Site characterization at Groningen gas field area through joint surface-borehole H/V analysis

Abstract

A new interpretation of the horizontal to vertical (H/V) spectral ratio in terms of the Diffuse Field Assumption (DFA) has fuelled a resurgence of interest in that approach. The DFA links H/V measurements to Green's function retrieval through autocorrelation of the ambient seismic field. This naturally allows for estimation of layered velocity structure. In this contribution, we further explore the potential of H/V analysis. Our study is facilitated by a distributed array of surface and co-located borehole stations deployed at multiple depths, and by detailed prior information on velocity structure that is available due to development of the Groningen gas field. We use the vertical distribution of H/V spectra recorded at discrete depths inside boreholes to obtain shear wave velocity models of the shallow subsurface. We combine both joint H/V inversion and borehole interferometry to reduce the non-uniqueness of the problem and to allow faster convergence towards a reliable velocity model. The good agreement between our results and velocity models from an independent study validates the methodology, demonstrates the power of the method, but more importantly provides further constraints on the shallow velocity structure, which is an essential component of integrated hazard assessment in the area.

Shear wave structure of a transect of the Los Angeles basin from multimode surface waves and H/V spectral ratio analysis

“…4a) demonstrate the good convergence of the H/V after stacking (e.g. Spica et al 2017b). The quality of H/V retrieval in this frequency band is further verified by the spatial continuity of the spectral H/V amplitude along the line A-A' (Fig.…”

“…Piña-Flores et al 2016). Independent information, such as surface wave dispersion (Scherbaum et al 2003;Piña-Flores et al 2016;Lontsi et al 2016) or H/V measurements recorded at different depths (Lontsi et al 2015;Spica et al 2017b) or locations (Perton et al 2017) all provide opportunities to reduce this non-uniqueness. Additionally, Perton et al (2017) suggested that the H and V components could be considered independently to assess the reliability of H/V and to characterize properties of the noise field illumination.…”

The Ambient Seismic Field at Groningen Gas Field: An Overview from the Surface to Reservoir Depth

“…Using borehole interferometry, Hofman et al (2017), Spica, Perton, Nakata, et al (2017), and Noorlandt et al (2018) retrieved P and S waves inside the G-array's boreholes and Zhou and Paulssen (2017) characterized P-and S-wave velocities of the reservoir using borehole interferometry using the SDM and ZRP arrays. Table 1 presents a summary of our observations related to the retrieved wavefield based on ASF correlations in the near ▴ Figure 6.…”

“…Fundamental-mode surface waves (Rayleigh and Love waves) are now routinely extracted from ASF to image the crust, the lithosphere, and the upper mantle (e.g., Bensen et al, 2008) at global (Nishida et al, 2009), regional (Shapiro et al, 2005), and local scales (e.g., Spica, Perton, and Legrand, 2017). Body-wave retrieval is more challenging; however, recent exam-ples attest to that possibility (e.g., Roux et al, 2005;Ruigrok et al, 2011;Poli et al, 2012;Nakata et al, 2015;Spica, Perton, Nakata, et al, 2017). In active producing fields (oil, gas, or geothermal), ASF interferometry of geophones in boreholes is emerging as a method well suited for permanent reservoir monitoring (e.g., Hillers et al, 2015;Behm, 2017) or to assess the P-and S-velocity structure of such reservoirs (e.g., Miya-zawa et al, 2008;Zhou and Paulssen, 2017).…”

Ground-motion networks in the Groningen field: usability and consistency of surface recordings

“…Records from all four geophones of the stations and their surface accelerograph (discussed in Sect. 2.3) have been used in work related to the site properties of the locations of the G-stations, such as the study of Spica et al (2017).…”