Quaternary loose strata are widely distributed in 18 cities under the jurisdiction of Henan Province, and there are abundant low-grade geothermal energy resources in its shallow soil and shallow groundwater. In order to rationally develop and utilize shallow geothermal energy resources in cities, Henan Geological Survey Institute applied to Henan Provincial Department of Land and Resources in 2006 for the project "Evaluation and Development and Utilization of Shallow Geothermal Energy in Key Cities in Henan Province", which was approved by Henan Provincial Department of Land and Resources and listed as "Key Scientific and Technological Project of Geology and Mineral Resources in Henan Province" (scientific research project No.02). At the beginning of 2007, the project design was compiled, and it was approved by Henan Provincial Department of Land and Resources in March 2007.
The research scope of the original project: Zhengzhou, Kaifeng, Xinxiang, Xuchang, Luohe, Zhoukou, Anyang, Puyang, Jiaozuo, Luoyang, Nanyang and other key cities 1 1 urban built-up areas and planning areas, covering an area of about 5000km2. During the study period, according to the social development, the working area was adjusted to the planned area in 2020.
The research scope of this book is based on expert opinions and combined with the actual situation in Henan Province, and the corresponding contents of seven cities, including Hebi, Jiyuan, Sanmenxia, Shangqiu, Pingdingshan, Zhumadian and Xinyang, have been added. At the same time, according to the Code for Exploration and Evaluation of Shallow Geothermal Energy (DZ/TO225—2009), the application suitability evaluation and zoning research content of ground source heat pump system have been added.
Second, the purpose of the study
The purpose of this project is to provide scientific basis for the scientific utilization and protection of shallow geothermal resources, the preliminary study on the types and potential of shallow geothermal resources in key cities of Henan Province, the development and utilization zoning, the rational development and utilization of shallow geothermal energy in cities of Henan Province, and the reduction of investment risks.
Third, the research content
In order to ensure the realization of the research objectives and tasks of this project, help tackle key scientific and technological problems and improve the scientific and technological level and practicability of the results, this book mainly studies from the following four aspects.
1. Study on buried distribution and circulation characteristics of shallow geothermal energy
Aiming at the hydrogeological units such as piedmont alluvial plain, river alluvial plain and valley basin where the city is located, this paper studies the buried distribution law and cycle sign of shallow geothermal energy, which is the basis of this research project, and focuses on the following contents.
1) Quaternary thickness and annual constant temperature layer depth.
2) The burial, distribution and circulation characteristics of shallow geothermal energy.
3) Dynamic changes of water level, water temperature and water quality and their influencing factors.
4) Establish and determine the evaluation parameter series of shallow geothermal resources, including permeability coefficient, water storage coefficient, geothermal gradient, recharge permeability coefficient, thermal conductivity and geothermal flow value.
5) Establish the conceptual model of shallow geothermal energy in typical cities and determine the boundary conditions.
2. Evaluation of shallow geothermal energy resources
This topic is the main basis for the rational development and utilization of urban shallow geothermal energy resources. According to different hydrogeological units, the main research contents are as follows:
1) According to the ground (water) temperature observation, pumping and recharging test and indoor test, calculate and determine the calculation and evaluation parameters of shallow geothermal energy resources.
2) Establish a mathematical model according to the conceptual model.
3) Using different evaluation methods to calculate the shallow geothermal energy reserves and recoverable resources.
4) According to the current exploitation and recoverable resources of shallow geothermal resources, calculate and divide the exploitation potential.
3. Research on shallow geothermal energy collection and recharge technology
This topic is also the main basis for the rational development and utilization of shallow geothermal energy. According to the geological and hydrogeological conditions of different hydrogeological units, combined with existing projects, recharge technology and field tests were carried out to study the effects of recharge quantity, water quality and water temperature on shallow geothermal energy storage conditions and recoverable resources. Study the construction technology and determine the technical conditions of shallow geothermal energy collection and recharge, including reasonable well depth, well spacing, well structure, mining depth reduction and recharge. Determine a reasonable scheme of "instant irrigation".
4. Zoning of comprehensive development and utilization of shallow geothermal energy
On the basis of the above research, the suitability zoning of shallow geothermal energy development and utilization is carried out; According to the technical conditions of development and utilization, determine the development and utilization mode of shallow geothermal energy; The corresponding protection measures and targets are put forward for groundwater resources and shallow geothermal energy resources.
