Regional maturity and source-rock potential of palaeozoic and mesozoic strata, Melville Island, Arctic Canada

PhD ThesisThe thermal maturity and source-rock potential of the Palaeozoic and Mesozoic sediments in Melville Island, Arctic Canada were studied using organic petrology and Rock-Eval pyrolysis. A total of 2,000 polished whole-rock samples were examined and their phytoclast reflectances (% Ro random) measured. In addition, selected samples Were analyzed qualitatively and quantitatively using ultraviolet excitation. Hydrogen-rich organic matter was dominated by alginite (Botryococcus and Iasmanites), dinoflagellate cysts and amorphous fluorescing matrix. Sporinite, cutinite, resinite and liptodetrinite formed the lesser hydrogen-rich organic matter. Vitrinite reflectance in Cretaceous sediments ranged from Ro = 0.36 to 0.65%; in Jurassic sediments it ranged from Ro = 0.40 to 1.0% and in Triassic sediments from Ro = 0.45 to 1.30%. Vitrinite showed an overall increase in %Ro with increasing depth of burial but Variations do occur, possibly due to the effects of mineral matrix (lithology) and liptinite Content. It was observed that when total liptinite percentage was high (20-30%), reflectance was lowered by a magnitude of 0.1 to 0.15%. In addition, the lowering of the reflectance, which was genuine and not experimental, was due to: 1) the effect of bitumen impregnation (staining); and 2) differences in the type of organic matter (hydrogen-rich Vitrinite of marine origin). A large number of shale samples exceeded the worldwide average total organic carbon (TOC) content of 1.05 wt% with the Jurassic-Cretaceous shales and siltstones having higher values than those of Triassic age. The Triassic Schei Point Group shales and siltstones contained organic matter of marine origin, whereas the predominantly Plant-derived organic matter present in the Jameson Bay, Ringnes and Deer Bay formations had a higher TOC. Among the Schei Point Group sediments, the Cape Richards and Eden Bay Members of the Hoyle Bay Formation were richer in TOC (>2.0 wt%) than the Murray Harbour Formation (Cape Caledonia Member), which may reflect differences in the level Of maturity or in the depositional environment (more anoxic conditions for the former). Higher average TOC contents (> 3.0 wt%) were reported in the Cape Richards Member in drill hole Hecla C-32, as well as in the Eden Bay Member in drill holes Hecla C-32, Roche Paint J-43 and North Sabine H-49, all located in Sabine Peninsula. The Schei Point Group sediments contained mainly liptinitic organic matter of marine origin, were Occasionally bitumen stained and have high potential for the generation of liquid hYdrocarbons. Organic matter in the Palaeozoic strata of the Franklinian miogeosyncline was represented mainly by bitumen in the Silurian and Devonian. Different bitumen types Were identified depending on their morphology, reflectance range and association with the enclosing mineral matrix. Thermal maturity of the Palaeozoic strata, based on vitrinite reflectance calculated from bitumen reflectance was high, an indication that the strata Were in the overmature stage of hydrocarbon generation and that only dry gas should be expected. There is petrological evidence that hydrocarbons were generated and Illigrated through the sediments. Regional variations in the level of thermal maturity of Mesozoic sediments in the Sverdrup Basin are a function of burial depth. The Mesozoic formations thicken towards the basin centre (N-NE direction), reflecting the general pattern of increasing thermal maturity north of the Sabine Peninsula. In addition, periods of high heat flow Illost likely existed during rifting episodes from Carboniferous to Early Tertiary. The contour pattern of the regional variation of maturity at the base ofnumerous Triassic formations is similar to that of the structural contours of the Sverdrup Basin, indicating that present-day maturation levels are largely controlled by basin subsidence.Institute of Sedimentary and Petroleum Geology, Geological Survey of Canada

Thermal history of the Northwestern Argentina, Central Andean Basin, based on first-ever reported graptolite reflectance data

The thermal maturity from the Early Paleozoic strata in Northwestern Argentina was studied using reflected light microscopy and Rock-Eval analyses. The graptolites were collected from the Acoite and Lipeón formations, at the Los Colorados section, Cordillera Oriental, and the Huaytiquina, and Muñayoc sections, Puna highland, corresponding to the “Coquena” Formation and the Cochinoca-Escaya Magmatic-Sedimentary Complex. Rock-Eval parameters were unreliable due to the low TOC, S1, and S2 values. The Cordillera Oriental region sediments have low maturity based on low reflectance (%GRo= 0.63%–1.11%) and anisotropy of graptolites. In contrast, the higher graptolite reflectance of samples from the Muñayoc and Huaytiquina sections (%GRo= 5.57%–6.62%), in the Puna region, indicates considerably higher maturity. This could result from the combination of hydrothermal fluids with a temperature range from 336 °C to 358 °C, associated volcanism, and deformation related to tectonics events, which produced a higher geothermal gradient in the Puna. The Los Colorados section's thermal maturity modeling shows a better fit considering erosion episodes at the Late Paleozoic and Early Cenozoic. However, more studies about geothermal parameters and stratigraphy are necessary to corroborate these preliminary models and propose new approaches for the Puna region.Fil: Herrera Sánchez, Nexxys Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Toro, Blanca Azucena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Ruiz Monroy, Ricardo. German Research Centre For Geosciences; AlemaniaFil: Gentzis, Thomas. Core Laboratories; Estados UnidosFil: Ocubalidet, Seare. Core Laboratories; Estados UnidosFil: Carvajal Ortiz, Humberto. Core Laboratories; Estados Unido

