dc.contributor.advisor Landrø, Martin nb_NO dc.contributor.author Rodríguez, Paola nb_NO dc.date.accessioned 2014-12-19T12:17:23Z dc.date.available 2014-12-19T12:17:23Z dc.date.created 2013-09-09 nb_NO dc.date.issued 2013 nb_NO dc.identifier 646883 nb_NO dc.identifier ntnudaim:9959 nb_NO dc.identifier.uri http://hdl.handle.net/11250/240090 dc.description.abstract 4D seismic is a relatively new technology used aggressively in the oil industry, over the years it has proved its potential. However, there is a need for development of new techniques with high precision that enable the record of subtle changes in seismic properties, where conventional monitoring methods have not succeeded. Experience shows that refraction time-lapse seismic might be a solution. By measuring timeshifts, between base and monitor surveys, on first arrival head-waves, the method aims the estimation of reservoir velocity changes at a much lower cost than conventional 4D seismic monitoring. Preliminary results show timeshifts in the order of $1ms$ to $10ms$, caused by variation in the reservoir P-wave velocity due hydrocarbon flow. Furthermore, the method offers an accurate estimation of lateral extension of the velocity anomalies, even when the extension is smaller than hundred meters. Limitations of this method are related with the existence of positive velocity contrast in the reservoir layer, existence of long offset data and repeatability of the seismic. Further investigation is needed, in order to identify crucial bottlenecks that are likely to meet for a real data case. nb_NO dc.language eng nb_NO dc.publisher Institutt for petroleumsteknologi og anvendt geofysikk nb_NO dc.title 2-D Finite Difference Modelling and Analysis of Shallow Gas Leakage Scenarios, Using Time-Lapse Refraction nb_NO dc.type Master thesis nb_NO dc.source.pagenumber 107 nb_NO dc.contributor.department Norges teknisk-naturvitenskapelige universitet, Fakultet for ingeniørvitenskap og teknologi, Institutt for petroleumsteknologi og anvendt geofysikk nb_NO
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