Characteristics of the geothermal field and sustainable exploitation of geothermal resources in northwest Shandong Province

This paper focuses on the core issues in the development of medium-low temperature hydrothermal geothermal resources in northwestern Shandong, such as geothermal water level decline, insufficient reinjection efficiency, and risk of thermal breakthrough. Based on regional geological surveys, geothermal drilling, geophysical exploration, geochemical testing and long-term monitoring data, this study systematically analyzes the geothermal field characteristics, geothermal reservoir properties and geochemical evolution of geothermal fluids using the thermal reservoir method and numerical simulation, evaluates the resource potential, and optimizes the intensive development well pattern using data from five typical production-injection projects. The results indicate a regionally high terrestrial heat flow. The geothermal field, controlled by basement structures, exhibits a pattern of "higher in the east and lower in the west, and higher in uplifted areas than in depressions." Geothermal gradient ranges from 3.0 ℃/100 m to 4.0 ℃/100 m, exceeding 4.0 ℃/100 m in local uplift zones. The main thermal reservoirs are the sandstones of the Neogene Guantao Formation and the Paleogene Dongying Formation, with reservoir temperatures between 54.4 ℃ and 85.9 ℃. The Guantao Formation is a high-porosity (22% to 32%) and high-permeability (averaging 596.3×10^-3μm²) reservoir. The Dongying Formation, with thicknesses up to 800 m in some areas, meets the conditions for large-scale development. The geothermal fluid is predominantly of the Cl-Na type, exhibiting weak to moderate scaling and corrosiveness. The region is rich in geothermal resources, with single-well water yields from the Guantao Formation ranging from 76.03 m³/h to 92.24 m³/h. An optimal production-injection well spacing of 450 m was determined. When combined with a staggered-row well network layout and 100% same-layer reinjection, the temperature variation within the thermal reservoir can be controlled within 0.5 ℃. This study elucidates the core mechanism of "structural control on heat distribution." By integrating multi-project field data with numerical simulation, it quantifies the impacts of well spacing and reinjection parameters on development efficiency. The research establishes a full-chain development framework encompassing "geological understanding→resource assessment→technical optimization→environmental impact prevention and control," providing a replicable model for the sustainable development of geothermal resources in similar sedimentary basins.