Modeling and Prediction of Tracer Tests in Dongli Lake Area in Tianjin, China

Abstract

The Jxw geothermal reservoir in the Dongli Lake area is an extensive, low temperature geothermal system hosted mainly by Mesoproterozoic dolomitic limestones. In order to study the flow paths and predict the recovery time and tracer concentration in the production well, a numerical method using Visual MODFLOW software were applied. For the most pessimistic case (longitudinal dispersivity equals to 383.5 m), the tracer will take more than a year to arrive at the production well, with concentration values outside of the detection limit. Results show that there is no direct connection between production and injection wells.

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

“…Geothermal recharge is carried out in the fissure thermal reservoir. Therefore, the direct channel connecting the recharge well and the mining well can be predicted according to the tracer test results, and the average velocity of recharge water movement can be calculated according to the peak time of the tracer concentration curve (Wang et al, 2018;Guo et al, 2019;Liu et al, 2019;Yue et al, 2019). In the tracer test of fractured thermal storage, we based on the following assumptions: 1) Recharge at a stable flow rate in one well, and produce at a stable flow rate in a nearby well; 2) Recharge water along a channel (such as a fracture zone) Flow from the recharge to the production well, and the flow in the channel is one-dimensional; 3) Ignoring the effect of molecular diffusion, a certain amount of tracer is put into the recharge well at one time, and a part of it goes to the production well along with the channel transport.…”

“…Improper placement of recharge wells may cause cooling of the thermal reservoir, reduce the water temperature or output of production wells. To select and evaluate the quality of recharge wells, it is necessary to study and analyze the seepage characteristics of the recharge water, such as the migration direction, rate, and sweeping situation, which are directly related to the actual operation effect of hot water recharge (Su et al, 2018;Wang et al, 2018;Bender et al, 2020;Wang et al, 2021). The tracer test provides a very good way to quantitatively calculate the migration rate of the recharge water in the thermal reservoir and the hydraulic connection between the production and recharge wells, has been carried out in Japan and Iceland, countries with mature recharge and exploitation technology, which provides important basic parameters for the good deployment scheme of the geothermal field (Kaya et al, 2011;Xu et al, 2018;Wu et al, 2019;Pang et al, 2020;Dong et al, 2021;Wu et al, 2021).…”

Fluidization and Application of Carbon Nano Agglomerations

“…This phenomenon is known as hysteresis and reflects the law of the bed layer falling back when the gas velocity decreases. [55,90] However, when the gas velocity decreases to the critical gas velocity U a (the minimum gas velocity of maintaining agglomerate fluidization), the bed height will suddenly drop and transition into a channel flow state. [88] Figure 5e shows the dependence of bed expansion of CNTs on gas velocity in a fluidized bed.…”