Estimating gas saturation in a thin layer by using frequency-dependent amplitude versus offset modelling

Various models have been proposed to link partial gas saturation to seismic attenuation and dispersion, suggesting that the reflection coefficient should be frequency-dependent in many cases of practical importance. Previous approaches to studying this phenomenon have typically been limited to single interface models. Here we propose a modelling technique which allows us to incorporate frequency-dependent reflectivity into convolutional modelling. With this modelling framework, seismic data can be synthesized from well logs of velocity, density, porosity and water saturation. This forward modelling could act as a basis for inversion schemes aimed at recovering gas saturation variations with depth. We present a Bayesian inversion scheme for a simple thin layer case and a particular rock physics model, and show that although the method is very sensitive to prior information and constrains, gas saturation and layer thickness can both theoretically be estimated in the case of interfering reflections

Quantitative gas saturation estimation by frequency-dependent amplitude-versus-offset analysis

Seismic amplitudes contain important information which can be related to fluid saturation. The amplitude-versus-offset (AVO) analysis of seismic data based on Gassmann’s theory and approximate of the Zoeppritz equations, has played an important role in reservoir characterization. However, this standard technique faces a long standing problem, which is unable to distinguish between partial gas and “fizz-water” with little gas saturation. In this paper, we studied seismic dispersion and attenuation in partially saturated poroelastic media by using frequency-dependent rock physics model, through which the frequency-dependent AVO (FAVO) response can be calculated as a function of porosity and water saturation. We propose a crossplotting of two attributes derived from FAVO response to differentiate amongst the three cases of full water, full gas and fizz-water saturation. One of the attributes measures a “low frequency” or Gassmann, reflectivity, while the other measures the “frequency-dependence” of reflectivity. This is in contrast to traditional AVO attributes, where there is typically no such separation. A rather pragmatic FAVO inversion scheme is also established by matching the theoretical FAVO response to the observed ones for quantitative estimation of gas saturation. The inversion scheme has the merit of being readily applicable to field data. A synthetic study is performed to explore the potential of the method to image gas saturation and porosity variations. An advantage of our work is that the method is in principle predictive, opening the way to further testing and calibration with field data. We believe that such work should guide and augment more theoretical studies of FAVO analysis

Quantitative seismic interpretation : applying rock physics tools to reduce interpretation risk

Demonstrating how rock physics can be applied to predict reservoir parameters, such as lithologies and pore fluids, from seismically derived attributes, this volume provides an integrated methodology and practical tools for quantitative interpretation, uncertainty assessment, and characterization of subsurface reservoirs. Including problem sets and a case-study for which seismic and well-log data and Matlab codes are provided on the Interne

Hvordan påvirker parallellimport av eksklusive motemerker til dagligvarebransjen, high-end segmentet i motebransjen?

Før vi startet arbeidet med denne bacheloroppgaven hadde vi et ønske om å belyse parallellimport for allmennheten. Til sammen har vi 10 års erfaring fra motebransjen hvor vi erfarte negative konsekvenser av parallellimport. Dette resulterte i et ønske om å utforske konsekvensene av parallellimport fra motebransjens high-end segment til dagligvarebransjen. Vi valgte deretter å fokusere på saken mellom Coop Norge og PJS International fordi det er en sak som har fått stor medieoppmerksomhet og har vært mye omtalt på folkemunnen. Ved å gjennomføre kvalitative dybdeintervjuer som en del av vår casestudie, føler vi at vi har representert de ulike bransjene fra et objektivt synspunkt. For å gi oppgaven en oversiktlig struktur, valgte vi å utvikle en forskningsmodell som har navigert oss gjennom hele oppgaven. Denne forskningsmodellen tar for seg alle leddene som rammes av parallellimport i verdikjeden innenfor vår avgrensing. Avslutningsvis oppsummeres våre funn fra analysene i forskningsmodellen. Vi har avdekket at parallellimport henger tett sammen med økt bransjeglidning, men at disse fenomenene ikke utelukkende kan sees i sammenheng. På bakgrunn av vårt forskningsprosjekt har vi i tillegg konkludert med at parallellimport i seg selv har negative konsekvenser for flere i motebransjens verdikjede