Shearwave (3C, 9C, 2D, 3D and 4D)
9C data, 2D, 3D and 4D: FairfieldNodal has been processing 3C and 9C shear wave data for over 20 years. We are one of the few companies who have processed pure land shear to shear data. Our experience includes not just 9C 3D data but also a handful 9C 4D projects. The time lapse aspects of both shear wave and p-wave data sets are an important part of the Colorado School of Mines Reservoir Characterization Project, (RCP). We have worked closely with Mines since the late 1980’s developing tools and processing flows to detect these reservoir changes. The focus over the years has been moving from static properties to dynamic properties. Static reservoir properties such as fracture orientation and lithology are still being analyzed but we are moving into detecting open fracture flows with CO2, water floods and pressure changes. We have also worked a few DOE projects for monitoring CO2 sequestration using 9C 4D seismic data.
FairfieldNodal's work also includes several years of processing for the EGL consortium out of Austin Texas on their shear wave data. Both of these consortiums have published several papers on the work we have done.
Figure 1 shows a CO2 sequestration 9C 4D project processed for the CSM and the DOE.
Figure 1
Due to the extremely low signal/noise ratio of land shear wave data, we have developed many tools and techniques for separating data from the noise. These tools were a must for 9C and 3C data processing but they have also been a great benefit in extremely difficult land p-wave data. Severely noisy carbonate basins can have similar noise problems as shear to shear data.
Figure 2 and 3: These two examples show the severe noise effect below the high mesa. The noise attenuation achieved from the knowledge gained doing years 9C data processing was critical in solving this merging of two 3D data sets.
Mouse over figure 2 to see figure 3.
2D and 3D converted wave data: With the explosion of high channel count land systems and 3C receivers over the last 5 years, we have processed many converted wave 2D and 3D projects. The processing of converted wave data is much more difficult then compressional or shear to shear data. One of the tools we have is the ability to pre-stack time migrate converted wave data. Our unique tool allows us to out put the data in converted wave time or back in p-wave time or out in shear to shear wave time.
Figure 4 shows a line from a 3D stack volume with a super gather unfolded to the right. The sinusoidal wave in the gather show anisotropy. The increase in anisotropy at the reservoir was due to a change in lithology. The overburden anisotropy is also seen in the super gather.
Figure 4
Figure 5 shows more converted wave processing: This is an example of comparing Radial rotated data to “fast and slow” rotated data. The regional anisotropy was subtle but detectable. Our two component rotation allowed us to better focus very subtle lithology change.
Figure 5