Organic matter of the Upper Jurassic deposits of the Izhma shale-bearing region of the Timan-Pechora basin

Based on pyrolytic data (3 995 samples from 208 wells) organic matter types of Bazhenov Formation are identified in the central part of Western Siberian basin. Zones of kerogen types I, II, III and mixed I-II and II-III are mapped. Content of sulfur, paraffins, resins and asphaltenes, viscosity, density, temperature and gas content in oils from Upper Jurassic and Lower Cretaceous sediments (3 806 oil pools) are mapped. Oil gradations are identified and distributed. The alternative model of zones of kerogen II and IIS types is presented. The established distributions of organic matter types can be used in basin modeling and in assessment of oil-and-gas bearing prospects.

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Genetic Types of Organic Matter and Oils (Western Part of Timan-Pechora Basin, Russia)

10.3997/2214-4609.201902722 ◽

2019 ◽

Author(s):

Pavel V. Trushkov ◽

Nikolay V. Oblasov ◽

Ivan V. Goncharov ◽

Vadim V. Samoilenko ◽

Svetlana V. Fadeeva ◽

...

Keyword(s):

Organic Matter ◽

Pechora Basin ◽

Genetic Types

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Estimating soilpCO2using paleosol carbonates: implications for the relationship between primary productivity and faunal richness in ancient terrestrial ecosystems

Paleobiology ◽

10.1666/11005.1 ◽

2012 ◽

Vol 38 (4) ◽

pp. 585-604 ◽

Cited By ~ 13

Author(s):

Timothy S. Myers ◽

Neil J. Tabor ◽

Louis L. Jacobs ◽

Octávio Mateus

Keyword(s):

Organic Matter ◽

Primary Productivity ◽

Western Europe ◽

Central Africa ◽

Terrestrial Ecosystems ◽

Upper Jurassic ◽

Morrison Formation ◽

Positive Correlation ◽

Terrestrial Environments ◽

Ancient Ecosystems

In this paper we present a method for estimating soilpCO2in ancient environments using the measured carbon-isotope values of pedogenic carbonates and plant-derived organic matter. The validity of soilpCO2estimates proves to be highly dependent on the organic δ13C values used in the calculations. Organic matter should be sourced from the same paleosol profiles as sampled carbonates to yield the most reliable estimates of soilpCO2. In order to demonstrate the potential use of soilpCO2estimates in paleoecological and paleoenvironmental studies, we compare samples from three Upper Jurassic localities. SoilpCO2estimates, interpreted as a qualitative indicator of primary paleoproductivity, are used to rank the Late Jurassic terrestrial environments represented by the Morrison Formation in western North America, the informally named Lourinhã formation in Western Europe, and the Stanleyville Group in Central Africa. Because modern terrestrial environments show a positive correlation between primary productivity and faunal richness, a similar relationship is expected in ancient ecosystems. When the relative paleoproductivity levels inferred for each study area are compared with estimates of dinosaur generic richness, a positive correlation emerges. Both the Morrison and Lourinhã formations have high inferred productivity levels and high estimated faunal richness. In contrast, the Stanleyville Group appears to have had low primary productivity and low faunal richness. Paleoclimatic data available for each study area indicate that both productivity and faunal richness are positively linked to water availability, as observed in modern terrestrial ecosystems.

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Glendonites from Mesozoic succession of eastern Barents sea: distribution, genesis and paleoclimatic implications

10.5194/egusphere-egu2020-19076 ◽

2020 ◽

Author(s):

Kseniya Mikhailova ◽

Victoria Ershova ◽

Mikhail Rogov ◽

Boris Pokrovsky ◽

Oleg Vereshchagin

Keyword(s):

