic are deepest and hence most prospective on the Nigerian side. Geophysical aeromagnetic interpretation has assisted to analyze the depth to basement configurations. Organic geochemical studies show that the dark shales and limestones of the Dukamaje Formation constitute the source rocks in the potential petroleum system. With averages for source rock thickness of 50m, area of basin of 60,000km2, TOC of 7.5wt%, and HI of 212mgHC/gTOC, charge modeling indicates 808.10 million barrels of oil equivalent extractable hydrocarbons in the Sokoto Basin, at current knowledge of the geology and if the appropriate maturity has been attained at deeper sections. The sandstones of the Illo/Gundumi Formation as well as in the Taloka and Wurno Formations and carbonates of the Kalambaina Formation provide potential reservoir packages. The paper shale of the Gamba Formation and the clays of the Gwandu Formation provide regional seals. If the presently mapped tectonic structures are ubiquitous in the whole basin, structural and stratigraphic traps may upgrade the petroleum system. Other petroleum systems may exist in the basin with either or both the Illo/Gundumi and Taloka Formation(s) providing the source and reservoir rocks. Keywords: Sokoto Basin, Dukamaje Formation, Hydrocarbons, Petroleum System, Reservoirs