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During the operation of an enhanced geothermal system (EGS), the non-equilibrium temperature, pressure, and hydrochemistry caused by fluid injection intensify water–rock interactions, induce the mineral dissolution and precipitation in the reservoir near an injection well (also referred to as the near-well reservoir), and change reservoir permeability, thus affecting continuous and efficient geothermal exploitation. Based on the investigation of the M-1 injection well of the EGS in the Matouying uplift of Hebei Province, China, a THC reactive solute transport model using the TOUGHREACT program was established in this study to explore the mineral dissolution and precipitation laws of the near-well reservoir and their influencing mechanisms on the reservoir porosity and permeability in the long-term fluid injection of this well. As indicated by the results, the dissolution of primary feldspar and chlorite and the precipitation of secondary minerals (mainly dolomite and illite) occurred and water–rock interaction significantly reduced the porosity and permeability of the near-well reservoir in the long-term continuous injection process. Appropriate reduction in the injection flow rate, injection temperature, and the Mg2+ and K+ contents in the injected water can help inhibit the formation of secondary minerals and delay the plugging process of the near-well reservoir. [ABSTRACT FROM AUTHOR]

The Enhanced Geothermal System (EGS) is an artificial geothermal system that aims to economically extract heat from hot dry rock (HDR) through the creation of an artificial geothermal reservoir. Chemical stimulation is thought to be an effective method to create fracture networks and open existing fractures in hot dry rocks by injecting chemical agents into the reservoir to dissolve the minerals. Granite is a common type of hot dry rock. In this paper, a series of chemical stimulation experiments were implemented using acid and alkaline agents under high temperature and pressure conditions that mimic the environment of formation. Granite rock samples used in the experiments are collected from the potential EGS reservoir in the Matouying area, Hebei, China. Laboratory experimental results show that the corrosion ratio per unit area of rock is 3.2% in static acid chemical experiments and 0.51% in static alkaline chemical experiments. The permeability of the core is increased by 1.62 times in dynamic acid chemical experiments and 2.45 times in dynamic alkaline chemical experiments. A scanning electron microscope analysis of the core illustrates that secondary minerals, such as chlorite, spherical silica, and montmorillonite, were formed, due to acid‐rock interaction with plagioclase being precipitated by alkaline‐rock interactions. Masking agents in alkaline chemical agents can slightly reduce the degree of plagioclase formation. A chemical simulation model was built using TOUGHREACT, the mineral dissolution and associated ion concentration variation being reproduced by this reactive transport model. [ABSTRACT FROM AUTHOR]

Background and Aims: Commercial plasma donation was introduced in China in the 1970s. Cases of non-A, non-B hepatitis (hepatitis C) continued to occur, with multiple outbreaks among plasma donors in Guan county, Hebei province between 1972 and 1990. The outcomes of hepatitis C virus (HCV) infection in these paid plasma donors from six villages of Guan county were followed up for 12-19 years. Methods: A total of 402 plasma donors with HCV infection were enrolled since anti-HCV-positive in 1991 or 1998. Follow up was maintained until death or the end of the observation period. No antiviral treatment was applied during the period of infection. Results: Follow up was lost in 23 cases. After a 12-19-year follow up, 31 donors died, with the cause of death directly related to liver disease in 15 cases, and an overall mortality of 8.18% (31/379). The incidence of liver cirrhosis was 10.03%, and hepatocellular carcinoma (HCC) was 2.90%. The rate of viral spontaneous clearing was 20.32% (77/379), and 13.69% (23/168) in males and 25.59% (54/211) in females. In May 2010, detections were performed in 348 cases. Abnormality of liver function was related to HCV viremia. Sex and alcohol intake impacted the outcome of HCV infection. There was no correlation between the viral spontaneous clearance with age of infection and genotype. Conclusions: This area has a high rate of chronicity in HCV infection due to plasma donation. Twenty-five years after virus infection, liver cirrhosis or HCC developed in one-tenth of patients, with an overall mortality of 8.18%. [ABSTRACT FROM AUTHOR]