(1. Shandong Bureau of Geology and Mineral Resources, Jinan 250013; 2. Shandong Geology and Mineral Engineering Group Co., Ltd., Jinan 250013; 3. Shandong Institute of Geology and Mineral Engineering, Jinan 2500 14)

About the author: Xu Junxiang (1961-), male, professor-level senior engineer, whose research interests are hydrogeology and environmental geology.

Based on the analysis of the distribution characteristics, geological conditions and the present situation of geothermal resources exploration and development in Shandong Province, this paper puts forward some suggestions on the exploration and development planning of geothermal resources, predicts the prospect of geothermal resources in Shandong Province, and provides the basis for relevant departments to formulate long-term development plans and guide the exploration and development of geothermal resources in Shandong Province.

Keywords: geothermal resources; Geothermal area; Development and utilization

Nowadays, geothermal energy has become one of the important alternative energy sources after coal and oil, and another important green new energy source after solar energy and wind energy. Geothermal resources integrate heat energy and water resources, which can be used not only for geothermal power generation, but also for heating, bathing, medical care, leisure and recuperation, breeding, planting, textile printing and dyeing, food processing and so on. In addition, the development and utilization of geothermal resources can promote the development of geothermal resources exploration, geothermal well construction, ground development and utilization engineering design and construction, geothermal equipment production, water treatment, environmental engineering, catering, tourism and holiday, etc. It is a new industry, which can greatly increase social employment, promote economic development and improve people's quality of life, with obvious social, economic and environmental benefits and broad development prospects.

1 Distribution characteristics of geothermal resources

Shandong province is rich in geothermal resources in China. At present, geothermal resources have been found in other cities 15 except Rizhao and Laiwu. According to statistics, there are five natural hot springs 15 in the province, and more than one geothermal borehole 100 is exposed manually. The geothermal resources in Shandong Province are mainly medium-low temperature geothermal resources that can be directly utilized, which are characterized by wide distribution, various types, moderate burial depth, mainly medium-low temperature and good development and utilization conditions. According to the investigation results of Shandong Bureau of Geology and Mineral Resources, it is preliminarily estimated that the shallow geothermal resources in the province with a depth of 3000m are about 3. 1863× 1020J, which is equivalent to the heat burned by15 billion tons of standard coal, and can be developed for heating, industrial utilization, hot water supply, bathing, health care, recuperation, entertainment and so on. According to the exploitable amount of geothermal resources, if it can be fully industrialized, the potential economic benefits can reach more than 10 billion yuan per year. At the same time, the employment problem of tens of thousands of people can be solved every year, which is conducive to social stability and the economic, social and environmental benefits will be immeasurable.

According to the comprehensive factors such as geological and structural conditions, types of thermal reservoirs, lithology and void characteristics, burial and shape of thermal reservoirs, Shandong Province can be divided into four geothermal areas: eastern Shandong geothermal area, Yishu fault zone geothermal area, central and southern Shandong geothermal area and northwestern Shandong geothermal area.

Ludong geothermal area: Ludong geothermal area is located in the east of Yishu fault zone, with Shandong Peninsula as the main body, and its administrative divisions include Weihai, Yantai and Qingdao, as well as parts of Weifang and Rizhao. It is an area where geothermal hot springs are exposed intensively, and the surface heat is obvious, with hot springs 13 exposed. Among them, there are 7 medium-temperature hot springs and 6 medium-high temperature hot springs.

Geothermal area of Yishu fault zone: located in Yishu fault zone, including Weifang, Linyi and Rizhao. The medium-high temperature hot spring 1 (Tangtou hot spring) is exposed naturally in this area, and the geothermal outcrop (geothermal hole) 1 is exposed artificially.

Central and South Shandong Geothermal Area: It is located in the vast area west of Yishu fault zone, south of Qihe-Guangrao fault zone and east of Liaocheng-Lankao fault zone, including Laiwu, Jining and Zaozhuang and parts of Weifang, Zibo, Jinan, Heze, Liaocheng, Dezhou and Binzhou. There is less surface heat display in this area, and the hot spring 1 is naturally exposed (Qiaogou hot spring), and the temperature is low; Artificially exposed geothermal outcrop (geothermal hole) 17. Among them, there are 7 low-temperature geothermal holes, 7 medium-temperature geothermal holes and 2 medium-high temperature geothermal holes.

