Chirp sub-bottom profilers (SBP) provide centi-to-decimetre resolution, seismic data with applications for various geophysical and geological purposes. To verify the field application of imaging of a buried target with a cost-effective and easy-to-apply pseudo-3D Chirp SBP survey, we explored the buried site of an ancient wooden shipwreck off the west coast of Korea before underwater excavations. The survey was conducted using a commercial 2D Chirp SBP system with a newly devised recording system that preserved the true polarity of the chirp signal. To produce high-resolution 3D Chirp SBP data from 2D Chirp SBP datasets recorded by the novel system, an optimal data processing sequence, consisting of a first phase of 2D data processing and a second phase of 3D data processing was designed. The first, 2D phase, included the estimation of a source sweep signature, cross-correlation, and deconvolution using an inverse filter. The resulting resolution of the 2D Chirp SBP data was better than that of the enveloped data provided by the commercial acquisition system. The second phase of 3D data processing included gathering 3D datasets, redistributing of ping positions, and static correction. To improve the consistency of the seismic events and reduce the repetitive corrections (swell, tidal, tie, and residual corrections), a static correction was based on multi-beam echo sounder data. The amplitude variation near the shipwreck was clearly apparent in the time slice from the final pseudo-3D Chirp SBP dataset with a bin size of 2.0 m (crossline) × 0.6 m (inline). Through 3D rendering, the buried ancient shipwreck with dimensions of 5 m (width) × 12 m (length) × 2 m (depth) was imaged successfully.

An autonomous surface vehicle, known as a wave glider, was used to record refracted and reflected signals from a seismic source penetrating the shallow subsurface. An integrated survey system consisting of a wave gilder and a human-operated source vessel was deployed. These survey systems are used to acquire wide-offset seismic survey data from specific areas, such as offshore structures. The wave gliders can collect seismic refraction and reflection data, which can be used to estimate subsurface information, e.g., acoustic wave velocity and subsurface structure. We processed raw data collected by a receiver equipped with the wave glider and used the relationship between travel time and offset distance to calculate the velocities of shallow sedimentary deposits and the acoustic basement. The velocities of the sedimentary deposits and basement were estimated to be 1557 and 3507 m/s, respectively. We then overlaid the velocities on subsurface data measured using a single-channel streamer. Our results indicate that unmanned equipment can be used for ocean exploration to aid offshore energy development.

A seismic survey identified a basalt flow that could consist of cap rock of CO₂ storage beneath saline aquifer sediment in the Southern Continental Shelf of Korea. To determine the precise depth of the basalt flow, specific depth-domain data processing of migration velocity analysis (MVA) was applied to the seismic survey data. The accurate depth measurement of a target structure provides crucial information when storing and stabilizing injected CO₂ beneath basalt cap rock. Strong reflections of seismic amplitude at the volcanic mounds were adjusted from the time domain to the exact depth domain by the iterated velocity using MVA. The confidence of the updated velocity was verified by the horizontal alignment of seismic events sorted according to their common reflection point (CRP). The depth difference in volcanic mounds before and after MVA application ranged from 32.5 to 60 m along the vertical axis, showing the eruption shape on the strong-amplitude contour map in detail. The eruption shape of the top of volcanic mounds was verified with spatial continuity in 3D geological interpretation. The presented results provide suitable information that can be used to locate drilling sites and to prepare CO₂ injection. The geological model obtained from both time- and depth-domain processing can significantly influence the calculation of the storage volume and can be useful for history matching studies.

Dynamic simulation of CO₂ migration requires a variety of modeling parameters fed by geomechanical models. The confidence of these parameters of material groups such as porosity and permeability is crucial in achieving successful simulations. Based on the geomechanical and geophysical parameters, we estimated porosity distributions on the Paaratte Formation in the Otway site, one of the CO₂ storage project in Australia. Considering the nonlinear relations between porosity logs and seismic data, we applied the neural network scheme that addresses the porosity value across a whole domain. With only one monitoring well and two injection wells at the site, seismic data are used to restore the spatial absence in porosity. The technique of the neural network was conducted based on the integration of the well logs to the seismic volume and the inversion of acoustic impedance. The results indicated that a correlation value of the well and the seismic tie is 75% and the value between the recorded and the estimated porosity is 87% on average. Further, the time slice maps of porosity at a depth of the injection interval demonstrated a CO₂ plume developed in the Paaratte formation of the Otway site.

Subsurface fluid distribution in marine sediments, typically manifested through seabed features such as vents and pockmarks, is crucial for understanding geological processes and structural formations. We collected survey data on shallow sediment of the Korea Strait to investigate depositional system of transient zone from onshore to offshore environment. This study examined the spatial distribution of fluid flow within the shallow sedimentary layers of the Korea Strait using integrated geophysical inversion techniques. We correlated well log data with seismic stacked sections to invert density, complemented by amplitude versus offset (AVO) inversion. The correlation value between logs and synthetic property from inversion exceeded 80% which has accurate expectation. Integration of density and AVO attributes revealed distinct fluid-charged regions within shallow sediments. The result displays fluid distribution patterns in lithological transitions between sand- and mud-dominated sediments. The method presented in this study can be expanded and applied to determine the distribution of fluid-saturated areas in shallow offshore sediments in three-dimensional space in the future, and its accuracy needs to be verified by correlating the core log properties together.

The Sleipner field in the North Sea has been a cornerstone in the study of aquifer CO₂ sequestration, with over 20 years of monitoring through time-lapse seismic analysis. This world-class project has provided critical insights into CO₂ storage by detecting anomalous events in seismic imagery, confirming CO₂ migration and stabilization within the subsurface. The study observed the growth of the CO₂ plume within the storage aquifer layer by analyzing the seismic amplitude differences between baseline and subsequent monitoring data. The availability of precise seismic datasets in the Sleipner Project has not only facilitated monitoring validation but also spurred further research into CO₂ quantification. This study focused on verifying the correlation between the amounts of stored CO₂ and seismic attributes. Reflection data previously acquired revealed seismic anomalies attributed to the subsurface CO₂ plume. The trace envelope attribute, which only registers positive values, was found to be particularly effective in delineating the primary boundary of the CO₂-affected region. To advance quantitative monitoring, a new CO₂ indicator attribute was developed, derived from the trace envelope and similarity variance. The application of this attribute resulted in an improvement in regression estimation accuracy, increasing from 0.9895 to 0.9906. The successful matching of CO₂ storage data with seismic attributes demonstrates that fluid substitution can be quantitatively assessed using seismic data manipulation over time, underscoring the potential of seismic analysis for accurate CO₂ monitoring in subsurface storage projects.