Fire-flooding Technologies in Post-Steam-Injected Heavy Oil Reservior:A Successful Example of CNPC

Abstract Steam injection is an effective technology for heavy oil development. With the increasing of the recovery percent, the technical effectiveness and economic efficiency of continuous steam injection will substantially decline. Therefore the fire- flooding can be considered as a follow up EOR technology in these steam-injected reservoir. Because of the complicated secondary water and steam channels distribution, fire flooding in post steam injected reservoir is far different from that in original reservoir. In this paper, the mechanism and problems associated with development engineering of fire flooding in post steam injected heavy oil reservoir was studied systematically by using 1D&3D physical simulation systems and reservoir numerical simulator. The temperature of combustion zone decreased and high temperature zone enlarged because there existed secondary water formed during steam injection which could absorb and carry heat towards producers out of combustion front during fire flooding, but high saturation of water in layer caused by secondary water had less influence on the quantity of fuel deposit and air consumption. There is a living example of fire-flooding in post-steam-injected heavy oil reservoir in Xinjiang oil field of CNPC, and it is the first major pilot of fire-flooding in this kind of reservoir, namely H1 Block Fire-flooding Pilot. H1 Block had been steam- injected for more than 10 years and oil recovery factor had nearly reached 30%. Before fire-flooding test, the reservoir had been abandoned for many years. In this paper, the fire-flooding model, well pattern, well spacing, and air injection rate was optimized based on the reservoir property and the existed well pattern in H1 Block, and the key techniques of ignition, lifting, and anticorrosion was also selected in the same time. The H1 Block Fire-flooding Pilot was carried out in the late of 2009. Up to now, more than 30 wells produced oil, 16 of them produced stably. The daily oil production increased from nearly 0 to 48t/d, water cup decreased from nearly 100% to 60%, and AOR decreased from more than 5000Sm3/m3 in the beginning to 2200 Sm3/m3 by far. The forecasted ultimate recovery factor will reach 65%.