Proceedings World Geothermal Congress 2005 Antalya, Turkey, 24-29 April 2005
Study of Geothermal Resources in Hebei Plain
Li Hongying and Zhang Dezhong Baoding Municipal Bureau of Land & Resources, The Third Hydrogeology Prospecting Team in Hebei [email protected]
Keywords: geothermal resources, reservoir characteristic, 1.2 Characteristics of Geothermal Resources non-abnormal geothermal area, geothermal utilization and development. 1.2.1 Earth-heat-flow Value Heat energy in the inner Earth transmits to the crust by the ABSTRACT way of transmission and counter-current. The basic physical As a renewable cleaning energy, geothermal resources have concepts describing earth heat status are: Earth-heat-flow been taken on more and more emphasis for development and value, geothermal temperature and geothermal gradient. The utilization worldwide. Hebei Plain is the richest area of changes of Earth-heat-flow value are closely related with the geothermal resources in North-China. The paper presents the tectonic structures among uplifts and depressions in the distribution, contributing factor, types, characteristics and upper mantle. The Plain edge is the depression zone in the upper mantle, whose Earth-heat-flow value is low, within development potential of geothermal resources in Hebei 2 Plain, is great significant for enhancing geothermal 26.3-39.3mW/m . The Plain and the Bohai Bay zone are the resources and promoting local economic development. uplift parts of the upper mantle, whose Earth-heat-flow value is high, within 63-77.7mW/m2. Most high Earth-heat- The human society has been into the 21 century. The next 10 flow value zone in Hebei Province distributes in the Plain 2 years will be the important stage of Chinese economic and the Bohai Bay, with its representative value 73mW/m , 2 2 development; more requirements will be on energy demands higher than the world average value (61mW/m ) . This and environmental protection. One of the essential national would be the great advantage of geothermal resources in policies of China is to develop new energy, protect Hebei Province. environment, and realize social economic sustainability. As a renewable cleaning energy, geothermal resources has been 1.2.2 Earth Temperature Field forming a new type energy industry and caused high The distribution of geothermal field in Hebei Plain is closely attention by government and all walks of life. related with its geological structure. Obvious diversity of its temperature field occurs in different structural part of Hebei Province is located in the north part of the North- geothermal field. Feature summary is as below: China Plain (Figure 1). Underground hot water is quite abundant within it during the long geological history. With (1) Zonal distribution among high-to-low temperature wide distribution, rich reserves and shallow burial, facieses occurs in most areas because of the geological geothermal resources have a great prospect for development uplift-depression structure, except a low temperature and utilization. zone with wideness 30-60km, temperature <35ºC, depth 1000m, caused by the natural cold water flow 1 INTRODUCTION disturbing in those piedmont plain areas. The cap rock geothermal gradient isopleths, 1000m depth and 2000m 1.1 Distribution of Geothermal Resources depth temperature isopleths are nearly identical with The form and distribution of geothermal resources in Hebei regional NE, NNE, NWW and nearly EW tectonic Plain is mainly controlled by deep geological tectonic strikes and basal uplift-depression outline. The conditions. The main types of reservoirs are tectonic- basement uplift zone is relatively high temperature fractured, fracture-karst and voids. The plain is controlled by areas, with temperature >55ºC at 2000m depth, reach to basal tectonics and has high value of geothermal 85-100ºC in some places, on the contrary the relatively background. The geothermal abnormal areas are mainly low temperature areas is corresponding to depression distributed at the uplift part of basal tectonics, uplift part in zone, and the lowest temperature area is at the center of depression, or water transmissive sides of deep fractures. the Cenozoic sediments. According to updated statistic data, there are 30 geothermal fields and abnormal areas with total area 16240km2 and the (2) Different geothermal types. Cenozoic cap rock total amount equivalent with 3.5 billion tons of coal in Hebei geothermal gradient is closely related with the depth of Plain 1 . The typical geothermal