Xiong’an New Area, located in the middle of the North China Plain, will have been built as a “city of the future.” Urban planning and construction need to comprehensively consider the constraints of hydrogeological conditions such as aquifer structure and parameters. As the main aquifer in this area, the paleo-channel is heterogeneous and anisotropic, and the two-dimensional hydraulic conductivity in each horizontal direction cannot be obtained from aquifer tests. Therefore, this study adopts a chemical kinetics method to calculate the ionic activity and mineral saturation indices of shallow groundwater, determine the groundwater chemical potential field, and construct a horizontal two-dimensional groundwater chemical kinetics model. This model is used to calculate the hydraulic conductivity, flow rate and retention time of groundwater in areas of different chemical kinetics, as well as evaluate horizontal heterogeneity of the Quaternary paleo-channel aquifer. The results indicate that the groundwater chemical potential field can reflect the characteristics of the groundwater seepage field in each horizontal direction. The paleo-channel is the main channel of groundwater circulation, which shows the statistical difference of its permeability. Alluvial and lacustrine strata affect groundwater circulation due to their different hydrogeological structures and permeability. The groundwater chemical kinetics results of hydraulic conductivity along the paleo-channel are approximately consistent with traditional hydrogeological calculation results derived from aquifer test data. Hydraulic conductivity is higher in the extension direction of the paleo-channel, and lower if the path crosscuts multiple paleo-channels. This feature can be used to build a hydrogeological structure model combined with drilling data. Furthermore, excessive groundwater exploitation will change the actual flow rate and retention time of groundwater, thereby affecting the groundwater circulation conditions. This study of groundwater circulation in Xiong’an New Area by means of chemical kinetics makes up for the deficiency in the study of the unconsolidated sedimentary aquifer anisotropy within the paleo-channel.

Tianjin possesses abundant geothermal resources, and geothermal reinjection is an effective strategy for maintaining the sustainable development and utilization of these resources. However, several issues have arisen in the reinjection of sandstone geothermal reservoirs in the Tianjin area, including a mismatch between the reinjection capacity and effluent capacity, as well as challenges related to continuous reinjection. Therefore, it is crucial to investigate the reinjection of exogenous water into sandstone pore-type geothermal reservoirs. This study focuses on the geothermal reservoir of the Guantao Formation in the Binhai New Area. The surface water treatment process for reinjection into sandstone geothermal reservoirs was determined through water treatment simulation experiments. Additionally, experiments examining the interaction between the reinjected water and reservoir rock were conducted to assess the feasibility of using treated surface water for reinjection into sandstone geothermal reservoirs. The hydrogeochemical response mechanisms and the impact on the reservoir under reinjection conditions were also investigated. The results indicate that a nanofiltration module and tubular microfiltration membrane are essential to ensure the stability of the system. The pH and TDS of water samples decreased after reinjecting mixed water (HHS) into the sandstone reservoir. The hydrochemical type consistently remained Cl-Na. The conventional water chemistry components and trace elements were influenced by the corresponding water–rock reactions. The reservoir minerals exhibited minimal precipitation, primarily consisting of K-feldspar and Fe-dolomite. The minerals produced during the experiment accounted for only 0.08% of the total cuttings’ mass, indicating a negligible impact on the reservoir structure. PHREEQC was employed to simulate the changes in mineral saturation index before and after the reinjection of mixed water and geothermal water, respectively. Notably, similar hydrogeochemical changes were observed in the geothermal fluids. Thus, this study demonstrates the feasibility of reinjecting treated surface water into sandstone geothermal reservoirs from a hydrogeochemical perspective. This research provides valuable insights for the development of external water reinjection projects in hot spring health care units, contributing effectively to the achievement of carbon peaking and carbon neutrality goals.

Soil moisture content continuously alters the types and forms of petroleum organic pollutants in the soil through processes such as dissolution, convection, and dilution, forming complex migration and transformation in a water–air–soil–NAPL system. Field investigations and traditional indoor simulation experiments have difficulty in terms of accurately diagnosing the state of different petroleum pollutants due to the influence of environmental factors and the difficulty of controlling single factors. Batch experiments were conducted to simulate the mobilization and differentiation processes of petroleum pollutants under the influence of soil water content. The results show that (1) the residual content of components is the lowest in coarse sand and the highest in clay, which is mainly affected by soil particles; meanwhile, the residual saturation value of octanoic acid is the largest, and that of toluene is the smallest, as determined in terms of their viscosity and volatility. (2) The infiltration processes of the components are affected by their properties and medium characteristics. Due to its small particle size and strong adsorption, clay has the highest residual saturation of petroleum pollutants (28.8%). This can even be more than twice that of coarse sand (13.3%). For different components, the residual saturations of octanoic acid and toluene are the highest and lowest, respectively (taking fine sand as an example: 25.3% and 13.2%), with a relatively large difference, as determined in terms of viscosity and solubility. (3) As the free phase can migrate freely, it is transformed most rapidly in the pores. The changes in the dissolved phase of each component are relatively small and tend to be gentle. The changes in the residual phase are mainly affected by volatility, viscosity, soil particles, and pore and cosmid content; the degree of change is ordered as follows: toluene > cyclohexane > hexadecane > octanoic acid.

