Petroleum Geology and Geochemistry of Sedimentary Basins

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Energies energies	3.0	6.2	2008	16.8 Days	CHF 2600
Geosciences geosciences	2.4	5.3	2011	23.5 Days	CHF 1800
Minerals minerals	2.2	4.1	2011	18 Days	CHF 2400
Quaternary quaternary	2.3	3.3	2018	43.4 Days	CHF 1600

17 pages, 6340 KiB

Open AccessArticle

Shale Oil Generation Conditions and Exploration Prospects of the Cretaceous Nenjiang Formation in the Changling Depression, Songliao Basin, China

by Wenjun Zhang, Wenyu Zhang, Shumin Lin, Xing Ke, Min Zhang and Taohua He

Minerals 2024, 14(9), 942; https://doi.org/10.3390/min14090942 - 15 Sep 2024

Viewed by 968

Abstract

Low-maturity shale oil predominates in shale oil resources. China’s onshore shale oil, particularly the Cretaceous Nenjiang Formation in the Songliao Basin, holds significant potential for low-maturity shale oil, presenting promising exploration and development prospects. This study delves into the hydrocarbon generation conditions, reservoir [...] Read more.

Low-maturity shale oil predominates in shale oil resources. China’s onshore shale oil, particularly the Cretaceous Nenjiang Formation in the Songliao Basin, holds significant potential for low-maturity shale oil, presenting promising exploration and development prospects. This study delves into the hydrocarbon generation conditions, reservoir characteristics, and oil-bearing property analysis of the mud shale from the Nen-1 and Nen-2 sub-formations of the Nenjiang Formation to pinpoint favorable intervals for shale oil exploration. Through the integration of lithology, pressure, and fracture distribution data in the study area, favorable zones were delineated. The Nen-1 sub-formation is widely distributed in the Changling Depression, with mud shale thickness ranging from 30 to 100 m and a total organic content exceeding 2.0%. Type I kerogen predominated as the source rock, while some samples contained type II kerogen. Organic microcomponents primarily comprised algal bodies, with vitrinite reflectance (R_o) ranging from 0.5% to 0.8%. Compared to Nen-1 shale, Nen-2 shale exhibited less total organic content, kerogen type, and thermal evolution degree, albeit both are conducive to low-maturity shale oil generation. The Nen-1 and Nen-2 sub-formations predominantly consist of clay, quartz, feldspar, calcite, and pyrite minerals, with minor dolomite, siderite, and anhydrite. Hydrocarbons primarily reside in microfractures and micropores, including interlayer micropores, organic matter micropores, intra-cuticle micropores, and intercrystalline microporosity, with interlayer and intra-cuticle micropores being dominant. The free oil content (S₁) in Nen-1 shale ranged from 0.01 mg/g to 5.04 mg/g (average: 1.13 mg/g), while in Nen-2 shale, it ranged from 0.01 mg/g to 3.28 mg/g (average: 0.75 mg/g). The Nen-1 and Nen-2 sub-formations are identified as potential intervals for shale oil exploration. Considering total organic content, oil saturation, vitrinite reflectance, and shale formation thickness in the study area, the favorable zone for low-maturity shale oil generation is primarily situated in the Heidimiao Sub-Depression and its vicinity. The Nen-2 shale-oil-enriched zone is concentrated in the northwest part of the Heidimiao Sub-Depression, while the Nen-1 shale-oil-enriched zone lies in the northeast part. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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21 pages, 11571 KiB

Open AccessArticle

Characteristics of Micropore-Throat Structures in Tight Oil Reservoirs: A Case Study of the Jiufotang Formation in the Houhe Region, NE China

by Guolong Zhang and Chenglong Ma

Minerals 2024, 14(9), 918; https://doi.org/10.3390/min14090918 - 6 Sep 2024

Viewed by 887

Abstract

In order to examine further the characteristics of micropore-throat structures of the tight oil reservoir in the Jiufotang Formation in the Houhe region, this study used whole rock X-ray diffraction, routine physical property analysis, and routine thin section observations to analyze the material [...] Read more.