Geothermal area in northwest Shandong: the geothermal storage area in northwest Shandong includes the area north of Qiguang fault and west of Liaokao fault. Including Dongying, Binzhou, Dezhou and Liaocheng, and parts of Heze. This area is the most widely distributed area of geothermal resources in the whole province, with 67 geothermal outcrops (geothermal holes) exposed artificially.

2 Geothermal geological conditions

2. 1 eastern Shandong geothermal area

There are two ridges and one depression (Jiaobei uplift, Jiaolai depression and Jiaonan uplift) in this area, which is called "herringbone" structure in eastern Shandong, and the two ridges and one depression are roughly northeast-northeast trending. Neotectonic activity is strong, neotectonic faults are developed, and the activity intensity increases from south to north. The bedrock lithology of Jiaobei and Jiaonan Uplifts in eastern Shandong geothermal area is dominated by granite and metamorphic rocks, which are brittle and have poor permeability, and mainly rely on cracks and fracture zones to conduct water. The distribution of thermal anomalies is controlled by the structure, and the hot springs are exposed at the intersection of two groups of faults or different contact zones of rock masses. The groundwater circulates along the faults in the recharge area and is heated by the deep ground temperature, and then rises to the shallow part under the action of hydraulic pressure difference to form thermal anomalies. Thermal storage is distributed in groundwater drainage areas, generally located in valleys, intermountain basins and piedmont plains, and hot water supply areas are located in hilly areas with high terrain. Because of the strong neotectonic activity in Jiaobei Uplift, the faults in it are often in an open state, the cracks are not easy to be blocked, and the water conductivity is enhanced, thus creating conditions for the circulation of underground water depth. Therefore, there are 13 of the hot springs in Ludong thermal storage area 14 located in Jiaobei Uplift. The neotectonic activity of Jiaonan uplift is weak, and most of the faults are gradually closed due to erosion and hydrochemical precipitation, which is not conducive to the formation of underground hot water circulation system, so no geothermal anomaly has been found in this uplift area so far.

Geothermal systems in thermal storage areas are all of deep circulation convection type. The thermal reservoir is buried shallowly, and the caprock is Quaternary sediments, with a thickness generally less than 50m and poor thermal insulation conditions. The type of thermal reservoir is fractured zonal thermal reservoir, and the thermal reservoir rocks are mainly Mesozoic granitic rocks and early CAMBRIAN metamorphic felsic rocks. Thermal reservoir thickness180 ~ 280m. Most of the thermal reservoirs are relatively independent hot water structural systems, and there is no obvious hydraulic connection between them. The chemical composition of water in adjacent thermal reservoirs is similar, but there are some differences in water temperature and chemical composition content. The genesis of thermal reservoir is that atmospheric precipitation seeps down to the deep along faults and contact zones of different rock masses, and then rises to the shallow along the channel after being heated by surrounding rocks, and the reservoir is formed in rock strata with good permeability. The thermal storage temperature is controlled by the fault structure, and the water temperature is relatively high, generally 65 ~ 90℃. The salinity of geothermal water is low, generally 500 ~ 2500 mg/L, and the hydrochemical types are complex, mainly HCO 3 SO 4-Na, Cl-Na and Cl-Na Ca. The spatial shape of geothermal reservoir in geothermal field is irregular and controlled by faults. It is mostly in the shape of belt or ellipse on the plane, and its long axis direction is consistent with the trend of thermal control faults. The spatial shape is like irregular mushroom, and its distribution area is small, generally less than 1km2.

2.2 The geothermal area of Shu fault zone

This area is an earthquake-prone area in Shandong Province, with strong neotectonic activity. There are four main faults in this area from west to east, namely Mianqi-Gegou fault, Yishui-Tangtou fault, Anqiu-Juxian fault and Changyi-Dadian fault. From the deep structure, the thermal storage area of Yishu fault zone is Moho uplift zone, and the geothermal flow density is 62mW/m2, which is higher than that of the thermal storage areas on both sides. Yishu fault zone is a high-temperature geothermal zone with thin crust, high upper mantle and shallow conductive layer. The geothermal system is of deep circulation convection type, and the thermal storage type is of fractured zonal thermal storage, which is distributed in the depression. The convex areas on both sides of the depression are hot water supply areas, and the higher heat flow value and the more developed neotectonic faults in the area create conditions for the formation of the geothermal system. Thermal reservoirs are mainly composed of metamorphic granitic rocks in early CAMBRIAN and Mesozoic igneous rocks, sand shale and so on, so thermal reservoirs can be formed at the edge of the depression and ideal structural parts. The thickness of thermal reservoir is150 ~ 250m, and the thermal storage area is not large, and the buried depth is generally shallow at 200m, the water temperature is around 60℃, and the salinity is about 3000mg/L..

