Combining geophysical data with a mathematical model to describe vertical two-phase flow

Abstract

This thesis combines a geological model with a mathematical model to describe the vertical propagation of a gas plume through layers with different physical properties. The geological model is based on geophysical data from the Sørvestsnaget Basin and the mathematical model is derived based on the classical Buckley-Leverett theory for two-phase flow. The model estimates the velocity of a vertical propagating plume based fluid and rock properties. Two different cases are displayed using the model. The first case evaluates how the plume propagates in a homogenous layer and the second case looks at how the plume behaves when crossing a horizontal interface between two different lithologies. For the first case, the model predicts that the plume evolution consists of three stages. The different stages can be characterised by a different amount of shock and rarefaction waves propagating with different velocities. The model also shows that changing the fluid and rock properties does not change the evolution of the plume. However, the time taken for it to reach the different stages changes significantly. For the second case the model predicts that gas accumulation will occur beneath a boundary if the permeability and porosity above it is not sufficient enough to support the gas flow from the layer below. This results in the formation of two shockwaves travelling in opposite directions with different velocities.