Kang Fengxin Shandong Provincial Bureau of Geology & Mineral Resources, China Wang Bingchen Ministry of Construction of China

Transcription

1 Permit process, city planning and geothermal development in China Kang Fengxin Shandong Provincial Bureau of Geology & Mineral Resources, China Wang Bingchen Ministry of Construction of China

2 Bohai Sea Beijing Shandong Tianjin Bohai Sea Yellow Sea East Sea

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5 Outline 1. Geothermal development in China 2. Main geothermal issues in China 3. Permit process, city planning and geothermal development

6 1. Geothermal development in China High temperature geothermal resources have been used for power generation in Yangbajain, Tibet. The operating installed capacity is MWe. Geothermal power satisfied 50% electricity demand in Lhasa, the capital of Tibet. 60% in winter

7 Low-medium temperature geothermal resources are directly used in various aspects in China: space heating, bathing, balneology, fish farming, sanatorium, swimming pool and greenhouse, etc..

8 In 2007, geothermal direct use in China reached 18,900 GWh, 470 million m 3 of thermal water, ranks first in the world

9 2. Main geothermal issues in Correspondingly, China

10 Continuous geothermal water level/pressure drawdown Due to the heavy development of geothermal resources, the reservoir pressure/water level has been decreasing dramatically.

11 Xiaotangshan geothermal field water level drawdown: 1.9m/yr, after reinjection, stable

12 Monthly production (10 4 m 3 ) Water level (m.a.s.l) Water level variations along with monthly production in SE urban geothermal field of Beijing --from Liu Jiurong

13 annual production rate(104m3) annual drawdown(m) production rare(104m3) draw dow n(m) ----from Wang Kun The history curve of water level drawdown and geothermal water production of the dolomite reservoir in Tianjin urban area from 1992 to2002 Since 1997, the annual water level drawdown has been over 3m, and even got to 10m in

14 At present, the depth to the water level varies between -40m and -120m in different areas The area of water level deeper than 90m:

15 At present, an annual drawdown of 6-9m ----although reinjection have been completely implemented.

16 How about the water level in 20 years? Nearly -300m How about this famous heating station? -300m, the depth of submersible pump Most of the pumps in geothermal wells can not be able to work again

17 Artesian geothermal well in Liaocheng, Shandong Free flow rate fluctuations earthquake monitoring along Liaokao fault through collecting different kind of gases from artesian water

18 Pressure variations

19 temperature decrease Corresponding to the water level drawdown, obvious temperature and TDS decrease occurred in some geothermal reservoirs, especially in natural warm spring areas Due to shallow colder groundwater or surface water inflow

20 Tangtou warm spring in Linyi, Shandong Province: before 1960 s: free flow rate=388m 3 /d, T=70, TDS= : Production from wells=435, T= : Production from wells=955, T=48, TDS=1.9 now: Production from wells=500, T=60, TDS=2.5

21 Qiaogou warm spring, Tai an, Shandong: 2000: depth to water level:3.3m, T= : Production increased to 3000 m 3 /d depth to water level >10m, T=25 some wells dry up

22 Yujiatang warm spring, Muping, Yantai, Shandong (m)

23 land subsidence Due to the heavy extraction of groundwater, especially the deep groundwater, the area of groundwater depression cone in China has reached 190,000 km2 in 50 cities, which are mainly concentrated in Yangtze River Delta, North China Plain and Fen-Wei River Basin.

24 Correspondingly, land subsidence has occurred for more than 90,000 km 2

25 for example, in Dezhou city of Shandong Province, the main water supply is sourced from the deep confined groundwater, which has been pumped since 1965.

26 D(m) H(m) Q(m 3 /d) In response to extended heavy pumping, the deepest depth to the groundwater level has fallen from 2 m to 130m, and a depression cone with an area of about 3,500 km2 has formed Fit: Y = * X Coef of determination, R-squared =

27 At present, the groundwater level is still decreasing at a rate of 2-3 m/year. Accompanying this significant lowering of groundwater level, land subsidence at a rate of mm/year has occurred.

28 The affected area by land subsidence basically coincides to the depression cone.

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30 So, it is believed that the heavy exploitation of geothermal water from sandstone aquifer will aggravate the existed land subsidence in North China Plain and other sedimentary basins

31 water and soil pollution Generally speaking, geothermal is renewable and clean energy, but the geothermal waste waters have higher salinity and contain pollutants as Fluorine (F), Boron (B), Mercury (Hg), Arsenic (As). Parts of pollutant contents exceed the national disposal water quality standard for drinking, irrigation and aquaculture water.

