沉积物体系中甲烷水合物平衡温度、压力条件实验模拟

Experimental simulation on equilibrium temperature and pressure of methane hydrate in sediment systems

研究沉积物中甲烷水合物的平衡温度和压力条件,对认识甲炕水合物的稳定性以及对未来准确评价和利用甲烷水合物能源非常重要。在温度为270.9～278.2K、压力为2.47～4.31MPa条件下,分别对平均孔径为53.2nm、27.2nm和15.5nm的沉积物体系中甲烷水合物的分解平衡温度和压力条件(即相平衡)进行了测定,结果表明,近自然沉积物的平均孔径大小会影响甲烷水合物的相平衡条件。相同温度条件下,纯水体系中甲烷水合物的平衡压力比在沉积物体系中的低;随着孔径的增大,甲烷水合物在相图中稳定区的面积逐渐增加,但当体系中温度降低到冰点以下或者沉积物孔径增大到超过60nm时,沉积物孔隙毛细管对甲烷水合物稳定性的影响非常小,与纯水中的重合或者接近。甲烷水合物在沉积物体系中的相平衡数据可以用经验热力学方程拟合,拟合结果能反映孔径大小与甲炕水合物平衡压力、温度条件的相互关系。

The research of equilibrium temperature and pressure of methane hydrate in porous sediments is important for learning the stability of methane hydrate and its evaluating and utilizing. Under the conditions of the temperature of 270.9-278.2K and the pressure of 2. 47 4. 31MPa, equilibrium temperature and pressure of methane hydrate dissociation in three sediment systems with average pore radii 53.2nm, 27.2nm, and 15. 5nm are measured, respectively. The results demonstrate that the average pore size of nature-like sediments has effects on phase equilibrium conditions of methane hydrate. Under the same temperatures, equilibrium pressures of methane hydrate in pure water are lower than that of in sediments. The stability zones of methane hydrate in the sediments increase gradually with the increase of the pore radii. However, the effect of the sediment capillary on the stability of the methane hydrate is little when the temperature is dropped under zero point or the pore diameter be enlarged upon 60nm. An empirical exponential equation is presented to calculate the equilibrium temperature and pressure of methane hydrate dissociation. The results also show that there was a rule between the phase equilibrium conditions of methane hydrate and the pore sizes of the sediment media.