Fractured Core Fabrication Method with Controllable Oil Phase Permeability and its Application

The representativeness of the core is a key issue in experimental simulation. In this study, a novel method for manufacturing artificial fractured cores with a certain oil phase effective permeability was proposed. Twenty-four matrix cores with low permeability were fractured applying the new method, and four cores were selected randomly to test the effective permeability of fractured cores under irreducible water saturation and confining pressure to confirm the robustness of the method. Then fractured cores were combined into two long cores with average permeabilities of 106.5 and 7.9 mD for exploitation experiments. In flooding experiments, water flooding had a larger displacement pressure difference than gas flooding. Compared with water, gas is easier to flow in porous media and gas breakthrough (BT) occurred earlier. After breakthrough, the growth rate of oil recovery decreased in all flooding experiments and the gas–oil ratio increased rapidly in gas flooding experiments like associated gas flooding, water alternating gas (WAG) and pulse gas injection. The high-permeability core had a larger oil recovery than low-permeability core in depletion, water flooding and gas flooding experiments. The most suitable recovery methods for high-permeability long core and low-permeability long core were, respectively, WAG and pulse gas injection, with oil recoveries of 63.33 and 64.3%. For gas or water flooding process in fractured reservoir, the flooding agents can easily channeling through the fracture; thus, the key issue for fractured reservoir exploitation is to put off breakthrough to enlarge sweep efficiency.