(Shandong Geology and Mineral Engineering Group Co., Ltd., Jinan 2500 13)
About the author: Zhu Youqiang (1956-), male, professor-level senior engineer, is currently the chairman and general manager of Shandong Geology and Mineral Engineering Group Company.
Abstract: The Yellow River Delta is rich in geothermal resources and has great development potential. Underground hot water mainly occurs in clastic sedimentary rocks of Neogene Guantao Formation and Paleogene Dongying Formation, belonging to layered pore-fracture thermal reservoirs, which constitute the main thermal reservoir groups in this area. There are 54 ~ 83℃ geothermal wells 14 in the area, and the heating area using geothermal energy reaches 4.0× 105m2, so the geothermal development prospect is very considerable.
Keywords: Yellow River Delta; Geothermal resources; development prospect
1 overview
The Yellow River Delta is one of the three largest estuarine deltas in China, and it is also the newest and developing delta in the world, with the advantage of being close to the river and the sea. Since 1964 organized an oil battle and gradually built Shengli Oilfield, the second largest oil field in China, all circles at home and abroad have paid great attention to the development of the Yellow River Delta. The state lists the Yellow River Delta as a comprehensive agricultural development zone and Dongying as a coastal economic development zone. Shandong Province lists the development of the Yellow River Delta as one of two trans-century projects. At the beginning of 200 1, the China Investment Promotion Office of the United Nations Industrial Development Organization (UNIDO) and Dongying signed the Cooperation Agreement on Supporting Sustainable Development Projects in the Yellow River Delta. The United Nations Industrial Development Organization listed the development and construction of the Yellow River Delta as a key support area and Dongying as an "international characteristic industry demonstration zone". At the Fourth Session of the Ninth National People's Congress, "developing efficient ecological economy in the Yellow River Delta" was included in the outline of the Tenth Five-Year Plan. All these indicate that the Yellow River Delta has entered a period of great development, which will certainly promote the economic development and prosperity of the middle and lower reaches of the Yellow River and even the whole Yellow River basin.
Geothermal energy, as a new renewable energy that can be developed and utilized, has great potential for economic development. Geothermal mineral water is widely used, easy to develop, low in cost and free from environmental pollution. It has been widely used in heating, family bathing, hot water physiotherapy, warm pool swimming, warm water breeding, greenhouse planting, efficient agriculture and other fields, and its development prospect is very broad. The exploration and development of geothermal resources will certainly provide technical support for the establishment and development of regional circular economy, efficient ecological economy and conservation-oriented society; It is of great significance to realize the overall goal of "rapid economic development, clean and beautiful environment and benign ecological cycle" proposed by Dongying Municipal Government, alleviate the energy shortage in the Yellow River Delta and promote sustainable economic development.
2 Geothermal geological background
2. 1 stratum and structure
The Yellow River Delta is located in the southeast of North China Plain and the east of Liaoning-Hebei syncline of North China Platform. Influenced by Yanshan movement and Himalayan movement since Mesozoic, it has slowly declined and deposited a huge Cenozoic stratum.
Metamorphic rocks (Ar) of Taishan Group constitute the basement of this area, and the buried depth of convex area is generally 1 ~ 2 km, and the deepest depth of concave area is 9km. In the late Paleogene, there were outcrops in Chengdong uplift, Chenjiazhuang-Qingtuozi uplift and southern Binxian uplift, and the lithology was red, brown and green granite gneiss. Cambrian-Ordovician is mainly exposed in the northeast of Chengdong Uplift, Yihezhuang Uplift, the northern part of Chenjiazhuang-Qingtuozi Uplift and Guangrao Uplift. The lithology is light gray, grayish yellow and grayish black limestone.