Fourth, the main research methods
1. Data collection and secondary development
During the implementation of the project, the social and economic development, regional geology, hydrogeology, shallow geothermal energy utilization, remote sensing, hydrology, meteorology, environmental protection, urban construction planning and urban energy saving planning of 18 key cities were widely collected and systematically sorted out. The research contents include: ① stratigraphic structure and structural characteristics; ② Hydrogeological conditions of shallow geothermal energy utilization layer; ③ Summarize the present situation and existing problems of shallow geothermal energy development and utilization.
2. Investigation and study on the present situation of shallow geothermal energy development and utilization
On the basis of ground investigation, the shallow geothermal energy utilization project in 18 urban area studied in this paper was investigated, including the project area, applied building area, number of pumping wells, well spacing, pumping quantity and groundwater temperature, recharge quantity and temperature, dynamic change of groundwater during operation, refrigeration (heat) effect, etc.
3. Research and monitoring of hydrodynamic methods
Shallow geothermal energy resources can be called a kind of movable resources mainly based on water. In order to study the runoff conditions of groundwater, the groundwater level was dynamically measured and monitored. In dry season, unified measuring points of groundwater level are deployed, and the density of unified measuring points is generally one point every 4km2; The existing shallow geothermal energy air conditioning system is selected for long-term monitoring to study the influence of underground water source heat pump system operation on groundwater environment. The monitoring time is not less than one hydrological year, and the monitoring contents include pumping quantity, recharge quantity, water level, water quality, water temperature and utilization efficiency. Among them, water samples are taken for water quality monitoring before, during and after the operation of shallow geothermal energy air conditioning system. The frequency of water level and water temperature observation is every 5 days 1 time.
4. Research and monitoring of water thermodynamic methods
In order to study the distribution characteristics of shallow ground temperature, the shallow groundwater temperature was investigated. In this paper, the measurement of groundwater temperature field distribution is mainly carried out in combination with hydrodynamic field research. The instrument adopts drilling thermometer (model JL- 1), and the density of measuring points on the plane is approximately every 25 m2 1 point. The density of vertical measuring points is every 2m 1 point, and the specific situation of well structure is determined according to sounding.
5. Hydrogeochemical research methods
The hydrochemical composition of groundwater reflects the formation environment and conditions of shallow geothermal energy. Through hydrochemical composition, we can study its origin and formation age to evaluate the scientific utilization of shallow geothermal energy. In order to analyze the influence of different water quality on shallow geothermal energy air conditioning system, the corresponding treatment measures are put forward. Combined with the existing data, water quality analysis samples were supplemented at the dynamic monitoring points of shallow geothermal energy air conditioning system and the research areas with relatively few hydrochemical data, and sent to the laboratory for testing.
6. Research on field experiment method
In order to understand the water abundance of aquifer, calculate hydrogeological parameters, study the influence of groundwater recharge, water quality and water temperature on shallow geothermal energy storage conditions and exploitation resources, and determine the reasonable scheme of "irrigation immediately after mining"; The scientific construction technology and completion structure of pumping recharge well suitable for fine-grained aquifer area in eastern plain are studied, and the applicable conditions of shallow geothermal energy collection technology are studied. According to different hydrogeological conditions, combined with existing or under construction shallow geothermal energy utilization projects, water injection tests and pumping tests are arranged. In order to obtain the thermophysical parameters of different formation lithology, 1 geological sampling holes were arranged in Zhengzhou City, and the samples were sent to the laboratory of Nanjing University for testing.
7. Model establishment and research
Establish a balance model of shallow geothermal energy supply, discharge and storage, and evaluate shallow geothermal energy resources; According to the hydrogeological conditions, the available resources of shallow geothermal energy are predicted and evaluated by heat flow method or numerical method; According to the development resources and the existing exploitation amount, the development and utilization potential of shallow geothermal energy is evaluated.
Geothermal profiles with abundant data and typical types are selected, and the migration of geothermal fluid is simulated by HST3D numerical simulation software. Forecast and evaluate the temporal and spatial variation trend of geothermal fluid temperature under the conditions of planned mining and shallow geothermal fluid utilization; Simulate the distribution characteristics of groundwater flow field and temperature field under different geological, hydrogeological and geothermal conditions; Evaluating the thermal storage function and thermal reserves of shallow groundwater provides scientific basis for rational and scientific development of shallow geothermal fluid resources.
8. Comprehensive research on development and utilization of shallow geothermal energy
On the basis of the above methods, the technical scheme of shallow geothermal energy collection under different geological and hydrogeological conditions is studied and put forward, and the rational development and utilization zoning of shallow geothermal energy in cities is formulated.
9. Database construction
The collected data and the newly obtained data are collated and bound into a book, the GIS software platform is used uniformly, and the database is established as required. Digitize the original image and the result image, and establish the graphic attribute library and plug-in attribute library.