The overall goal of this procedure is to illustrate how to extract sills and conduits of subsurface volcanoes from seismic data cubes. This method can help answer key questions in volcanology, as the structure and the morphology of the plumbing systems can provide key information about eruption rate and the style of basaltic lava fields. The main advantage of this technique is that the 3D structure of subsurface volcanoes are extracted from industrial 3D reflection seismology images for overall exploration.
In this study, we process seismic data cubes from the Tarim Basin in China, to illustrate how to visualize sills and the conduce of subsurface volcanoes. To begin the calculation, first import the seismic acoustic data cube into an appropriate data processing program. Display the data in 2D and 3D, and adjust the data set appearances, as desired.
Then open the settings menu for the well of interest, and open the Time sub menu. Select Create new and name the time log. Use the velocity function DT data to create a one-way time log from the acoustic log.
Next, in the 3D data window, select TWT, to display the data in the two-way time domain. Set the newly-created one-way time log as the active time-depth relationship. Select the wired logs of interest to display their seismic profiles in the 3D window.
Then, use the Manipulate plane tool to adjust the profile, until it intersects the well. Next, in the Seismic tree, uncheck one plane. In the Well tops tree, select the corresponding well filter and set it to surface.
Enable annotations for the Well tops and verify that wired log domains are displayed with the seismic profile. Next, open the Seismic well tie menu. Set the study to Integrated seismic well tie and select the well of interest.
Set the TDR to the calibrated one-way time log. and select the seismic data cube. Select any log from the RC calculation method options and fill in the corresponding parameters.
Use the Wavelet tool box to create or edit a Ricker wavelet. Click OK to generate the synthetic seismogram. Repeat the process if the synthetic trace does not satisfactorily match the seismic data.
Then open the one-way time log created from the acoustic log. Identify a real continual seismic horizon that intersects the well of interest. Add a small increment of time to the Well Log, to adjust the depth of the synthetic trace.
Open the calculator tool. Compare the Well log and the seismic horizon. Continue adjusting the Well log in this way to maximize the overlap of the high amplitude reflectors in the synthetic and real traces.
The synthetic seismogram from the wired log we have force features. Because the log imaging does not perfectly fit with the burgherwalls. Regional geological information, and a vertical seismic profile are needed to correct and optimize the seismogram.
Open the Seismic interpretation menu, and select Insert a Horizon probe. In the individual probe settings, open the Horizons tab, and select two high amplitude surfaces encasing the sills of interest. Select the new probe to display a seismic cube in the 3D window.
Open the probe settings, and select the opacity tab. Use the seismic amplitude histogram, to decrease the opacity of low amplitude reflections, leaving only the basaltic sills of interest. Adjust the histogram repeatedly, until the desired shape of the interested geobody of igneous rocks, is achieved.
Next, open the Volume attributes menu. Set the category to Structural methods and the Attribute to variance. Set the seismic cube as the input.
Enable the Realize option to improve performance and run the process. Choose the variance cube, and select Insert time slice intersection. Use the Manipulate plane tool, in the 3D window, to move the slices to optimize the visualization of discontinuities, corresponding to vertical feeding conduits.
Repeat this process with the Seismic amplitude cube. Adjust the two-way time, and vary the slicing depths, to find the best visualization parameters for the data. A 3D seismic data cube, from the Northern Tarim Basin, was processed with this technique.
Separated lava lobes were observed in the extracted horizontal sills, suggesting that the lava flow, moves from the dome center to the rim of the dome. Time slices were obtained from the seismic cube, and from a variance data cube to visualize vertical volcanic conduits. Different slicing depths were required for the seismic and variance cubes to visualize the conduits.
While attempting this procedure, remember to obtain adequate knowledge of regional geology, the stratigraphic framework, and the characteristics of the marker horizons. After it's development, this technique paved the way for researchers in the field of volcanology, to investigate the 3D structures of the subsurface parts of ash in volcanoes. After watching this video, you should have a good understanding of how to image subsurface volcanoes using our industrial, 3D seismological data cube.
