Vertical radar profiling: Combined analysis of traveltimes, amplitudes, and reflections

Abstract

Vertical radar profiling (VRP) is a single-borehole geophysical technique, in which the receiver antenna is located within a borehole and the transmitter antenna is placed at one or various offsets from the borehole. Today, VRP surveying is primarily used to derive 1D velocity models by inverting the arrival times of direct waves. Using field data collected at a well-constrained test site in Germany, we evaluated a VRP workflow relying on the analysis of direct-arrival traveltimes and amplitudes as well as on imaging reflection events. To invert our VRP traveltime data, we used a global inversion strategy resulting in an ensemble of acceptable velocity models, and thus, it allowed us to appraise uncertainty issues in the estimated velocities as well as in porosity models derived via petrophysical translations. In addition to traveltime inversion, the analysis of direct-wave amplitudes and reflection events provided further valuable information regarding subsurface properties and architecture. The used VRP amplitude preprocessing and inversion procedures were adapted from ray-based crosshole ground-penetrating radar (GPR) attenuation tomography and resulted in an attenuation model, which can be used to estimate variations in electrical resistivity. Our VRP reflection imaging approach relied on corridor stacking, which is a well-established processing sequence in vertical seismic profiling. The resulting reflection image outlines bounding layers and can be directly compared to surface-based GPR reflection profiling. Our results of the combined analysis of VRP, traveltimes, amplitudes, and reflections were consistent with independent core and borehole logs as well as GPR reflection profiles, which enabled us to derive a detailed hydrostratigraphic model as needed, for example, to understand and model groundwater flow and transport.

Substrate‐sensitive relationships of dielectric permittivity and water content: implications for moisture sounding

“…; Takahashi et al . ; Kirsten ; Tronicke and Hamann ). TDR, local moisture sounding (LMS; a method for small‐scale geoelectrics), and GPR are based on electromagnetic sounding, which requires knowledge of the relationship between effective relative dielectric permittivity and soil properties.…”

“…(), Nussberger (), Lauer (), Roth (), Salat and Junge (), Takahashi et al . (), and Tronicke and Hamann () have all made significant contributions to this field. Most of these studies determine the relationship between permittivity and moisture content for a specific mineral or mineral composition.…”

“…Two-and three-dimensional monitoring by ground-penetrating radar (GPR) also allows the visualisation of preferential water flow in soils, as well as irrigation and storage effects (van der Kruk et al 2011;Takahashi et al 2012;Kirsten 2014;Tronicke and Hamann 2014). TDR, local moisture sounding (LMS; a method for small-scale geoelectrics), and GPR are based on electromagnetic sounding, which requires knowledge of the relationship between effective relative dielectric permittivity and soil properties.…”

“…All these studies were based on complex natural soil compositions or on two-component mixing systems. Topp et al (1980), Roth et al (1992), Nussberger (2005), Lauer (2008), Roth (2008), Salat and Junge (2010), Takahashi et al (2012), and Tronicke and Hamann (2014) have all made significant contributions to this field. Most of these studies determine the relationship between permittivity and moisture content for a specific mineral or mineral composition.…”

Reservoir monitoring using borehole radars to improve oil recovery: Suggestions from 3D electromagnetic and fluid modeling

“…To overcome the limitation of surface GPR, borehole radar is used by deploying antennas under the surface (Sato and Takayama, 2007;Kuroda et al, 2009). Cross-hole, single-hole, and vertical radar profiling measurements have been conducted for fracture and cavity detection, metal ore exploration, and underground water assessments Sato, 2000, 2004;Ellefsen et al, 2011;Tronicke and Hamann, 2014;Yang et al, 2015). Some novel types of GPR antennas have been designed suitable for downhole materials and structures.…”