2.3 South Shandong geothermal area

The geothermal reservoir area in central and southern Shandong Province is a Luxi uplift area on the tectonic unit, with Weishan Lake-Jining-Pingyin as the boundary. According to the different characteristics of thermal reservoir, it is further divided into two sub-regions, namely, hilly and mountainous areas in central and southern Shandong Province and latent uplift areas in southwestern Shandong Province. After the Late Jurassic, under the action of Yanshan movement and Himalayan movement, the original unified basement broke, forming a series of convex zones and concave zones along the fault. The convex zones suffered erosion and the concave zones accepted Mesozoic and Cenozoic sedimentation. The Moho surface in the hilly and mountainous sub-region of central and southern Shandong Province is deeply buried, and the geothermal flow density is 48 ~ 50mW/m2, which is the lowest in Shandong Province. Geothermal anomalies in this area are generally located near the intersection of uplift and depression and at the intersection of NW-trending, NE-trending and SE-trending neotectonic faults controlling the depression. The sub-region of the submarine uplift in southwest Shandong is an active alternating zone of groundwater runoff near the hilly and mountainous areas, and groundwater activities have a great influence on its geothermal field. According to the stratigraphic and structural characteristics, the Niujiaodian-Liulisi fault in the east of chiping is divided into south and north sections, and the northern section is the northern margin of Taishan uplift, which is a monoclinal structure with gently inclined strata to the north. The Cenozoic strata are lower Paleozoic Carboniferous-Permian and Ordovician-Cambrian. The southern section consists of a series of bulges and depressions arranged alternately. The bulges are Neogene Lower Futaishan Group and Lower Paleozoic, while the depressions are deposited with thick Cenozoic and Mesozoic Jurassic strata, and the lower part is Paleozoic.

The types of thermal reservoirs in the hilly sub-region of central and southern Shandong are zonal thermal reservoirs and CAMBRIAN-Ordovician carbonate karst fractured layered thermal reservoirs. The former is metamorphic rocks with well-developed fractures in the Early Cambrian, and the thermal reservoir thickness is150 ~ 260 m; The latter is mainly limestone with thermal storage thickness120 ~ 200 m. It is a deep circulation convection type. Hot springs and underground hot water wells are mostly distributed in the intersection of NW-trending and near-SN, NE-trending or near-E-trending faults or in the contact zone between Mesozoic rock mass and Paleozoic limestone. Hydrochemical types are Cl-Na type or Cl. SO4-Ca. Na type. The salinity is 4500 ~1700 mg/l, and the temperature of geothermal well is 27 ~ 71℃. The thermal reservoirs in the northern part of the sub-region of southwestern Shandong Province are Ordovician limestone, Carboniferous and Permian sandstone and limestone. The thermal reservoirs have the characteristics of fault belt and layer, and the water abundance is quite different. The thermal reservoirs in the southern section are mainly Ordovician karst fracture thermal reservoirs and Neogene pore thermal reservoirs, mainly conductive ones. The Ordovician limestone thermal reservoirs are mainly distributed in Yanggu, Heze and Qingguji bulges, with a water temperature of 50 ~ 60℃ and a large area, which has the characteristics of both layered and banded thermal reservoirs. The buried depth of thermal storage is generally between 200 ~1600 m. The water temperature is between 40℃ and 80℃, the salinity of hot water is 400 ~ 3500mg/L, and the hydrochemical type is SO4 Cl-Na Ca.

