Department of Petroleum and Geosystems Engineering, University of Texas at Austin, Austin, TX, USA.
Department of Petroleum and Geosystems Engineering, University of Texas at Austin, Austin, TX, USA.
J Colloid Interface Sci. 2018 Jan 1;509:132-139. doi: 10.1016/j.jcis.2017.08.100. Epub 2017 Sep 1.
Previous work on Pickering emulsions has shown that bromohexadecane-in-water emulsions (50% oil) stabilized with fumed and spherical particles modified with hexadecyl groups develop a noticeable zero shear elastic storage modulus (G') of 200Pa and 9Pa, respectively, while in just 50mM NaCl. This high G' can be problematic for subsurface applications where brine salinities are higher and on the order of 600mM NaCl. High reservoir salinity coupled with low formation pressure drops could prevent an emulsion with a high G' from propagating deep into formation. It is hypothesized that G' of an emulsion can be minimized by using sterically stabilized silica nanoparticles modified with the hydrophilic silane (3-glycidyloxypropyl)trimethoxysilane (glymo).
Bromohexadecane-in-water emulsions were stabilized with low and high coverage glymo nanoparticles. Oscillatory rheology was used to monitor G' asa function of nanoparticle concentration, oil volume fraction, salinity, and pH. Cryogenic scanning electron microscopy was used to make observations on the emulsion microstructure.
G' of bromohexadecane-in-water emulsions were minimized by using particles with a high coverage of glymo on the particle surface, which reduced the Ca/silanol site interactions. Emulsions that were stabilized with low surface coverage particles had noticeably higher G', however, their G' could be reduced by a factor of 3.3 by simply lowering the solution pH to 3. Cryo-SEM images showed that nanoparticle bridging was more pronounced with nanoparticles that had low glymo coverage as opposed to high coverage.
以前关于 Pickering 乳液的研究表明，用十六烷基官能化的烟炱和球形颗粒稳定的溴代十六烷-水乳液（50%油）在仅 50mM NaCl 中分别发展出可观的零剪切弹性储能模量（G'）为 200Pa 和 9Pa。在地下应用中，盐水盐度较高，约为 600mM NaCl，这种高 G'可能会出现问题。高储层盐度加上低地层压降可能会阻止具有高 G'的乳液在深层地层中传播。据推测，可以通过使用亲水性硅烷（3-缩水甘油氧基丙基）三甲氧基硅烷（glymo）修饰的空间稳定化硅纳米粒子来最小化乳液的 G'。
用低覆盖度和高覆盖度 glymo 纳米粒子稳定溴代十六烷-水乳液。振荡流变学用于监测 G'作为纳米粒子浓度、油体积分数、盐度和 pH 值的函数。低温扫描电子显微镜用于观察乳液的微观结构。
通过使用表面覆盖有高 glymo 的粒子最小化溴代十六烷-水乳液的 G'，这降低了 Ca/硅醇基位点相互作用。用低表面覆盖度粒子稳定的乳液具有明显更高的 G'，然而，通过将溶液 pH 值降低至 3，其 G'可以降低 3.3 倍。低温 SEM 图像表明，与高覆盖度纳米粒子相比，低覆盖度纳米粒子的纳米粒子桥接更为明显。