In order to examine further the characteristics of micropore-throat structures of the tight oil reservoir in the Jiufotang Formation in the Houhe region, this study used whole rock X-ray diffraction, routine physical property analysis, and routine thin section observations to analyze the material composition and physical properties of the tight oil reservoir. CT scanning, high-pressure mercury infiltration, and other test methods were employed to analyze the characteristics of the pore-throat structures in the tight oil reservoir. In addition, the Pearson correlation coefficients quantified the relationships between nine parameters and pore-throat structures. The parameters with high correlations were optimized for analysis, and a comprehensive classification scheme for micropore-throat structures in the tight oil reservoir in the study area was established. The results show that the reservoir in the Jiufotang Formation in the Houhe region is composed of feldspathic and lithic arkosic sandstone, with feldspar and clast pore dissolution pores as the main type of reservoir pore space. The tight oil reservoir has small pore-throat radius, complex structures, poor connectivity, and high heterogeneity. It generally contains micron-sized pores with submicron to nanometer throat widths and small- and medium-sized pores to fine micropore-throat structures. Porosity, permeability, coefficient of variation, skewness coefficient, and average pore-throat radius, were selected for k-means cluster analysis. The micropore-throat structures of the tight oil reservoir were divided into three categories: classes I, II, and III. The study area is dominated by class II pore throats, accounting for 58%. Diagenesis mainly controls the pore-throat structure. These results provide an effective reference for the identification and evaluation of favorable sweet spots in tight oil reservoirs in similar blocks in China. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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17 pages, 4948 KiB

Open AccessArticle

Hydrocarbon Accumulation and Overpressure Evolution in Deep–Ultradeep Reservoirs in the Case of the Guole Area of the Tarim Basin

by Zhanfeng Qiao, Tianfu Zhang, Ruyue Wang, Yahao Huang, Yifan Xue, Jiajun Chen, Haonan Tian, Anjiang Shen and Chunsong Si

Minerals 2024, 14(8), 790; https://doi.org/10.3390/min14080790 - 31 Jul 2024

Cited by 1 | Viewed by 1103

Abstract

Usually, deep oil and gas accumulation is often controlled by strike–slip faults. However, in the Tarim Basin, deep Ordovician oil and gas accumulations are also found in areas far from the fault zone. The process of oil and gas accumulation in deep reservoirs [...] Read more.

Usually, deep oil and gas accumulation is often controlled by strike–slip faults. However, in the Tarim Basin, deep Ordovician oil and gas accumulations are also found in areas far from the fault zone. The process of oil and gas accumulation in deep reservoirs far from strike–slip fault zones is still unclear at present. The source and evolution of Ordovician fluids were analyzed using inclusion geochemical methods and the U–Pb dating technique. The analysis of rare earth elements and carbon–oxygen–strontium isotopes in the reservoirs showed that the reservoirs were weakly modified by diagenetic fluid. The fluid was derived from the fluid formation during the same period as the seawater, and no oxidizing fluid invaded the reservoir. The late oil and gas reservoirs had good sealing properties. The U–Pb dating results combined with homogenization temperature data revealed that the first-stage oil was charged during the Late Caledonian Period, and the second-stage natural gas was charged during the Middle Yanshanian Period. The evolution of the paleo-pressure showed that the charging of natural gas in the Middle Yanshanian was the main reason for the formation of reservoir overpressure. The strike–slip fault zone was basically inactive in the Middle Yanshanian. During this period, the charged natural gas mainly migrated to the reservoir along the unconformity surface and the open strike–slip fault zone in the upper part of the Ordovician reservoir. The source of the fluid shows that the reservoir in the late stage had good sealing properties, and there was no intrusion of exogenous fluid. The overpressure in the reservoir is well preserved at present. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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19 pages, 17422 KiB

Open AccessArticle

Evaporative Fractionation as the Important Formation Mechanism of Light Oil Reservoirs in the Dongying Depression, NE China

by Rongzhen Qiao, Meijun Li, Donglin Zhang, Zhonghong Chen and Hong Xiao

Energies 2024, 17(15), 3734; https://doi.org/10.3390/en17153734 - 29 Jul 2024

Cited by 3 | Viewed by 1247

Abstract

Light oil, a high-quality energy resource abundant in deep basins, is prevalent in the northern zone of the Dongying Depression. To elucidate the formation mechanism of light oil reservoirs, this study investigates the molecular and stable isotope composition, biomarkers, light hydrocarbons, and diamondoid [...] Read more.