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

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

Short-Term Sea Level Changes of the Upper Cretaceous Carbonates: Calibration between Palynomorphs Composition, Inorganic Geochemistry, and Stable Isotopes

Widespread deposition of pelagic-hemipelagic sediments provide an archive for the Late Cretaceous greenhouse that triggered sea level oscillations. Global distribution of dinoflagellate cysts (dinocysts) exhibited a comparable pattern to the eustatic sea level, and thus, considered reliable indicators for sea level and sequence stratigraphic reconstructions. Highly diverse assemblage of marine palynomorphs along with elemental proxies that relate to carbonates and siliciclastics and bulk carbonate δ13C and δ18O from the Upper Cretaceous Abu Roash A Member were used to reconstruct short-term sea level oscillations in the Abu Gharadig Basin, southern Tethys. Additionally, we investigated the relationship between various palynological, elemental, and isotope geochemistry parameters and their response to sea level changes and examined the link between these sea level changes and Late Cretaceous climate. This multiproxy approach revealed that a long-term sea-level rise, interrupted by minor short-term fall, was prevalent during the Coniacian-earliest Campanian in the southern Tethys, which allowed to divide the studied succession into four complete and two incomplete 3rd order transgressive-regressive sequences. Carbon and oxygen isotopes of bulk hemipelagic carbonates were calibrated with gonyaulacoids and freshwater algae (FWA)-pteridophyte spores and results showed that positive δ13Ccarb trends were consistent, in part, with excess gonyaulacoid dinocysts and reduced FWA-spores, reinforcing a rising sea level and vice versa. A reverse pattern was shown between the δ18Ocarb and gonyaulacoid dinocysts, where negative δ18Ocarb trends were slightly consistent with enhanced gonyaulacoid content, indicating a rising sea level and vice versa. However, stable isotope trends were not in agreement with palynological calibrations at some intervals. Therefore, the isotope records can be used as reliable indicators for reconstructing changes in long-term sea level rather than short-term oscillations

Paleoenvironmental Conditions and Factors Controlling Organic Carbon Accumulation during the Jurassic–Early Cretaceous, Egypt: Organic and Inorganic Geochemical Approach

The Jurassic–Early Cretaceous was a time of variable organic carbon burial associated with fluctuations of marine primary productivity, weathering intensity, and redox conditions in the pore and bottom water at paleo-shelf areas in north Egypt. This time interval characterized the deposition of, from old to young, the Bahrein, Khatatba, Masajid, and Alam El Bueib Formations in the north Western Desert. Although several studies have been devoted to the excellent source rock units, such as the Khatatba and Alam El Bueib Formations, studies on paleoenvironmental changes in redox conditions, paleoproductivity, and continental weathering and their impact on organic carbon exports and their preservation for this interval are lacking. This study presents organic and inorganic geochemical data for the Jurassic–Lower Cretaceous sediments from the Almaz-1 well in the Shushan Basin, north Western Desert. A total of 32 cuttings samples were analyzed for their major and trace elements, carbonates, and total organic carbon (TOC) contents. Data allowed the reconstruction of paleoenvironmental conditions in the southern Tethys Ocean and assessment of the changes in paleo-redox, paleo-weathering, and marine primary productivity, and the role of sediment supply. Additionally, factors that governed the accumulation of organic matter in the sediment were interpreted. Results showed that the Khatatba Formation was deposited during a phase of enhanced marine primary productivity under prevalent anoxia, which triggered enhanced organic matter production and preservation. During the deposition of the Khatatba Formation, significant terrigenous sediment supply and continental weathering were followed by a limited contribution of coarse clastic sediment fluxes due to weak continental weathering and enhanced carbonate production. The Bahrein, Masajid, and Alam El Bueib Formations were deposited during low marine primary productivity and prevalent oxygenation conditions that led to poor organic matter production and preservation, respectively. A strong terrigenous sediment supply and continental weathering predominated during the deposition of the Bahrein Formation and the lower part of the Alam El Bueib Formation compared to the limited coarse clastic supply and continental weathering during the deposition of the carbonate Masajid Formation and the upper part of the Alam El Bueib Formation. Such conditions resulted in the enhanced dilution and decomposition of labile organic matter, and, thus, organic carbon-lean accumulation in these sediments

Evaluating Molecular Evolution of Kerogen by Raman Spectroscopy: Correlation with Optical Microscopy and Rock-Eval Pyrolysis

Vitrinite maturity and programmed pyrolysis are conventional methods to evaluate organic matter (OM) regarding its thermal maturity. Moreover, vitrinite reflectance analysis can be difficult if prepared samples have no primary vitrinite or dispersed widely. Raman spectroscopy is a nondestructive method that has been used in the last decade for maturity evaluation of organic matter by detecting structural transformations, however, it might suffer from fluorescence background in low mature samples. In this study, four samples of different maturities from both shale formations of Bakken (the upper and lower members) Formation were collected and analyzed with Rock-Eval (RE) and Raman spectroscopy. In the next step, portions of the same samples were then used for the isolation of kerogen and analyzed by Raman spectroscopy. Results showed that Raman spectroscopy, by detecting structural information of OM, could reflect thermal maturity parameters that were derived from programmed pyrolysis. Moreover, isolating kerogen will reduce the background noise (fluorescence) in the samples dramatically and yield a better spectrum. The study showed that thermal properties of OM could be precisely reflected in Raman signals