Abstract:
Development of software that performs Gassmann’s fluid substitution, plot Petrophysical well log
and visualizes velocity changes involves writing a computer program using Csharp (C#)
programming language and windows form using object-oriented programming and Gassmann
algorithm. Gassmann relations are essentially used to perform fluid substitution and predict how
reservoir behaves in the presence of one fluid to another which cause velocity changes. In order to
model velocity changes, resulting from different fluid types and saturations, the bulk and shear
moduli of the rock at initial reservoir fluids conditions must be obtained. Subsequently, the bulk
and shear moduli must then be estimated for the drained porous rock frame. Once estimated, new
bulk and shear moduli are calculated using different fluid types and saturations. This research
work, attempts to remove the black box approach from fluid substitution and visualizes well log
data and velocity changes by providing a comprehensive understanding of Gassmann’s equation
and discuss the properties of the rock and the pore-filling fluids. Also discussed is the assumptions
involved in the derivation of Gassmann’s equation in order to understand its limitation and avoid
unrealistic results. Based on the equations and processes presented in this research work, a
computer program was developed to help users easily perform fluid substitutions, plot
petrophysical well log data and visualize the effects of fluid saturations on seismic velocities.