2.4 Northwest Shandong geothermal area

The geothermal area in northwest Shandong belongs to a part of Mesozoic and Cenozoic fault basin developed on the North China platform. It is based on Archean metamorphic rock series, and a set of lower Paleozoic dominated by marine carbonate rocks and upper Paleozoic with land-sea interaction to continental facies are developed on it. The Moho surface in the geothermal area of northwest Shandong is shallow, and it has a relatively high heat flow value and strong water-rich thermal reservoir compared with other thermal reservoirs, so it is the area with the greatest development potential of hot water resources. The hot water supply source in the area is atmospheric precipitation, and the supply mode is lateral runoff supply. Generally speaking, the geothermal system is a warm water geothermal resource formed under the mechanism of geothermal flow dominated by heat conduction, and there is also the possibility of a convective geothermal system near the deep fault zone in the bedrock thermal reservoir in the convex area. Its formation and distribution are controlled by geological structure and stratigraphic lithology. The thermal storage system is mainly divided into pore type and karst-fracture type is distributed locally. Underground hot water mainly exists in pores and fractures of Neogene clastic rocks, CAMBRIAN-Ordovician karst-fractures and fractures of Taishan Group metamorphic rock series. The caprock is composed of cohesive soil and sandy soil with a thickness of 900 ~1000 m, and the heat source mainly comes from the deep crust and the upper mantle to conduct heat flow. The thermal storage water temperature of clastic rocks is 40 ~ 80℃, and that of bedrock is 50 ~ 90℃, and the geothermal gradient is generally 3 ~ 4.5℃/100m.

Neogene layered pore thermal reservoir is a set of interbedded deposits of sandstone and mudstone dominated by extremely thick fluvial facies, with a thickness of 500 ~1300 m and a floor burial depth of 700 ~1600 m. The main thermal reservoirs are Guantao Formation and Dongying Formation. The lower Paleozoic karst fracture thermal reservoir is distributed in the Cenozoic or upper Paleozoic strata in the uplift area, which is scattered in islands and has a small area. Karst fracture thermal storage has the characteristics of both layered and fault zone thermal storage, and the characteristics of thermal storage depend on geological structure and karst development. The water content of limestone thermal storage directly covered by Neogene is much higher than that covered by Carboniferous-Permian. Near the fault, the water-rich property is strongest and the temperature is higher, while far away, the water-rich property is poor and the temperature is low. Karst fractured thermal reservoir is an important thermal reservoir in the region, which is characterized by higher water temperature and water abundance than Cenozoic thermal reservoir. According to the data of three karst fracture geothermal wells in northwest Shandong thermal storage area/kloc-0, the water abundance of limestone thermal storage is quite different, and the salinity of karst fracture thermal storage hot water is high, reaching 6.30 ~14.37 g/L.

3 Geothermal resources exploration, development and utilization status

The exploration of geothermal resources in Shandong Province began in 1950s. 1958 The Bureau of Geology and Mineral Resources of Shandong Province carried out geothermal exploration in Zhaoyuan, Wendeng, Weihai and Jimo of Jiaodong Peninsula, and found some hot water spots on the basis of the original hot spring dew point. To 1996, the geothermal fields (points) such as Tangtou, Weihai, Zhaoyuan, Jinan, Fujiazhen, Zibo, Muping Longquan and Feicheng Anjiazhuang were explored successively. Since the end of 1990s, with the attention of local governments at all levels to the problems of resources and environment, great progress has been made in the exploration of geothermal resources in Shandong Province, including the Yellow River Delta, northwest Jinan, northern Shandong and other key areas, and the exploration of key areas in dozens of counties with geothermal prospects. More than 30 geothermal wells have been newly constructed in Heze, Liaocheng, Dezhou, Binzhou, Dongying, Jinan and other areas with layered thermal storage, and the water temperature is between 42 and 80℃. At present, the exploration of geothermal fields in the province has reached 140 times, and the accumulated investment is more than 50 million yuan.

Shandong province has a long history in geothermal utilization, which can be traced back to 1000 years ago according to relevant data. Officially as a resource development began in the 1920s, but it was only used for bathing. Since the reform and opening up, especially since the 1990s, the geothermal development projects in Shandong Province, which mainly aim at health care, recuperation and heating, have developed rapidly, but there is a big gap compared with other provinces and cities and rich geothermal resources. At present, there are 46 geothermal development units in the province, and the main development projects include hot spring bathing, heating, swimming, domestic hot water supply, planting, breeding and tourism, etc. In 2003, the geothermal heating area in the province was 5.5× 105m2, an increase of 17 m2 compared with 3× 104m2 in 2000.

