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Petroleum system and thermal history of the Upper Rhine Graben : implications from organic geochemical analyses, oil-source rock correlations and numerical modelling
No full textThe Upper Rhine Graben (URG) forms the central section of the European Cenozoic Rift System and is a mature hydrocarbon province. During previous exploration periods, about 50 oil fields and several gas fields were discovered accompanied by a huge number of exploration and production wells and numerous seismic profiles. Surprisingly, in 2003 a geothermal well found oil in the Buntsandstein reservoir and discovered unexpectedly the Römerberg oil field, which promptly doubled the total recoverable reserves (produced oil plus remaining reserves) in the German part of the URG. This discovery opened-up a new exploration play and implicated a review and revaluation of the petroleum system of the URG. Four distinct oil families occur in the URG. Three of those are of economic interest. The oldest oils are derived from the Liassic Black Shales (oil family C). These are the major source rocks for oil fields in the Alsace and southern URG as well as for the large oil fields Pechelbronn, Landau and Römerberg. Furthermore, several Tertiary source rocks exist. At many places high wax oils occur, which originated from early Tertiary (Eocene) coaly shales and sapropelic coals (oil family B). Oils from the Rupelian Fish Shale (Hochberg-Subfm.) occur especially in the northern and central URG (oil family D). In addition, highly viscous, sulphur-rich and early mature oils generated from the Corbicula- and Hydrobienschichten exist (Oil family A). These oils occur especially in the Micoene to Quaternary subsidence center, the Heidelberg-Mannheim-Graben. The oil family A oils are economically not relevant, but are of interest in order to derive kitchen areas and directions of migration.In this regard, the dissertation is subdivided into three studies. The first one focuses on a source rock characterisation of the Rupelian Fish Shale, which is the major source rock of the large oil fields Stockstadt, Eich-Königsgarten, and further smaller oil fields in the northern URG, where the Liassic source rocks are eroded. Based on petrographic and geochemical analyses the Fish Shale was characterised as good to very good source rock containing typical type II kerogens, 4-5.5 % TOC and Hydrogen Index (HI) values of 450-550 mg HC/g TOC (at an immature state). Special biomarkers such as characteristic sterane distributions, age-related markers such as oleanane, or a highly branched isoprenoid C25 with origin from marine diatoms enable reliable oil-source rock correlations. The Fish Shale is distributed in the entire graben in uniform facies. Thus, the thickness and thermal maturity are the factors controlling the amount of generated hydrocarbons. The latter is the limiting factor for missing oils derived from the Fish Shale in the Alsace and southern URG (south of Karlsruhe). This was shown by a vitrinite reflectance map, which distinctly identifies kitchen areas of the Fish Shale. Existing reservoired oils derived from the Fish Shale were correlated to these kitchen areas and migration pathways and directions were identified.The second part analyses the Liassic source rocks with focus on their thermal maturity. An investigation beyond the borders of the URG showed that the Posidonia Shale (Lias ε) reached a maturity of about 0.5-0.6 % VRr within the graben area and its surroundings before the formation of the URG in the Eocene. Liassic outcrops situated at the graben margin, in the Alsace, in the Swabian Alb, in the foreland of the Alps, and samples from shallow wells (ca. 550 mg HC/g TOC characterise the Posidonia Shale at an immature stage. Moreover, the bituminous Lias α marls and shales have important additional source rock potential and contributed to the oils of family C.Furthermore, new insights on source rocks of the different oil families and several new oil-source rock correlations are presented and the distribution of oil families in regard to migration pathways is discussed. The high wax oils (Family B) are heterogeneously distributed, but occur especially in the northern and central URG, in the latter predominantly in the western part. These oils are stemming from early Tertiary, locally occurring, coaly shales and sapropelic coals. The hydrocarbon generation potential of these source rocks is rather difficult to evaluate because of significant variations in thickness and source rock characteristics. Rock-Eval pyrolysis and bulk kinetic measurements of the sapropelic coals indicate a partly extraordinary high oil generation potential. These source rocks contributed also to the large Landau oil field. Interestingly, the large oil fields Pechelbronn, Landau and Römerberg, which are all predominantly charged by the Liassic source rocks, occur in areas where the Liassic source rocks are already eroded or