Picking seismic stacking velocity based on structures in a subterranean formation

#The present disclosure generally relates to an approach for picking seismic stacking velocity based on structures in a subterranean formation.

#In geology, sedimentary facies are bodies of sediment that are recognizably distinct from adjacent sediments that resulted from different depositional environments. Generally, geologists distinguish facies by aspects of the rock or sediment being studied. Seismic facies are groups of seismic reflections whose parameters (such as amplitude, continuity, reflection geometry, and frequency) differ from those of adjacent groups. Seismic facies analysis, a subdivision of seismic stratigraphy, plays an important role in hydrocarbon exploration and is one key step in the interpretation of seismic data for reservoir characterization. The seismic facies in a given geological area can provide useful information, particularly about the types of sedimentary deposits and the anticipated lithology.

#In reflection seismology, geologists and geophysicists perform seismic surveys to map and interpret sedimentary facies and other geologic features for applications, for example, identification of potential petroleum reservoirs. Seismic surveys are conducted by using a controlled seismic source (for example, a seismic vibrator or dynamite) to create a seismic wave. The seismic source is typically located at ground surface. The seismic wave travels into the ground, is reflected by subsurface formations, and returns to the surface where it is recorded by sensors called geophones. The geologists and geophysicists analyze the time it takes for the seismic waves to reflect off subsurface formations and return to the surface to map sedimentary facies and other geologic features. This analysis can also incorporate data from sources, for example, borehole logging, gravity surveys, and magnetic surveys.

#FIG. 1 is a schematic view of a seismic survey being performed to map subterranean features such as facies and faults.

#FIG. 2 illustrates a three-dimensional cube representing a subterranean formation.

#FIG. 3 illustrates a stratigraphic trace within the three-dimensional cube of FIG. 2.

#Like reference symbols in the various drawings indicate like elements.

#This specification describes an approach for automatically picking stacking velocities while making subsurface seismic images. This approach incorporates SOS. SOS is a filtering technique that smooths an image along structures embedded in the image. The smoothing can prevent the picking algorithm from selecting rapid velocity jitters, so the picked velocity follows the trend of the stacking velocity variation in space. This approach can also incorporate using an anti-multiple Gaussian discriminator and regularized velocity inversion. The anti-multiple Gaussian discriminator uses a Gaussian filter to decrease the semblance energy that potentially results from stacking multiple seismic traces. After the stacking velocity is picked, a regularized inversion algorithm is used to punish for rapid vertical and spatial interval velocity variations. This approach provides stacking velocities that are smooth and follow the geological velocity trend of the subterranean formation.

#This approach is based on the observation it is important to follow the spatial variation trend of the stacking velocity. The described systems and methods reflect the spatial variations in the stacking velocity by smoothing the velocity semblance spectrums used as input to the velocity picking process. Smoothing the velocity semblance spectrums along structures in the subterranean formation allows these systems and methods to account for non-horizontal structures that limit the effectiveness Gaussian-type of isotropic smoothing.