4 Shandong geothermal resources development and utilization of ecological and environmental significance

Structural pollution is very prominent in Shandong province, with the total emission of main pollutants such as sulfur dioxide ranking in the forefront of the country, and the environmental quality of major cities is at a low level. Coal-burning air pollution in Shandong province is particularly prominent in winter heating period, and the contribution rate of coal to air pollution is above 70%. The pollutants emitted by coal combustion are harmful to the ecological environment, especially to human health. Emissions such as sulfur dioxide, nitrogen oxides, ozone and carbon monoxide can cause human respiratory diseases, and the incidence of lung cancer increases. According to relevant research data, air pollution is closely related to the incidence of lung cancer. Polycyclic aromatic hydrocarbons attached to particulate matter are usually the main substances causing lung cancer, represented by benzo (a) pyrene, which is the product of coal burning at a certain temperature. If the concentration of benzo (a) pyrene in the air increases by one ten thousandth, the cancer mortality rate of residents will increase by 5%. The development and utilization of geothermal resources for heating will change the energy structure, greatly reduce the air pollution caused by coal burning, greatly improve the ecological environment quality of the city, and promote the health and quality of life of residents. While saving traditional energy, many countries use geothermal resources to exert their remarkable ecological and environmental benefits. Because geothermal energy has replaced most of the fuel and coal, the atmospheric environment in Reykjavik, Iceland, has been fundamentally improved, and the carbon dioxide content, the chief culprit of the greenhouse effect, has been reduced from 270,000 tons in 1960 to 3,000 tons in 2000 (a decrease of 98.9%). Thanks to the clean air brought by geothermal development, Iceland has just become one of the three most suitable countries for human habitation named by the United Nations. Compared with coal-fired boiler heating, the geothermal heating in Diequan Residential District of Tianjin is only 4× 104m2, reducing sulfur dioxide emission 18 t/a, soot 30 t/a and coal ash 580 t/a..

The geothermal resources in Shandong province are widely distributed and rich in reserves, which has laid a good foundation for the development of heating. Geothermal heating can be used in Jinan, Dongying, Dezhou, Liaocheng, Heze, Linyi and other large and medium-sized cities and parts of other cities. At present, Dezhou, Dongying, Liaocheng, Heze and other cities have made a good start in geothermal heating. Geothermal heating in Dezhou City has developed from the blank of 1998 to 3.0× 105m2 in 2003, which only reduces the annual emission of sulfur dioxide 135t/a, dust 225t/a and coal ash 4250t/a.. In Dongying City, geothermal heating increased by 2.5× 105m2 in three years. According to the development and utilization plan and trend forecast of geothermal resources in this city, the geothermal heating in this city will develop to1.5× 106m2 in the next10, thus reducing the emission of sulfur dioxide, smoke and dust 1 125 t/a and coal ash 2 every year. It is predicted that the geothermal heating area in the whole province will reach 6.4× 106m2 in the next 1 0 year, and the annual emission of sulfur dioxide, soot and coal ash will be reduced by 2,880t/a (table1).

Table 1 Forecast Statistics of Geothermal Heating and Pollutant Emission Reduction in Shandong Province

Continued

5 Suggestions on geothermal resources exploration and development planning

Geothermal is a non-renewable or poor renewable resource. In this sense, it has similar exploration and development properties with natural gas, coal and other mineral resources in the region. The exploration and development of geothermal resources is a high-risk and high-input industry. In order to reduce blindness and detours, the prospect of geothermal resources is predicted, which provides a basis for relevant departments to formulate long-term development plans and guide the exploration and development of geothermal resources in the province.

5. 1 Evaluation of exploration and development conditions of geothermal resources

5. 1. 1 area with good geothermal exploration and development conditions

All geothermal sub-regions in Linqing Depression, most geothermal sub-regions in Jiyang Depression and part of Chengning Uplift, northern margin of Jiaobei Uplift and Jiaolai Basin in eastern Shandong geothermal region, Liaodong-Yanggu Uplift, Heze Uplift and the western segment of Qinggu Uplift have great geothermal resources potential. Within the accessible depth of 2000m, the geothermal resources of Neogene thermal storage and Paleozoic Cambrian-Ordovician thermal storage are extremely rich, with good water quality, moderate water temperature and excellent exploration and development conditions. In particular, the Neogene thermal storage reservoir is shallow buried, the exploration technology is difficult and the cost is low, so it is the first choice for geothermal exploration and development.

