电阻率在天然气水合物三维生成及开采过程中的变化特性模拟实验

An experimental study of resistivity variation in the 3D simulation of methane hydrate generation and production

为获取更多的清洁高效能源,全球范围内都正在开展与天然气水合物(以下简称水合物)开采相关的研究,其中电阻率作为表征水合物变化的一个重要参数也被纳入了重点研究范畴,但其在水合物三维生成及开采过程中的变化特性尚未见报道。为了得到三维系统下水合物的电阻率变化数据,利用三维水合物反应釜,实验室模拟研究了水合物在多孔介质中生成及利用双水平井注热开采实验过程中电阻率的变化特性。结果发现:①电阻率总体上随着水合物的生成而升高,随着其分解而下降;②电阻率与水合物饱和度并不呈完全的线性关系,当水合物饱和度升高到一定程度时,电阻率变化减缓;③在水合物生成过程中发现水合物生成存在"爬壁效应"——水合物在多孔介质中的生成并不同步,水合物在边界区域明显多于中心区域;④在水合物开采过程中发现电阻率不仅随水合物分解的变化而变化,而且还与开采过程中的流体流动有着较大关系,所以利用电阻率作为水合物开采的特征指标时需要先排除流体流动的干扰。

To solve the global energy crisis and global warming, the related research about the discovery and extraction of natural gas hydrate has been and is being developed alI over the world, among which the resistivity of hydrate, a research focus, is a significant parameter to characterize how the methane hydrate changes in the process of its generation and production. However, few literatures on such subject have ever been found. In view of this, a laboratory simulation study was carried out in a 3D hydrate reactor, focusing on the characteristics of resistivity variation respectively when methane hydrate was generated in a multi-porous medium and when it was extracted through the heat stimulation method in the dual horizontal wells. The following findings were obtained, a. The resis- tivity rises in the process of hydrate generation but falls with the hydrate dissociation, b. The resistivity is not directly proportional to the hydrate saturation; when the hydrate saturation climbs to a certain level, the change of resistivity starts to get slow. c. The phenomenon of ＂climbing effect＂ is observed in the hydrate formation process. That is, the formation of methane hydrate in the multi pore medium is asynchronous, so the generated hydrates are obviously more in the boundary areas than those in the central are- a. d. In the process of hydrate production, the resistivity is not only related to the hydrate dissociation, but to the flow of fluids like gas and water; that is why the interference of fluid flow should be eliminated before the resistivity is used as a characteristic parame- ter of hydrate production.