Use of CO2 as Solvent during Steam-Over-Solvent Injection in Fractured Reservoirs (SOS-FR) Method for Heavy Oil Recovery

摘要

Due to low efficiencies and the high cost of individual injection of steam and solvent for heavy-oil recovery, their hybrid applications have gained significant attention recently. Although numerous laboratory studies exist and there are a considerable number of field projects for sandstone environments, fractured carbonates lack technologies to drain matrix oil efficiently. An alternative methodical injection of solvent and steam was proposed and tested earlier (Babadagli and Al- Bahlani, 2008). This process applies steam initially to condition the matrix oil for succeeding solvent injection and injection of steam to retrieve solvent in the matrix and to recover additional upgraded oil. In this application, hydrocarbon solvents were tested. The present study uses CO2 as a solvent in this type of application. To clarify the physics of the process and to test the applicability of the method for different reservoir and injection conditions, we conducted a series of experiments by first injecting steam, followed by CO2 injection. In the third cycle, steam was injected again to produce upgraded oil in the matrix. The experiments were performed under static conditions (soaking sand and carbonates samples into steam or CO2 chambers) at different temperatures and pressures to determine optimal application conditions for mutual goals: heavy oil recovery and CO2 storage in the matrix.