Even and Odd Carbon Predominance Coexisting N-Alkanes in Paleogene Dark Shale in Jinhu Sag of Subei Basin

2013 ◽  
Vol 312 ◽  
pp. 871-875
Author(s):  
Ning Song ◽  
Mei Jun Li ◽  
Jin Chuan Zhang
Keyword(s):  
Organic Matter ◽  
Eastern China ◽  
Sedimentary Environment ◽  
Distribution Patterns ◽  
Depositional Environments ◽  
Source Rocks ◽  
Ancient Lake ◽  
High Gamma ◽  
Original Organic Matter ◽  
Β Carotene

Gas chromatograms of saturated hydrocarbons of shale rock extracts show three patterns of n-alkanets in the second member of Funning formation (E1f2) in Jinhu Sag of Subei basin, eastern China. Three patterns of n-alkanets are the odd-to-even carbon predominance, the even-to-odd carbon predominance, and the even and odd carbon predominance coexisting, respectively. In this paper, the characteristics of n-alkanet coexisting even and odd carbon predominance and its origin and sedimentary environment are investigated only. The short-chain n-alkanets and long-chain n-alkanets are characterized by pronounced odd carbon predominance, with the dominant carbon of nC15, nC17 and of nC25, nC27, nC29 and nC31. The mid-chain n-alkanets are dominated by even carbon predominance, with the dominant carbon of nC20 and nC22. The composition of biomarkers are characterized by phytane preference, high gamma cerate abundance, the presence of β-carotene and C24-tetracyclic terrapin, which indicate that the organic matter in source rocks deposited in an anoxic, hyper saline lacus trine environment. The biomarkers are no homogeneous, which shows that salinity and redo is not constant in pale-lacus trine. The n-alkanets are mainly derived from algae in the ancient lake and macro pyres on land or around the edges of the ancient lake. The n-alkanets distribution patterns of the dark shales studied are believed not to be dependent on the redo in the depositional environments or the salinity of the water body, but to be associated with original organic matter composition.

Liquid hydrocarbon characterization of the lacustrine Yanchang Formation, Ordos Basin, China: Organic-matter source variation and thermal maturity

2017 ◽  
Vol 5 (2) ◽  
pp. SF225-SF242 ◽  
Author(s):  
Xun Sun ◽  
Quansheng Liang ◽  
Chengfu Jiang ◽  
Daniel Enriquez ◽  
Tongwei Zhang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Source Rock ◽  
Ordos Basin ◽  
Depositional Environments ◽  
Source Rocks ◽  
Type I ◽  
Hydrocarbon Generation ◽  
Type Ii ◽  
Thermal Maturity ◽  
Yanchang Formation

Source-rock samples from the Upper Triassic Yanchang Formation in the Ordos Basin of China were geochemically characterized to determine variations in depositional environments, organic-matter (OM) source, and thermal maturity. Total organic carbon (TOC) content varies from 4 wt% to 10 wt% in the Chang 7, Chang 8, and Chang 9 members — the three OM-rich shale intervals. The Chang 7 has the highest TOC and hydrogen index values, and it is considered the best source rock in the formation. Geochemical evidence indicates that the main sources of OM in the Yanchang Formation are freshwater lacustrine phytoplanktons, aquatic macrophytes, aquatic organisms, and land plants deposited under a weakly reducing to suboxic depositional environment. The elevated [Formula: see text] sterane concentration and depleted [Formula: see text] values of OM in the middle of the Chang 7 may indicate the presence of freshwater cyanobacteria blooms that corresponds to a period of maximum lake expansion. The OM deposited in deeper parts of the lake is dominated by oil-prone type I or type II kerogen or a mixture of both. The OM deposited in shallower settings is characterized by increased terrestrial input with a mixture of types II and III kerogen. These source rocks are in the oil window, with maturity increasing with burial depth. The measured solid-bitumen reflectance and calculated vitrinite reflectance from the temperature at maximum release of hydrocarbons occurs during Rock-Eval pyrolysis ([Formula: see text]) and the methylphenanthrene index (MPI-1) chemical maturity parameters range from 0.8 to [Formula: see text]. Because the thermal labilities of OM are associated with the kerogen type, the required thermal stress for oil generation from types I and II mixed kerogen has a higher and narrower range of temperature for hydrocarbon generation than that of OM dominated by type II kerogen or types II and III mixed kerogen deposited in the prodelta and delta front.