Light oil, a high-quality energy resource abundant in deep basins, is prevalent in the northern zone of the Dongying Depression. To elucidate the formation mechanism of light oil reservoirs, this study investigates the molecular and stable isotope composition, biomarkers, light hydrocarbons, and diamondoid compositions of petroleum. The results reveal that the gas primarily consists of oil-cracking gas from a late filling event, mixed with oil-associated gas generated during the source rock’s “oil window” maturity phase. Methane exhibits enriched light carbon isotopes, indicating noticeable migration fractionation effects. The crude oil in the same deep strata exhibits high maturity, originating from both terrestrial and aquatic organic matter in the source materials. Molar proportions of n-alkanes and light hydrocarbon indices (Tol/nC₇, nC₇/MCH) indicate significant evaporative fractionation in the petroleum reservoirs. This fractionation process modified early-formed oil reservoirs due to the late filling of highly mature gas reservoirs. The evaporative fractionation at different stages has varying effects on the diamondoid ratio (1- + 2-MA)/(3- + 4-MD). It is considered a pivotal mechanism in the formation of deep condensate reservoirs and volatile oil reservoirs. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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21 pages, 9618 KiB

Open AccessArticle

Trace Elements Distribution in the k₇ Seam of the Karaganda Coal Basin, Kazakhstan

by Aiman Kopobayeva, Irina Baidauletova, Altynay Amangeldikyzy and Nazym Askarova

Geosciences 2024, 14(6), 143; https://doi.org/10.3390/geosciences14060143 - 24 May 2024

Cited by 6 | Viewed by 1615

Abstract

We investigated the distribution patterns and evaluated the average contents of trace elements in the k₇ seam of the Karaganda coal basin in Central Kazakhstan. This paper presents the results of studying the geochemistry of 34 elements in 85 samples of the [...] Read more.

We investigated the distribution patterns and evaluated the average contents of trace elements in the k₇ seam of the Karaganda coal basin in Central Kazakhstan. This paper presents the results of studying the geochemistry of 34 elements in 85 samples of the k₇ seam. The study employed a suite of advanced high-resolution analytical methods, including atomic emission spectrometry with inductively coupled plasma (ICP–OES) and mass spectrometry with inductively coupled plasma (ICP–MS), along with their processing and interpretation. It was determined that the concentrations of trace elements in the k₇ seam are primarily associated with lithophile elements, revealing high concentrations of Li, V, Sc, Zr, Hf, and Ba. Additionally, increased concentrations of Nb, Ta, Se, Te, Ag, and Th were observed compared to the coal Clarke. Specific Nb(Ta)–Zr(Hf)–Li mineralization accompanied by a group of associated metals (Ba, V, Sc, etc.) was identified. The study revealed lateral and vertical heterogeneity of the rare elements’ distributions in coals, attributed to the formation dynamics of the coal basin. A correlation between Li and Al₂O₃ with a less positive relationship with K₂O suggests the affinity of certain elements (Li, Ta, Nb, and Ba) to kaolinite. Clay layers showed increased radioactivity, with Th—13.2 ppm and U—2.6 ppm, indicating the possible presence of volcanogenic pyroclastic rocks characterized by radioactivity. Taken together, these data reveal the features of the rock composition of the source area, which is considered a mineralization source. According to geochemical data, it was found that the source area mainly consists of igneous felsic rocks, indicating that the formation occurred under conditions of a volcanic arc. This study’s novelty lies in estimating the average trace elements in the k₇ seam, with elevated concentrations of certain elements that suggest promising prospects for industrial extraction from coals and coal wastes. These findings offer insights into considering coal as a potential source of raw material for rare metal production, guiding the industrial processing of key elements within coal. The potential extraction of metals from coal deposits, including from dumps, holds significance for industrial and commercial technologies, as processing critical coal elements can reduce disposal costs and mitigate their environmental impact. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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22 pages, 9492 KiB

