混积岩微观力学非均质性及其对裂缝扩展机制的控制作用OA

Diamictite is widely distributed in unconventional oil and gas enrichment zones such as continental lake basins and marine shelves.Its meso-mechanical behavior and spatial heterogeneity serve as important basis for reservoir mechanical evaluation,fracture morphological interpretation,and stimulation effectiveness assessment.To reveal the micro-scale mechanical heterogeneity of diamictite and its control on fracture propagation,this paper systematically measures the elastic modulus,hardness,fracture toughness,and energy parameters of various mineral phases through nanoindentation array tests,together with XRD and SEM-EDS mineral identification,and then characterizes their spatial distribution patterns through two-dimensional interpolation reconstruction and statistical analysis.In addition,the influence of meso-mechanical differences of diamictite on fracture initiation and propagation pathways is discussed.The following results are obtained.First,rigid minerals such as quartz exhibit high modulus,hardness and elastic energy storage capacity,whereas clay minerals and some carbonate minerals show low modulus and significant plastic energy dissipation.Second,parameter-field reconstruction indicates that the high-value zones of elastic modulus,hardness and fracture toughness commonly form rigid clusters,the high-value zones of plastic energy occur mainly as banded weak zones,and those of fracture energy are concentrated at strong-weak boundaries or parameter-gradient areas.Third,the fracture propagation in diamictite is jointly controlled by the energy storage in rigid clusters,the energy dissipation in weak bands,and the cracking sensitivity in transition zones.When weak high-plasticity bands are distributed in the continuous or semi-continuous strip pattern,fractures tend to deflect along low-rigidity and high-energy dissipation zones,and branch at strong-weak boundaries,exhibiting the trend of developing into complex networks.When rigid clusters with high elastic modulus,hardness and fracture toughness are continuous and weak bands are discontinuous,the load transfer paths are relatively stable,and the main fracture is more likely to propagate continuously.In conclusion,these findings reveal the causal chain from mineral heterogeneity to fracture propagation pattern,providing a meso-scale reference for mechanical evaluation,interval selection,and fracturing parameter optimization of diamictite reservoirs.