Velocity: The Essential Thing
In the search for hydrocarbons, geophysicists use seismic data primarily to better define subsurface structures and stratigraphy, as well as interpreting the amplitudes, phase, and frequencies to characterize rocks and pore fluids. In all cases, seismic velocity remains the essential detail. An accurate velocity, including anisotropy, is the key to obtain:
- an accurate image that ties the wells and flatten the gathers
- reliable gathers for AVO/AVA
- an excellent attribute for seismic analysis, interpretation
- the most important input for pore pressure prediction
In-Depth’s success can be attributed to its steadfast focus on the essence of seismic imaging: velocity.
Recently, full-waveform inversion (FWI) has become one of the most reliable methods to estimate velocities from seismic. Extensive on-going research and application has shown how effective FWI can be in overcoming one of the biggest subsurface challenges in the seismic industry: producing reliable estimations of subsurface properties from seismic data. Clearly, the application of FWI not only extends to defining a high-resolution subsurface velocity model, but it also aids in characterizing the overburden pressure, shallow hazards identification, pore-pressure prediction, and using FWI-generated velocity as a seismic attribute. Despite some limitations, great progress has been made over the past decade in producing higher fidelity subsurface velocity models using FWI. Yet, FWI's full potential in estimating accurate subsurface properties in highly complex offshore and onshore settings has yet to be fully realized. This moves beyond basic acoustic and isotropic earth assumptions.
Today, FWI remains the most effective tool in producing high-resolution and high-quality velocity models. As seismic acquisition methods advance in providing reliable low-frequency, long-offset, wide-azimuth, multicomponent data, and compressive sensing, FWI will also expand its benefits and accuracy.
In-Depth's proprietary FWI+ has been applied in numerous basins around the world.
Perhaps in the not-so-distant future, high-resolution rock-property images, output by FWI, will complement—and possibly displace—seismic sections to become the primary tools for subsurface characterization and to de-risk exploration and development projects.