Development of the method for evaluation of subusurface fracture permeability by the multiplet-clustering analysis

开展了太阳面裂缝渗透率评价方法的开发研究。我采用了评价渗透性的方法。在之前研究结果的基础上，我提出了通过多重聚类分析确定的源位置时移分布，可以估计流体的流动方向和渗透性裂缝系统的生长过程。我还利用法国Soultz HDR油田的诱发声发射数据，揭示了地热储层水力压裂过程中裂缝的压力梯度和临界孔隙压力可以通过构造应力场与裂缝方向和声发射源位置时距分布的整合来估算。我还表明，由于事件的数量不足，并且源没有分布在整个储层，因此很难估计压力传播的速度。另一方面，我证明了可以通过细化地震矩释放的增加速率和震源面积的增加速率来评价储层中流体的流动程度。研究了地下裂缝的动态行为，其中识别类似微地震（多波组）的频带与多波组震源位置所描绘的结构之间的关系。在此基础上，提出了利用多重聚类分析方法在精确确定源位置的基础上对地热储层裂缝渗透率进行评价的方法，并揭示了评价的局限性。

I have carried out the research for the development of the method to evaluate the permeability of sunsurface fracture. I have taken form the method for the evaluation of permeability. On the basis of the results which obtained through the research before, I have shown that it is possible to estimate the direction of fluid flow and the growing process of permeable fracture system by the time lapse distribution of source location determined by the multiplet-clustering analysis. I have also revealed that the pressure gradient as well as the critical pore-pressure of fractures during the hydraulic stimulation of geothermal reservoir can be estimated by the integration of the tectonic stress field and the fracture orientation and the time lapse distribution of AE source location, where I used the induced AE data at the Soultz HDR field in France. I have also shown that it is difficult to estimate the velocity of pressure propagation because the number of events is insufficient number and the source does not distribute all over the reservoir. On the other hand, I have demonstrated that the degree of fluid flow in the reservoir can be evaluated by refining the increasing rate of seismic moment release and the increasing rate of source area. The dynamic behavior of subsurface fracture was also examined, where the relationship between the frequency band for identifying similar microearthquakes (multiplet) and the structures delineated by the source location of multiplet.As the results, I have developed the procedure to evaluate the fracture permeability in the geothermal reservoir on the basis of the precisely determined source location by the multiplet-clustering analysis, and also revealed the restriction on the evaluation.