immature, in case of Pechelbronn. Consequently, oils of the Liassic source rocks migrated mainly laterally in northwestern directions and successively into older stratigraphic units. The Opalinuston-Fm., Liassic claystones and basal Tertiary marls are acting in this context as important seals. In this progress, faults provide - in particular for the Pechelbronn field with numerous small, segmented fault blocks in the fetch area - entry points especially into younger (Tertiary) but also older (Triassic) reservoirs. However, as a consequence of the structural configuration during the early formation of the URG, faults are not indispensable for the migration of Liassic oil into older stratigraphic units. All in all, a comprehensive overview on the distribution of oil families in the URG with respect to their vertical and lateral migration pathways is given in this thesis
Assessment of palaeozoic unconventional shale oil and shale gas in Northwest Europe: Examples from Scotland and Western Germany based on geochemical data and numerical basin modeling
No full textIn recent years, petroleum source rocks at different levels of thermal maturity have not only been studied as source of conventional hydrocarbons, but also with respect to direct production from these rocks. In northwest Europe different Palaezoic sequences can be regarded as prolific for such unconventional hydrocarbon assessment, including Devonian and Carboniferous shales and Carboniferous coals. Here, Devonian coals from northern Scotland and Carboniferous shales and coals from western Germany have been investigated by geochemical, petrological and numerical basin modeling approaches.The assessment of unconventional shale oil of the Mid Devonian lacustrine flagstones present within the Orcadian Basin and unconventional Carboniferous shale gas and coalbed methane in western Germany provides insight on how fluctuation in depositional environments has a significant role on lithofacies and hydrocarbon potential. The variation in depositional environments influences the amount of organic matter content as well as kerogen type. For example, the flagstones were deposited in alluvial lacustrine environments at variable environmental conditions. Biomarker analysis indicated that the sediments with their inherent organic matter were not deposited under permanently anoxic bottom water conditions. Consequently, the organic carbon content of the flagstones varies between 0.21 -1.83% and type I-III kerogen is present. Besides, the hydrogen index (HI) values are quite variable (e.g. HI from 79 to 744 mg HC/g Corg). The burial depth of the flagstones in the onshore area barely reached 2000-3000 m (now eroded) coupled with temperatures of about 100°C and vitrinite reflectance of 0.5-0.7 (%Ro). Little petroleum has been generated and expelled there, which contrasts to more favorable (deeper) burial expected for the offshore area. In the Mississippian sequence of western Germany and neighboring countries, the Lower and Upper Alum Shales (LAS, UAS) present important black shale intervals. There is a rather sharp lithological contrast in the sequence between the deep marine Kulm and shallow marine “Kohlenkalk” facies. The Mississippian is comprised of shallow marine carbonates with abundant dark, organic matter-rich shales as well as cherts and coarser-grained clastics. The Ziegelschiefer Fm (upper Namurian B, Marsdenian) represents the oldest dark, marine shale horizon within the Pennsylvanian thus indicating the transition between deeper marine Mississippian and transgressive, shallow marine-paralic Pennsylvanian black shales. The average organic carbon content of LAS is 2.37% and UAS is 3.56%. Deposition of these shales took place in an oxygen-depleted marine environment where hydrogen-rich type II kerogen was preserved in the sediments. The Ziegelschiefer has an average organic carbon content of 1.20% and deposition of these shallow marine shales took place under suboxic to oxic bottom water environments. The strong terrestrial influence is also revealed by differences in sulphur contents and organic carbon/sulphur ratios. Further to the north, thick Pennsylvanian is present including many coal seams and black shales. The integration of geological and geochemical data into numerical basin modeling provides a powerful tool in studying burial and temperature history as well as petroleum generation. The 1 and 3 dimensional basin modeling performed here documents the evolution of the foreland basin during the Carboniferous and the following evolution during the Meso- and Cenozoic. Differential subsidence and amount of erosion has significant influenced on thermal maturation and hydrocarbon potential. In the Münsterland basin the Pennsylvanian shale and coal layers reached substantial depth of often more than 3500 m and erosion usually ranges between 2000-4000 m leading to temperatures reached 200 °C and thermal maturity clearly above 1.3% vitrinite reflectance in much of the sequence, especially the deeper parts as well as central parts of the basin. The basin modeling revealed that 40-80% of the hydrocarbon potential was indeed transformed and that the wet gas to dry gas window was reached in large parts of the basin
