Improved upscaling and reservoir simulation of enhanced oil recovery processes in naturally fractured reservoirs
Abstract
Naturally fractured reservoirs (NFR) contain a significant amount of remaining
petroleum reserves and are now considered for Enhanced Oil Recovery (EOR)
schemes that involve three-phase flow such as water-alternating-gas (WAG) injection.
Accurate numerical simulation of flow in NFR is essential for sound
reservoir management decisions to maximise oil recovery and minimise the cost
of field development. In this thesis, two important issues related to flow simulation
in NFR are investigated. First, a step-wise upscaling approach is developed
to evaluate the accuracy of dual porosity models in estimating matrix-fracture
transfer duringWAG injection. It was found that the classical dual porosity models
generally overestimate recovery from matrix blocks. Hence, a double block
model was developed and extended to a multi-rate dual porosity (MRDP). The
multi-rate double block model showed significant improvements in matching detailed
fine grid simulations of three-phase matrix-fracture transfer. Second, the
accuracy of upscaling discrete fracture networks (DFN) is assessed and its impact
on history matching was investigated on a real fractured reservoir. A new
method to upscale the shape factors needed for MRDP models from DFN is presented.
This method is a notable step towards more accurate but still efficient
reservoir simulation in NFR.