Paleogene belongs to fluvial-lacustrine facies and piedmont alluvial facies formed under the conditions of arid temperate zone-subtropical climate, and its sedimentary thickness varies greatly, with the thickness of depression reaching 1500 ~ 2000 m without uplift. The Kongdian Formation (Ek) is widely distributed, but it is only missing in each convex area. Mainly interbedded with purplish red and brownish red mudstone, sandstone, calcareous sandstone and siltstone. Shahejie Formation (Es) is only missing in each convex area, and it is divided into four sections from bottom to top. The fourth member of Shahejie Formation is gray, taupe mudstone and shale, and locally contains carbonate, oil shale or dolomite. The third member of Shahejie Formation is mainly composed of massive fine sandstone, siltstone, oil shale, mudstone and shale. The second member of Shahejie Formation in Dongying Depression is well developed, which is mainly composed of gray-green, dark gray and purplish red mudstone, sandstone and gravel sandstone. The first member of Shahejie Formation is gray mudstone mixed with limestone, dolomite, oil shale and siltstone. Dongying Formation is mainly developed in Dongying sag and Zhanhua sag, and the upper part is grayish green and grayish white sandstone, fine sandstone and mudstone. The middle part is brownish red mudstone and fine conglomerate; The lower part is gray-white and gray-green fine conglomerate, fine sand and mudstone.
Neogene Guantao Formation (Ng) is widely distributed in this area, with good stability, but it is only missing in some areas of Chenjiazhuang uplift. It is mainly composed of grayish-white gravelly sandstone, fine sandstone, grayish-green fine sandstone and brownish-red mudstone, and the bottom is gravelly sandstone and glutenite containing timely and black flint. Neogene Minghuazhen Formation (Nm) is widely distributed, mainly khaki, brownish red mudstone, sandy mudstone and grayish white sandstone. Quaternary plain strata (Q) are widely distributed, with light brownish yellow, light green and gray sandy clay in the upper part, clay mixed with clayey siltstone; The lower part is light yellow, light gray green silty clay or light gray green clayey silty sand.
The Yellow River Delta region belongs to the eastern part of Liaoning-Hebei syncline (Ⅱ1) of North China Platform (Ⅰ) in terms of tectonic units. Lingxian-Bohai Farm Fault divides it into two tertiary structural units, namely Chengning Uplift (Ⅲ1) and Jiyang Depression (Ⅲ 2). Chengning uplift is composed of Chezhen sag (Ⅳ1) and Yihezhuang uplift (Ⅳ 2). Jiyang Depression consists of Zhanhua Depression (Ⅳ 3), Gudao Uplift (Ⅳ 4), Chenjiazhuang Uplift (Ⅳ 5), Qingtuozi Uplift (Ⅳ 6), Dongying Depression (Ⅳ 8), Guangrao Uplift (Ⅳ 9) and other structural units.
Influenced by Yanshan movement and Himalayan movement, the fault structures in this area are developed, which constitute the boundaries of the main structural units in this area, and all of them are concealed under Neogene. The main faults are Qihe-Guangrao fault, Yinan fault, Joy Chen fault and Guangnan fault. The fault strike is mainly east-west, northwest and northeast. During Himalayan movement, this area was dominated by fault block fracture and differential uplift movement, accompanied by a small amount of basalt and other magmatic activities.
2.2 Geothermal field characteristics
The Yellow River Delta is located in the east-west Moho uplift belt, and the Moho depth is about 32 km (Chen Moxiang, 1988). The geothermal gradient is higher than that in other plain areas, with the highest value of 4.5 ~ 7.2℃/ 100 m and the geothermal density of 56 ~ 79 MW/m2. The temperature of the constant temperature zone is 14 ~ 15℃, and the corresponding constant temperature zone depth is 15 ~ 17m. According to the statistics of deep hole temperature measurement data in this area, the geothermal gradient of Guangrao, Gudao and Yihezhuang bulges is greater than 4.5℃/ 100m, and the northern side of Chenjiazhuang bulge is greater than 4.0℃/100m. The geothermal gradient in the depression area is generally 3.1~ 4.0℃/100 m.
2.3 Geochemical field characteristics
The hydrochemical processes of underground hot water in the Yellow River Delta are mainly ion exchange, concentration and biochemical action, so the salinity and some elements are high, and they are rich in trace elements. In Dongying sag, the chemical type of layered hot water reservoirs in loose rocks such as Guantao Formation and Dongying Formation is mainly Cl-Na type water, but the salinity is quite different. Guantao Formation is generally 8 ~ 20g/L, Dongying Formation is 18 ~ 23g/L ... The chemical type of hot water reservoir in CAMBRIAN-Ordovician karst fractures is also Cl-Na type, and the salinity is 3 ~10g/L. The thermal reservoir of Guantao Formation in uplift area is often well connected with CAMBRIAN-Ordovician, with hydrochemical characteristics. Above the bulge, the salinity of underground hot water in Guantao Formation is increasing. In the vertical direction, the salinity of underground hot water also tends to increase gradually from shallow to deep.