PETROLEUM POTENTIAL OF THE NEOPROTEROZOIC WESTERN OFFICER BASIN, WESTERN AUSTRALIA, BASED ON A SOURCE ROCK MODEL FROM EMPRESS-IA

1999 ◽  
Vol 39 (1) ◽  
pp. 322 ◽  
Author(s):  
G.M. Carlsen ◽  
S.N. Apak ◽  
K.A.R. Ghori K. Grey ◽  
M.K. Stevens
Keyword(s):  
Organic Matter ◽  
Western Australia ◽  
Depositional Environments ◽  
Source Rocks ◽  
Petroleum Potential ◽  
Organic Facies ◽  
Organic Growth ◽  
Rock Model ◽  
Depositional Controls ◽  
The Impact

The sedimentology, palaeontology and geochemistry of Neoproterozoic, organic-rich, clastic and related carbonate deposits in Western Australia provide new insights into the first-order depositional controls on hydrocarbon source rocks in the Neoproterozoic. Organic facies are correlated with depositional facies, revealing the impact of organic productivity and transport of organic rich sediments on the accumulation of organic matter in different depositional environments. Sedimentation is largely limited to ramp, platform, shoal, lagoon and sabkha environments.Growth of benthic organisms in the photic zone was the primary process controlling the production of organic matter in the ramp-shoreline system of the Kanpa Formation. Storms and floods were the primary mechanism for moving organic rich sediments into dysoxic and anoxic depositional environments. Variations in organic facies are indicated by: 1) changes in the palynomorph assemblages, particularly the increase in acritarchs within shallow-water ramp facies and cyanobacterial filaments in quiet-water sediments; 2) organic-rich laminae, containing abundant cyanobacterial filaments and mat material; and 3) the oxidation state of preserved organic remains.Periods of high organic growth rates or periods of mass mortality may have led to the development of an anoxic zone at the water-sediment interface. In the shoal and lagoonal settings, higher rates of clastic sediment dilution combined with oxygenated conditions resulted in lower TOC and hydrogen depleted organic facies.Condensed sections overlying stromatolitic dolomites represent the most effective organic facies of all of the potential source laminae sampled in Empress–IA. Most of the Officer Basin succession is currently within the oil-generating window and hydrocarbon shows encourage further exploration.

An integrated organic–inorganic geochemical characterization of Paleogene sediments in No.1 Structural Belt of the Nanpu Sag, Bohai Bay Basin, eastern China: implications for the origin of organic matter

2020 ◽  
Vol 21 (1) ◽  
pp. geochem2019-060
Author(s):  
Yu Guo ◽  
Wenzhe Gang ◽  
Gang Gao ◽  
Shangru Yang ◽  
Chong Jiang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Higher Plants ◽  
Eastern China ◽  
Source Rocks ◽  
Bohai Bay ◽  
Type Ii ◽  
Lacustrine Environment ◽  
Anoxic Conditions ◽  
Supplementary Material ◽  
Nanpu Sag

Paleogene sediments, especially the third member of the Dongying Formation (Ed3) and the first and third members of the Shahejie Formation (Es1 and Es3), have been regarded as the most important source rocks in the Nanpu Sag. Organic and inorganic analyses, including Rock-Eval pyrolysis, gas chromatography-mass spectrometry, and element geochemistry, in 91 mudstone samples, were used to reconstruct the palaeoenvironmental conditions, such as palaeoclimate, palaeo-salinity and palaeo-redox conditions, and to recognize the origin of organic matter. The results show that Es3 has a higher TOC content than Es1 and Ed3. Hydrocarbon genetic potential (S1 + S2) of the samples indicate fair to good hydrocarbon potential. The kerogen type of Ed3 and Es1 source rocks are Type II1–II2, while Es3 source rocks are dominated by Type II2–III kerogens. Biomarkers and inorganic geochemical indicatives of source rocks, such as Pr/Ph, V/(V + Ni) and Cu/Zn, indicate a lacustrine environment with fresh to brackish water under suboxic to anoxic conditions during deposition. Ed3 source rocks are characterized by low G/C30H (gamacerane/C30hopane) (<0.1), TT/C30H (tricyclic terpane/C30hopane) and S/H (serane/hopane), high Pr/Ph (pristane/phytane) and C24TeT/C23TT (C24tetracyclic terpane/C23tricyclic terpane), indicating mixed input of both algae and terrestrial higher plants, dominated by terrestrial higher plants. Es1 source rocks display medium G/C30H, TT/C30H, S/H, Pr/Ph and C24TeT/C23TT, indicative of a mixed input of both algae and terrestrial higher plants. Es3 source rocks are characterized by high G/C30H (>0.1), TT/C30H and S/H, low Pr/Ph and C24TeT/C23TT, typical of a mixed input of algae and terrestrial higher plants, with algal dominance. Ed3, Es1 and Es3 source rocks were mostly deposited in semi-arid to humid-warm climate conditions, with an average temperature higher than 15°C. This study suggests that suitable temperatures, a fresh to brackish lacustrine environment and suboxic to anoxic conditions could result in a high organic matter concentration and preservation, thus providing prerequisites for the formation of high-quality source rocks.Supplementary material: Tables S1–S3 are available at https://doi.org/10.6084/m9.figshare.c.5227684