Organic Matter ◽

Calcium Carbonate ◽

Sulfate Reduction ◽

Early Cretaceous ◽

Lower Cretaceous ◽

Middle Jurassic ◽

Barents Sea ◽

Upper Jurassic ◽

Anaerobic Oxidation Of Methane ◽

Oxidation Of Methane

Glendonites often used as paleoclimate indicator of cold near-bottom temperature, as these are calcite pseudomorphs of ikaite, a metastable calcium carbonate hexahydrate, precipitates mostly under low temperature (mainly from 0-4oC) and may be stabilized by high phosphate concentrations that occurs due to anaerobic oxidation of methane and/or organic matter; dissolved organic carbon, sulfates and amino acid may contribute ikaite formation as well.&#160; Therefore, glendonites-bearing host rocks frequently include glacial deposits that make them useful as a paleoclimate indicator of near-freezing temperature.Our study is based on material collected from five wells drilled in eastern Barents Sea: Severo-Murmanskaya, Ledovaya &#8211; 1,2; Ludlovskaya &#8211; 1,2. The studied glendonites, mainly represented by relatively small rhombohedral pseudomorphs (0,5-2 cm) and rarely by stellate aggregates, collected from Middle Jurassic to Lower Cretaceous shallow marine clastic deposits. They scattered distributed throughout succession. Totally 18 samples of glendonites were studied. The age of host-bearing rocks were defined by fossils: bivalves or ammonites, microfossils or dinoflagellate. Bajocian-Bathonian glendonites were collected from Ledovaya &#8211; 1 and Ludlovskaya &#8211; 1 and 2 wells; in addition to these occurrences Middle Jurassic glendonites are known also in boreholes drilled at Shtockmanovskoe field. Numerous &#8216;jarrowite-like&#8217; glendonites of the Middle Volgian (~ latest early Tithonian) age were sampled from Severo-Murmanskaya well. Unique Late Barremian glendonites were found in Ledovaya &#8211; 2 well.&#948;18O values of Middle Jurassic glendonite concretions range from &#8211; 5.4 to &#8211;1.7 &#8240; Vienna Pee Dee Belemnite (VPDB); for Upper Jurassic &#8211; Lower Cretaceous &#948;18O values range from &#8211; 4.3 to &#8211;1.6 &#8240; VPDB; for Lower Cretaceous - &#948;18O values range from &#8211; 4.5 to &#8211;3.4 &#8240; VPDB. Carbon isotope composition for Middle Jurassic glendonite concretions &#948;13C values range from &#8211; 33.3 to &#8211;22.6 &#8240; VPDB; for Upper Jurassic &#8211; Lower Cretaceous &#948;13C values range from &#8211; 25.1 to &#8211;18.4 &#8240; VPDB; for Lower Cretaceous - &#948;13C values range from &#8211; 30.1 to &#8211;25.6 &#8240; VPDB.Based on &#948;18O data we supposed that seawater had a strong influence on ikaite-derived calcite precipitation. Received data coincide with &#948;18O values reported from other Mesozoic glendonites and Quaternary glendonites formed in cold environments. Values of &#948;13C of glendonites are close to bacterial sulfate reduction and/or anaerobic oxidation of methane or organic matter. Glendonites consist of carbonates forming a number of phases which different in phosphorus and magnesium content. Mg-bearing calcium carbonate and dolomite both include framboidal pyrite, which can indicate (1) lack of strong rock transformations activity and (2) presence of sulfate-reduction bacteria in sediments.To conclude, Mesozoic climate was generally warm and studied concretions indicate cold climate excursion in Middle Jurassic, Upper Jurassic-Early Cretaceous and Early Cretaceous.&#160;The study was supported by RFBR, project number 20-35-70012.

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Geologic Characteristics of Reservoir Accumulation in Suganhu Depression in North Margin of Qaidam Basin

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.616-618.19 ◽

2012 ◽

Vol 616-618 ◽

pp. 19-25 ◽

Cited By ~ 1

Author(s):

Cheng Zhang ◽

Guang Yang ◽

Yong Shu Zhang

Keyword(s):

Organic Matter ◽

Middle Jurassic ◽

Qaidam Basin ◽

Upper Jurassic ◽

Mature Stage ◽

Braided River ◽

Large Area ◽

Reservoir Properties ◽

Cap Rock ◽

Low Porosity

Based on the analysis and testing data of rocks, the basic geologic characteristics of Suganhu depression is discussed. It is concluded that the 200m thickness dark mudstone of inshore shallow lake face in the middle–lower Jurassic stratum is the only source rock of this region. It has the characteristics of high abundance of organic matter and in high mature stage. And the type of organic matter is Ⅱ2.The reservoir properties is controlled by the influences of both the sedimentation and the diagenesis and belong to the low porosity and low permeability ones. The mudstone of Upper Jurassic is the local cap, the ones of braided river face and braided river delta face which existed in the up-middle of the middle Jurassic can be qualified as sealing bed between the sand bodies. Paleocene–eocene mudstone is the regional cap rock. The ability of upper Jurassic sealing bed is good because of the low porosity and permeability and high break pressure. The regional cap rock has the characteristics of big thickness and large area. Both the local and regional cap rock had been able to seal the petroleum and gas before the time of hydrocarbon accumulation of middle Jurassic. In general, Mesozoic formed reservoir–cap combination with the features of lower–generation and upper–reservoir, upper–cap.

