NGI utilize commercial and in-house software for in the area of applied geophysics. Special attention has been on the transition from shallow towards deeper applications, filling in the gap between more traditional deep petroleum geophysics and the shallow geophysics for geotechnical site investigations. This is based on NGI's comprehensive knowledge on static and dynamic behaviour of soil and rock.
- Analysis of surface waves for site characterization; Dispersion/Multiple modes, High-resolution shallow surface characterization, Anisotropy, Attenuation/material damping. NGI utilizes in-house code: LAYSAC, ngi_lm and tailor-made COMSOL models.
- Analyzing seismics for establishing geomechnical input parameters for geomechanical models.
- AVO/ Prestack simultaneous inversion for reliable estimates of P-wave velocity, S-wave velocity and density, from which both fluid and lithology properties can be predicted. NGI utilize Hampson-Russell's industry standard STRATA inversion software program.
- Pore pressure predictions from seismic through integrated seismic and geomechanical analysis
- Application of shear wave dynamics for synthetic shear wave profiles and linking shear waves to strength and stiffness
- 4D timeshift analysis in combination with geomechanical modeling. The geomechanical model (2D or 3D) simulate reservoir compaction, fault movement, change in stresses and resulting overburden stretch that can be related to the 4D timeshifts.
- Microseismic and acoustic emission. Combination of laboratory testing, field testing and interpretation of field data (through NORSAR cooperation) and integrated geomechanical analysis of fracturing.
Dispersion curves extracted from field data after stacking the spectra for Scholte and Love waves (left). Comsol MultiPhysics finite-element simulation of mono-frequency (16 Hz) movement and the wavefields generated from the shear wave vibrator source (right).
NGI has a world-leading laboratory and holds research facilities for specialized geophysical tests (axial and radial velocity measurements for anisotropy, acoustic emission setup, and triax in CT scanner for visualisation) as well as standard characterization equipment.
Geophysical testing in the laboratory with instrumentation for sonic anisotropic velocity and acoustic emission (LEFT), and streamlined setup for acquisition (MIDDLE), processing and interpretation (RIGHT).
Research activities within geophysics
The laboratory setup at NGI provide excellent opportunity for linking geophysics to geomechanics through advanced laboratory measurements with combined measurements of geophysical and geomechanical parameters:
- Shear wave vs. shear strength and shear modulus relationship
- Dynamic vs. static relationships
- Velocity anisotropy as a function of lithology and mineralogy
- Stress dependent behavior of velocities