Arrest Mechanisms of Buoyant Hydraulic Fractures

Hydraulic fracturing (HF) treatments can form widespread fractures. Understanding their containment at depth is critical, given the positive buoyancy contrast between the fracturing fluid and the surrounding rock, promoting upward growth. We study arrest mechanisms for established buoyant HF, restricting our investigation to fully planar fractures. We show that changes in the fracturing toughness (KIc) (E, and v remain unchanged) are inefficient in arresting buoyant HFs. A fracture size-dependent, apparent KIc can only prevent buoyant fractures from emerging but not stop their ascent. Sudden changes of KIc between layers need to be significant to arrest a buoyant HF KIc−2/KIc−1 ≥ 2 − 3. Contrary, a stress barrier efficiently arrests buoyant fractures for stress contrasts as little as Δσ ≥ 1.00 (MPa). We further demonstrate that the interaction with a high-leak-off layer is more efficient in arresting fracture ascent than an equivalent uniform leak-off value. Moderate to high leak-off arrests fractures before they become buoyant or without significant uprise. All considered arrest mechanisms can stop the propagation of a buoyant HF, implying that combining several mechanisms likely prevents buoyant HFs from reaching shallow formations or even the surface.