Coupling mechanism of volume strain and water level in the Fuxin well located in a geothermal area before and after the 2011 Mw 9.1 Tohoku earthquake
Coupling mechanism of volume strain and water level in the Fuxin well located in a geothermal area before and after the 2011 Mw 9.1 Tohoku earthquake
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DOI：
10.13168/agg.2016.0028
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发表时间：
2016-09
影响因子：
0.9
通讯作者：
Yan Zhang
中科院分区：
文献类型：
--
作者：
Yan Zhang
根据以前报告的观测结果，低频（~0.01-500 Hz）地震波可以提高渗透性并改变孔隙压力分布，这反过来又会提高地热能/石油产量。为了量化低频动应力刺激对多孔介质中流体流动和原位孔隙压力变化的影响，在远场Mw9.1东北大地震前后在阜新井（位于中国东北的地热区）进行了观测。这样做可以获得地震引起的应力、应变、含水层特性和流体流动参数的精确测量值。我们应用潮汐分析的体积应变和水位数据的井。结果表明，中心频率为0.02 Hz的远震波对含水层的不排水孔隙弹性参数几乎没有影响，表明远震波虽然能增强含水层的渗透性，引起孔隙压力的传递，但不能直接引起含水层介质的破坏。结合同震振幅变化的位相、标志以及体应变和水位的同震和震后变化图象，得到体应变变化与水位变化的耦合机制：震前，潮汐体应变引起水位变化（水位位相滞后于体应变位相）。相比之下，地震时，远震波使渗透率增强，水位（孔隙压力）由高压区向阜新井传递，引起体应变的膨胀（相移急剧增大，表明水位的变化与体应变的变化相吻合）。最后，在地震后的短时间内，水位和体应变相互作用，并不断变化（相移接近0°）。产品信息
According to previously reported observations, low-frequency (~0.01–500 Hz) seismic waves can enhance permeability and alter the distribution of pore pressure, which in turn, enhance geothermal energy/oil production. To quantify the effects of low-frequency, dynamic stress stimulation on fluid flow and in-situ pore pressure variations in porous media, observations were conducted in the Fuxin well (located in a geothermal area in north-eastern China), before and after the far-field Mw 9.1 Tohoku huge earthquake. In doing so, precise measurements of earthquake-induced stress, strain, aquifer characteristics and fluid flow parameters could be obtained. We apply tidal analysis to the volumetric strain and water level data of the well. We demonstrate that the tele-seismic waves with a central frequency of 0.02 Hz hardly had an impact on the undrained poroelastic parameters of the aquifer, indicating that the tele-seismic waves cannot induce the disruption of the aquifer medium directly, although it can easily enhance permeability and induce the transfer of pore pressure in the aquifer. Together with the phases, the signs of the co-seismic amplitude change as well as the co-seismic and post-seismic patterns of volumetric strain and water level, we obtain the coupling mechanism of the volume strain change and the water level change: Before the earthquake, tidal volumetric strain induced the change of water level (the phase of the water level lagged behind that of the volume strain). In comparison, during the earthquake, the permeability enhanced by tele-seismic waves, water level (pore pressure) transferred from high pressure region to the Fuxin well, and induced the dilatation of volume strain (phase shifts increased sharply, indicating the change of water level caught up with that of volume strain). Finally, during the short time span after the earthquake, the water level and volumetric strain interacted with each other and changed consistently (phase shifts approach 0°). ARTICLE INFO