Mechanism of fracture permeability in crystalline rock under controlled stress and temperature conditions

本研究在围压为5-10 MPa、温度为20-90℃的条件下，对花岗岩单条裂缝进行了渗流试验。在室温下，裂缝孔径和渗透率随时间单调减小，达到准稳态。然后，在温度升高到90℃后，在其余实验中，孔径再次减小。从出口提取流体样品，通过电感耦合等离子体原子发射光谱（ICP-AES）评估元素浓度。元素浓度随温度升高而升高。渗流实验结束后，利用扫描电镜结合能量色散x射线能谱（SEM-EDX）对断口进行观察。揭示了硅石、方解石等几种沉淀矿物的形成。降水局限于局部和小区域。然而，沉淀矿物似乎对渗透率有一定的影响。

In this study, flow-through experiments on a single fracture in granite has been carried out under confining pressures of 5-10 MPa, and at temperatures of 20-90℃. The fracture aperture and the permeability monotonically decreased with time at room temperature, and reached a quasi-steady state. Then, after the temperature was raised to 90℃, the aperture decreased again throughout the rest of the experiments. Fluid samples were taken from the outlet to examine the elemental concentrations that were evaluated by inductively-coupled plasma atomic emission spectrometry(ICP-AES). The elemental concentrations increased with increase of temperature. After the flow-through experiments, the fracture surface was observed by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy(SEM-EDX). The formation of a few kinds of precipitated minerals such as silica and calcite was revealed. The precipitation was limited to quite local and small areas. However, the precipitated minerals seemed to have had some influences on the permeability.