fields are: Niutuo Town its roof in the special geological structure of the plain geothermal field, Langfang geothermal field, Ningjin area, consequently the shallower the basement depth geothermal field, Hengshui geothermal field, Dacheng the higher the temperature gradient. geothermal field, Huanghua geothermal field, and Qingxian geothermal field. In accordance with the development of (3) Partial geothermal anomaly. Partial geothermal geothermal geological theory and improvement of mining anomaly caused by rock horizontal and vertical heat technology, some relatively low temperature areas in heterogeneous in the shallow crust, or partial faults depression, i.e., non-abnormal geothermal areas, because of their suitable burying depth, can be the valuable geothermal occurs. fields for utilizing, such as Shenzhou geothermal field and The vertical temperature changes related with not only the Cangzhou City geothermal field (Figure 2). structural position of the field, but also the rock characteristics. At the same depth, temperature is higher in fractures and uplift parts than that in depression parts, i.e. 1 Li and Zhang
Cenozoic geothermal gradient value at the basement uplift or main aquifers are carbonate rocks in mid-Ordovician the top of unfold stratum is higher than that at the depression Fengfeng formation, Cixian formation and Nanjiagou or the shaft of downfold stratum. formation, and early Ordovician Liangjiashan formation, Yeli formation, late-Cambrian Fengshan formation and early The depth of constant temperature layer is about 25m, with Cambrian Fujunshan formation. Total thickness is 600- 15ºC in the Plain. Down to the constant temperature layer, 800m. Production rates of single well are 150-1500m3/d, ground temperature has direct proportion with its depth; with water temperature 50-60ºC at 1000m depth. especially typical feature of transmisive ground temperature field appears in Cenozoic porous formation. Change of Mid-Upper-Proterozoic reservoirs, including Qingbaikou temperature gradient within it is light and temperature formation, Jixian formation and Changcheng formation, are increases by the depth. Ground temperature gradient a set of shallow ocean facieses sediments. Main rocks are decreases obviously down to rock basement through cap clastic rock, clay and carbonate rocks. Total thickness is rock, micro-counter-current feature appears. In normal over 300-1000m. High conductivity caused by rich karst and cases, in non-aquifers such as clay and shale, temperature fissures in this reservoir makes production rates of single gradient tends slightly increasing to 1.5-2.5ºC/100m, but in well reach to 400-1500m3/d, with temperature 60-80ºC, up aquifers such as sandstone and dolomite, temperature to 104ºC. gradient decreases obviously to less than 1ºC/100m because of the affection of hydrodynamic circulation 3 . Hence after Achaean reservoirs: it is a set of crystallized metamorphic drilling into rock formations, it is not desirable to obtain rock such as mixing granite, with burying depth 60-140m, in high temperature water rely on adding well depths even some possibly tectonic parts, natural warm spring with meeting water aquifers in geothermal reservoirs. temperature 34-55ºC occurs, e.g., Changli geothermal field. 1.2.3 Features of Geothermal Reservoir 1.2.4 Features of Geothermal Water Quality Two types of geothermal reservoirs can be divided in Hebei Chemical types of hot water in Upper Tertiary reservoir are Plain, one is low-moderate temperature reservoir formed by mainly Na-HCO and Na-Cl-HCO , with different TDS, heat conduction controlled by Earth heat flow action, i.e. 3 3 often are neutral water with low F- concentration. Some Tertiary reservoir; another is deep cycling fractural reservoir water consists of beneficial elements such as Si, P, Br, I, Li, co-acted by heat transmission and heat counter-current, i.e. Sr, Zn and Mn, can be mineral water. rock reservoir. Upper Tertiary reservoir distributes widespread in Hebei Plain, Lower Tertiary reservoir Chemical types of hot water in basement reservoirs are distributes only in depression areas. Rock reservoir forms mainly Na-Cl, Na-Cl-HCO3, Na-HCO3 and Na-Cl-SO4. The by Paleozoic, Proterozoic and Archean formations mainly water is brackish or salinity, with high hardness. It consists distributed in uplift areas of above 3000m depths. many special chemical contents, so all are F- mineral water, Respective characteristics are as below: next are Radon (Rn) water, Be water and Sr water.
