Expandable diverting agents to improve efficiency of refracturing treatments

The use of chemical diverters in refracturing operations has been increasing and taking the place of mechanical diverters, which were a prevailing technique for years. Chemical diverters consist of particles or liquid that can temporarily clog pre-existing fractures, allowing diversion of the fracturing fluid to create new fractures inside the reservoir and generate a more complex fracture network. The success or failure of a re-stimulation treatment largely depends on the diverter placement and effective isolation of previous fractures. In this work, we propose a novel class of materials as a diverting agent that after pumping into the formation expands to temporarily plug the existing fractures and allow the frac energy to concentrate on generating new fracture strands. Biodegradation and chemical dissolution can be utilized at the end of the treatment to resume the flow from isolated fractures. Proof-of-concept experiments were carried out using a particle-plugging apparatus to demonstrate the bridging ability of the expandable diverter. The fracture sealing process is observed with the steep increase in the fluid pressure. In order to further tune the performance of this diverter and simulate its performance in reservoir conditions, we developed a numerical model to simulate its placement and expansion. The coupled computational fluid dynamics-discrete element method approach can track the diverting particles individually and simulate the frac fluid flow within the fractures. Multiple scenarios were tested, with different particle sizes and networks of fractures.