Study on Optimization of Geothermal Tail Water Reinjection Process in Moderately Deep Sandstone

Abstract

The existing test methods of geothermal tail water reinjection effect in sandstone geothermal reservoirs are not suitable for moderately deep and deep sandstone geothermal reservoirs, resulting in the poor filtration performance of fine-grained reservoirs. Therefore, a test method for the geothermal tail water reinjection effect in a moderately deep sandstone geothermal reservoir is proposed. This paper studies the static compatibility of raw water and geothermal tail water under different mixing ratios, determines the indexes affecting the reinjection effect of moderately deep sandstone geothermal reservoir tail water, analyzes the weight set of each influencing factor, and formulates a test standard for the reinjection effect of geothermal reservoir tail water. Finally, a tracer is selected to trace the reinjected tail water in the geothermal reservoir, and the tracer is used to obtain the result of each previously determined index. Eventually, the final reinjection effect of the geothermal tail water is obtained. The experimental results show that the fine-grade filtration performance, silt-grade filtration performance, and coarse-grade filtration performance of this method are improved compared with those of other methods; thus, the particle filtration performance is better, and the reinjection effect of geothermal reservoir tail water is better, which has a great significance for the geothermal resource exploitation of moderately deep sandstone.

Karst thermal reservoir tracer test and seepage characteristics analysis in Niutuozhen geothermal field in Xiong’an New Area

“…For geothermal recharge, tracers should meet the following requirements: 1) The thermal reservoir should generally not exist, or the concentration is stable and far below the expected concentration at the tracer monitoring site during the test; 2) The selected tracer should not react with or be adsorbed by reservoir rocks; 3) It should still have good stability at high temperature; 4) It should be cost-effective and environmentally benign; 5) It should be easy to place, sample and analyze. Therefore, sodium fluorescein was selected as the tracer in this study, and 50 kg of tracer was placed at one time Frontiers in Earth Science frontiersin.org (Ungemach, 2003;Kaya et al, 2011;Li et al, 2021;Wu et al, 2021). On 30 January 2013, well WQHY 2 (recharge well) was selected as the tracer injection well, and another 10 production wells within 1 km around the recharge well were used as observation wells and tracer sampling wells for sampling and analysis (Figure 3).…”

“…Geothermal water is the main medium for exploiting geothermal energy. With the large-scale exploitation of geothermal water, the thermal reservoir pressure decreases greatly, resulting in a gradual increase in energy consumption (Wang et al, 2020;Li et al, 2021;Erol et al, 2022). Recharge technology can alleviate the decrease of the pressure of underground thermal reservoirs and the water level, and improve the utilization rate of geothermal resources, which has been widely used in the exploitation of geothermal resources (Chrysikopoulos, 1993;Aydin et al, 2018;Aydin and Akin, 2020).…”