Downhole Services Company, CNPC Bohai Drilling Engineering Company Limited, Renqiu 062552, Hebei, China.
School of Energy Resource, China University of Geosciences, Beijing 434000, China.
J Environ Public Health. 2023 Jul 7;2023:5298404. doi: 10.1155/2023/5298404. eCollection 2023.
As a rock mass with shallow burial, high temperature, and large-scale development, the study of its mechanical and seepage characteristics plays an important role in the efficient development of geothermal energy. With the development of geothermal energy in China, a breakthrough has been made in the exploration of dry-hot rocks, and the realization of efficient development of dry-hot rocks has become the focus of attention. Systematic research on rock mechanics and seepage characteristics of dry-hot rocks has become a key research topic. Granite is the most typical dry-hot rock. In this paper, granite in the Qinghai area is selected as the research object, and experiments on physical characteristics, mechanical parameters, and seepage characteristics of granite are carried out to study the effects of different depths and temperatures on mechanical parameters and seepage characteristics of granite. The results show that the physical parameters of granite in Qinghai do not change obviously with the increase of depth, and granite has the characteristics of low water absorption and low porosity. At the same time, the parameters of water absorption and porosity at different depths are close, and the dispersion is small, so the rocks are very dense. The rocks have relatively high P-wave velocity and low S-wave velocity, and the elastic wave velocity changes little at different depths. With the increase of confining pressure, the strength of granite rock increases. Under different confining pressures, the rock shows brittle failure characteristics after the peak stress. According to Hoek-Brown and Mohr-Coulomb strength curves, the strength value is 173.52 MPa. After high temperature treatment, a complex fracture network is formed in the granite. With the increase of temperature, the permeability and porosity of the granite increase continuously, and 500°C is the temperature threshold. When the temperature is lower than 300°C and the stress is less than 30 MPa, the granite has negative Poisson's ratio, and the permeability and effective stress of dry-hot rocks are piecewise linear functions. The research results provide theoretical guidance for fracturing of dry-hot rocks and exploitation of geothermal energy.
作为一种具有浅层埋深、高温和大规模发育的岩体，研究其力学和渗流特性对地热能源的高效开发具有重要意义。随着中国地热能的发展，干热岩的勘探取得了突破，干热岩的高效开发成为关注的焦点。对干热岩的岩石力学和渗流特性进行系统研究已成为一个关键研究课题。花岗岩是最典型的干热岩。本文以青海地区的花岗岩为研究对象，开展了花岗岩物理特性、力学参数和渗流特性实验，研究了不同深度和温度对花岗岩力学参数和渗流特性的影响。结果表明，青海花岗岩的物理参数随深度的增加变化不明显，花岗岩具有吸水率低、孔隙率低的特点。同时，不同深度下吸水率和孔隙率的参数接近，离散性小，因此岩石非常致密。岩石具有较高的 P 波速度和较低的 S 波速度，不同深度下弹性波速度变化不大。随着围压的增加，花岗岩的强度增加。在不同的围压下，岩石在峰值应力后表现出脆性破坏特征。根据 Hoek-Brown 和 Mohr-Coulomb 强度曲线，强度值为 173.52 MPa。高温处理后，花岗岩中形成了复杂的断裂网络。随着温度的升高，花岗岩的渗透率和孔隙度不断增加，500°C 是温度阈值。当温度低于 300°C 且应力小于 30 MPa 时，花岗岩具有负泊松比，干热岩的渗透率和有效应力呈分段线性函数。研究结果为干热岩压裂和地热能开发提供了理论指导。