32 Thermal pollution Cascaded and comprehensive use of geothermal water in China is not so common Discharge water with higher temperature

33 Dongying

34 Sea water intrusion

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36 3. Permit process, city planning and geothermal development Even though geothermal resources are considered renewable, their production capacity is not unlimited Over exploitation has occurred in some of geothermal reservoirs in China

37 For the purpose of suitable development of geothermal energy, primary permit system has already been established in China Generally, its process include:

38 Registration for exploration license Exploration license application and well drilling permit Exploration report, allowable production capacity evaluation, to submit geothermal reserve, and apply allowable withdraw Well drilling Mining permit application, with prerequisite of submitting utilization plan, geo-hazards dangerous evaluation report, environmental impact report Development and utilization

39 Dr Liu Jiurong and Dr Wang Kun have already given us very detailed introduction

40 So, highlight will be focused on the issues existed in the permit process, city planning and geothermal development, and how to solve them For the purpose of long-term sustainable development of geothermal energy

41 issues Permit of allowable production capacity is just based on the single well pumping test, but not based on interference pumping test and detailed numerical modelling Interferences of different geothermal wells are not taken into account Main reason for over allocation

42 Production Potential calculation and allocation The prerequisite of calculating production potential is to determine a rational maximum allowable drawdown of the production wells in the reservoir, within a time frame. ----to avoid over allocation, i.e. to avoid continuous decline of water level and temperature In other words, the production potential is restrained by the maximum allowable drawdown of the reservoir within a time frame.

43 Sedimentary geothermal reservoir Sedimentary geothermal reservoirs, which are widely distributed in North China Plain, are characterized by large areal extent, rather homogeneous aquifers, quite productive wells and great energy potential Geothermal anomalies concentrate on horst areas in sedimentary basin, which are conduction-dominated reservoirs.

44 Main aquifers: Sandstone (Neogene) Limestone, dolomite (Jixian, Cambrian and Ordovician) Manifestation: (Artesian) wells( m, C)

45 Considering constraints in the sedimentary geothermal reservoir, including setting depths of submersible pumps design of the production wells land subsidence the maximum allowable drawdown is determined as m within years.??

46 Fractured geothermal reservoir Controlled by: Neotectonisms and large- and deep faults convective heat flow Main aquifers: Granite and metamorphic rocks Manifestations: Natural hot springs( C) Distribution: East coastal zone, e.g.shandong Peninsula

47 Main restrictions: risk of colder water inflow (surface water, ground water, and sea water) --temperature decrease

48 the maximum allowable drawdown is defined as 9-38 m in Shandong Peninsula.

49 Detailed numerical modeling is an effective method for production potential calculation Take interference of different wells into account, also consider the reservoir boundary conditions, open or close or in between? With drastically different longterm behavior To evaluate the production potential by calculating and predicting water level behaviors for different future production scenarios

50 Three-dimensional Finite-difference z y x t y x q r n h K z y h z y h p K z h z h K y h K x h K t h t z y z h K z y h K y x h K x t h S n t z y x z y x 0,,,, 0,,,,

51 For a new discovered reservoir, which has not been heavily extracted, it is essential to build a conceptual and numerical model to carry out sustainable yield evaluation based on interference pumping test and water level response observation.

52 Whereas for a developed geothermal reservoir, it is essential to evaluate production potential in view of longterm groundwater level response and the constraints of unacceptable environmental groundwater issues.

53 Water level(m) Scenario I Scenario II Time

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55 Pressure(bar) Scenario II Scenario I Time

56 Observed and simulated water level variations

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59 Baoquantang warm spring: Smax=9m, 920m 3 /d Under the prerequisite of maximum drawdown of 9 m, the allowable production capacity is determined as 920m 3 /d

60 Wenquantang warm spring Smax=24m, Q=1350m 3 /d

61 Qilitang warm spring Smax=38m, Q=1534m 3 /d

62 Aishan warm spring Smax=30m, Q=2070m 3 /d

63 Huleitang warm spring Smax=20m, Q=2100m 3 /d

64 Dong warm spring Smax=20m, Q=1670m 3 /d

65 Daying warm spring Smax=20m, Q=2300m 3 /d

66 If the permit is based on this, it is believed that the sustainable development of geothermal energy can be achieved. i.e. The water level and temperature will be maintained in the allowable limit at the end of the time frame. At this status, the production potential can be determined as Sustainable yield of wells and reservoir Reviewed based on long-term monitoring data regularly

67 City planning and geothermal development To find balance point between city planning and geothermal development

68 Green area: large geothermal potential, reservoir condition is in natural state Geothermal exploration and development should be encouraged.

69 Yellow area: geothermal energy has been heavily exploited, the water level and temperature are within the limit. New geothermal development should be controlled. Sustainable yield should be reviewed based on the long term observation of reservoir behavior. To maintain the water level and temperature within the limit at the end of time frame.

70 Red area: Geothermal reservoir is in overexploitation: water level ( temperature )decreasing continuously, and has already exceed the maximum allowable water level drawdown. New geothermal development should be forbidden. To decrease geothermal production, and increase reinjection

71 It is believed that the geothermal resources in China can meet the increasing demand under the condition of sustainable management!

72 Thank you!