Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Langmuir. 2012 May 29;28(21):8001-9. doi: 10.1021/la2044587. Epub 2012 May 15.
When supercritical carbon dioxide (scCO(2)) is injected into deep subsurface reservoirs, much of the affected volume consists of pores containing both water and scCO(2), with water films remaining as the mineral-wetting phase. Although water films can affect multiphase flow and mediate reactions at mineral surfaces, little is known about how film thicknesses depend on system properties. Here, the thicknesses of water films were estimated on the basis of considerations of capillary pressure needed for the entry of CO(2) and disjoining pressures in films resulting from van der Waals and electric double-layer interactions. Depth-dependent CO(2) and water properties were used to estimate Hamaker constants for water films on silica and smectite surfaces under CO(2) confinement. Dispersion interactions were combined with approximate solutions to the electric double layer film thickness-pressure relationship in a Derjaguin-Landau-Verwey-Overbeek (DLVO) analysis, with CO(2) as the confining fluid. Under conditions of elevated pressure, temperature, and salinity commonly associated with CO(2) sequestration, adsorbed water films in reservoir rock surfaces are typically predicted to be less than 10 nm in thickness. Decreased surface charge of silica under the acidic pH of CO(2)-equilibrated water and elevated salinity is predicted to compress the electric double layer substantially, such that the dispersion contribution to the film thickness is dominant. Relative to silica, smectite surfaces are predicted to support thicker water films under CO(2) confinement because of greater electrostatic and dispersion stabilization.
当超临界二氧化碳（scCO₂）注入深部地下储层时，受影响的大部分体积包含同时含有水和 scCO₂的孔隙，其中水膜作为亲水性相保留。尽管水膜会影响多相流并调节矿物表面的反应，但人们对水膜厚度如何取决于系统特性知之甚少。在这里，根据 CO₂进入所需的毛管压力和范德华和电双层相互作用产生的水膜的离差压力来估算水膜的厚度。使用与 CO₂限制下二氧化硅和蒙脱石表面上水膜的哈梅克常数相关的深度相关的 CO₂和水性质来估算。将分散相互作用与电双层膜厚度与压力关系的近似解结合在德贾古因-兰德au-韦尔拜-奥弗贝克（DLVO）分析中，其中 CO₂为限制流体。在通常与 CO₂封存相关的高压、高温和高盐度条件下，储层岩石表面上吸附的水膜通常预计小于 10nm。在 CO₂平衡水的酸性 pH 和升高的盐度下，二氧化硅的表面电荷减少预计会大大压缩电双层，使得分散对膜厚度的贡献占主导地位。与二氧化硅相比，由于更强的静电和分散稳定作用，蒙脱石表面在 CO₂限制下预计会支撑更厚的水膜。
