Experimental investigation on improving sweep efficiency through temperature-resistant gel foam in heavy oil reservoirs

As global demand for crude oil increases, the problem of steam channeling faced in the thermal recovery of heavy oil reservoirs seriously affects the oil recovery and operation cost. Due to the limitations of profile control in traditional foams, the aim of this experimental investigation is to develop a high-temperature-resistant gel foam system to plug steam channeling paths. Gel foam can compensate for the defect of poor thermal stability in single-component foam, and shows great potential in oil reservoir development. This paper mainly expounds that the gel foam system (0.5 wt% foaming agent AOS + 0.5 wt% polymer HPAM + 0.4 wt% crosslinker PE + 0.5 wt% stabilizer), as a profile control agent for improving the recovery, has better performance than the single foaming agent AOS. Through the experiments on the foam volume and the half - life of liquid separation, the foaming agent AOS has the highest foam complex index both at room temperature and under the high temperature condition of 200 °C. Subsequently, AOS is selected to be compounded with the gel, and the formula of the gel foam system with good gel - forming performance is determined: 0.5 wt% AOS +0.5 wt% HPAM +0.4 wt% PE + 0.5 wt% stabilizer. In the profile control experiment, when the gas-liquid ratio is 1:1, the addition of AOS to the gel can increase its resistance factor by 14 times, which confirms that compared with AOS, this system can effectively block the high - permeability dominant channels and improve the sweep volume, demonstrating great potential for enhancing oil recovery. Moreover, after the gel foam system is aged at 200 °C for 48 h and then subsequent water flooding of 15 PV is carried out, the plugging rate of the gel foam system is still as high as 86.4 %, which also indicates that this system can carry out long - term and effective profile control. Moreover, the heavy oil recovery of the gel foam slug is 6.3 % higher than that of the AOS slug. Therefore, as a profile control agent for improving the sweep efficiency, the gel foam system has greater advantages than AOS profile control.