Influenced by surrounding rocks, alternating conditions of underground hot water circulation and hydrogeochemical environment, trace elements such as metaboric acid, metasilicic acid, fluoride, bromide, strontium, iron, lithium and barium are all enriched to varying degrees. The contents of bromide and strontium in geothermal water of Guantao Formation are 8 ~ 30 mg/L and 22.8 ~ 49.72 mg/L, respectively. They are. The contents of bromide and strontium in geothermal water of Dongying Formation are 39.43 mg/L and 62.56 mg/L, respectively. They are. The contents of metasilicic acid and strontium in underground hot water of CAMBRIAN-Ordovician limestone thermal storage are 59 mg/L and 48 mg/L, respectively, both reaching the standard of mineral water.
3 Geological characteristics of thermal reservoirs
The economic geothermal resources in the Yellow River Delta are warm water and hot water, accompanied by low-temperature geothermal resources. The rocks in the thermal reservoir of Neogene Minghuazhen Formation are mostly cohesive soil with compact structure and good thermal resistance, but poor water abundance and low thermal conductivity. In addition, it is shallow buried and has low temperature, so it is studied as the thermal insulation cover of the underlying thermal reservoir (Liu Guiyi et al., 200 1). The Palaeozoic and Paleogene Kongdian formations in the depression are buried deeply, and the drilling depth is difficult to reach at present. Although the buried depth of Shahejie Formation is not large, the sand layer is cemented, mostly low porosity and fractured aquifer, which is the main oil-bearing layer. Most of the underground hot water contains oil pollution, and its hot water development has great influence on oil and gas production. Therefore, the geothermal water of Kongdian Formation and Shahejie Formation is not suitable for the development and utilization of geothermal resources. There is almost no water in the cracks of Mesozoic strata, Carboniferous-Permian sandstone and pre-Sinian granite gneiss, which belongs to "thermal waterless" layer and cannot form thermal reservoirs. Guantao Formation and Dongying Formation are widely distributed in this area, and the thickness of sand body is large. The lithology of thermal reservoir is loose or semi-cemented glutenite, with general burial conditions and relatively simple structural conditions. In Dongying sag, Zhanhua sag and Chezhen sag, geothermal water mainly occurs in clastic sedimentary rocks of Neogene Guantao Formation and Paleogene Dongying Formation, belonging to layered pore-fracture thermal reservoirs, which constitute the main thermal reservoir groups in this area. There is also a lower Paleozoic Cambrian-Ordovician limestone thermal reservoir under the Neogene thermal reservoir in the uplift area, with a buried depth of 1 0,000 ~1500m. Due to the influence of faults, karst and fractures are well developed and belong to karst fracture thermal reservoir.
3. 1 thermal reservoir of Neogene Guantao Formation
Except for the middle part of Chenjiazhuang uplift, the thermal reservoirs of Guantao Formation are almost widely distributed in the whole region. It is in unconformity contact with the underlying Dongying Formation, Cambrian-Ordovician and Archaean strata. The buried depth of roof is 850 ~ 1250m, and the thickness of sand layer is generally 80 ~ 240m, accounting for 20% ~ 40% of the total thickness of this layer. The lithology of thermal reservoir in Guantao Formation is gray-white gravel sandstone, fine sandstone, gray-green fine sandstone and brown mudstone interbedded, with gravel sandstone and glutenite at the bottom, containing timely and black flint. Gravel diameter 1 ~ 8 mm, medium roundness. Gravel layer has poor diagenesis and porosity of 25% ~ 35%. According to the data of Here 1 geothermal well in the estuary area, the thermal reservoir section 1793 ~ 1948m, the orifice water temperature is 73℃, the water yield is 1920m3/d, the hydrochemical type is Cl-Na type, and the salinity is10.60.
