Field Stack in Minutes: No Velocity Picking, No Nmo Stretch

Motivated by the ideas of automatic common-midpoint (CMP) stacking without normal-moveout (NMO) correction, hence NMO stretch, and automatizing the velocity model building, we propose a cross-correlation/cross-coherence-based approach. It is a two-step method where the first step is cross-correlation/cross-coherence of zero-offset traces with all other traces in corresponding CMP gathers. This step removes the NMO effect of different hyperbolic events, resulting in CMP gathers with flat events without any stretching effect. Following this, horizontal summation across different CMP gathers is done, resulting in a velocity-free data-driven production of time-domain stacked seismic section. The second step takes advantage of the cross-correlation lags via data-driven k-means cluster analysis to separate lags corresponding to individual hyperbolic events in the CMP gather into distinct clusters. Different norm fittings to lags within individual clusters are evaluated and the lowest residual one automatically selected, resulting in a velocity and zero-offset two-way traveltime time per cluster. These form a base to build an average velocity model for migration and time-to-depth conversion. We demonstrate the efficiency of the proposed method using synthetic and field shear-wave data acquired in southwestern Sweden.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Geophysics and Petrophysic

Introduction to the special issue on “Cost-effective and innovative mineral exploration solutions”

Accepted Author ManuscriptApplied Geophysics and Petrophysic

Improved target illumination at Ludvika mines of Sweden through seismic-interferometric surface-wave suppression

In mineral exploration, new methods to improve the delineation of ore deposits at depth are in demand. For this purpose, increasing the signal-to-noise ratio through suitable data processing is an important requirement. Seismic reflection methods have proven to be useful to image mineral deposits. However, in most hard rock environments, surface waves constitute the most undesirable source-generated or ambient noise in the data that, especially given their typical broadband nature, often mask the events of interest like body-wave reflections and diffractions. In this study, we show the efficacy of a two-step procedure to suppress surface waves in an active-source reflection seismic dataset acquired in the Ludvika mining area of Sweden. First, we use seismic interferometry to estimate the surface-wave energy between receivers, given that they are the most energetic arrivals in the dataset. Second, we adaptively subtract the retrieved surface waves from the original shot gathers, checking the quality of the unveiled reflections. We see that several reflections, judged to be from the mineralization zone, are enhanced and better visualized after this two-step procedure. Our comparison with results from frequency-wavenumber filtering verifies the effectiveness of our scheme, since the presence of linear artefacts is reduced. The results are encouraging, as they open up new possibilities for denoising hard rock seismic data and, in particular, for imaging of deep mineral deposits using seismic reflections. This approach is purely data driven and does not require significant judgment on the dip and frequency content of present surface waves, which often vary from place to place.Applied Geophysics and Petrophysic

Seismic imaging using an e-vib: A case study analyzing the signal properties of a seismic vibrator driven by electric linear synchronous motors (LSM's)

Seismic imaging characteristics of a prototype electrically driven, linear synchronous motor-based, vertical-force seismic vibrator ("e-vib") were evaluated at a site in the Netherlands. The system weighs 1.65 t and excites seismic signals with a peak force of 6.7 kN. Data were recorded along two collocated geophone-based nodal and landstreamer microelectromechanical system - MEMS-based sensor 2D seismic profiles. To obtain a broad bandwidth data set, the e-vib operated with a 1-200 Hz linear sweep. Shot gathers of the merged nodal-landstreamer data set indicated good-quality seismic data of a broadband nature. The processed merged data set demonstrates high-resolution reflections of the stratigraphic members from approximately 200 m to 2 km, with visible reflections as deep as 2.5-2.9 km. As a reference, we also processed a legacy 3D microspread data set acquired at the same site with a magnitude stronger (14.1 t, 67.5 kN) hydraulic vibrator. Comparison of our nodal-landstreamer seismic section versus 2D slices extracted from the processed microspread seismic volume suggested similar signal penetration depth and the same key marker horizons seen in both. Analysis of the reaction mass and base-plate accelerometer signals recorded with the e-vib source operating on grass and on asphalt surfaces indicates that the e-vib has low total harmonic distortion. The results obtained indicate that, although relatively small, the e-vib is capable of generating high-quality broadband seismic data.Accepted Author ManuscriptApplied Geophysics and Petrophysic