Open AccessArticle

Geochemistry and Petrology of Reservoir and Cap Rocks in Zar-3 Pilot CO₂ Storage Complex, SE Czechia

by Juraj Francu, Daniela Ocásková, Petr Pařízek, Jakub Vácha, Miroslav Pereszlényi, Petr Jirman, Vladimír Opletal and Monika Ličbinská

Geosciences 2024, 14(5), 119; https://doi.org/10.3390/geosciences14050119 - 28 Apr 2024

Cited by 1 | Viewed by 1590

Abstract

The planned pilot CO₂ storage Zar-3 is an oil field with a gas cap in the final production stage in the SE Czech Republic. It is composed of a dolomite Jurassic reservoir sealed by three different formations that differ significantly in lithology. [...] Read more.

The planned pilot CO₂ storage Zar-3 is an oil field with a gas cap in the final production stage in the SE Czech Republic. It is composed of a dolomite Jurassic reservoir sealed by three different formations that differ significantly in lithology. Previous studies left open questions on the nature of pore space and connectivity and the quality of the seal in the future CO₂ storage complex. Microscopic petrography of the reservoir suggests dolomitisation in shallow water followed by karstification and brecciation with fracture-correct-dominated porosity. The seal horizons have porosity limited to the micro- and nanoscales. The oil consists of significantly biodegraded black oil of Jurassic origin mixed with less biodegraded gasoline-range hydrocarbons. Biomarkers in the caprock bitumens trapped in nanopores show a genetic relationship to the reservoir oil. Gas in the not yet fully depleted gas cap of the field is of thermogenic origin with no contribution of microbial methane. The formation water has total dissolved solids typical of isolated brines not diluted by infiltrated fresh water. The geochemical characteristics of the storage system together with the fact that the initial oil column is about 105 m tall with another 150 m of gas cap suggest that the seals are efficient and the Zar-3 future storage complex is tight and safe. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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27 pages, 33432 KiB

Open AccessArticle

A Multi-Faceted Approach to Determining the Provenance of the Lacustrine Rift Basin in the Initial Rifting Stage: A Case Study of the Paleocene Qintong Sag, Subei Basin, East China

by Rui Jiang, Zhen Liu, Shiqiang Xia, Maolin Zhu, Jianxin Tang, Gongyi Wu and Wei Wu

Minerals 2024, 14(4), 420; https://doi.org/10.3390/min14040420 - 18 Apr 2024

Viewed by 1350

Abstract

Research on the provenance of sedimentary systems is key to better understanding the sedimentary framework and improving exploration-associated decision-making and deployment. With regard to the provenance of sedimentary systems, there is still poor understanding in the initial rifting stage due to imbalanced and [...] Read more.

Research on the provenance of sedimentary systems is key to better understanding the sedimentary framework and improving exploration-associated decision-making and deployment. With regard to the provenance of sedimentary systems, there is still poor understanding in the initial rifting stage due to imbalanced and insufficient exploration and a common lack of seismic data, which have seriously hindered oil exploration in the Qintong Sag, Subei Basin. This study aimed at investigating the provenance in the direction of the fault-terrace zone in the southeast part of the Qintong Sag and aimed to examine whether large-scale sedimentary systems are formed by these sediment sources. Integrated analysis of heavy minerals, sandstone petrologic maturity, drilling cutting dates, 3D seismic data, and well logs was employed to identify the provenance. This study is the first time that large-scale provenance from the direction of the fault-terrace zone has been discovered in the third member of the Paleocene Funing Formation (referred to as the third Mbr of the Funing Fm in this paper) in the Subei Basin, east China. The documentation shows that sediments from the northwest Wubao Low Uplift and the southeast Taizhou Uplift can be distinguished in the Qintong Sag, with the large-scale delta system in the central and eastern part of the Qintong Sag comprising sediments from the Taizhou Uplift, improving upon previous understanding of the sedimentary framework. The deposition formed by the Taizhou Uplift provenance system was characterized by gradual weakening of the hydrodynamic forces, a decreasing sediment supply, and shrinking of the retrogradational delta depositional systems with good reservoir qualities, which are characterized by high-quality source–reservoir–cap combinations and are likely to develop into a hydrocarbon-rich belt. The discovery of the Taizhou Uplift provenance proves that there may be major provenance and large-scale sedimentary systems from the fault-terrace zone of the rift basins in the initial rifting stage. The experience of rapid retrogradation showed that these large-scale delta systems are likely to only flourish in the initial rifting stage. This study is helpful for improving the understanding of sediment provenance and the sedimentary framework of lacustrine rift basins in the initial rifting stage. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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21 pages, 14051 KiB

