Palaeozoic petroleum systems of the Orcadian Basin to Forth Approaches, Quadrants 6 - 21, UK

This report synthesises the results of the 21CXRM Palaeozoic project to describe the Carboniferous and Devonian petroleum systems of the Orcadian Basin to Forth Approaches area (Quadrants 6 – 21). Petroleum systems of the Orcadian study area that involve significant Palaeozoic elements are not wholly contained within Devonian, Carboniferous and Permian strata. A number of producing fields attest to two main proven petroleum systems; i. Co-sourced Devonian oil (with Jurassic oil) within a Jurassic reservoir: the Beatrice, Jacky and Lybster fields; ii. Jurassic-sourced oil in a Devonian and/or Carboniferous reservoir: the Buchan, Stirling, Claymore, Highlander fields. (Jurassic-sourced oil in a Permian (Zechstein) reservoir is also proven in the Carnoustie, Ettrick and Claymore fields, and in a Rotliegend reservoir in the Dee discovery). A number of additional unproven petroleum system elements are considered in this report; i. Possibilities for Devonian and Carboniferous sourcing or co-sourcing (with Jurassic oil) of Devonian, Carboniferous and Permian (Rotliegend) reservoirs in those areas underlain by proven Palaeozoic source rock; ii. Possibilities for migrated Jurassic and/or Devonian and/or Carboniferous hydrocarbons onto horst blocks and the regional Grampian High, into basement, Palaeozoic or younger reservoirs. Focusing on frontier areas north and east of the Inner Moray Firth and from the north-eastern Forth Approaches to Grampian High, integration of a large volume of seismic, well, geophysical, organic geochemistry, maturity and reservoir property data at regional scale has established: Source rocks A wide extent of potential Devonian lacustrine source rocks mapped seismically from the Inner Moray Firth to the East Orkney Basin and north of the Halibut Horst. Geochemically-typed Devonian-sourced oil shows, oil seep data outside the area of mature Kimmeridge Clay Formation, burial depth and a limited organic geochemistry/maturity dataset indicative of Devonian source rocks that are potentially mature for oil generation outside the Inner Moray Firth. Good quality gas- and oil-prone Carboniferous source rocks are mapped from the Witch Ground Graben to north eastern end of the Forth Approaches. Wells drilled on highs indicate oil-window thermal maturity levels. Oil and gas shows and basin modelling indicate Carboniferous strata buried more deeply in adjacent basins may reach gas maturity levels, with Cenozoic maturation. Key source rock intervals are: o Lower Devonian, lacustrine Struie Formation (Quadrants 11, 12), oil prone. o Middle Devonian, lacustine Orcadia Formation and Eday Group (Quadrants 11- 15 and possibly Quadrants 19, 20), oil prone. o Visean – Namurian (lower-mid Carboniferous) fluvio-deltaic Firth Coal Formation, gas and oil prone. (This unit is age-equivalent of the Scremerston and Yoredale Formations, Cleveland Group source rocks in Quadrants 25-44

THE SIMORAMIC ANALYSER AS THE INVERSE OF THE MULTIPLEX SPECTROMETER

The Simoramic analyser is a commercially available analogue Fourier transformer in which the amount of hardware is economised by an ingenious use of re-circulation. Unlike an ordinary scanning wave-analyser (for example) it is multiplex and phase-sensitive. These properties favour its use as an inverse to a multiplex interferometric Fourier spectrometer, but there are also some difficulties, and it appears to be useful mainly for high-speed applications. Special-purpose Fourier transformers can be very valuable in multiplex spectrometry, but it is concluded that low cost is essential if they are to compete with modern general-purpose digital computers. This is so especially because Fourier inversion is only one step in the interpretation of an interferogram, and this is itself only a step towards analysing the resultant spectrum.L'analyseur Simoramic est un transformateur de Fourier analogique, commercialement disponible, dans lequel le volume de circuits nécessaires est réduit grâce à l'emploi ingénieux d'une circulation en boucle fermée. A la différence d'un analyseur harmonique ordinaire à balayage (par exemple), c'est un dispositif multiplex et sensible à la phase. Ces propriétés rendent avantageux son emploi comme inverseur de l'interférogramme produit par un spectromètre multiplex interférentiel de Fourier ; cependant quelques difficultés se présentent et l'appareil semble utile surtout pour des applications à vitesse élevée. Des transformateurs de Fourier spécialisés peuvent être très utiles en spectrométrie multiplex, mais nous concluons qu'un bas prix de revient est essentiel pour qu'ils puissent entrer en compensation avec les calculateurs digitaux modernes non spécialisés. Ceci vient essentiellement du fait que la transformation de Fourier est seulement une étape dans l'interprétation de l'interférogramme, qui elle-même, est une étape dans l'analyse du spectre ainsi produit

MULTICHANNEL SPECTROMETRY

Author Institution: Lick ObservatoryThe sensitivity of infrared detectors is already so close to fundamental limits that further large increases seem unlikely. Improvements in the performance of spectrometers are possible by increasing the area of the source that is used, either by increased dispersion or by multislit techniques. It is theoretically possible to increase the intensity of the source almost without limit if the random thermal processes of radiation can be replaced by a coherent mechanism such as occurs in a radio antenna. This principle is the basis of modern microwave spectrometry, but there is no immediate prospect of it being extended to infrared frequencies. Semicoherent spark techniques perhaps deserve more attention than they have been given in recent years. Further improvements must depend on using more efficient methods of observation. A scanning spectrometer is very inefficient in that at every instant it rejects all but one element of the incident spectrum. This loss is avoided in a spectrograph by having effectively a separate radiation detector for each spectral element. Sensitive infrared image detectors are not at present available, but the spectral elements can be measured simultaneously by a single detector if mutually orthogonal modulation patterns are impressed on the separate elements. A convenient method of producing the required modulation is by varying the path difference in a two-beam interferometer. No dispersing system, such as prism or grating, is then required. The theory of this method, which may be termed multichannel spectrometry, has been investigated in detail, and it has been confirmed experimentally that the method gives spectra with the expected resolution and that the theoretical increase in sensitivity is realized. The multichannel method is especially appropriate to astronomical spectrometry, where no improvement in intensity or area of the source is possible

CONCLUSIONS ON MULTIPLEX METHODS

Developments in multiplex spectrometry are reviewed with particular reference to the results communicated at the present Conference. It is emphasised that the multiplex, interferometric and Fourier attributes are distinct, both logically and in a practical sense. The history of multiplex methods is outlined, and recent developments are discussed under the headings of applications, configurations and methods, performance, computation, commercial availability, technical developments and optical theory. It is concluded that in most respects multiplex methods are now capable of giving spectrometric performance as good as has yet been attained by any method. Solution of the initial technical problems has enabled the advantages of the basic simplicity of the multiplex interferometric method to be realised in practice.Les développements récents de la spectrométrie multiplex sont passés en revue, en utilisant particulièrement les résultats présentés durant la conférence. Nous insistons sur le fait que les propriétés multiplex, Fourier et interférentielles sont distinctes à la fois logiquement et en pratique. L'histoire des méthodes multiplex est donnée et les développements récents discutés sous les rubriques : Applications, Méthodes et dispositifs, Résultats, Calculs, Réalisations commerciales, Développements techniques et Théorie optique. Nous concluons que dans la plupart des cas les méthodes multiplex sont capables de donner des résultats aussi bons que ceux obtenus par toute autre méthode. La solution des problèmes techniques a permis aux avantages dus à la simplicité fondamentale de la méthode multiplex interférentielle de donner des résultats pratiques