Characteristics of Propped Fracture Propagation in Volcanic Clastic Reservoirs: A Multiscale Study of Conductivity Sustainability and Fracture Network Complexity
摘要
Hydraulic fracturing in heterogeneous volcanic breccia reservoirs faces critical challenges in optimizing proppant placement and fracture networks. This study systematically investigates proppant transport dynamics and conductivity evolution in Carboniferous volcanic reservoirs of the Junggar Basin through integrated triaxial experiments, CT imaging, and fractal analysis. Experimental results demonstrate that conventional proppants (100–200 mesh) maximize primary fracture conductivity (3.2 × higher than micro-proppants at 30 MPa) but fail to prop 62% of secondary fractures due to aperture constraints (< 0.2 mm). Conversely, micro-proppants (300–500 mesh) enhance fracture complexity via microfracture infiltration yet exhibit 55% lower absolute conductivity. Fracture tortuosity induces 18–24% aperture reduction under closure stress (> 40 MPa) via proppant embedment and gravel-induced strain incompatibility, with high-strength gravels promoting bypass-dominated networks and low-strength gravels enabling intra-granular branching. Micro-proppants demonstrate superior sustainability, maintaining 48-h conductivity versus 31 h for conventional systems through self-propping mechanisms. This work establishes a predictive framework for proppant optimization in volcanic reservoirs, advocating engineered gradation strategies to balance conductivity and fracture complexity. The findings redefine proppant selection criteria for conglomerate-bearing formations, offering transformative insights for enhancing stimulated reservoir volume in tight oil systems.
Highlights Summarise the settlement patterns of different proppants near gravels with varying strengths and contents. Novel mechanistic into stress-driven closure via fracture tortuosity analysis. Validation of micro-proppant self-propping enabling secondary fracture preservation.