What is AVO seismic?

In geophysics and reflection seismology, amplitude versus offset (AVO) or amplitude variation with offset is the general term for referring to the dependency of the seismic attribute, amplitude, with the distance between the source and receiver (the offset).

What are AVO attributes?

AVO attributes have been developed to validate seismic amplitude anomalies to be correlated with gas sands. The seismic was illustrated as a zero phase, with a trough for decreasing acoustic impedance or a peak for increasing acoustic impedance.

What is AVO modeling?

Since AVO modeling is able to link rock properties to offset-dependent amplitude responses, it is a tool in assisting data processing, data calibration, and interpretation. This paper attempts to provide an insight in the current applications of AVO modeling.

What is DHI in seismic?

A hydrocarbon indicator (HCI) or direct hydrocarbon indicator (DHI), is an anomalous seismic attribute value or pattern that could be explained by the presence of hydrocarbons in an oil or gas reservoir. DHIs are particularly useful in hydrocarbon exploration for reducing the geological risk of exploration wells.

Why is seismic inversion?

Because of its efficiency and quality, most oil and gas companies now use seismic inversion to increase the resolution and reliability of the data and to improve estimation of rock properties including porosity and net pay. There are many different techniques used in seismic inversion.

What is intercept and gradient in AVO?

The intercept is the zero offset or normal incidence reflection amplitude/coefficient of an event while the gradient is the change in reflection amplitude/coefficient with offset or incidence angle. Some authors refer to intercept as A or P and gradient as B or G.

Why AVO analysis is performed?

AVO analysis is a technique by which geophysicists attempt to determine thickness, porosity, density, velocity, lithology and fluid content of rocks. Successful AVO analysis requires special processing of seismic data and seismic modeling to determine rock properties with a known fluid content.

What is flat spot in seismic?

In reflection seismology, a flat spot is a seismic attribute anomaly that appears as a horizontal reflector cutting across the stratigraphy elsewhere present on the seismic image. Its appearance can indicate the presence of hydrocarbons.

What is acoustic impedance in seismic?

Acoustic impedance, the product of seismic velocity and density, is a basic physical property of rocks. Seismic traces are converted into pseudoreflection‐coefficient time series by appropriate initial processing, then into acoustic impedance by the inversion of the time series.

How does seismic inversion work?

Seismic inversion is essentially a very simple procedure. In a seismic inversion the original reflectivity data, as typically recorded routinely, is converted from an interface property (i.e. a reflection) to a rock property known as impedance, which itself is the multiplication of sonic velocity and bulk density.

What is seismic attribute analysis?

Seismic attribute analysis involves extracting or deriving a quantity from seismic data that can be analysed in order to enhance information that might be more subtle in a traditional seismic image, leading to a better geological or geophysical interpretation of the data.

What is intercept and gradient seismic?

What is an example of Class I AVO response?

The Class I example is a tight gas sand with an approximate interval velocity 4600 m/s (Figure 11). The bandwidth for this case is 10/15 – 100/120 Hz. When the gas sand has a thickness of 18m, the Class I AVO response is a peak at near offsets that dims with offset and then reverses polarity at far offsets.

What is the difference between Class III AVO and Class IV AVO?

Class III AVO corresponds to lower impedance gas sands. The top of the reservoir corresponds to a trough that brightens with offset. Class IV AVO corresponds to lower impedance gas sands. The top of the reservoir corresponds to a trough that dims with offset.

What is AVO modeling in seismic processing?

AVO Modeling in Seismic Processing and Interpretation Part 1. Fundamentals AVO analysis is an effective technique in reservoir characterization and its success relies on not only the quality of recorded seismic data but also data processing and understanding of rock physical properties.

What is the Class I AVO response of sand?

When the gas sand has a thickness of 18m, the Class I AVO response is a peak at near offsets that dims with offset and then reverses polarity at far offsets. As the thickness is reduced, (Figure 11b) this Class I AVO anomaly becomes a completely different AVO response: a trough at near offsets becoming a peak at far offsets.