Method Study Of Time-lapse Seismic Full Waveform Inversion

With the improvement in the level of oilfield development,reservoir monitoring technology based on time-lapse seismic data has become an important development of reservoir technology.With this technology,we can obtain the difference of elastic parameters after reservoir development.Combining with rock physics theory we can establish the relationship between formation elastic parameters and formation physical parameters,and further explorate the distribution of remaining oil,and finally optimize injection scheme,enhance oil recovery.Full waveform inversion(FWI)is a kind of method to obtain the properties of underground medium,and it can reveal the geological structure detail for it makes full use of the kinematic and dynamic information contained in the seismic data.So once FWI is applied in time-lapse seismic,we will obtain high-resolution images that enable us to track dynamic changes in physical properties,especially fluid parameter variations in target areas.Combining FWI and time-lapse seismic,three strategies can be used to assess the physical parameter changes,such as parallel difference(two separate inversions of baseline and monitor data sets),sequential difference(inversion of the monitor data set starting from the recovered baseline model)and double-difference(inversion of the difference data starting from the recovered baseline model)strategies.Using base FWI model for the initial model of monitor FWI,both sequential difference and double-difference strategy can produce better result and has fewer artefacts.The double-difference strategy can deliver more accurate time-lapse variation since it can focus to invert the difference data.However,the double-difference strategy requires a preprocessing step on data sets such as time-lapse binning to have a similar source/receiver location between two surveys,while the sequential difference needs less this requirement.