Estimation of CO2 saturation during both CO2 drainage and imbibition processes based on both seismic velocity and electrical resistivity measurements
Estimation of CO2 saturation during both CO2 drainage and imbibition processes based on both seismic velocity and electrical resistivity measurements
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DOI：
10.1093/gji/ggt232
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发表时间：
2013-10-01
影响因子：
2.8
通讯作者：
Matsuoka, Toshifumi
中科院分区：
文献类型：
--
作者：
Kim, Jongwook;Nam, Myung Jin;Matsuoka, Toshifumi
为了监测注入的二氧化碳(CO2)，在贝里亚砂岩的排水(注入CO2)和渗吸(注水)过程中，同时测量了地震速度和电阻率。在排水阶段，将超临界CO2(在40布尔或C下注入10兆帕)注入水饱和的贝里亚砂岩，并通过同步测量进行监测。注入超临界CO2后，在渗吸阶段向注入CO2的砂岩注入新鲜蒸馏水。根据电阻率指数和Gassmann流体置换方程，利用排水阶段和吸胀阶段获得的电阻率和P波速度测量来估算CO2饱和度(S-CO2)。将S-CO_2饱和度估计值与体积推算的S-CO_2饱和度估计值进行了比较，通过对排水过程中注入和排液体积的分析，得出结论：Gassmann-Brie和电阻率指数分别适用于基于纵波速度和电阻率的评价。当S二氧化碳浓度较大(<0.15)时，基于R-t估计的估计能较好地跟踪S二氧化碳的变化；而当S二氧化碳浓度较小时(<0.1)，基于V-p的估计对S二氧化碳浓度的变化比较敏感。利用Gassmann-Brie和电阻率指数，在同步测量的基础上估计S-CO_2的变化提供了S-CO_2的上下限，即使在S-CO_2较大(<0.1)时也是如此，而当S-CO_2较小时(<0.1)则适当地估计了S-CO_2。监测二氧化碳吸收过程可确认样品中残留的二氧化碳饱和度。
In order to monitor injected carbon dioxide (CO2), simultaneous measurements of seismic velocity and electrical resistivity are employed during the drainage (CO2 injection) and imbibition (water injection) processes of a Berea sandstone. Supercritical CO2 (10 MPa at 40 boolean OR C) was injected into a water-saturated Berea sandstone in the drainage stage and monitored via simultaneous measurements. After the injection of supercritical CO2, fresh distilled water was injected into the CO2-injected sandstone during the imbibition stage. Electrical resistivity and P-wave velocity measurements acquired during the drainage and imbibition stages were employed to evaluate CO2 saturations (S-CO2) based on the resistivity index and the Gassmann fluid-substitution equations, respectively. Comparing estimated values for S-CO2 saturation against those from volume-derived S-CO2, based on analysis on injected and drained fluid volumes in the drainage process, we conclude that Gassmann-Brie and resistivity index are suitable for the evaluation based on P-wave velocity and electrical resistivity, respectively. R-t-based estimation properly tracks the variation in S-CO2 even when S-CO2 is large (> 0.15), while V-p-based estimation is sensitive to the variation in S-CO2 when S-CO2 is small (< 0.1). Employing the Gassmann-Brie and resistivity index, estimation of variation in S-CO2 based on the simultaneous measurements provides the upper and lower bounds of S-CO2 even when S-CO2 is large (> 0.1), while properly estimating S-CO2 when S-CO2 is small (< 0.1). Monitoring the CO2 imbibition process confirms residual CO2 saturation within the sample.