Masters Thesis Defence by Mats Gulbrandsen – Niels Bohr Institutet - Københavns Universitet

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Masters Thesis Defence by Mats Gulbrandsen

Abstract: The Metropolis algorithm is a general tool in seismic inversions, and in this study used with geological constraints. The a priori information contains geological knowledge based on lithology information from five boreholes sited in southern Jutland, Denmark. The obtained geological knowledge is assigned the algorithm by the use of Markov models and contains information about the stochastic behavior of layered lithology sequences. The seismic trace inverted is created on the basis of the lithology profile of the Løgumkloster-1 well. The transformation from the lithology log to a seismic trace is a result of several steps, namely lithology to acoustic impedance, acoustic impedance to reflectivity, and the convolution of the reflectivity log and a Ricker-wavelet. The knowledge of the true model parameter makes it easy to evaluate the solutions to the inverse problem and even though geological constraints are assigned the inversion algorithm, there are no unique solutions to the problem. Several good solutions, due to misfit analysis, are studied, but the ambiguity of the results is very evident.