The most promising counties and cities for exploration and development are: Hekou, Dongying District, Kenli, Lijin County and northern Guangrao County of Dongying City; Binzhou Bincheng, Yangxin, Zhanhua, Huimin and Boxing counties; Dezhou Decheng, Linyi, Pingyuan, Yucheng, Qihe, Xiajin, Wucheng and other counties and cities; Dongchangfu, Yanggu, Linqing, guanxian, Shenxian and Gaotang in Liaocheng; Juancheng, Dongming, Peony, Caoxian and Dingtao counties in Heze City; Shanghe, Jiyang County, Tianqiao and Licheng District in the north of Jinan; Feicheng, Tai 'an City; Zhaoyuan and Muping in Yantai City; Huancui in Weihai City and hot outcrops in various places, etc.

5. 1.2 area with good geothermal exploration and development conditions

The areas with good geothermal exploration and development conditions include the geothermal sub-region of Chengning Uplift in the geothermal area of northwest Shandong, the depression of the geothermal area of Yishu fault zone and the Yishui-Linyi area in the south section, and the hidden Ordovician limestone section of Donge Niujiaodian-Linzi-Shouguang-Niutou Town in the geothermal area of western Shandong. The geothermal resources in these areas have great potential and are rich. The Neogene Guantao Formation thermal reservoir is thin and has little development value, but the top surface of Cambrian-Ordovician thermal reservoir is shallow and the exploration technology is not difficult.

The counties and cities with exploration and development prospects are: Zouping and Wudi in Binzhou City; Ningjin, Leling, Qingyun and northwest Lingxian in Dezhou; Chiping in Liaocheng City; Gaoqing, Huantai, Zhoucun, Zhangdian, Zichuan and Linzi in Zibo; Zhangqiu, Penglai, Taian, Yinan, Laiwu, Qufu, Xintai and other places.

5. 1.3 Geothermal exploration and development conditions general area

The geothermal resources in Linzi, the east of Luxi geothermal area, the Changyi-Dadian fault zone, and the Yuan Gu Yu limestone and marble section underlying Mesozoic in Jiaolai Basin have great potential. The thermal reservoir of Neogene Guantao Formation is thin and its resources are small. The Cambrian-Ordovician thermal storage resources are large, and the buried depth of the top interface is shallow, so the exploration and development technology is not difficult.

The counties and cities with general prospects for exploration and development are: Changqing, Pingyin, Weifang, Qingzhou, Zhucheng, Anqiu, Gaomi, Changle, Changyi, Laizhou, Qixia, Muping, Haiyang, Pingdu, Jimo, Jiaonan, Jiaozhou, Rongcheng, Rushan, Dong 'e, Wenshang, Dongping, Ningyang, Yanzhou, Surabaya and Wuyang.

5.2 Evaluation of Main Exploration and Development Thermal Storage

Geothermal resources in Shandong Province are widely distributed and have considerable potential. Neogene hot water and part of buried hill CAMBRIAN-Ordovician karst fissure hot water exist in the accessible depth of 2000m, which are the main target layers for finding and exploring geothermal resources in the future.

(1) Located in the geothermal area in northwest Shandong, north of Qihe-Guangrao fault and west of Liaocheng-Lankao fault, including Linqing depression, Jiyang depression and Laoling, Qingyun and Wudi uplift of Chengning uplift, the thermal storage reservoirs of Neogene Guantao Formation and Paleogene Dongying Formation are the main exploration and development targets.

(2) In the western Shandong geothermal area south of Qihe-Guangrao fault and east of Liaocheng-Lankao fault, the CAMBRIAN-Ordovician carbonate karst-fractured hot water is the main target layer for exploration and development. While exploring and developing the hot water of Neogene Guantao Formation in Chengning Uplift, Linqing Depression and Jiyang Depression Uplift, we can also take into account the exploration and development of karst-fractured hot water of Lower Paleozoic Ordovician-Cambrian carbonate rocks. The vicinity of the junction of the uplift and depression in the geothermal area of western Shandong and the intersection of the NW-trending, NE-trending and SE-trending neotectonic faults controlling the depression should also be the focus of exploration.

(3) The geothermal area in eastern Shandong is explored and developed into the hot spring intensive area in Jiaobei Uplift and the northern edge of Jiaolai Basin, and the Yuan Gu Yu limestone and marble area underlying Jiaolai Basin.

(4) The exploration and development of geothermal area in Yishu fault zone mainly focus on the edge of depression and ideal structural parts, early Cambrian metamorphic granitic rocks, thick Mesozoic igneous rocks and sand shale, and at the same time, pay attention to the banded areas near both sides of Yishu fault zone.

