Complex Fracture Networks Prohibit Safe Fracturing Fluid Recovery

ABSTRACT The recovery of fracturing fluid (HF), necessary for subsurface energy production and carbon storage, is generally low, raising concerns about HF fate in the subsurface and its potential to contaminate water aquifers. This study examines the migration of fracturing fluid and tracks its distribution in fractured reservoirs using a two‐dimensional finite element model that accommodates multi‐phase and multi‐component flow. The influence of fracture network complexity and its temporal evolution—driven by pressure changes—on fracturing fluid recovery is assessed. Results indicate that increasing network complexity leads to greater fluid loss into the formation. Furthermore, the relationship between subsurface permeability structure and recovery is complex; recovery rates increase with the permeability of faults but decrease as the permeability of the layers surrounding the HF zone increases. The research also underscores the significant role of pressure‐dependency of permeability, particularly how fractures and cracks behave during high‐pressure injection and subsequent release, in influencing flow‐back recovery. These fractures and cracks typically open under high pressure and may close or only partially reopen once the pressure decreases, trapping the fluid. This phenomenon helps explain the commonly observed low fluid recovery rates. Additionally, the study finds that the time required for trapped fracking fluid to migrate to nearby aquifers ranges from a few months to hundreds of years, emphasizing the need to consider the long‐term impacts of hydraulic fracturing practices. The associated environmental risks may take several years to become apparent or detectable.