天然气水合物是突破世界能源瓶颈的重要潜在能源,广泛分布于深海沉积物和陆域永冻土.水合物赋存在高压低温环境下,储层厚度达数十至百米,大尺度储层重力场显著影响其开采时的液气渗流、储层变形和传热过程,进而影响开采产气效率且可能诱发工程灾变.研发了一套能够在超重力场下模拟大尺度水合物储层长历时开采演变过程的离心模型试验装置,主要由高压釜系统、水合物制备模块、水压力控制模块、水合物开采模块、监测与响应模块组成.该装置能够在100g超重力下伺服调控高压釜内气液压力和温度环境,在模型尺度上有效再现水合物储层应力、温度和荷载条件.在系统介绍装置研发思路和技术特色的基础上,通过100g下水合物储层模型降压分解试验探析了原位等效重力场下储层不同深度处孔压演化规律及开采产气特性,再现了Nankai海槽原位试采产气速率峰值模式,为揭示水合物储层开采相变多相多场耦合机制和灾变防控提供了新的研究手段.
The natural gas hydrate,widely distributed in deep sea sediment and terrestrial permafrost,is considered as an important potential energy to solve the increasingly serious energy crisis.Hydrate is formed under high pressure and low temperature conditions,where the reservoir is tens of meters in thickness.The gravity field of large-scale reservoir significantly affects the process of fluid seepage,skeleton deformation and heat transfer during exploitation,changing the gas production rate and further inducing possible engineering disasters.An in-flight centrifuge apparatus,which is composed of high-pressure vessel,hydrate synthesis module,water pressure control module,hydrate exploitation module and monitoring module,for modelling hydrate exploitation is developed.The apparatus can servo control the pressure and temperature conditions in the high-pressure vessel under 100g hyper gravity,and effectively reproduce the stress,temperature and loading conditions of hydrate reservoir in the model scale.A hydrate exploitation modelling test via depressurization at 100g is then carried out.The evolution of pore pressure at different depths and the gas production characteristics under the field scale stress gradient are analyzed,and the gas production characteristics of field production tests in Nankai trough are reproduced.The developed apparatus provides a novel experimental approach to investigate the multiphase coupling mechanics and disasters prevention during hydrate exploitation.