X-CT法研究砂岩中甲烷水合物动态分布规律

Research of Methane Hydrate Distribution in Sandstone's Pore Space during Hydrate Formation and Dissociation based on X-CT

采用Berea砂岩作为沉积物,利用自主研制的反应釜进行甲烷水合物生长和分解实验,运用高分辨X-CT进行甲烷水合物微观观测,研究了其在Berea砂岩孔隙内的分布规律。结果表明:水合物形成初期在沉积物孔隙内以悬浮模式为主,后期以接触模式为主,中期以接触与悬浮共存模式为主;水合物的升温分解过程与其生长过程分布规律正好相反;水合物降压分解初期以接触与悬浮共存模式为主,后期以悬浮模式为主;相对于升温过程,水合物分解过程对压力下降表现得更灵敏。

Based on the high resolution X-ray computerized tomography（CT）,the pore scale distribution of methane hydrate was observed and discussed.According to the results,there are 3 kinds of methane hydrate distribution models in the pores.At the first stage of hydrate formation,hydrates are mainly growing as a floating model.At the last stage of hydrate formation,the hydrate grains connect the sediment particles,described as a contacting model.In the middle stage of hydrate formation,hydrate distribution is between floating and contacting model.Two methods of hydrate dissociation,heating and depressurization were used in this study.The hydrate distribution models at heating decomposition process are just opposite to the formation stage.While in the depressurization process,the hydrate distribution at the first stage is between contact and floating model,then the hydrate distribution turns to floating model.Compared with increasing the heating decomposition process,hydrate decomposition is more sensitive to pressure than temperature.