Upper Tertiary reservoir As presented above, geothermal water in Hebei Plain has Minghuazhen formation reservoir: distributes in total Hebei characteristics of high temperature, large reserves and wide Plain, but its thickness is not same in different places distribution, also has taken great benefits for local economic effected by basement structure, for example, the thickness is development. Meanwhile, some problems such as lack of 500-1100m in Jizhong fold sink but 600-1200m in comprehensive utilization and discharge pollution shall be Huanghua fold sink, the dominated rocks are thick interbed attention. sandstone and shale. Single aquifer thickness reaches to 1- 5m, up to several ten meters. Production rates of single well 2. FORMING MECHANISM OF GEOTHERMAL are 1000-1500m3/d, with temperature 36-50ºC, up to 85ºC. FIELD The water belongs to confined aquifer (Figure 3) . 2.1 Heat Source Guantao formation reservoir: mostly lack or thin in the rise Analysis and study of geology, hydrogeology and part of the basement in Hebei Plain, with thickness 200- distribution characteristics show that heat source of 900m. The rock is river-fancies coarse sand. Single aquifer geothermal field comes from decay heat of radioactive thickness reaches to 3-13m. Sandstone in total formation is elements in the inner Earth and the upper mantel. The bury 40-50% but 60% in north area of Huanghua fold sink with depth of Moho discontinuity in Hebei Plain is 34-37km. porosity 29%. Production rates of single well are over Comparing with neighbor areas, the Moho is relatively 1000m3/d, with temperature 56-82ºC. shallower, so is favorable for heat energy conduction in the mantel. On the other hand, huge granite at depth 8-16km Lower Tertiary reservoir release radioactive heat, which takes dominated action on heat flow at above sediments crust. The Tianjin Geological Lower Tertiary reservoir, including Dongying formation, Survey data shows that 62% of heat flows in Hebei Plain Shahejie formation and Kongdian formation, commonly come from deep crust and 38% comes from the upper distributed in deep parts of depression areas, are in closed or mantel. semi-closed lake basin. Total thickness of the reservoir is 5000-7000m. The dominated rock is shale, which is the oil- oriented system. Production rates of single well are less than 2.2 Heat Reservoir and Heat Flow Paths 50m3/d. TDS of groundwater is over 10g/l, up to 50-70g/l. Good heat energy reserving space in the Upper Tertiary The reservoir is not valuable for mining at present condition rocks and basement provides plenty space for geothermal for its deep depth, low productive capacity and high TDS. field in Hebei Plain, meanwhile, advantage geological conditions such as tectonic uplift-depression, deep fractures Basement reservoir and vast distribution of huge carbonate with high heat- conductivity provides heat energy transmission and Paleozoic reservoirs are mainly fissure-karst reservoirs concentration. consists of Ordovician and Cambrian carbonated rocks. The
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2.3 Cap Rock with total area reaching million square miters, and main The Quaternary sediments are 400-550m thick in Hebei using areas are Xiong County, Hengshui, Shenzhou, Plain, so the suitable thickness and low heat-conductivity Cangzhou and Huanghua. Geothermal non-smoking city prevent heat loss and keep the heat energy reserve. programme has been proposed in some places such as Hengshui, Shenzhou, Huanghua, etc. 3. GEOTHERMAL RESOURCES IN NON- ABNORMAL GEOTHERMAL AREAS IN HEBEI 4.5 Industrial and Agricultural uses PLAIN Geothermal utilization for leather processing, mushroom and Total area of Hebei Plain is about 80,000km2. In accordance potato dehydration put solid foundation for oriented with Cenozoic ground temperature gradient 3.0ºC/100m, economy development and export. geothermal abnormal area is about 16,000km2, 20% of the total area. By the consequent technological improvement of 5. STATUS ANALYSIS OF GEOTHERMAL geothermal prospecting and development, geothermal RESOURCES resources in non-abnormal area, which occupies 80% of the 5.1 Market Demand-supply Situation and Future area, has been taken attention to geothermal workers. Since Prediction 80s of 20 century, geothermal resources have been developed quite actively and the scale enlarged continually. By the energy tensity and environmental protection Enhancement of geothermal resources in non-abnormal area conscious enlarging, as a cleaning renewable energy, has been taken on the working agenda. Many beneficial tests geothermal resources has been caused high attention by have been conducted in geology institutes and enterprises. governments and enterprises, and its development and Geothermal development and utilization is in urgent in utilization is expanding rapidly. large-mediate cities especially, hence improved study and development of geothermal resources in non-abnormal area. Geothermal resources have incomparable advantages more than other resources, that is, co-use of water and heat, Although in some legislation of geothermal resources especially on space heating and bathing. Hence, in the future underground water over 25ºC is considered as low- district space heating and bathing, geothermal resources will temperature geothermal resources , it is suitable for be in urgent developing and has vast prospect for many groundwater over 35ºC according to the present enterprises preparing to invest to geothermal utilization. technological condition in Hebei Plain. Working scope for geothermal workers in non-abnormal area is limited in the In accordance with the related study, geothermal