Combining borehole and surface seismic data for velocity field estimation through slope tomography

Abstract

International audienceA joint traveltime and slope (or slowness) tomography method of marine surface reflections and walk-away transmitted arrivals is investigated. Based on our previous developments of 2-D isotropic slope tomography dedicated to reflection data, the transmitted arrivals are added into the inversion scheme. The results of the transmitted arrival tomography are compared to those of the joint (transmitted and reflected arrivals) tomography on synthetic data. Moreover, a quality control (QC) procedure is proposed. Finally, walk-away transmitted arrivals, surface reflected arrivals and joint tomography of both arrivals are applied on real data sets from Oseberg, North Sea. These data include 2-D surface and walk-away lines along the same direction. The resulting velocity fields are used for pre-stack depth migration, allowing us to conclude that joint inversion leads to significantly improved images both in terms of focusing and event location. A key point is that improvements are not restricted in the area covered by transmitted arrivals. As the number of available borehole receivers is small, this case study demonstrates the strong impact direct arrivals that may have on depth imaging

Towards a more robust input for stereotomography

“…Several improvements to stereotomography have been proposed in the literature. These include evaluation of the gradient with the adjoint‐state method (Plessix, 2006); application of a PP/PS formulation in a two‐dimensional ocean bottom cable seismic data (Alérini et al ., 2008); investigation of several regularization functions (Costa et al ., 2008); implementation of the picking stage after the data migration, in‐depth domain (Nguyen et al ., 2008); presentation of different formulations combining borehole and surface seismic data (Gosselet and Le Bégat, 2009) and seismic reflected and transmitted data (Prieux et al ., 2013); use of eikonal solvers to generate the modelled data (Tavakoli et al ., 2017); proposal of an extension to the tilted transversely isotropic acoustic media (Tavakoli et al ., 2019); a parsimonious formulation of stereotomography that uncouples the velocity and the ray attributes associated with a scattering point in the inversion process (Sambolian et al ., 2019); and a reformulation of the parsimonious stereotomography as a hypocentre–velocity method (Sambolian et al ., 2021). Furthermore, several of these works highlight the importance of providing accurate input data to stereotomography by high‐quality slope estimation and picking methods (Billette et al ., 2003; Lambaré et al ., 2004; Tavakoli et al ., 2017; Sambolian et al ., 2019, 2021).…”

Contributions to the initialization of seismic slope tomography

“…It was later, in the work of Billette et al [2003], that the strategy of multi-step inversion was employed to estimate the velocity macro-model from a given initial velocity model. This strategy has been extensively employed in tests with synthetic and field data ever since this work [Lambaré et al, 2004, Le Begat et al, 2004, Lambaré, 2008, Gosselet and Le Bégat, 2009, Prieux et al, 2013, Tavakoli et al, 2017. The work of Billette et al [2003] also approached practical aspects related to the picking stage of stereotomography.…”

“…The way of dealing with this problem is by employing methods of regularization to choose a velocity model. This has been extensively discussed in the work of Costa et al [2008], but also approached in the works of Gosselet and Le Bégat [2009], Prieux et al [2013], Tavakoli et al [2017].…”

“…Another interesting comparison, this time between stereotomography and normal-incident-point (NIP) wave tomography [Duveneck, 2004], was presented in Dümmong et al [2008]. In Gosselet and Le Bégat [2009], the authors combine borehole and surface seismic data in stereotomography, by modeling the borehole seismic data together with the seismic reflection data, in stereotomography formulation. In Prieux et al [2013], the authors also perform a combination of seismic reflected data, this time with seismic data from transmitted waves, in the framework of stereotomography.…”