S U M M A R YConverted phase (CP) elastic seismic signals are comparable in amplitude to the primary signals recorded at large offsets and have the potential to be used in seismic imaging and velocity analysis. We present an approach for CP elastic wave equation velocity analysis that does not use source information and is applicable to surface-seismic, microseismic, teleseismic and vertical seismic profile (VSP) studies. Our approach is based on the crosscorrelation between reflected or transmitted PP and CP PS (and/or SS and CP SP) waves propagated backward in time, and is formulated as an optimization problem with a differential semblance criterion objective function for the simultaneous update of both P-and S-wave velocity models. The merit of this approach is that it is fully data-driven, uses full waveform information, and requires only one elastic backward propagation to form an image rather than the two (one forward and one backward) propagations needed for standard reverse-time migration. Moreover, as the method does not require forward propagation, it does not suffer from migration operator source aliasing when a small number of shots are used. We present a derivation of the method and test it with a synthetic model and field micro-seismic data.Key words: Inverse theory; Body waves; Seismic tomography; Computational seismology; Wave propagation. I N T RO D U C T I O NIn recent years, full waveform seismic imaging and velocity analysis methods have become standard and the use of elastic waves is now drawing more attention. Converted phase (CP) waves are an integrated part of the recorded elastic seismic signal and are investigated in numerous studies in the research areas of vertical seismic profile (VSP) data (e.g. Esmersoy 1990; Stewart 1991; Xiao & Leaney 2010), surface reflection (e.g. Purnell 1992;Stewart et al. 2003;Hardage et al. 2011) and transmission seismic data (e.g. Vinnik 1977;Vinnik et al. 1983;Bostock et al. 2001;Rondenay et al. 2001;Brytic et al. 2012;Shang et al. 2012;Shabelansky et al. 2013). In particular, for example Xiao & Leaney (2010) and Shang et al. (2012) showed that the CP seismic images can be calculated using one elastic propagation without using source information (i.e. location, mechanism and time-function). Source information is generally considered mandatory in standard seismic imaging and velocity analysis. However, in * Now at: Earth Sciences Department, Memorial University of Newfound- passive monitoring source information is generally not available and in active source surveys seismic data require special treatment for frequency matching due to coupling differences between soil and vibro-seis or dynamite casing. These factors affect the accuracy of the imaging and velocity estimation and add computational and processing cost. Moreover, CP elastic seismic imaging is shown to have higher resolution in Xiao & Leaney (2010) and fewer artifacts than reflection type imaging in Shabelansky et al. (2012). In this study, we present a source-independent CP (SICP) velocity anal...

We have developed crosscorrelational and deconvolutional forms of a source-independent converted-wave imaging condition (SICW-IC) and show the relationship between them using a concept of conversion ratio coefficient, a concept that we developed through reflection, transmission, and conversion coefficients. We applied the SICW-ICs to a two half-space model and the synthetic Marmousi I and II models and show the sensitivity of the SICW-ICs to incorrect wave speed models. We also compare the SICW-ICs and source-dependent elastic reverse time migration. The results of SICW-ICs highlight the improvements in spatial resolution and amplitude balancing with the deconvolutional forms. This is an attractive alternative to active and passive source elastic imaging.

SUMMARYMulti-component elastic seismic data collected at large offsets have the potential to be used in seismic imaging and velocity analysis. In this study, we present an approach for convertedphase elastic-transmission migration velocity analysis with an application for VSP and micro-seismic studies. Our approach is based on the cross-correlation between converted-phase Pand S-waves propagated backward in time, and is formulated as an inverse problem with a differential semblance criterium objective function for the simultaneous update of both P-and S-wave velocity models. The merit of this approach is that it is fully data-driven and requires only one elastic backward propagation to form an image rather than the two (one forward and one backward) acoustic propagations needed for standard RTM. Moreover, as the method does not require forward propagation, it does not suffer from migration operator source aliasing when a small number of shots are used. We present a derivation of the method and test it with the synthetic Marmousi model. We also show the differences between the standard reflection offset domain common image gathers and the converted-phase image gathers that we use for model updates.

Heating heavy oil reservoirs is a common method for reducing the high viscosity of heavy 7 oil and thus increasing the recovery factor. Monitoring of these viscosity changes in the 8 reservoir is essential for delineating the heated region and controlling production. In this 9 study, we present an approach for estimating viscosity changes in a heavy oil reservoir. The 10 approach consists of three steps: measuring seismic wave attenuation between reflections 11 from above and below the reservoir, constructing time-lapse Q and Q −1 factor maps, and 12 interpreting these maps using Kelvin-Voigt and Maxwell viscoelastic models. We use a