Mapping Reservoir Changes Using 4D Seismic on the Norne G-segment, Norwegian Sea

Abstract

Time-lapse seismic can be an important tool for monitoring and planing further development of a producing hydrocarbon field. Use of 4D seismic can make itpossible to detect production changes over a relatively large area and match thesechanges with production data acquired from wells. Undepleted pockets, pressurebarriers and injectors out of range can be revealed when interpreting a 4D data set.This can be valuable information when updating reservoir models and when planingnew wells an hence, lead to an increased recovery from the field.The reservoir interval and the oil column in the Norne G-segment are relatively thin.The pore pressure in the segment has been in the range of the bubble point of thehydrocarbons in place. This has led to gas going out of solution and back to oil againas a result of variations in pore pressure. The producer 6608/10-E-4 has extractedthe hydrocarbons from the segment while injector 6608/10-F-4 has given pressuresupport to the producer by injection of water down flank in the water zone. Waterhas flushed oil as a result of the production of the hydrocarbons and injection ofwater. All this factors introduces more than one effect that may have affected theseismic response form the field at the same time, making the 4D interpretation inthis segment challenging.In this Master?s thesis interpretation of pressure and saturation changes in the NorneG-segment have been performed for the time interval between 2001 and 2006. Thework is done by use of amplitude difference data and AVO attributes on the seismichorizon representing top reservoir in addition to time shift analysis on a horizon belowthe reservoir. Seismic data from 2001, 2003, 2004 and 2006 and well informationincluding paths, production and injection history has been available for this thesis.