Effects of Igneous Intrusion on the Organic Content of Irati Formation, Paraná Basin, in Sapopema (PR) (original) (raw)
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Brazilian Journal of Geology
The organic geochemistry of organic-rich facies including shales, marls, and carbonates (Assistência Member) of the Irati Formation, Paraná Basin, Brazil, were analyzed to evaluate the thermal effects of igneous intrusions upon the kerogen present in these facies. Total organic carbon (TOC) content and hydrocarbon source potential (S 2) of the Irati source rocks range from 0.03 to 20.4% and 0.01 to 112.1 mg HC/g rock, respectively, indicating excellent potential as a source for hydrocarbon generation. Hydrogen index (HI) values reveal that the kerogen is predominantly type I (HI: up to 892.6 mg HC/g TOC) and, therefore, an oil source, except for samples having low TOC content due to severe maturation caused by the heat from diabase intrusions. The thickness of igneous intrusions in the 64 wells investigated in this study ranged from 2 to 231 m. They clearly had a major impact on TOC, HI, and S 2 values, which decrease in the vicinity of intrusions, indicating a gradual increase in maturation toward the igneous body. In wells without the influence of igneous intrusions, T max values of Rock-Eval pyrolysis and %Ro indicate that the organic matter is immature for the generation of hydrocarbons.
Journal of Sedimentary Environments
Currently, the Irati Formation, in Paraná Basin, Brazil, represents one of the world's largest reserves of oil shale. Among the shale-derived products stands out the fuel oil, gas, naphtha, fuel, liquefied gas, and sulfur, in addition to byproducts that can be used by the asphalt, cement, agricultural, and ceramics industries. This study describes and illustrates features of organic-rich shales of the Lower Permian Assistência Member, Irati Formation, scanning electron microscopy (SEM) was combined with energy-dispersive x-ray spectrometric (EDS), x-ray diffraction (XRD), total organic carbon (TOC), total sulfur (S), insoluble residue (IR) and Rock-Eval pyrolysis to characterize the mineral composition, organic matter distribution and different types of pore at the micrometer scale. These analyses were performed on samples from well SP-32-PR located in the Sapopema township, Northeast Paraná State, in South of Brazil. The investigations demonstrated that the Assistance Member ha...
Journal of Sedimentary Environments, 2019
Igneous intrusions in sedimentary basins are commonly related with mineralogical association changes in host-rock. At Sapopema region (Paraná State, southern Brazil), an extensive diabase sill (associated to Serra Geral Formation) was emplaced in pelitic-carbonate succession during post-Triassic. The sedimentary host-rock association includes mostly shale, siltstone and carbonate of the Permian Irati Formation. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) data revealed that heat transfer was not enough to cause modifications in mineral assemblage of the Taquaral Member (quartz + albite + muscovite + illite + kaolinite + chlorite). However, mineralogical content from Assistência Member presented changes probably caused by the intrusion of diabase sill (talc + pyrophyllite + calcite). Talc and calcite were formed due to the reaction between dolomite and quartz, while pyrophyllite was the product of reaction between kaolinite and ...
Journal of South American Earth Sciences, 2020
Shale samples from outcrops of the Irati Formation (Permian), Paraná Basin, Brazil were analyzed based on organic geochemistry, palynofacies, and stable carbon isotopes with the aim of evaluating thermal effects of igneous intrusions on the kerogen. The potential for hydrocarbon generation, the depositional paleoenvironment, and the input of the organic matter were also studied. Most samples have high total organic carbon content, excellent hydrocarbon source potential, and type I kerogen, except some samples which showed changes in their compositional characteristic due alteration in the depositional paleoenvironment and due to the high maturation caused by the heat of diabase intrusions. The composition and distribution of saturate and aromatic biomarkers and stable carbon isotopes provided evidence that the composition of organic matter in the shales is marine, except at the upper part of the outcrops where the shales have contribution of terrestrial organic matter. Saturate biomarkers results indicated thermal immaturity for hydrocarbon generation, except the samples that were influenced by the heat of intrusive rocks.
Journal of Sedimentary Environments, 2016
Total organic carbon (TOC), total sulfur (S) and Rock-Eval pyrolysis analyzes were performed in 41 samples collected along the SP-60-PR core, from the Irati Formation, northwestern of Paraná Basin. This work aims to show how organic matter content evolved vertically in the Irati Formation and therefore to contribute to the identification of the most attractive levels to generate hydrocarbons, in thermally immature sediments. The results of these analyses allowed to recognize sharp changes in the types of organic matter and paleoenvironmental conditions, giving rise to eight chemicalstratigraphic units, labeled as A, B and C (Taquaral Member) and D, E, F, G and H (Assistência Member). The units A and C display low organic carbon content and predominance of organic matter type IV, which indicate an oxic environment. The unit B, with higher TOC content, has organic matter predominantly of type II and should be associated to a disoxic environment. The Assistência Member, mainly with organic matter type II, is differentiated from the previous units by their sharply higher TOC content and hydrogen index values, suggesting a more restricted environment, characterized by disoxic to anoxic conditions. The bituminous shale of the units E and H have the highest TOC, sulfur and hydrogen index values, representing the units where conditions of the autochthonous organic matter (type II) preservation was more efficient (anoxic environment). Despite being found organic matter thermally immature in the Assistência Member, the layer with the highest generation potential is the unity H. The comparison with data of other studied wells evidenced a strong reduction in the potential generator of the Irati Formation toward the north of Paraná Basin.
