Master Thesis defense by Rasmus Juncher – Niels Bohr Institute - University of Copenhagen

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Master Thesis defense by Rasmus Juncher

Seismic amplitude reflections- A litterature study in AVO analysis


Abstract:
In the intensive search for hydrocarbons around the world, amplitude versus offset (AVO) analysis plays a crucial part of the seismic exploration done by oil and gas companies. In a business where enormous sums are at risk, AVO analysis can be a tool to minimize the cost of an exploration.
AVO is a geophysical technique that assesses variation of the seismic reflection amplitude by changes in the distance (angle) between transmitter and receiver. The analysis of the AVO allows the interpreter to assess rock properties such as density, porosity and fluid content amongst others.
The theory for this analysis is rather complex. Knott (1899) and Zoeppritz (1919) carried out the theoretical background, where they developed the equations necessary for the AVO. Given the P- and S-wave velocities and the densities of two media at each side at an interface of two half spaces, they developed equations for the reflection amplitude as a function of the incident angle. But these equations are of very little physical understanding, so several approximations to these Zoeppritz equations have been developed.
This thesis presents the most prominent and widely used approximations, from Aki and Richards (1980) over Shuey (1985) to Gray et al. (1995), each with different assumptions and advantages. These approximations form the basis of the different Hydrocarbon Indicators (HCI). A common literature example shows how the theory is implemented into real data.
Supervisor: Klaus Mosegaard