Geochemistry and depositional history of the Union Springs Member, Marcellus Formation in central Pennsylvania

2015 ◽  
Vol 3 (3) ◽  
pp. SV17-SV33 ◽  
Author(s):  
Anna K. Wendt ◽  
Mike A. Arthur ◽  
Rudy Slingerland ◽  
Daniel Kohl ◽  
Reed Bracht ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Water Column ◽  
Appalachian Basin ◽  
Depositional Environments ◽  
Source Rocks ◽  
Geochemical Data ◽  
Inorganic Elements ◽  
Central Pennsylvania ◽  
Marcellus Formation

Debate continues over paleoenvironmental conditions that prevail during deposition of organic-carbon (C)-rich marine source rocks in foreland basins and epicontinental seas. The focus of disagreement centers largely on paleowater depth and the prevalence of anoxia/euxinia. The issues of paleodepth and water column conditions are important for prediction of lateral variations in source quality within a basin because the viability of a hydrocarbon play depends on a thorough understanding of the distribution of source rock quality and depositional environments. We used inorganic geochemical data from the Middle Devonian Marcellus Shale in the Appalachian Basin to illustrate interpretive strategies that provided constraints on conditions during deposition. Source evaluation typically relies on the analysis and interpretation of organic geochemical indicators, potentially also providing evidence of the degree of thermal maturity and conditions of the preservation of the organic matter. The Marcellus Formation is thermally mature, making the evaluation of the organic-carbon fraction for geologic interpretation inadequate. Because most labile organic matter has largely been destroyed in the Marcellus Formation, analysis of inorganic elements may be used as an alternative interpretative technique. Several inorganic elements have been correlated to varying depositional settings, allowing for their use as proxies for understanding the paleodepositional environments of formations. A high-resolution geochemical data set has been constructed for the Union Springs Member along a transect of cores from proximal to distal in the Appalachian Basin in central Pennsylvania using major, minor, and trace elemental data. Our results suggested that during deposition, the sediment-water interface, and a portion of the water column, was anoxic to euxinic. As deposition continued, euxinia was periodically interrupted by dysoxia and even oxic conditions, and a greater influx of clastic material occurred. Such variations were likely related to fluctuations in water depth and progradation of deltaic complexes from the eastern margin of the Appalachian Basin.

Facies, rock attributes, stratigraphy, and depositional environments: Yanchang Formation, Central Ordos Basin, China

2017 ◽  
Vol 5 (2) ◽  
pp. SF15-SF29 ◽  
Author(s):  
Stephen C. Ruppel ◽  
Harry Rowe ◽  
Kitty Milliken ◽  
Chao Gao ◽  
Yongping Wan
Keyword(s):  
Organic Matter ◽  
Clay Mineral ◽  
Ordos Basin ◽  
Depositional Environments ◽  
Source Rocks ◽  
Late Triassic ◽  
Great Promise ◽  
Yanchang Formation ◽  
X Ray ◽  
Stacking Patterns

The Late Triassic Yanchang Formation (Fm) is a major target of drilling for hydrocarbons in the Ordos Basin. Although most of the early focus on this thick succession of lacustrine rocks has been the dominant deltaic sandstones and siltstones, which act as local reservoirs of oil and gas, more recent consideration has been given to the organic-rich mudstone source rocks. We used modern chemostratigraphic analysis to define vertical facies successions in two closely spaced cores through the Chang 7 Member, the primary source rock for the Yanchang hydrocarbon system. We used integrated high-resolution X-ray fluorescence and X-ray diffraction measurements to define four dominant facies. Variations in stable carbon isotopes mimic facies stacking patterns, suggesting that terrigenous organic matter (although minor in volume) is associated with the arkoses and sandstones, whereas aquatic organic matter is dominant in the mudstones. Facies stacking patterns define three major depositional cycles and parts of two others, each defined by basal mudstone facies that document basin flooding and deepening (i.e., flooding surfaces). Unconfined compressive strength measurements correlate with clay mineral abundance and organic matter. Comparisons of core attributes with wireline logs indicate that although general variations in clay mineral volumes (i.e., mudstone abundance) can be discerned from gamma-ray logs, organic-matter distribution is best defined with density or resistivity logs. These findings, especially those established between the core and log data, provide a powerful linkage between larger scale facies patterns and smaller scale studies of key reservoir attributes, such as pore systems, mineralogy, diagenesis, rock mechanics, hydrocarbon saturation, porosity and permeability, and flow parameters. This first application of modern chemostratigraphic techniques to the Yanchang Fm reveals the great promise of applying these methods to better understand the complex facies patterns that define this lacustrine basin and the variations in key reservoir properties that each facies displays.

