Seismic wave attenuation can potentially be used for the investigation of the fluid phase and flow properties in a fractured reservoir. However, seismic attenuation estimation is easily affected by various factors, such as tuning effects, source and receiver coupling, and effects from near-surface weathering layers. Time-lapse seismic attenuation estimation can avoid these problems because the above factors are canceled between surveys. We conducted time-lapse attenuation estimation using three reflection seismic surveys with different timings acquired in the Kakkonda geothermal field during a 12-day period spanning a well shut-in period. To investigate geothermal fluid changes associated with increased pore pressure, we propose an approach for estimating attenuation changes between time-lapse seismic surveys. Firstly, three seismic reflection sections were obtained from the corresponding time-lapse seismic data using the modified prestack time migration method, which can handle the uncertainties of migration velocity estimation in a highly fractured and structurally very complex medium, for which accurate velocity estimation is difficult to achieve using conventional methods. Then, time-lapse attenuation was evaluated for two of the three seismic reflection sections using the spectral ratio and the centroid frequency shift methods. Numerical modeling was conducted to verify our proposed procedure. Careful preprocessing was carried out to enhance the repeatability of time-lapse seismic data, especially on the frequency content, which is indirectly related to seismic attenuation. Finally, we demonstrated an increase of attenuation associated with an increase of pore pressure in and around the known super-shallow vapor-dominated reservoir during a short period (7 days) spanning from one day before the shut-in of producing well to a week after that. A possible cause of this short-period attenuation increase could be the vapor-liquid phase transition in the reservoir.

地震波衰减可潜在地用于研究裂缝性储层中的流体相和流动特性。但是，地震衰减估计很容易受到各种因素的影响，例如调谐效果，源和接收器耦合以及来自近地表风化层的影响。延时地震衰减估计可以避免这些问题，因为在两次勘测之间抵消了上述因素。我们在关井期间的12天期间，使用了在Kakkonda地热田中获得的不同时间的三个反射地震勘测进行了时移衰减估计。为了研究与增加的孔隙压力有关的地热流体变化，我们提出了一种用于估计随时间推移地震勘测之间的衰减变化的方法。首先，使用改进的叠前时间偏移方法从相应的时移地震数据中获得了三个地震反射剖面，该方法可以处理在高度断裂且结构非常复杂的介质中偏移速度估计的不确定性，因此难以实现准确的速度估计使用常规方法。然后，使用频谱比和质心频移方法对三个地震反射剖面中的两个进行了时移衰减评估。进行了数值建模，以验证我们提出的程序。进行了认真的预处理，以提高时移地震数据的可重复性，尤其是在频率含量上，这与地震衰减间接相关。最后，我们证明，从关闭生产井前的一天到此后的一周内，在短时间内（7天）内，与已知的超浅蒸汽为主的油藏及其周围的孔隙压力增加相关的衰减增加。 。这种短期衰减增加的可能原因可能是储层中的汽液相转变。