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Timing of oil expulsion from source rocks and a revitalization of the pre-1970 model

10.31223/x5cw49 ◽

2021 ◽

Author(s):

Per Arne Bjørkum

Keyword(s):

Organic Matter ◽

Source Rock ◽

Heavy Oil ◽

Low Temperatures ◽

Upper Jurassic ◽

Hydrogen Gas ◽

Source Rocks ◽

Co2 Gas ◽

Chemical Attributes ◽

Oil Expulsion

New data from North Sea Upper Jurassic source rock samples show no decline in the total amount of organic matter (TOC) within the oil expulsion window between 120 and 150°C which is a key prediction by today’s model for oil expulsion. However, today’s model for oil expulsion is not consistent with either subsurface source rock TOC data or chemical attributes of shallow oils. Instead, these data are more consistent with oil expulsion occurring at much lower temperatures and shallower depths, more similar to models advocated by most oil explorers prior to 1970 where the oil was assumed to have expelled at burial depths less than ~2km. In this paper, main oil expulsion has been determined to be take place at burial depths less than 1km and approximately 30°C. The oil is mobilized by CO2 gas which is generated from decomposing organic matter and is predicted to migrate out of the source rock and into nearby high-permeable rocks via horizontal fractures that originate from loadbearing swelling organic lamina and in a direction towards decreasing overburden. The thermally immature (heavy) oil is then converted to light crude within the reservoir oil starting at 60-70°C by hydrogenation. Hydrogen gas is common in subsurface fluids and is provided to pooled oil from coalification of organic matter in mudstones. Thus, if the supply of hydrogen is limited, in-reservoir thermal upgrading will be hampered. In this model, most of the heavy oil accumulations encountered are immature rather than due to biodegradation of mature oil at low temperatures.

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Organic Geochemistry Of The Middle To Upper Jurassic Source Rocks Succession In Balad-1 Well, Balad Oil Field, Central Iraq

Bulletin of the Geological Society of Malaysia ◽

10.7186/bgsm71202111 ◽

2021 ◽

Vol 71 ◽

pp. 125-138

Author(s):

Fawzi M.O. Albeyati ◽

◽

Rzger A. Abdula ◽

Rushdy S. Othman ◽

Keyword(s):

Organic Matter ◽

Organic Geochemistry ◽

Equilibrium Phase ◽

Organic Matter Content ◽

Upper Jurassic ◽

Matter Content ◽

Oil Field ◽

Source Rocks ◽

Content Type ◽

Depositional Setting

Thirty four cuttings samples from the Jurassic rock succession in well Balad-1 in the Balad Oil Field, Central Iraq have been collected. Using various organic geochemical techniques, the organic matter’s quantity, quality, maturity, and their source rock’s depositional setting were determined. The samples were evaluated to determine the amount of their organic matter content, type of organic matter, δ13C carbon isotopes abundance for both saturated and aromatic, and molecular properties. The results of organic geochemistry analysis show that Sargelu, Gotnia, and Chia Gara formations contain fair to decent amounts of organic matter. Naokelekan Formation encompasses fair to excellent organic matter, while Najmah Formation comprises very high to exceptional organic matter. The analyzed samples revealed the existence of kerogen types III and II/III mainly within oil window. Thermal maturity related biomarkers are in a good agreement with Rock-Eval parameters, but did not reach equilibrium phase. Source related biomarkers show that these rock units rich in organic matter were mainly deposited in an anoxic marine depositional setting which consists of carbonate influenced by terrestrial input.

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Organic Petrology and Thermal Maturity of Dispersed Organic Matter from the Ramalhal-1 Well (Lusitanian Basin, Portugal)

Minerals ◽

10.3390/min11121415 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1415

Author(s):

Paula Alexandra Gonçalves ◽

João Graciano Mendonça Filho ◽

Deolinda Flores

Keyword(s):

Organic Matter ◽

Upper Jurassic ◽

Inorganic Materials ◽

Mature Stage ◽

Thermal Maturity ◽

Solid Bitumen ◽

Organic Petrology ◽

Almost All ◽

Lusitanian Basin

Organic petrology is an important tool used to characterize dispersed organic matter (DOM) in sediments and sedimentary rocks, and to assess its thermal maturity. This study was carried out on 33 cutting samples (Middle-Upper Jurassic) from the Ramalhal-1 well to characterize the particulate organic matter and to evaluate its thermal maturity. The samples were submitted to optical petrography analysis (reflected white and blue incident lights) and the mean random reflectance was measured. Microscopic observations revealed a low DOM content, characterized by the predominance of macerals of the inertinite group (including charcoal), followed by solid bitumen. Huminite/vitrinite is usually small in size and quantity. Liptinite macerals were also present, represented by sporinite, cutinite, liptodetrinite and rare bituminite. A type III-IV kerogen was defined for the Ramalhal-1 sequence. Huminite/vitrinite mean random reflectance varied between 0.38% and 0.75%, pointing to an immature-to-mature stage of the organic matter. Multi-populations of solid bitumen occurred in almost all the samples, filling voids and fractures in the inorganic materials (mainly carbonates). The bitumen populations were quite heterogeneous, concerning both the optical characteristics and distribution, displaying different thermal maturities. No relationship between vitrinite and bitumen reflectance was established, indicating that these bitumens were not generated in situ.

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