Spectral induced polarization of the three-phase system CO2 – brine – sand under reservoir conditions
Spectral induced polarization of the three-phase system CO2 – brine – sand under reservoir conditions
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DOI：
10.1093/gji/ggw389
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发表时间：
2017
影响因子：
2.8
通讯作者：
J. Börner;V. Herdegen;J. Repke;K. Spitzer
中科院分区：
文献类型：
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作者：
J. Börner;V. Herdegen;J. Repke;K. Spitzer
在与二氧化碳（CO2）的相互作用过程中，含水砂的光谱复电导率受到多个同时发生的过程的影响。这些过程包括部分饱和，由于导电孔隙水与CO2和化学反应的CO2与流体和颗粒-水界面的替代。我们提出了一个实验室研究的光谱激发极化的含水砂在暴露和流通的CO2。电导率谱成功地测量在压力高达30 MPa和80 °C期间的主动流动和在稳态条件下集中在0.0014和100 Hz之间的频率范围。事实证明，0.1至100 Hz之间的频率范围最能指示潜在的监测应用。所提供的数据表明，CO2对电解质电导率的影响可能会被覆盖的孔隙水电导率，这取决于盐度，压力和温度的模型，并已来自早期的调查孔隙水相。涵盖三相系统CO2-盐水-砂的新数据进一步表明，化学相互作用导致表面电导率降低近20%，这可能与酸性环境中CO2溶解和碳酸解离导致的低pH值有关。总CO2效应的量化可用作监测封存饱和度期间的校正。我们表明，这导致正确的重建流体饱和度从电气测量。此外，与矿物溶解或沉淀过程相关的内表面积变化的指标可以从电导率的虚部计算。在0.0014和0.1 Hz之间的低频范围显示了额外的特性，这些特性偏离了较高频率下的行为。德拜分解的方法被应用到隔离的功能占主导地位的数据在低频率。我们得出结论，从我们的研究，电导率不仅是一个高度敏感的指标CO2饱和度在孔隙空间。当它以其全光谱和复杂的形式进行测量时，它包含有关系统化学状态的额外信息，这具有通过一种监测方法获得饱和度和界面特性的潜力。
The spectral complex conductivity of a water-bearing sand during interaction with carbon dioxide (CO2) is influenced by multiple, simultaneous processes. These processes include partial saturation due to the replacement of conductive pore water with CO2and chemical interaction of the reactive CO2with the bulk fluid and the grain-water interface. We present a laboratory study on the spectral induced polarization of water-bearing sands during exposure to and flow-through by CO2. Conductivity spectra were measured successfully at pressures up to 30 MPa and 80 °C during active flow and at steady-state conditions concentrating on the frequency range between 0.0014 and 100 Hz. The frequency range between 0.1 and 100 Hz turned out to be most indicative for potential monitoring applications. The presented data show that the impact of CO2on the electrolytic conductivity may be covered by a model for pore-water conductivity, which depends on salinity, pressure and temperature and has been derived from earlier investigations of the pore-water phase. The new data covering the three-phase system CO2-brine-sand further show that chemical interaction causes a reduction of surface conductivity by almost 20 per cent, which could be related to the low pH-value in the acidic environment due to CO2dissolution and the dissociation of carbonic acid. The quantification of the total CO2effect may be used as a correction during monitoring of a sequestration in terms of saturation. We show that this leads to a correct reconstruction of fluid saturation from electrical measurements. In addition, an indicator for changes of the inner surface area, which is related to mineral dissolution or precipitation processes, can be computed from the imaginary part of conductivity. The low frequency range between 0.0014 and 0.1 Hz shows additional characteristics, which deviate from the behaviour at higher frequencies. A Debye decomposition approach is applied to isolate the feature dominating the data at low frequencies. We conclude from our study that electrical conductivity is not only a highly sensitive indicator for CO2saturation in pore space. When it is measured in its full spectral and complex form it contains additional information on the chemical state of the system, which holds the potential of getting access to both saturation and interface properties with one monitoring method.