Plugging Method for HDR Reservoir Using Hydrothermal Processing of Smectite Clays to Improve Recoverry Efficient

Abstract

Recent progress in geothermal technology enables us to explore the hot dry rock (HDR) as a promising massive energy source. Viscous gelation through hydrothermal processing of the smectite clays has proved to facilitate water control of flowing and plugging in the HDR fracture network. Utility of the hectorite and saponite agents prepared to comprise the individual smectite raw components in low concentrated slurry has been confirmed by water control test with the simulator of a flow type autoclave equipment. The flow path between the granite fragments in the reactor tube is successfully plugged with in situ formed hectorite gel when the low concentrated (more than 2%) slurry is consecutively injected ino the reactor heated at 200 and 250?C. Effective plugging is adequately endurable for more than 30 days when the relatively higher concentrated 6% slurry is processed. The saponite agent also reveals endurable plugging for more than 10 days when the 3% slurry is processed at 300?C. The montmorllonite agent is not useful for effective plugging because of its lesser viscous gelation when hydrothermally processed. Among them the hectorite agent is so functional in quality of plugging and endurance that it could make easier fundamental design of the HDR system, e.g., temporary or eterrnal blocking of the minute fractures in the HDR reservoir could prevent water leakage and therefore improve the recovery of the circulating water.