Moorjani Bhavesh, Adhikari Jhumpa, Hait Samik
Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Indian Oil Corporation Ltd. R&D Centre, Faridabad 121007, India.
J Chem Phys. 2024 Sep 14;161(10). doi: 10.1063/5.0220841.
Understanding the underlying physics of natural gas hydrate dissociation is necessary for efficient CH4 extraction and in the exploration of potential additives in the chemical injection method. Silica being "sand" is already present inside the reservoir, making the silica nanoparticle a potential green additive. Here, molecular dynamics (MD) simulations have been performed to investigate the dissociation of the CH4 hydrate in the presence and absence of ∼1, ∼2, and ∼3 nm diameter hydrophilic silica nanoparticles at 100 bar and 310 K. We find that the formation of a CH4 nanobubble has a strong influence on the dissociation rate. After the initial hydrate dissociation, the rate of dissociation slows down till the formation of a CH4 nanobubble. We find the critical concentration and size limit to form the CH4 nanobubble to be ∼0.04 mole fraction of CH4 and ∼40 to 50 CH4 molecules, respectively. The solubility of CH4 and the chemical potential of H2O and CH4 are determined via Gibbs ensemble Monte Carlo simulations. The liquid phase chemical potential of both H2O and CH4 in the presence and absence of the nanoparticle is nearly the same, indicating that the effect of this additive will not be significant. While the formation of the hydration shell around the nanoparticle via hydrogen bonding confirms the strength of interactions between the water molecules and the nanoparticle in our MD simulations, the contact of the nanoparticle with the interface is infrequent, leading to no explicit effect of the nanoparticle on the dynamics of methane hydrate dissociation.
了解天然气水合物分解的基础物理过程对于高效开采甲烷以及探索化学注入法中的潜在添加剂至关重要。二氧化硅作为“沙子”已存在于储层中，这使二氧化硅纳米颗粒成为一种潜在的绿色添加剂。在此，我们进行了分子动力学（MD）模拟，以研究在100巴和310K条件下，存在和不存在直径约为1、2和3纳米的亲水性二氧化硅纳米颗粒时甲烷水合物的分解情况。我们发现甲烷纳米气泡的形成对分解速率有很大影响。在初始水合物分解后，分解速率会减慢，直到形成甲烷纳米气泡。我们发现形成甲烷纳米气泡的临界浓度和尺寸极限分别约为甲烷的0.04摩尔分数和约40至50个甲烷分子。通过吉布斯系综蒙特卡罗模拟确定了甲烷的溶解度以及水和甲烷的化学势。在存在和不存在纳米颗粒的情况下，水和甲烷的液相化学势几乎相同，这表明这种添加剂的影响并不显著。虽然在我们的分子动力学模拟中，通过氢键在纳米颗粒周围形成水合壳证实了水分子与纳米颗粒之间相互作用的强度，但纳米颗粒与界面的接触并不频繁，导致纳米颗粒对甲烷水合物分解动力学没有明显影响。
