Seismic data can provide not only structural information but also rock property information like P and S velocity, porosity, fluid saturation, etc. Amplitude corresponds to the dynamic feature of seismic data and its behavior with respect to incidence angle (AVA) or offset gives information about both the fluid type and fluid saturation in the rock Chen and Sidney (1997); Ostrander (1984).
Velocity, another rock property, is a key factor not only for the rock property estimation but also for the final image in the seismic processing step. Different sources of velocity information (well data, seismic data) yield different velocity values, partly because of the frequency dependence of this rock property (scale effect). A connection between the different velocity values is a key factor for reservoir characterization studies.
This paper presents a study of the effect of pore fluid type on seismic data, and an analysis of the differences between seismic and well velocities. This study is based on the information of well data only; in order to achieve our goal, a three dimensional interpolation of the well data is required.
Geostatistics is a field which has many algorithms for handling the 3D interpolation problem. Kriging is a technique which is very useful, especially when dealing with sparsely sampled data, such as wells in 3D. In this project, an ordinary kriging operator is applied to the well data White (1998).
This work intends to give not only relations between pore fluids and seismic data but also compares well velocities and seismic velocities based on well data interpolation and 2D seismic modeling. The use of Gassmann's equation for fluid substitution (brineoil, brinegas) will help to study the fluid saturation effects. Seismic modeling over the sections after and before fluid substitution shows AVO differences due to the pore fluid. A second seismic modeling is done for velocity analysis purposes, this velocity analysis presents differences between seismic and well velocities.