What is a time migration?

1. n. [Geophysics] A migration technique for processing seismic data in areas where lateral velocity changes are not too severe, but structures are complex. Time migration has the effect of moving dipping events on a surface seismic line from apparent locations to their true locations in time.

What is depth migration?

1. n. [Geophysics] A step in seismic processing in which reflections in seismic data are moved to their correct locations in space, including position relative to shotpoints, in areas where there are significant and rapid lateral or vertical changes in velocity that distort the time image.

What is prestack depth migration?

Kirchhoff Pre-Stack Depth Migration (Pre-SDM) is the most commonly used pre-stack migration algorithm and it is well suited for moderately complex geology settings. The algorithm handles steep dips imaging and produces common image gathers for further velocity analysis.

What is prestack migration?

Prestack migration is done by summing the amplitudes along the nonzero offset diffraction times. As in the zero-offset case, seismic velocities determine the shape of the hyperbola (the migration operator) along which the summation is performed.

What really is the difference between time and depth migration a tutorial?

Time migration differs from depth migration in how it uses velocity models. The key distinction is that time migration takes its velocity model and creates local one-dimensional models for each image trace in the output. Depth migration takes its velocity model and uses it as a single physical space.

What is reverse time migration?

Reverse time migration is an ultrahigh-end prestack two-way wave-equation migration for accurate imaging in and below areas with both great structural and velocity complexities, such as sedimentary areas with steep salt inclusions.

What is migration algorithm?

The one-way-in-depth scalar wave equation is the basis for common migration algorithms. These algorithms do not explicitly model multiple reflections, converted waves, surface waves, or noise. Any such energy present in data input to migration is treated as primary reflections.

Why do we apply seismic migration?

The goal of migration is to ultimately increase spatial resolution and one of the basic assumptions made about the seismic data is that it only shows primary reflections and all noise has been removed.

What is Kirchhoff migration?

A method of seismic migration that uses the integral form (Kirchhoff equation) of the wave equation. All methods of seismic migration involve the backpropagation (or continuation) of the seismic wavefield from the region where it was measured (Earth’s surface or along a borehole) into the region to be imaged.

How does reverse time migration work?

The basic idea of RTM is a three-step procedure of (a) forward modelling of a wave field through an appropriate velocity model as well as (b) back propagation of the measured data through the very same model and (c) superposition of both using an imaging condition.

What is migration in seismic reflection?

Seismic migration is the process by which seismic events are geometrically re-located in either space or time to the location the event occurred in the subsurface rather than the location that it was recorded at the surface, thereby creating a more accurate image of the subsurface.

Which is correct depth migration or time migration?

Depth migration, on the other hand, images these two reflectors, accurately, if the velocity-depth model input to depth migration is the true model as in the case of Figure 8.2-6. Although we used the true velocity-depth model, time migration produced the incorrect image of the base-salt boundary and the subsalt region.

Which is more accurate depth migration or prestack?

Prestack depth migration generates more accurate images (left) reducing exploration risk and improving reservoir definition. Kirchhoff prestack time migration (PSTM) can accurately image steep or overturned events, provided that turning rays and anisotropy are taken into account.

When to use 2 d or 3 d time migration?

In practice, 2-D/3-D poststack time migration is used most often for a good reason — it is the least sensitive to velocity errors, and it often yields results acceptable for a reliable interpretation. Table 4-1 is an overview of different migration strategies applied to different types of seismic data (2-D, 3-D, stacked, and unstacked).

What are the different types of migration strategies?

The spectrum of migration strategies extend from 2-D poststack time migration to 3-D prestack depth migration. Depending on the nature of the subsurface geology, any other in-between combination can be selected.