Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (4): 430-437.DOI: 10.13745/j.esf.sf.2021.11.4

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Scaling process simulation and anti-scaling measures in karst geothermal field in Baoding, Hebei

HE Yujiang1,2(), LIU Xiao3, XING Linxiao1,2,4, TAN Xianfeng3, BU Xianbiao5,*()   

  1. 1. Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang 050061, China
    2. Technology Innovation Center of Geothermal & Hot Dry Rock Exploration and Development, Ministry of Natural Resources, Shijiazhuang 050061, China
    3. Shandong Provincial Lunan Geo-engineering Exploration Institute (The Second Geological Brigade of Shandong Geological Exploration Bureau), Jining 272100, China
    4. School of Environment, China University of Geosciences (Wuhan), Wuhan 430074, China
    5. Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China
  • Received:2021-05-01 Revised:2021-07-05 Online:2022-07-25 Published:2022-07-28
  • Contact: BU Xianbiao

Abstract:

Scaling is a serious problem in geothermal power plants and certain geothermal projects in China hindering large-scale development and utilization of geothermal energy. At present, anti-scaling theory and technology is urgently needed in the geothermal market where calcium carbonate scaling is the most common problem. To solve this problem, the karst geothermal field in Baoding, northern China was selected to investigate the scale composition and the scaling mechanism, position and process as well as anti-scaling measures in a geothermal well. According to the study results, (1) the main cause of calcium carbonate scaling is flashing due to system pressure drop, caused primarily by carbon dioxide release from the liquid phase to the gas phase. (2) By combining the wellhead parameters with the laws of conservation of mass, momentum and energy and the theory of two-phase flow pressure drop, the scaling process can be simulated, and the scaling position as well as the pressure, temperature, steam quality and partial pressure of carbon dioxide at different depths can be calculated and determined. (3) Two anti-scaling measures could be implemented after identifying the flashing pressure and depth. One measure was to increase system pressure in order to prevent flashing thus inhibit carbon dioxide release. A minimum pressure was recommended via simulation. The other measure was to use chemical scaling inhibitor. An injection device was developed, anti-scaling experiment was carried out, and the chemical scaling inhibition effect was evaluated to show that chemical inhibitor could inhibit more than 90% of scaling, and thus the carbonate scaling problem could be effectively solved. From the above study, a set of valuable experiences—from scaling cause analysis, scaling position calculation, scaling process simulation, anti-scaling technology and equipment developments to field experiments and anti-scaling evaluation—were obtained. These experiences can be referenced in general for scaling control in geothermal wells.

Key words: karst reservoir, anti-scaling and scale removal, calcium carbonate scale formation, scaling simulation, flashing point, geothermal scaling, scale inhibitor

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