Since modern seismology began in the 1920’s, there have been two eras. The first era (2D seismic) lasted from the 1920’s through the early 1980’s when the second era – the era of 3D seismic – began. Although 2D and 3D seismic have served the E&P industry well, many of the underlying technologies are reaching the limits of their effectiveness.
ION believes the emerging third era – the Digital, Full-wave Era – is now upon us. By using digital, full-wave seismic, geophysicists will have a better chance to develop higher quality, higher utility images of the subsurface. The result will be finding more oil and gas, at lower cost, and at lower levels of financial and health, safety, and environmental (HSE) risk.
When geophysicists are attempting to locate large, well-defined structures or to capture a single image early in the life of a reservoir, 3D seismic is often adequate. However, as the E&P industry hunts for targets that are deeper or harder-to-image, conventional 3D seismic may no longer suffice. This is where digital, full-wave seismic comes in. Full-wave seismic delivers benefits generally, but especially in extremely challenging imaging environments. Whether seismic data is acquired onshore or offshore, full-wave offers great promise. Benefits and application areas include:
- Improving vertical and spatial resolution of the seismic image
- Imaging thin, stratified, or steeply-dipping reservoirs
- Delivering low frequency data (down to 1-2 HZ) needed to apply certain AVO and seismic inversion techniques
- Delineating lithology (rock type) changes
- Determining fluid types and fluid movements, especially in 4D programs
- Dealing with abrupt, near-surface velocity changes in the Arctic or in deserts
- Accounting for anisotropy in the subsurface
- Mapping fracture networks in reservoirs
- Re-shooting near existing oil & gas fields, where ambient noise from drilling or production operations impedes seismic imaging
- Acquiring seismic data in offshore locations, where gas clouds or production infrastructure is a problem
The development of high-fidelity digital sensors (like VectorSeis) over the last several years has enabled geophysicists to more accurately and cost-effectively record all of the reflected seismic energy that the Earth returns. By recording the full seismic wavefield, including both the P-waves and the S-waves, geophysicists can better determine where reflected seismic energy came from in the subsurface. In addition, they can capture a broader frequency bandwidth of reflected energy, which translates into a higher definition image.
Beyond enhancing the subsurface image, digital full-wave sensors also deliver improved field efficiencies during acquisition by facilitating single-point recording. Since receiver arrays are no longer needed to attenuate noise during onshore acquisition, single-point digital sensors can be more rapidly and densely deployed during field operations. The result is not only an improved image, but an image obtained in a shorter timeframe.
ION’s vision for full-wave is about more than just the sensor. It’s also about how surveys are designed, how the data is acquired in the field, and how the data is processed.
Processing is a key element in our full-wave vision. We have developed vector filtering techniques to filter noise mathematically in pre-processing rather than mechanically through arrays. This allows us to preserve, or even enhance, the P-wave signal. We have developed a leading anisotropic processing technique to take account of azimuthal velocity heterogeneities in the subsurface. And our GX Technology group is processing converted wave data both onshore and offshore as required by the imaging objective.
