Study on High Temperature Resistant Gel System for Channeling Plugging in Heavy Oil Thermal Recovery Wells

Thermal recovery by steam injection is an effective development method for heavy oil reservoirs. However, the dominant channel of steam channeling generally appears in the late stage of multi-round steam stimulation, which often leads to low periodic oil-steam ratio and rapid production decline. In order to improve the efficiency of steam injection in heavy oil reservoirs, it is very important to block the steam channeling channel, and the channeling plugging system with high temperature resistance, long distance migration and long validity is the key to control the steam channeling problem. However, the inorganic channeling plugging system represented by ultrafine cement is difficult to migrate for a long distance, and the organic channeling plugging system represented by polymer gel is insufficient in temperature resistance. The existing technology is difficult to meet the channeling plugging requirements of heavy oil reservoirs. In this paper, a tannin gel system with high temperature resistance is constructed by using sulfonated tannin extract and environmentally friendly crosslinking agent as raw materials. The gelation time of this system at 150 ℃ is 4~6 h, and the final gelation strength is G~H grade, which can be applied to steam channel plugging. Based on the analysis of the experimental results of gelling performance and aging stability performance evaluation, the shut-in time of oil wells should be more than 24 h after the injection of channeling plugging system. The system can be considered as a channeling plugging slug in the transition zone to the far well zone of heavy oil thermal recovery wells. The laboratory sealing effect evaluation experiment shows that the breakthrough pressure gradient of the high temperature resistant gel system after gelation is 27.19 MPa/m, and the plugging rate is 96.78%, which has the field application potential of channeling plugging in heavy oil thermal recovery wells.