5.3 Geothermal resources development and utilization evaluation

Geothermal resources in Shandong Province belong to medium and low temperature hot water type, which is suitable for direct development and utilization. However, due to the differences in water quality and quantity, it has different uses in direct utilization. In the geothermal-rich northwest of Shandong Province, the temperature of the lower member of Neogene Minghuazhen Formation is low, generally 35 ~ 45℃, and the water quality is good, with the salinity of1~ 2g/L, which can be directly used for domestic water and industrial and agricultural water. The hot water temperature of Neogene Guantao Formation is 45 ~ 70℃, and the salinity is 2 ~15g/L. It is rich in various trace elements beneficial to human health, suitable for both water and heat, and can be used for comprehensive utilization in heating, bathing, recuperation, greenhouse planting and aquaculture. The karst fissure hot water of Dongying Formation and Ordovician-Cambrian carbonate rocks has high temperature and high salinity (5-20 g/L salt water), and is rich in trace elements and radioactive elements such as radon, which are beneficial to human body, and is suitable for both water and heat. Focus on the development and utilization of medical care, hot spring vacation, heating, planting and breeding and industrial processes. In other areas, due to the small amount of geothermal resources and low corresponding heat, most of them are natural hot springs, which are generally suitable for hot spring recuperation except for some areas that meet the heating requirements.

Countermeasures and suggestions for exploration, development, utilization and protection of geothermal resources

The exploration, development and utilization of geothermal resources in Shandong Province are in a partial and sporadic initial stage. With the reform and opening up and the rapid development of social economy in the region, the level of urban modernization in the region has been continuously improved, and geothermal energy, as a green energy source, has higher and higher development and utilization value. The exploration and development of geothermal resources should focus on cities and key economic development areas, carry out key exploration and development experiments, and provide exemplary experience for the comprehensive development and utilization of geothermal resources in the province.

(1) correctly understand the characteristics of geothermal resources. Geothermal resources are formed under specific geological, structural, hydrogeological and hydrogeochemical conditions. Because of its deep burial, long supply route and weak regeneration ability, its resources are limited, not inexhaustible. It is necessary to maintain the long-term, continuous and stable exploitation of its resources, achieve planned and rational development and utilization, and prevent the loss of resources and environmental geological problems caused by blind and disorderly exploitation. Therefore, we must pay attention to and do well the protection of geothermal resources.

(2) Formulate and strictly implement the plan for the development, utilization and protection of geothermal resources. In order to develop, utilize and protect geothermal resources scientifically and reasonably, its development and utilization should follow the principle of paying equal attention to both open source and throttling and development and protection; According to different uses, layered exploitation and layered management of geothermal resources.

(3) The exploration, development and utilization of geothermal resources should be closely combined with the construction of ecological province, urban environmental protection, tourism development and the development of efficient ecological agriculture. Through the development and utilization of geothermal resources, we can improve and protect the environment, stimulate economic development, promote consumption and improve people's living standards.

(4) The exploration, development and utilization of geothermal resources should implement the comprehensive development and utilization policy of "combination of exploration and mining", "cascade development and multi-use of one water", and adhere to the principle of "easy first, then difficult, shallow first, then deep, and combination of depth and depth". For the central city of geothermal area in northwest Shandong province, which is rich in geothermal resources, concentrated in thermal anomalies and superior in traffic location, centralized exploration and development will be carried out. Strengthen the research on geothermal development and utilization, and develop bathing, medical treatment, aquaculture and tourism based on the development of geothermal resources. Make full use of the waste oil wells in oil exploration and exploitation to develop geothermal resources, and on the basis of comprehensive research, find feasible technical methods and routes to transform some waste oil wells into hot water wells.

(5) Establishing geothermal conservation zone. According to the needs of economic development and people's life, the rational exploitation scheme and environmental protection scheme of geothermal resources are formulated. In the development process, it is necessary to work out the well layout scheme according to the burial and distribution of geothermal resources, and strictly follow the recoverable amount of hot water to prevent environmental geological problems such as resource depletion and land subsidence caused by over-exploitation.

(6) Strengthen the dynamic monitoring in the development of geothermal resources. The amount of geothermal resources is limited, and its regeneration ability is weak. During the mining process, its water level, water quantity, water quality and water temperature will change with the mining process. In order to monitor the dynamic information of geothermal resources development in time and avoid environmental geological disasters such as land subsidence and hot water resource depletion due to over-exploitation, we should strengthen the dynamic monitoring of geothermal resources development.