3.2 Paleogene Dongying Formation Thermal Reservoir
Yihezhuang Uplift, Chengdong Uplift, Chenjiazhuang Uplift, Qingtuozi Uplift, Guangrao Uplift and Paleogene Dongying Formation in the south of the work area are short of thermal storage. The buried depth of roof is generally 1200 ~ 1700 m, and the stratum thickness is generally 200 ~ 500 m (Figure 1). From bottom to top, it can be divided into three sedimentary cycles from coarse to fine, which have obvious positive cycle and positive rhythmic sedimentary characteristics. The top is grayish green and grayish white sandstone, fine sandstone and mudstone interbedded, mainly sandstone; The middle part is mainly brownish red mudstone and fine conglomerate; The bottom is grayish green and grayish white gravel sandstone, fine sandstone and mudstone. Looking at the sand layer of Dongying Formation, the lower part of the three sedimentary cycles is bounded by thick sandstone, and the thick gravel layer at the bottom is the largest. All three sedimentary cycles can only occur in the most developed part of Dongying Formation. This group of glutenite is loose, with poor particle sorting, and the porosity varies greatly in different regions. The porosity of Dongying sag is 26% ~ 3 1%. Zhanhua sag is 20% ~ 25%. According to the data of Dongre 1 1 geothermal well in Dongying Xicheng, the thermal reservoir interval 1586 ~ 1722m, the orifice water temperature is 74℃, the water yield 1954m3/d, the hydrochemical type is Cl -Na type, and the salinity/. Among the trace elements, the strontium content is 35.62mg/L, which is strontium geothermal mineral water.
Figure 1 Isothickness Map of Dongying Formation in Dongying Depression
(According to the data of Shengli Oilfield 1990)
1 —— the stratum pinchout line of Dongying Formation; 2— Isogram of formation thickness of Dongying Formation (m)
3.3 Cambrian-Ordovician thermal storage
Cambrian-Ordovician thermal reservoir is hidden in buried hill thermal reservoir under Cenozoic. Thermal reservoirs are controlled by stratigraphic structure, karst development and structure. It is mainly distributed in the south and north of Yihezhuang Uplift, Chengdong Uplift, Gudao Uplift, Chenjiazhuang Uplift and Guangrao Uplift. Controlled by the structure, the buried depth of CAMBRIAN-Ordovician roof in each uplift area is quite different. The Cambrian-Ordovician is dominated by gray and grayish white limestone. Yihezhuang uplift is special. Besides gray and grayish white limestone, there are oolitic limestone, leopard limestone limestone and dolomitic limestone. The development of karst fractures in Cambrian-Ordovician limestone is controlled by lithology, structure and burial conditions. Generally speaking, shallow buried carbonate rocks are more developed and have greater porosity than deep buried carbonate rocks. Porosity and permeability near large faults are greater than those far away; Ordovician limestone is more developed than CAMBRIAN fracture karst and has greater porosity. The fractured karst stratum covers an area of 15% ~ 25% of the total thickness of the stratum, the water inflow of a single well 1000 ~ 2000m3/d, the salinity of 3 ~ 10g/L and the wellhead water temperature of 70 ~ 90℃.
4. Exploration, development and utilization status and prospect analysis
The discovery of geothermal resources in the Yellow River Delta originated from oil exploration in Shengli Oilfield in 1970s. In petroleum exploration, more than a dozen geothermal wells with water temperature higher than 50℃ have been drilled, among which the wellhead water temperature of 12 geothermal well in the area where No.5 pile is located reaches 98℃, ranking first in Shandong Province. These geothermal wells are all formed in the process of developing oil, and the quality of wells is very poor, and the degree of development and utilization of geothermal resources is very low. It is only used for bathing, aquaculture and earthquake observation and research, and most of it has not been developed and utilized. The real geothermal exploration and development began in the late 1990s. Since 1998, with the development of economy, the higher authorities and Dongying City have conducted a special investigation on geothermal resources in the Yellow River Delta, initially delineated geothermal prospect areas, and started a demonstration project of geothermal well drilling. At the same time, Shandong Geology and Mineral Engineering Group Corporation and some geothermal development enterprises raised more than 20 million yuan for commercial geothermal risk exploration and development. The applied exploration area is about 600km2, and three geothermal investigation reports have been submitted. A total of 4 geothermal wells with water temperature of 54 ~ 83℃ 14 were drilled in Dongxicheng, Hekou and Gudao of Dongying, and the water output of each well was above1500m3/d. On the one hand, these works started the exploration and development of geothermal resources in the Yellow River Delta; On the other hand, it provides technical support for geothermal development in the Yellow River Delta.