Open AccessArticle

Diagenetic Impact on High-Pressure High-Temperature Reservoirs in Deep-Water Submarine Fan Sandstone of Qiongdongnan Basin, South China Sea

by Lin Hu, Wei Luo and Benben Ma

Minerals 2024, 14(4), 361; https://doi.org/10.3390/min14040361 - 29 Mar 2024

Cited by 1 | Viewed by 1349

Abstract

The diagenetic evolution of sandstone is very complicated under the conditions of high temperatures and pressures in deep-water, deep-buried regimes, which have great influence on reservoir quality. This study investigates the typical reservoir target of Neogene deep-water, submarine-fan sandstones under high-temperature, high-pressure regimes [...] Read more.

The diagenetic evolution of sandstone is very complicated under the conditions of high temperatures and pressures in deep-water, deep-buried regimes, which have great influence on reservoir quality. This study investigates the typical reservoir target of Neogene deep-water, submarine-fan sandstones under high-temperature, high-pressure regimes in the Qiongdongnan Basin, South China Sea. Utilizing a thin section, scanning electron microscope (SEM), mineral geochemistry combined with burial history evolution, complex diagenetic events, and main controlling factors of the sandstone in the Neogene Meishan Formation were determined. The results show that the evolution of sandstone reservoirs is initially controlled by depositional framework compositions and subsequently modified by eogenetic and mesogenetic alterations during progressive burial. Eogenetic alterations mainly include the following: (1) mechanical compaction; (2) dissolution of feldspar; (3) low-Fe calcite cementation. Mesogenetic events were identified as the following: (1) dissolution of feldspar; (2) ferroan calcite and ankerite formation; (3) precipitation of quartz and clay mineral. Mechanical compaction is greatly influenced by the original depositional framework composition, and sandstone samples enriched in high contents of detrital clay matrix always experienced extensive mechanical compaction. Different phases of carbonate cement during different diagenetic regimes lead to continuous destruction on reservoir porosity. The dissolution of unstable feldspar minerals during eogenetic and mesogenetic environments leads to the development of secondary porosities and would enhance the quality of the reservoir. Overpressure formation is pervasively developed owing to early disequilibrium compaction and subsequent natural gas charging. Only well-sorted sandstones with low contents of detrital clay matrix could resist early mechanical compaction, lead to ample residual original porosities, and then undergo extensive mineral dissolution to generate sufficient secondary porosities. Subsequently, these porosities would be effectively protected by overpressure formation. Poor-sorted sandstones with high contents of detrital clay matrix would experience strong mechanical compaction and extensive destruction of original porosities. Thus, these sandstones are difficult to have significant dissolution and are unable to be effectively protected by overpressure formation. Therefore, the interplay between the original framework composition and the corresponding diagenetic pathways coupled with overpressure formation would result in strong reservoir heterogeneity for the deep-buried sandstones during progressive burial. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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18 pages, 20044 KiB

Open AccessArticle

New Age Constraints of the Bilong Co Oil Shale in the Qiangtang Basin, Northern Tibet: Evidence from In Situ U–Pb Dating and Palaeontology

by Haowei Zhang, Jian Wang, Ahmed Mansour, Jianyong Zhang, Hengye Wei, Xiugen Fu, Lijun Shen, Shaoyun Xiong, Mohamed S. Ahmed and Thomas Gentzis

Minerals 2024, 14(3), 246; https://doi.org/10.3390/min14030246 - 28 Feb 2024

Cited by 5 | Viewed by 1742

Abstract

The Bilong Co oil shale is one of the most significant source rocks in the Mesozoic Qiangtang Basin (Northern Tibet); however, its absolute chronology remains controversial. In this study, in situ carbonate U–Pb isotope dating analysis was carried out for the first time. [...] Read more.

