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中文核心期刊

含水合物粉质黏土压裂成缝特征实验研究

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

  • 摘要: 水力压裂技术是一种重要的油气井增产、增注措施,已经广泛应用于页岩油气等非常规资源的商业开采中.目前对于粉质黏土水合物沉积物的水力压裂成缝能力尚不清楚.本文采用南海水合物沉积层的粉质黏土制备沉积物试样,并与实验室配制的粉细砂土沉积物对比,分析粉质黏土沉积物的水力成缝能力及主控因素.实验结果表明含水合物和冰的沉积物破裂压力较高,这与粉质黏土沉积物特殊的应力-应变特征和渗透性有关.当沉积物应变高于6%时, 试样强度迅速上升, 呈现应变强化的特征,对水力拉伸裂缝的扩展具有一定的阻碍作用. 粉质黏土沉积物粒径细小, 渗透性差,难以通过渗透作用传递压力, 提高了沉积层的破裂压力. 此外,粉质黏土水合物沉积层裂缝扩展存在明显延迟效应,说明裂缝扩展受到流体压力和热应力的共同影响. 适当延长注入时间,保持流体与沉积层充分接触, 会起到分解水合物、降低破裂压力的作用.该研究成果有利于深入理解水力裂缝在水合物沉积层中的扩展规律,对探索压裂技术在水合物沉积层开发中的应用具有重要意义.

     

    Abstract: 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.

     

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