Geothermal resources in the Yellow River Delta belong to low-temperature hot water type, and the wellhead temperature is 54 ~ 83℃, which is suitable for direct utilization. At present, more than ten geothermal wells in this area have been developed and utilized to varying degrees. The main development projects include hot spring bathing, bath swimming, domestic water supply and heating. Dongying Hotel, Gudao Furong, Gudao Military Racecourse, Luban Apartment of China Construction Eighth Bureau, and Gong Jianxin Village in Shengdong use geothermal heating area of 3.0× 105m2. The development of bathing, swimming, bathing and entertainment also has its own characteristics, which has initially formed a certain scale, achieved remarkable social, economic and environmental benefits and showed broad development prospects. According to preliminary calculation, the Yellow River Delta can utilize geothermal resources of 5.888×10/9j and hot water resources of 5.63× 108m3/a, which is equivalent to standard coal of 2.009× 109t, and the potential economic value is as high as1000. With the development of economy and the improvement of people's awareness of environmental protection, geothermal energy, as an alternative energy source after oil depletion, is gradually accepted by people, and its development prospect is very considerable.
5 Main suggestions for geothermal exploration and development
The development and utilization of geothermal energy in the Yellow River Delta is still in its infancy, and the scale of development and utilization and the economic benefits obtained need to be further improved. Therefore, it is recommended that:
(1) Accelerate the formulation of geothermal resources exploration and development planning. The Yellow River Delta is rich in geothermal resources, but it lacks a reasonable and systematic development plan and blueprint for geothermal resources. To some extent, it has affected the development of geothermal industry and the improvement of the overall economic benefits of geothermal development.
(2) The accuracy of geothermal exploration needs to be further improved. The geothermal prospect area of the Yellow River Delta is 7425km2, and the actual investigation area of geothermal special investigation is less than 600km2. The identified geothermal resources only account for112 of the total resources, and the geothermal geological exploration dedicated to finding deep-buried thermal reserves has not yet started. Strengthen the exploration of geothermal resources, improve the level of resource reserves and ensure the sustainable supply of geothermal resources.
(3) Enhance the awareness of comprehensive development and utilization, and accelerate the industrialization process of geothermal application. The geothermal development in the Yellow River Delta only stays in a few projects such as heating and bathing, and is in the stage of spontaneous, decentralized and extensive utilization. Geothermal enterprises have extensive management, few and single development and utilization, and low comprehensive development and utilization rate. Blind pursuit of high profits leads to serious waste of geothermal resources.
(4) Establish demonstration projects and scientific research institutions of geothermal resources application with leading role. The comprehensive research on the development and utilization of geothermal resources at home and abroad has gone through the process of geothermal resources exploration, demonstration project establishment and comprehensive development. Establishing an integrated demonstration project of geothermal resources development and utilization in Industry-University-Research is the best way to promote the industrialization process of geothermal resources cascade development and comprehensive utilization.
(5) Strengthen the management of geothermal exploration and the construction of geothermal professional laws and regulations. Geothermal is a kind of mineral resources, which belongs to the adjustment scope of mining law, but the management between departments is chaotic at present. It has affected the orderly development of geothermal resources exploration and development and utilization.
refer to
Chen Moxiang. 1988. Geothermal energy in North China. Beijing: Science Press.
Liu Guiyi, Meng Qingfeng. 200 1. Study on low-temperature geothermal resources and their development and utilization in Dezhou City. See: Selected Papers on Important Achievements of Geological Science and Technology in the Ninth Five-Year Plan. Beijing: Geological Publishing House.