We perceived a trend in the study and practice of petroleum-contaminate sites. Monitored natural attenuation (MNA) can reduce the contaminant concentrations in the soil and groundwater, and it is a method that can remediate the petroleum-contaminated site effectively. MNA is becoming a research focus. This study evaluated MNA using a series of lab-based bench-scale experiments and a large amount of monitoring data from field samplings. Based on the in-site total petroleum hydrocarbon (TPH) results, we used statistical methods, the Mann-Kendall test, and mass fluxes in order to evaluate the MNA of petroleum-contaminated sites in groundwater. The results showed that the TPH concentrations were decreasing, and the plume became smaller. The attenuation rate was from 0.00876 mg/d to 0.10095 mg/d; remediating the petroleum contamination site would cost 1.3 years to 10.6 years. The plume reached a quasi-steady state, and mass flux declined. The most essential process of MNA was biodegradation, and the second was sorption. During the monitoring period, 393 g of TPH was attenuated, including 355 g of TPH gradated by microbes. Biodegradation upstream of the plume was more serious. Iron(Ⅲ) and manganese were the main electron acceptors utilized by microbes during the monitored period. MNA was in progress, and it can be an effective method to remediate the petroleum-contaminated site. Lab-based bench-scale experiments were performed with much monitoring data from the field samplings in order to understand the fate and transport mechanism of the petroleum contamination from the land surface to shallow groundwater according to site conditions.

Efficient reinjection is critical for maintaining reservoir pressure and ensuring the sustainable development of sandstone geothermal systems. However, complex thermal–hydraulic–chemical (THC) interactions often lead to progressive permeability reduction, significantly impairing injection performance. This study systematically investigates the coupled effects of injection flow rate, temperature, and suspended particle size on permeability evolution during geothermal reinjection. Laboratory-scale core flow-through experiments were conducted using sandstone samples from the Guantao Formation in the Huanghua Depression, Bohai Bay Basin. The experimental schemes included graded flow rate tests, temperature-stepped injections, particle size control, long-term seepage, and reverse-flow backflushing operations. The results reveal that permeability is highly sensitive to injection parameters. Flow rates exceeding 6 mL/min induce irreversible clogging and pore structure damage, while lower rates yield more stable injection behavior. Injection at approximately 35 °C resulted in a permeability increase of 15.7%, attributed to reduced fluid viscosity and moderate clay swelling and secondary precipitation. Particles larger than 3 μm were prone to bridging and persistent clogging, whereas smaller particles exhibited more reversible behavior. During long-term seepage, reverse injection implemented upon permeability decline restored up to 98% of the initial permeability, confirming its effectiveness in alleviating pore throat blockage. Based on these findings, a combined reinjection strategy is recommended, featuring low flow rate (≤5 mL/min), moderate injection temperature (~35 °C), and fine filtration (≤3 μm). In addition, periodic backflushing should be considered when permeability loss exceeds 30% or a sustained injection pressure rise is observed. This study provides robust experimental evidence and practical guidance for optimizing geothermal reinjection operations.

Reinjecting the geothermal reservoir with allogenic water during the non-heating period can effectively alleviate the pressure drop of the thermal reservoir and realize the sustainable utilization of geothermal resources. In the Dongli Lake area of Tianjin, the development and utilization of geothermal resources are concentrated and have relatively abundant surface water resources, which are the necessary conditions for surface water to reinject the thermal reservoir. This project drilled three geothermal reinjection wells, formulated the surface reinjection process, built the reinjection station, installed the monitoring system, carried out the reinjection experiments, and so on. This project used Dongli Lake water to reinject the thermal reservoir of Wumishan Formation of Jixian System. It can meet the requirements of 450 m³ /h reinjection water quality treatment, and the cost is 2.26 yuan/m³. During the operation, the water quantity and quality of the produced water were stable which met the requirements of reinjection. This project provides a new idea for the supply of geothermal reservoirs by allogenic water and opens up a new direction for the protection of geothermal resources. It can provide a demonstration for the construction of similar surface water reinjection projects whose development prospects is broad. It ensures the sustainable utilization of geothermal resources, so as to effectively develop new productivity and help achieve the ‘double carbon goal’.