The Bilong Co oil shale is one of the most significant source rocks in the Mesozoic Qiangtang Basin (Northern Tibet); however, its absolute chronology remains controversial. In this study, in situ carbonate U–Pb isotope dating analysis was carried out for the first time. Detailed field geological investigations yielded some age-diagnostic ammonites, enabling a re-evaluation of the stratigraphic age of the Bilong Co oil shale. A total of 61 spots of U–Pb isotope dating from the middle part of the Bilong Co oil shale section suggests an average age of 181 ± 13 Ma. Elemental geochemistry and diagenetic analysis indicate that the proposed age represents the early deposition of the calcite, and the oil shale was deposited during the Early Jurassic time. This estimated age is further supported by the newly discovered ammonite assemblage of Hildoceratidae–Tiltoniceras sp. at the top part of the oil shale section, which confirms the deposition of the oil shale during the Toarcian age of the late Early Jurassic. Consequently, the Bilong Co oil shale can be assigned to the Quse Formation, which is attributed to the Lower Jurassic rather than the Middle Jurassic. The re-assessment of the stratigraphic age of the Bilong Co oil shale is of great significance for regional evaluation and exploration activities of hydrocarbon source rock layers in the Qiangtang Basin as well as for global stratigraphic correlation of the late Early Jurassic Toarcian oceanic anoxic event. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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42 pages, 71568 KiB

Open AccessArticle

Assessment of Oil and Gas Potential in Vychegda Trough in Connection with the Identification of Potential Petroleum Systems

by Sergey Krivoshchekov and Andrey Botalov

Geosciences 2024, 14(3), 57; https://doi.org/10.3390/geosciences14030057 - 21 Feb 2024

Cited by 1 | Viewed by 1914

Abstract

At present, the study of the oil and gas potential of poorly explored areas of oil and gas basins in the Russian Federation is of great importance due to the possibility of discovering large hydrocarbon accumulations in them. The Vychegda Trough in the [...] Read more.

At present, the study of the oil and gas potential of poorly explored areas of oil and gas basins in the Russian Federation is of great importance due to the possibility of discovering large hydrocarbon accumulations in them. The Vychegda Trough in the north of the Volga–Ural basin is considered to be one of such areas. The research is devoted to the assessment of the oil and gas potential of the Vychegda Trough based on the concept of “petroleum systems”, which is widely used in oil and gas geology. A comprehensive analysis of geological and geophysical, petrophysical and geochemical data was carried out, and modern technologies for studying the oil and gas potential of sedimentary basins were applied: paleotectonic, paleogeographic reconstructions and basin modeling. The results of the research allowed us to determine a sufficiently high potential for the discovery of hydrocarbon accumulations and to identify three potential petroleum systems in the basin section: Riphean, Vendian and Devonian–Permian. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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15 pages, 3558 KiB

Open AccessArticle

Applying Statistical Analysis and Economics Models to Unscramble the Depositional Signals from Chemical Proxies in Black Shales

by Karin Goldberg and Lucas Goldberg Da Rosa

Geosciences 2024, 14(2), 43; https://doi.org/10.3390/geosciences14020043 - 3 Feb 2024

Viewed by 1787

Abstract

The complex controls on the accumulation of organic-rich rocks remain elusive, despite their economic importance as source rocks and unconventional reservoirs, partially due to the multitude of factors that may impact production and preservation of organic matter in sediments. The complexity of Earth [...] Read more.