Shale oil potential and depositional environment of the Lower Toarcian Posidonia Shale in NW Europe
No full textThis doctoral thesis deals with a suite of drilling cores and outcrop samples of the Lower Toarcian Posidonia Shale (PS) collected from multiple locations covering a vast area including the Swabian Alb (SA) and Franconian Alb (FA) of Southwest-Germany, Wenzen well (WEN) of Hils syncline, northern Germany, Runswick Bay of UK, Loon op Zand well (LOZ-1) of the West Netherlands Basin (WNB) and the Esch-sur-Alzette, Luxembourg (LU). Based on a series of laboratory measurements, firstly, shale oil potential was assessed including thermal maturity. In order to quantify the petroleum generation potential of the rocks a large set of experimental analyses was conducted including elemental analysis, Rock-Eval pyrolysis, organic petrographic investigations and molecular hydrocarbon analyses. Secondly, three types of depositional environments of the Posidonia Shale from these six different sampling localities were deduced mainly based on organic geochemical characteristics.The Lower Toarcian Shale is more carbonate-rich (about 30 % on average) in SW-Germany, NW-Germany and Luxembourg, and is instead more silicate-rich in UK and NL with carbonate contents of about 15% on average. However, HI values are similar, approx. 500-700 mg HC/g TOC on average at all sampling localities, exhibiting typical type II kerogen with excellent hydrocarbon generation potential. Samples from outcrops of the Lower Toarcian Shale from Runswick Bay, UK, have reached the early stage of the oil window, with quite uniform Tmax values (425-438°C, avg. 433 °C) and a narrow range of PI (production index) values (0.10-0.19), substantiated by mature fluorescing characteristics of telalginite and lamalginite and vitrinite reflectance values of 0.6-0.7%. Wider ranges of Tmax values (421-443°C, avg. 427°C), vitrinite reflectance (0.4-0.8%) and production indices (0.06-0.29) suggest more variable thermal maturation ranging from immature to almost peak oil generation at the LOZ-1 well, NL, although only some intervals indicate advanced thermal maturity there. Non-indigenous light hydrocarbons occur at the LOZ-1 well, NL, evidenced by unexpectedly high production indices and abundant low molecular weight, short-chain n-alkanes extending from n-C10 to n-C16 together with a sharp decrease of n-alkanes concentration towards the heavier, long-chain components (>n-C20). In contrast, the Lower Toarcian marlstones from the Swabian and Franconian Alb of SW-Germany are clearly immature, similar to the samples from Luxembourg. In NW-Germany, the Posidonia Shale covers a wide spectrum of maturity ranging from immature to overmature.Organic geochemical characteristics were comprehensively analyzed and compared for these six different sampling localities on a series of sterane, hopane and aromatic biomarkers. Results indicate that highest thermal maturity occurs in the PS of Runswick Bay, UK, equivalent to ca. 0.7% VRr, whereas samples from other sampling localities did not exceed the early stage of oil generation or are immature with merely slight variations. Comparable, immature to marginally mature source rocks make it possible to compare their depositional environments based on biomarker characteristics. Accordingly, three different types of redox conditions are established on the basis of biomarker indicators for these six sampling localities during deposition of the PS in NW Europe. (1) Ferruginous conditions are discriminated by low dibenzothiophene/ phenanthrene (95% of < 7 µm in diameter) which are postulated to be partly generated within the water column due to immediate reaction of Fe2+ and H2S derived from bacterial sulfate reduction. (2) In contrast to the iron-rich, low-sulfidic conditions, sulfidic (euxinic) bottom waters possibly with enhanced water salinity and stratified water column prevailed due to restricted iron supply in the Esch-sur-Alzette of LU. Similar but slightly less reducing and less sulfidic conditions occurred in the FA of SW-Germany as well as WEN of northern Germany which was also probably less saline. (3) For the PS of SA, a more oxygenated (dysoxic) water column associated with anoxic sediments (anoxic/dysoxic boundary close to the sediment/water interface) is indicated
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
(Table 1) Low-molecular-weight hydrocarbon concentrations, organic carbon contents, and Rock-Eval pyrolysis hydrogen indices at DSDP Hole 75-530A
No full text(Table 1) Low-molecular-weight hydrocarbon concentrations, organic carbon contents, and Rock-Eval pyrolysis hydrogen indices at DSDP Hole 75-530
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