Research on Geochemical Response Characteristics of Dry Hot Rocks Injected with Scale Removal pH Modified Fluid

Geothermal energy has abundant reserves, is clean and environmentally friendly, and is an important alternative energy source for future oil and gas resources. However, during the development of dry hot rock geothermal energy, scaling in hydraulic fractures can easily lead to a decrease in water injection and thermal recovery capacity, affecting the effectiveness of thermal recovery. By comparing the differences in the temperature of the produced liquid in the enhanced dry hot rock geothermal system before and after scaling, the impact of scaling on geothermal development was analyzed, thereby proving the necessity of scale removal in the dry hot rock development process. The influence of different factors on the geochemical response characteristics of dry hot rocks during the descaling process using pH modified fluids was explored. The research results indicate that the generation of precipitates such as calcium carbonate in cracks can lead to a gradual decrease in the temperature of the produced liquid during geothermal development. During the experiment, the temperature of the extracted liquid decreased from the initial 178°C to the final 90°C. In addition, when the pH of the injected liquid is 4.5, the generation of precipitates such as calcium carbonate in hydraulic fractures is minimal, resulting in better geothermal development and the highest temperature of the produced liquid. However, when designing the pH value of the injection solution, it is still necessary to consider the corrosive and destructive effects of the injection solution’s acidity and alkalinity on the development system. Finally, due to the sufficient heat exchange between injected water and dry hot rock at lower injection rates, the temperature of produced water will be higher. However, the effectiveness of geothermal development will deteriorate with the increase of injection rate, so it is more reasonable to design the injection rate of injected water at 6 L/min. Research can provide theoretical basis and technical support for the efficient development of dry hot rock geothermal resources.