Abstract:

A thermal-hydrologic-mechanical (THM) coupling model during the carbon dioxide plume geothermal system (CPGS) heat exploitation process was established. An ideal geothermal reservoir geothermal exploitation process was studied numerically, which combined with five-spot well pattern and a three-dimensional multi-rock formation geometric model. The rock deformation performance of CPGS geothermal exploitation process and the influence of rock deformation and geothermal reservoir initial porosity to CPGS heat exploitation were studied. The results showed that the rock significantly shrinkages during the process of the CPGS operation, reduces the volume, and increases the porosity of the reservoir. The deformation also helps increasing the permeability of thermal reservoir, accelerating the rate of exploitation process, and thus enhancing the geothermal exploitation process. While the porosity was lower, the influence of rock deformation was more obvious. Under the consumption that the initial permeability is the same, the smaller the initial porosity, the greater the increase in permeability caused by rock deformation, and the faster the thermal recovery rate of the system.

Key words: rock formation, geothermal reservoir, THM coupling, carbon dioxide, geothermal system, porous media, numerical simulation

摘要：

建立了CO₂羽流地热系统（CPGS）热开采过程的热流固（THM）耦合模型，结合五点布井方案和多岩层三维几何模型，对一理想热储进行CPGS热开采数值模拟。分析了CPGS热开采过程中热储内的岩体变形特征及其对系统采热性能的影响，并研究了THM耦合下热储初始孔隙率对CPGS热开采的影响。结果表明：CPGS的运行会引起岩体的冷却收缩，造成热储表观体积的减小和热储孔隙率的增大，这有助于提高热储渗透率，加快地热开采速率，从而对地热开采产生积极影响。初始孔隙率越小，岩体变形对热开采的影响越明显。在假设初始渗透率相同的情况下，初始孔隙率越小，岩体变形引起的渗透率增幅越大，系统的热开采速率越快。

关键词: 岩层, 热储, 热流固耦合, 二氧化碳, 地热系统, 多孔介质, 数值模拟