Research on the Law of Crack Propagation in Oil Well Fracturing Process

Abstract

In the field of oilfield fracturing development, a profound understanding of the evolution and propagation of damage during the fracturing process is crucial for preventing well water coning and channeling. This study aimed to unravel the complexity of damage evolution during fracturing and elucidate the causes of well water flooding phenomena. To accurately describe the damage propagation laws, a damage constitutive model considering compaction and post-peak correction parameters was established in this research. The model, through parameter adjustment, enhances the precision of stress calculation during the rock compaction phase and accounts for the stress degradation pattern subsequent to damage. This model was applied to simulate the damage evolution under various conditions in oil layer profiles and wellbore cross-sections, including the impact of different perforation angles, natural fracture patterns, and the ratio of longitudinal to transverse boundary pressures. The research concludes that well water channeling and flooding are primarily caused by damage propagation and the connectivity with adjacent water-bearing formations. The proposed rock damage constitutive model demonstrated an accuracy improvement of more than 3% compared to previous studies. Additionally, the study discovered that when the angle between the perforation section and the formation exceeds 30°, the risk of fracture propagation into adjacent layers increases, leading to an elevated risk of post-fracturing water flooding. The presence of natural fractures in the oil layer provides a conduit for damage propagation, accelerating the process of damage in the oil layer. Furthermore, the perforation angle and the ratio of boundary pressure loads during the fracturing process were identified as the main factors influencing the direction change of fracture propagation. The conclusions drawn from this study provide a scientific basis for preventing post-fracturing water channeling and flooding issues and offer new perspectives for the development of well fracturing technology, aiding in the resolution of water flooding problems associated with well fracturing.