石英砂中甲烷水合物注热水分解实验

DECOMPOSITION OF METHANE HYDRATE IN QUARTZ SAND BY INJECTING HOT WATER

为了了解自然条件下天然气水合物的分解性质,在20～40目石英砂中进行了甲烷水合物常压注热水分解实验。结果表明,与温度一样,电阻是甲烷水合物形成和分解良好的标示性参数：当水合物形成时,电阻快速增大;而水合物分解时,电阻则快速减小。实验研究与模拟计算均表明,在热水注入与水合物快速分解两个起始时刻之间有1.45min左右的时差,此时热水带来的热量主要用于加热石英砂—水合物体系;实验结果还表明,注入热水后,水合物分解界面自注入端开始向另一端移动,由于热水渗透时经沿途冷却,分解界面的移动速度是逐渐减小的。同时在假定分解速率常数和传质推动力为常量的前提下,得出了石英砂中甲烷水合物常压注热水分解速率常数为6.29×10^-5mol/（min·m^2）。

In order to obtain the decomposition properties of in-situ hydrate, this study carried out a lab test investigating on the decomposition of methane hydrate in sands, between 20 to 40 mesh, by injecting hot water at atmospheric pressure. The test showed that electric resistance, just like temperature, is an excellent indication index for the formation and decomposition of methane hydrate, i. e., that resistance augments apparently when hydrate is forming; and decrease sharply when hydrate is decomposing. Through experimental study and simulation calculation, this study demonstrated that a time difference of about 1.45 min. existed between the two points of initial time at which hot water started to inject and hydrate began its fast decomposition. This study also showed that after injecting hot water, the hydrate decomposition interface would move from the injecting side to another in decreasing rate because the hot water had been cooled while filtering. To make a premise of assuming the decomposition rate and mass transfer driving force to be constant, this study obtained the rate constant of methane hydrate dissociation in sand at atmospheric pressure, Kde, to be 6.29×10-5mol/(min·m2).