EXPERIMENTAL STUDIES ON THE PROPAGATION CHARACTERISTICS OF HYDRAULIC FRACTURE IN CLAY HYDRATE SEDIMENT

Hydraulic fracturing technology is an important oil and gas well stimulation measure, which has been widely used in commercial development of unconventional resources such as shale oil and gas. The propagation characteristics of hydraulic fracture is not well known in hydrate sediment. In this study, the hydrate sediment samples are prepared, and the influencing factors are analyzed. The experimental results show that the breakdown pressure of hydrate sediment sample and hydrate-ice sediment sample is much larger, which is related to the special stress-strain characteristics and water permeability. When the strain of silty sediment is higher than 6%, the strength rises rapidly to present the characteristics of strain hardening. It has a certain hindrance to the expansion of hydraulic tensile fractures. The silty sediment is composed of small particle and characterized by poor permeability. It is difficult for water to rapidly transfer pressure, thereby increasing the breakdown pressure. In addition, there is a significant delay effect on the fracture propagation of silty sediment sample, indicating that the fractures extend under the combined action of fluid pressure and thermal stress. Extending the injection time contributes to heating and decomposing the hydration. The research results are helpful for understanding the propagation law of hydraulic fractures in hydrate sediments. It is of great significance to explore the application of fracturing technology in the development of hydrate sediments.