Abstract

Today, most unconventional reservoir simulations are performed within a single-porosity framework. Very fine, high permeability gridblocks are used to represent the discrete fractures. Geometric spacing of blocks away from the fractures is necessary to capture the pressure gradients and simultaneously keep the number of gridblocks manageable. Without further subgridding the effects of desorption, diffusion, and transport through macro- and micro- fractures must be lumped resulting in a possible loss of transient fidelity. Yet these processes readily lend themselves to analysis with additional porosity types where the transport sequence can be preserved and studied. In this paper, we use a full production simulator to explore the advantages and disadvantages of simulating unconventional reservoirs with one-, two-, three-, and four-porosity systems. Kerogen, macro-fractures, micro-fractures, and an inorganic matrix are represented directly in the four-porosity system.

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