Hydraulic Fracture Propagation in Three Meter-Scale Reconstituted Tight Conglomerate Specimens Under Different Formulation Conditions

A tight conglomerate is mechanically heterogeneous because gravel particles, the matrix, and their contacts can perturb hydraulic-fracture paths. This study presents an exploratory comparison of three 2.0 m × 2.0 m × 1.0 m reconstituted conglomerate specimens, identified as specimen 97 (Condition A), specimen 98 (Condition B), and specimen 99 (Condition C). One meter-scale specimen was tested under each formulation condition using the same applied boundary stresses, nominal pumping rate, and fluid viscosity. Post-fracturing surface observations, inlet-pressure histories, and laboratory acoustic-emission (AE) event locations were examined. After event-quality control, DBSCAN-based spatial filtering was performed in Z-score-standardized coordinates, and three-dimensional alpha shapes were constructed from the retained event coordinates in meters to calculate geometric AE-event-envelope volumes. The external surface-fracture traces were more spatially distributed in specimen 97 and more localized in specimen 99. The available DBSCAN–alpha-shape calculation outputs yielded geometric AE-event-envelope volumes of 0.2832, 0.2460, and 0.0937 m3 for specimens 97, 98, and 99, respectively. Because only one specimen was tested under each condition, the specimen formulations and gravel characteristics were not identical, the gravel–matrix interfacial properties were not measured directly, and the pumping histories differed, the observations were interpreted as descriptive case differences rather than as a statistically validated single-factor relationship.