Experimental Study on Temporary Plugging and Unblocking Performance of Water-Soluble Preformed Gel for Specific Shale Reservoirs

Abstract

Shale gas reservoirs usually have well-developed fractures and joints, and the fracturing development process is prone to forming complex fracture networks near the wellbore, which is not conducive to the effective migration and efficient development of shale gas. The development of temporary plugging agents related to shale fracturing reservoir transformation is a key technology to solve this problem in the shale gas development process. Therefore, a water-soluble preformed gel temporary plugging agent was developed, and its expansion/swelling characteristics and temporary plugging performance were analyzed through experiments. At the same time, experimental evaluation was conducted on its unblocking performance. Research has found that although there are differences in the swelling rate of temporary plugging agents at different stages, they gradually increase during plugging operations. The volume of the temporary plugging agent expanded nearly 8.24 times throughout the entire experimental process. In addition, temporary plugging agents can temporarily seal micro fractures and rapidly expand hydraulic fractures, thereby significantly improving shale gas recovery rate. The shale gas recovery rate when temporary plugging agents are used in fracturing operations is about 12.3% higher than when temporary plugging agents are not used. In addition, the increase in working fluid temperature and the concentration of surfactants will mostly stimulate the activity of water molecules, thereby stimulating the hydrolysis of temporary blocking agents in microcracks. Taking into account the development cost and efficiency, it is reasonable to control the temperature of the working fluid and the concentration of surfactant during the unblocking process after the fracturing operation between 110-140°C and 0.75 g/m3, respectively. In order to provide technical support and design basis for the efficient development of shale gas through this study.