scholarly journals Changing depositional environments in the semi-restricted Late Jurassic Lemeš Basin (Outer Dinarides; Croatia)

Facies ◽  
2021 ◽  
Vol 68 (1) ◽  
Author(s):  
Michael A. J. Vitzthum ◽  
Hans-Jürgen Gawlick ◽  
Reinhard F. Sachsenhofer ◽  
Stefan Neumeister
Keyword(s):  
Organic Matter ◽  
Deep Water ◽  
Carbonate Platform ◽  
Upper Jurassic ◽  
Depositional Environments ◽  
Source Rocks ◽  
Terrestrial Organic Matter ◽  
Kerogen Type ◽  
Marine Algal ◽  
Rock Eval

AbstractThe up to 450 m-thick Upper Jurassic Lemeš Formation includes organic-rich deep-water (max. ~ 300 m) sedimentary rocks deposited in the Lemeš Basin within the Adriatic Carbonate Platform (AdCP). The Lemeš Formation was investigated regarding (1) bio- and chemostratigraphy, (2) depositional environment, and (3) source rock potential. A multi-proxy approach—microfacies, Rock–Eval pyrolysis, maceral analysis, biomarkers, and stable isotope ratios—was used. Based on the results, the Lemeš Formation is subdivided from base to top into Lemeš Units 1–3. Deposition of deep-water sediments was related to a late Oxfordian deepening event causing open-marine conditions and accumulation of radiolarian-rich wackestones (Unit 1). Unit 2, which is about 50 m thick and Lower early Kimmeridgian (E. bimammatum to S. platynota, ammonite zones) in age, was deposited in a restricted, strongly oxygen-depleted basin. It consists of radiolarian pack- and grainstones with high amounts of kerogen type II-S organic matter (avg. TOC 3.57 wt.%). Although the biomass is predominantly marine algal and bacterial in origin, minor terrestrial organic matter that was transported from nearby land areas is also present. The overlying Unit 3 records a shallowing of the basin and a return to oxygenated conditions. The evolution of the Lemeš Basin is explained by buckling of the AdCP due to ophiolite obduction and compressional tectonics in the Inner Dinarides. Lemeš Unit 2 contains prolific oil-prone source rocks. Though thermally immature at the study location, these rocks could generate about 1.3 t of hydrocarbon per m2 surface area when mature.

scholarly journals Source Rock Characterization of Silurian Tanezzuft and Devonian Awaynat Wanin Formations the Northern Edge of the Murzuq Basin, South West Libya

2020 ◽  
Vol 4 (1) ◽  
pp. 1-13
Author(s):  
Aboglila S
Keyword(s):  
Organic Matter ◽  
Source Rock ◽  
Depositional Environments ◽  
Source Rocks ◽  
Thermal Maturity ◽  
Maturity Level ◽  
Geochemical Parameters ◽  
Northern Edge ◽  
Rock Characterization ◽  
Tanezzuft Formation

Drill cutting samples (n = 92) from the Devonian Awaynat Wanin Formation and Silurian Tanezzuft Formation, sampled from three wells F1, G1 and H1, locate in the northern edge of the Murzuq basin (approximately 700 kilometers south of Tripoli). The studied samples were analyzed in the objective of their organic geochemical assessment such as the type of organic matter, depositional conditions and thermal maturity level. A bulk geochemical parameters and precise biomarkers were estimated, using chromatography-mass spectrometry (GC-MS) to reveal a diversity of their geochemical characterizations. The rock formations are having varied organic matter contents, ranged from fair to excellent. The total organic carbon (TOC) reached about 9.1 wt%, ranging from 0.6 to 2.93 wt% (Awaynat Wanin), 0.5 to 2.54 wt% (Tanezzuft) and 0.52 to 9.1 wt% (Hot Shale). The cutting samples are ranged oil-prone organic matter (OM) of hydrogen index (HI) ranged between 98 –396 mg HC/g TOC, related kerogen types are type II and II/III, with oxygen index (OI): 6 - 190 with one sample have value of 366 mg CO2/g. Thermal maturity of these source rocks is different, ranging from immature to mature and oil window in the most of Tanezzuft Formation and Hot Shale samples, as reflected from the production index data (PI: 0.08 - 034). Tmax and vitrinite reflectance Ro% data (Tmax: 435 – 454 & Ro%: 0.46 - 1.38) for the Awaynat Wanin. Biomarker ratios of specific hydrocarbons extracted from represented samples (n = 9), were moreover used to study thermal maturity level and depositional environments. Pristine/Phytane (Pr/Ph) ratios of 1.65 - 2.23 indicated anoxic to suboxic conditions of depositional marine shale and lacustrine source rock.

