Unravelling fracture plugging behavior of granular temporary plugging agents for a sustainable geothermal development

Geothermal energy is vital for the global energy transition due to its sustainability and low environmental impact. Hydraulic fracturing is key to using unconventional underground energy, and temporary plugging and diverting fracturing (TPDF) is a promising avenue for hydraulic fracturing due to its high energy extraction efficiency. A major challenge in TPDF is forming a strong fracture plugging zone using temporary plugging agents (TPAs). However, the plugging behavior of TPAs and how they handle pressure in changing fracture widths are poorly understood. This research aims to provide effective experimental and theoretical support for the field application of TPDF technology in the development of geothermal energy. To address this, we developed a dynamic fracture width plugging simulation device to model the dynamic fracture plugging process accurately. By analyzing pressure, fracture displacement curves, and plugging zone structures from experiments, we gained insights into the failure mechanisms of the plugging zone and the behavior of dynamic fractures. Our results show three stages in the formation process of dynamic fracture plugging zones: transport, bridging, and plugging. Ineffective plugging in dynamic fractures includes “mouth sealing,” ineffective bridging, inadequate accumulation and filling, and weak mechanical strength. Plugging zone failures are categorized as local structural failure and overall structural failure. Improving the pressure-bearing capacity of dynamic fracture plugging zones can be achieved by optimizing the particle size distribution and concentration of TPAs, and by choosing the right TPA type and carrier fluid injection rate. These findings provide a basis for the optimization and design of TPDF technology, which is vital for geothermal energy extraction.