The complex controls on the accumulation of organic-rich rocks remain elusive, despite their economic importance as source rocks and unconventional reservoirs, partially due to the multitude of factors that may impact production and preservation of organic matter in sediments. The complexity of Earth systems is comparable to the intricacies of Economics, and application of statistical and econometrics methods and models to analyze geological data may assist interpretation of the processes controlling organic burial. Chemical indices calculated for mudrock datasets from modern sediments and the Woodford Formation were used as proxies for detrital input, primary productivity, redox conditions, and upwelling, and a series of statistical analyses were run to test whether these methods were useful to discriminate different depositional conditions and establish the controls on total organic carbon (TOC) in the sediments. Model results showed that chemical proxies reliably predict not only TOC but also indicate correlations between indices. Our results suggest that detrital input, primary productivity and bottom-water anoxia are relevant drivers of organic content in the sediments, but the first two appear to have a more significant role in organic burial, illustrating the usefulness of these methods to assess depositional parameters in organic-rich rocks. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)

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23 pages, 16660 KiB

Open AccessArticle

Organic Matter Assessment and Paleoenvironmental Changes of the Middle Jurassic Main Source Rocks (Khatatba Formation) in the North Western Desert, Egypt: Palynofacies and Palynomorph Perspectives

by Ahmed Mansour, Sameh S. Tahoun, Aya Raafat, Mohamed S. Ahmed, Francisca Oboh-Ikuenobe, Thomas Gentzis and Xiugen Fu

Minerals 2023, 13(4), 548; https://doi.org/10.3390/min13040548 - 13 Apr 2023

Cited by 2 | Viewed by 2405

Abstract

The Middle Jurassic in the north Western Desert, Egypt, was a time of complex tectonics and increased environmental perturbations attributed to the predominant sedimentation of organic carbon-rich fine siliciclastic and carbonate deposits of the Khatatba Formation. Although some studies have addressed the hydrocarbon [...] Read more.

The Middle Jurassic in the north Western Desert, Egypt, was a time of complex tectonics and increased environmental perturbations attributed to the predominant sedimentation of organic carbon-rich fine siliciclastic and carbonate deposits of the Khatatba Formation. Although some studies have addressed the hydrocarbon potential and source rock characteristics of the Khatatba Formation, a regional-scale investigation of the prevalent paleoenvironmental conditions and organic matter characteristics is still necessary. In this study, the Khatatba Formation is investigated for detailed palynofacies analysis and palynomorph composition to assess organic matter kerogen types and reconstruct the depositional paleoenvironmental patterns on a regional scale. For this purpose, 116 drill cuttings were collected from five wells in the Matruh, Shushan, and Dahab-Mireir Basins. Moderately diverse assemblages of spores, pollen, and dinoflagellate cysts are reported. Age-diagnostic dinoflagellate cysts, including Adnatosphaeridium caulleryi, Dichadogonyaulax sellwoodii, Korystocysta gochtii, Wanaea acollaris, and Pareodinia ceratophora, along with occasional records of Systematophora areolate and Systematophora penicillate, defined a Bajocian–Callovian age. Based on particulate organic matter (POM) composition, four palynofacies assemblages (PFAs) are identified. PFA-1 is the most common within the Khatatba Formation in the five studied wells. It contains high proportions of phytoclast fragments versus low contents of amorphous organic matter (AOM) and palynomorphs and is defined by a gas-prone kerogen Type III. PFA-2 is comprised of moderate abundances of AOM and phytoclast characteristics of oil-prone kerogen Type II. PFA-3 is dominated by phytoclasts and moderate to low proportions of AOM and palynomorphs of kerogen Type III, whereas PFA-4 consists of AOM and palynomorphs defining kerogen Type II. PFA-1 indicates predominant deposition in proximal active fluvio-deltaic sources to marginal marine conditions with enhanced contributions of terrestrial/riverine influx. PFA-2 and PFA-3 reveal deposition under an enhanced dysoxic to anoxic proximal inner neritic shelf due to the abundant occurrences of spores and coastal to shallow marine dinoflagellate cysts. PFA-4 suggests deposition under enhanced suboxic to anoxic distal inner neritic conditions because of enhanced AOM and abundant proximate and some chorate dinoflagellate cysts. Thus, the Middle Jurassic experienced a predominantly marginal to shallow water column in this part of the southern margin of the Tethyan Ocean where the Matruh, Shushan, and Dahab-Mireir Basins were located. Full article

(This article belongs to the Topic Petroleum Geology and Geochemistry of Sedimentary Basins)
(This article belongs to the Section Mineral Exploration Methods and Applications)

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