Investigating Thermally Assisted Gas-Oil Gravity Drainage Process in Heavy-Oil Fractured Carbonate Reservoirs-Phase 1

Heavy oil contained in naturally fractured reservoirs is an important resource of oil reserves. However, maximizing recovery from such reservoirs is problematic due to the low flow rate of oil in the later part of field life. Before the 1980s it was believed that when steam was injected into fractured reservoirs it would result in very early steam breakthrough through the connected fractures. Consequently, the oil would not be recovered. However, the results of experimental tests, theoretical analysis and field pilots, published in the literature since the early 1980s, have shown the economic potential of steam injection for the recovery of heavy oil in naturally fractured reservoirs. One EOR method that is of particular interest is Thermally Assisted Gas-Oil Gravity Drainage (TA-GOGD). In this process, steam is injected into the reservoir. This heats the rock matrix blocks through the higher permeability fracture network and improves oil recovery principally by reducing the oil viscosity and thus increasing the rate of gravity drainage through the matrix. The process of recovery is complex as not only drainage is important but also the effect of steam on the reservoir properties and fluids complicate the modelling of the process and make it harder to interpret the results.