水合物储层工程地质参数评价系统研发与功能验证

Development of engineering-geological parameters evaluation system for hydrate-bearing sediment and its functional verification

  • 摘要: 海洋天然气水合物储层的工程力学参数对准确评价水合物开采过程中的工程地质风险至关重要。静力触探和十字板剪切技术结合能够获得储层原位纵向连续性良好的工程力学参数,在天然气水合物开发工程-地质一体化探测与评价方面具有巨大潜力,但目前鲜见该系列技术在水合物勘查及试采中的应用。为了摸清天然气水合物储层的静力触探参数、十字板剪切参数响应规律及影响因素,进而为水合物储层工程地质特征现场评价提供依据,自主研发了天然气水合物储层工程地质参数评价试验系统。该系统能够开展含水合物沉积物五桥静力触探测试(锥尖阻力、侧摩阻力、孔隙水压力、电阻率、摄像),十字板剪切测试,并与电阻率层析成像测试结合,解释天然气水合物储层的工程地质参数响应机理。基于该系统分别针对砂土、粉砂质黏土沉积物(不含水合物)开展了功能验证性实验,并与南海神狐海域粉砂质黏土层的现场实测数据进行比对,结果证明试验数据重复性良好,试验结果与现场实测数据有可比性,系统可靠。该系统对于验证新型水合物开发工程-地质参数一体化探测技术提供了基础平台。

     

    Abstract: Engineering-geological parameters are crucial for evaluation of geohazard potential in marine hydrate exploitation. The combination of piezocone penetration and vane shear test may help gain longitudinally continuous and reliable parameters for hydrate reservoir, which has great perspective in integrated engineering and geological field survey. However, application of these techniques to marine hydrate survey has remained vacant so far. To better understand the penetration or shearing behaviors and their influencing factors in hydrate-bearing sediment (HBS), we developed a novel engineering-geological parameters evaluation system, which may satisfy the need of five-bridge piezocone penetration test and vane shear test. The tip resistance, side frictional resistance, excess pore pressure, electrical resistance, and video along the penetration path could be obtained through five-bridge piezocone penetration test. The method of electrical resistivity tomography is firstly combined with piezocone penetration and vane shear technology in this system to explain the relationships between engineering geological parameters and hydrate saturation. The sandy sediment and clayey-silt sediment (free of hydrate) are involved to verify the functions of the system. The results show favorable fitness with the field-obtained data. Repeated experiments show high reproducibility of the data. This system proved the possibility of establishing quantitative evaluation models of engineering geological parameters in HBS, and also provided a basic platform for novel probing device test in the integrative engineering-and-geological hydrate survey.

     

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