Modelling of gas injection with constant pressure boundaries

Liu, Xiaolong (2013) Modelling of gas injection with constant pressure boundaries. Masters thesis, Memorial University of Newfoundland.

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Abstract

Gas injection is one of the most widely applied enhanced oil recovery methods. Existing analytical solutions to gas injection processes are based on the standard fractional flow assumption of a constant flow rate. Realistically, most reservoirs are operated with constant injection and production pressures where the total volumetric flux varies with time. An analytical model for the gas injection process with constant pressure boundaries and a numerical compositional model are developed in this thesis. By using the standard fractional flow analysis, the Riemann problem associated with the ternary gas injection process is solved. Based on the solution of the eigenvalue and elementary waves, the time dependent total flux, pressure distribution, and saturation profile with constant pressure boundaries are directly calculated by applying the approach developed by Johansen and James (2012). The analysis of the ternary gas injection problem provides the fundamental method for systems with higher numbers of components. -- The solution from the two-dimensional numerical model interprets the effects from the component property and heterogeneity in the reservoir to the displacement performance. The analytical solution is compared with the numerical solution. It shows that the grid block refinement plays a significant role in the behaviour of the numerical solution. By studying both the analytical and numerical methods, agreement and disparity of solutions between the two approaches can be investigated.

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