resources area of geothermal gradient over 2.0ºC /100m as well as also has advanced prospect on planting and aquiculture. The burying depth of reservoir over 1000m. study result shows that in north area production value in non-geothermal-utilizated and geothermal utilized areas are: traditional corn and wheat planting 2000/mu and vegetable 4. DEVELOPMENT AND UTILIZATION OF planting 10,000-20,000/mu, vegetable planting 30,000- GEOTHERMAL RESOURCES 40,000/mu and flower planting 100,000-300,000/mu and Geothermal utilization is late but has great potential in Hebei tropical fish feeding and high value tropical water Plain. The expanding new energy technology, hydrogeology production 400,000-700,000/mu, respectively 4 . It is and geothermal survey and oil prospecting since 80s of 20 believed that scientific and reasonable geothermal utilization century provided a lot of geothermal information and can improve land production value largely, and the achievements. Local space heating, bathing, aquiculture and improvement grade is closely related with industry choice planting have been improved rapidly. The statistic used and capital and technical investment. geothermal wells are over 100, and most gained advanced economic and social benefits. Up to now main types of 5.2 Total Reserves and Analysis of Safeguard Resources geothermal utilization are: Level The calculated volumetric reserve of the upper Tertiary 4.1 Planting 8 3 Minghuazhen reservoir in Hebei Plain is 9482.004×10 m , Greenhouses are mainly used to solve winter vegetables and and the minable resource is 474.1×108m3, heat energy flowers supply in north areas. 578.3×1016J, which is equivalent with coal 19.732×108t; the volumetric reserve of the Upper Tertiary Guantao reservoir 4.2 Aquiculture is 4654.851×108m3, and the minable resources is 232.742×108m3, heat energy is 435.85×1016J, equals with Geothermal utilizing for mother shrimp feeding, fry 8 producing and snail feeding in winter opens a new way for coal 14.87×10 t. cold season aquiculture industry in north areas. The volumetric reserve of the basement reservoir is 393.456×108m3, the minable resources is 98.366×108m3, 4.3 Bathing and Medical Treatment heat energy is 245.43×1016J, equals with coal 0.837×108t. When trace elements in geothermal water reach to national standard the water can be drinking mineral water or hot According to the statistic calculation, there are 13 large medical mineral water. At present different scale geothermal geothermal fields, 13 medium and 4small ones, which bathing rooms and sanatoriums are in using in places such as equals with 3.5439 billion tons coal in Hebei Plain. Xiong County, Changli County, Huanghua District, Xian County, Renqiu District, Cangzhou City and Hengshui City. Annual utilizing geothermal resources equals with coal 200,000t. Calculated for 100-year lifetime of geothermal 4.4 Space heating field, total utilizing quantity is less than 6% of the minable resources, which shows the huge potential of geothermal Geothermal space heating replacing fossil fuel heating can resources. reduce emission of CO2, SO2 and dust, hence benefits to air and ecological environmental protection. Geothermal space heating has been used in nearly 60 places in Hebei Province, 3 Li and Zhang
6. CONCLUSION AND SUGGESTION Efficient measures should be carried out immediately to control it. Cascaded utilization of geothermal resources 6.1 Conclusion should be enlarged to increase the geothermal potential and Geothermal resources are quite abundant in Hebei Plain. A keep the sustainable utilization. As a kind of mineral study on geothermal distribution, contributing factor, types resource, geothermal resources should be managed by and reservoir characteristics, especially on non-abnormal professional organizations of national land and resources geothermal area, provides more widespread prospects for department. geothermal development and utilization. Scientific and reasonable geothermal utilization will definitely promote REFERENCES local economic and social development. Zhang Dezhong: Global Science, Journal of China University of Geology Science, 2001 6.2 Suggestion Comprehensive utilization level is still very low in Hebei Chen Moxiang: Geothermal in North China, Beijing: Plain. Most utilizing places are concentrated in the Science Press, 1988 countryside where geothermal fields are located, hence Chen Moxiang, W & D: Geothermal Resources in China, problems such as disordered development, heavy waste, lack Beijing: Science Press, 1994 of systematic management, shortage of union programme, geological prospecting unbalance and low precision, etc, Yan Zunshi & Yu: Geothermal Assessment and Utilization occurred. Geological work has seldom been done in more in Jing-Jin-Ji oil area, Wuhan: China University of than 20 geothermal fields and abnormal areas except some Geology Science Press, 2000 geothermal survey and prospecting work carried out in a few Li Hongying: Geothermal Environmental Impact places such as Niutuo Town, and Cangzhou City. Besides, Assessment Studies in Hebei Province, the UNU overextraction of geothermal water caused continual Geothermal Training Programme Report 2000 decrease of water level in large scale developing fields.
Figure 1: Map of Hebei Province Source: Geothermal Environmental Impact Assessment Studies in Hebei Province (Li Hongying, 2000)
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Figure 2: Distribution of Geothermal Resources in Hebei Plain
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Figure 3: Geological Profile Chart of Niutuo Town Geothermal Field
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