碳酸盐岩热储对外源水回灌的地球化学响应及储层渗透率变化规律

水热型地热资源的大规模、可持续开发利用对改善北方地区雾霾、减少温室气体排放意义重大。但长期的采灌不平衡使开采区水位持续下降，且热储尾水直排也造成了诸多环境问题。基于碳酸盐岩储层易回灌的优势，本课题提出利用外源水回灌碳酸盐岩热储来恢复热储水量，达到可持续开发的目的，但外源水回灌对储层的影响和作用机理还不清楚。本课题拟选择天津东丽湖地区雾迷山组碳酸盐岩热储，利用水-岩相互作用实验（反应、驱替实验）和反应运移模拟，结合现场试验监测，（1）刻画不同时间尺度上热储对外源水回灌的地球化学响应（包括流体组分和同位素特征、矿物溶解沉淀特征等）；（2）定量评价不同回灌情景下（回灌水类型、回灌量、回灌温度和时间等）热储渗透率的变化趋势及其对回灌的影响；（3）碳酸盐岩非均质性对回灌的响应；（4）基于不同回灌情景对热储的影响，给出外源水回灌碳酸盐岩热储科学、可行的方案，为相关政策制定提供依据。

Large-scale and sustainable exploitation of hydrothermal resources are important and necessary to help improving air quality and mitigating greenhouse gases emissions. However, longtime disequilibrium between production and reinjection causes continuous declining of water table and direct discharge of waste water leads to various environmental problems. Taking the advantages of high reinjectivity of carbonate reservoir, it’s proposed that using water from other sources reinjection to increase the total recharge, but its effects on reservoir and the mechanisms are unclear. With consideration of understanding the processes and its effects of reinjection using water from other sources, carbonate reservoir of Wumishan formation in Donglihu area of Tianjin city is chosen to carry out the water-rock interaction experiments and numerical simulations to study: (1) geochemical responses (including water chemistry, isotopes, minerals precipitation and dissolution) of carbonate reservoir to reinjection of water from other sources on different time scales; (2) quantitative assessment of changes of permeability of carbonate reservoir and its effects on reinjection within different conditions (e.g., water type, total volume, temperature and time for reinjection ); (3) effects of carbonate heterogeneity on reinjection; (4) possibility and optimization of reinjection to carbonate reservoir using water from other sources based on results of experiments and simulations. This can provide scientific basis for policy makers when considering reinjection by water from other sources.