Sedimentology, Geochemistry, and Reservoir Potential of the Organic-Rich Tuwaiq Mountain, Hanifa and Jubaila Formations, Abu Dhabi, UAE

2021 ◽  
Author(s):  
Madhujya L. Phukan ◽  
Saad A. Siddiqi ◽  
Abdulla Alblooshi ◽  
Maryam Alshehhi ◽  
Ashis Shashanka ◽  
...  
Keyword(s):  
Organic Matter ◽  
Quantitative Description ◽  
Clay Fraction ◽  
Depositional Environments ◽  
Source Rocks ◽  
Carbonate Sediments ◽  
Pore Scale ◽  
Gas Generation ◽  
Unconventional Gas ◽  
Rock Eval

Abstract Objectives/Scope: The late Callovian to early Kimmeridigian deposited Tuwaiq Mountain, Hanifa and Jubaila Formations are among the most prolific source rocks in the middle east. These sediments have recently been considered as potential unconventional gas reservoir in UAE. This study integrates sedimentological, structural, geochemical and pore-scale datasets to provide a better understanding of the depositional framework and its effects on the reservoir properties. Methods, Procedures, Process: Dunham Classification (1962) which was later modified by Embry & Klovan (1971) is the basis of the descriptive lithofacies scheme used to characterize the organic-rich carbonate sediments. The association of these classified lithofacies based on their genetic relationship reflects their corresponding depositional environments. Petrographical and geochemical assessment including Rock-Eval pyrolysis were performed on selected samples. Mineralogical assessment was performed via whole-rock and clay-fraction XRD analysis, whereas pore-scale fabric/textural investigations were performed via conventional transmitted light microscopy and SEM using backscattered electron mode BS-SEM. Results, Observations, Conclusions: Sedimentological characterization of mud-dominated carbonate sediments indicates that they accumulated in a clastic starved, intrashelf basinal setting. The lack of textural variation is observed, highlighted by the dominance of mudstones noted across the Tuwaiq Mountain Fm., Hanifa and Jubaila Formations. Wackestones are the second most abundant texture observed. Wacke-packstones and packstones are rare but are present in the Tuwaiq Mountain Formation. also dominated by mudstone textures show presence of wackestones in form of thin beds. The occurrences of planktonic foraminifera along with thin shelled bivalves further emphasizes the low-energy, distal depositional setting. A quantitative description of the nature, density, and trends of the fracture network highlights the tectonic and structural history of the sediments. A certain degree of brittleness is associated with the organic-rich sediments, which is evident from the mineralogical analysis showing the abundance of calcite (&gt;82%). Rock-Eval data revealed high TOC content of the sediments. An evaluation of the HI and Tmax indicates that the sediments are dominantly gas prone (HI&lt;150mg HC/g TOC). Based on the calculated reflectance data (Ro: 0.06-3.30), the sediments display varied levels of thermal maturity, from immature to over mature. The vitrinite reflectance equivalent (%VRE) values assessed from microscopic investigations a range between 1.24-1.64, with the lower values suggesting late maturity with wet (condensate) gas generation and the higher values suggesting post maturity with dry gas generation. The TOC and TRA data highlight that the organic-rich, laminated mudstones associated with the Hanifa and Tuwaiq Mountain Formations have the highest TOC values (up to 4.25wt%) and the highest bulk volume (up to 3.39 %BV). It is also noted that the petroleum storage potential in these sediments largely resides with the mineral matrix pores along with the porosity hosted by the organic matter, which has been assessed by BS-SEM analysis. Novel/Additive Information: This integrated approach sheds light on the development of unconventional gas reservoirs. In addition, this study shows how the changes in depositional environment may have controlled the organic matter preservation. For a plausible way forward, this current understanding may be extrapolated to uncored intervals for representativeness.

Sign in / Sign up

Export Citation Format

Share Document