Journal of South American Earth Sciences, 2019
Coal, shale and siltstone samples from the Serra Alta, Irati, Palermo and Rio Bonito formations (Early Permian: Kungarian, Artinskian and Sakmarian) were collected from borehole CBM001-ST-RS (core ST) over a depth range from 496.40 to 637.75 m. This core was evaluated by geochemical parameters to identify organic matter type, depositional environment and hydrocarbon generation potential. The effects of igneous intrusion on the maturity parameters from the shale and carbonaceous shale from Rio Bonito Formation between 605.45 to 610.90 m were also evaluated. Regardless the geological formation, the mineralogical composition along the ST core shows few variations in quartz, Na-plagioclase, illite, kaolinite, carbonates such as calcite and ankerite and some contributions of pyrite. Samples are characterized by a predominance of terrigenous organic matter and the evaluation of the depositional environment indicates two types: fluvial-deltaic environment, where the organic matter was subjected to suboxic or periodically dysoxic conditions, and marine environment related to source rocks deposited under anoxic conditions. All samples are at present time at a maturity near the peak of the oil window (except samples in contact or near igneous intrusions), and have poor to fair hydrocarbon generative potential. In the stratigraphic interval of the Rio Bonito Formation, specifically in samples close to diabase intrusions (coal seam ST-5 and shale ST-6), TOC, bitumen, and SARA composition showed significant variations that are probably caused by the contact with igneous intrusions. In this interval, saturated biomarkers did not represent values indicating an advanced maturity degree. They seem not having reached their equilibrium or endpoint values of maturity. This behavior is attributed to the development of rapid heating rates probably caused by high temperatures associated with the diabase intrusions. However, aromatic
Minerals
Even being the more studied of the interior basins of Northeast Brazil, the Araripe Basin still lacks research in organic geochemistry designed to support interpretations of depositional systems and conditions of formation. This work aims to investigate the organic behavior of evaporites and shales from the Santana Group (Lower Cretaceous), as well as discuss their role in the evolution of its depositional systems. A total of 23 samples, 17 shales and six evaporites, were collected in outcrops and quarries. Analyses of Total Organic Carbon (TOC), Total Sulfur (TS), Rock Eval pyrolysis, and the δ34S isotope ratio were performed. The TOC results revealed high organic content for seven intervals, of which only five had high TS content. From the Rock Eval pyrolysis, dominance of the Type I kerogen was verified, thus corresponding to the best type of organic matter (mainly algal) for the generation of liquid and gaseous hydrocarbons. The Lower Cretaceous (probably Aptian) response to the...
Clays and Clay Minerals, 2010
Shales and claystones in the Permian Irati Formation consist of Al-rich or Fe-Mg clay minerals in its southern/central and northern parts, respectively. The constrasting compositions indicate particular geological and paleo-environmental conditions. The purpose of this study was to determine the conditions of formation by characterizing the black shales and claystones from different sections of the northern edge of the basin, some of which reveal the presence of intruded diabase sills. Black shales consist of saponite or saponite-talc mixed layers, talc, lizardite, nontronite, and quartz. Green claystones are nontronite-rich but also contain lizardite, talc, and quartz. The chemical compositions of the black shale and claystones, except for one sample (POR-56), exhibit a positive correlation of the TiO 2 , Cr, and P 2 O 5 contents with Al 2 O 3 , which typically results from weathering processes. The presence of saponite, nontronite, and some accessory minerals (spinel, pyroxene, native silver) suggests altered basic-ultrabasic rocks as sediment sources, consistent with the rare earth element (REE) composition being less than the Post-Archean Average Shale (PAAS) or North American Shale Composite (NASC) levels and with negative Ce and Eu anomalies. Sample POR-56 consists largely of nontronite and is anomalously rich in zircon, monazite, and apatite. Chemically, sample POR-56 is different from the black shales and claystones, being richer in Al 2 O 3-Fe 2 O 3 , MgO-poor, and having greater REE contents than the PAAS or NASC standards. The POR-56 bed is probably a bentonite resulting from the alteration of volcanic ash in sea water (strong, negative Ce anomaly). The Zr/TiO 2 vs. Nb/Y relation indicates that the magmatism was andesitic. During the Upper Permian, intermediate to basic volcanic activity was recorded in the Mitu Group of the Central Andes. Close to the diabase sill, the black shales and claystones contain saponite, talc, and lizardite but nontronite is absent. Saponite and talc crystals, however, exhibit a larger coherent scattering domain size (CSDS) and are randomly oriented with respect to the sedimentary bedding. The thermal metamorphism effect is confirmed by the presence of secondary enstatite-augite and albite crystals.