scholarly journals Numerical Investigation of Influence of Reservoir Heterogeneity on Electricity Generation Performance of Enhanced Geothermal System

Processes ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 202 ◽  
Author(s):  
Yuchao Zeng ◽  
Liansheng Tang ◽  
Nengyou Wu ◽  
Jing Song ◽  
Zhanlun Zhao
Keyword(s):  
Energy Efficiency ◽  
Pump Power ◽  
Electric Power ◽  
Electricity Generation ◽  
Production Performance ◽  
Geothermal System ◽  
Enhanced Geothermal System ◽  
Slight Effect ◽  
Reservoir Heterogeneity ◽  
Well Spacing

The enhanced geothermal system (EGS) reservoir consists of a heterogeneous fracture network and rock matrix, and the heterogeneity of the reservoir has a significant influence on the system’s electricity generation performance. In this study, we numerically investigated the influence of reservoir heterogeneity on system production performance based on geological data from the Gonghe Basin geothermal field, and analyzed the main factors affecting production performance. The results show that with the increase of reservoir heterogeneity, the water conduction ability of the reservoir gradually reduces, the water production rate slowly decreases, and this causes the electric power to gradually reduce, the reservoir impedance to gradually increase, the pump power to gradually decrease and the energy efficiency to gradually increase. The fracture spacing, well spacing and injection temperature all have a significant influence on electricity generation performance. Increasing the fracture spacing will significantly reduce electric power, while having only a very slight effect on reservoir impedance and pump power, thus significantly decreasing energy efficiency. Increasing the well spacing will significantly increase the electric power, while having only a very slight effect on the reservoir impedance and pump power, thus significantly increasing energy efficiency. Increasing the injection temperature will obviously reduce the electric power, decrease the reservoir impedance and pump power, and thus reduce energy efficiency.

scholarly journals Numerical Study on the Influence of Well Layout on Electricity Generation Performance of Enhanced Geothermal Systems

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1474
Author(s):  
Yuchao Zeng ◽  
Fangdi Sun ◽  
Haizhen Zhai
Keyword(s):  
Energy Efficiency ◽  
Electric Power ◽  
Electricity Generation ◽  
Horizontal Well ◽  
Production Performance ◽  
Electricity Production ◽  
Fracture Permeability ◽  
Fracture Spacing ◽  
Vertical Well ◽  
Well Spacing

The energy efficiency of the enhanced geothermal system (EGS) measures the economic value of the heat production and electricity generation, and it is a key indicator of system production performance. Presently there is no systematic study on the influence of well layout on the system energy efficiency. In this work we numerically analyzed the main factors affecting the energy efficiency of EGS using the TOUGH2-EOS1 codes at Gonghe Basin geothermal field, Qinghai province. The results show that for the reservoirs of the same size, the electric power of the three horizontal well system is higher than that of the five vertical well system, and the electric power of the five vertical well system is higher than that of the three vertical well system. The energy efficiency of the three horizontal well system is higher than that of the five vertical well system and the three vertical well system. The reservoir impedance of the three horizontal well system is lower than that of the three vertical well system, and the reservoir impedance of the three vertical well system is lower than that of the five vertical system. The sensitivity analysis shows that well spacing has an obvious impact on the electricity production performance; decreasing well spacing will reduce the electric power, reduce the energy efficiency and only have very slight influence on the reservoir impedance. Fracture spacing has an obvious impact on the electricity production performance; increasing fracture spacing will reduce the electric power and reduce the energy efficiency. Fracture permeability has an obvious impact on the electricity production performance; increasing fracture permeability will improve the energy efficiency and reduce the reservoir impedance.

scholarly journals Effect of Vertical Permeability Heterogeneity in Stratified Formation on Electricity Generation Performance of Enhanced Geothermal System

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 744
Author(s):  
Yuchao Zeng ◽  
Fangdi Sun ◽  
Haizhen Zhai
Keyword(s):  
Energy Efficiency ◽  
Pump Power ◽  
Electric Power ◽  
Production Rate ◽  
Electricity Generation ◽  
Injection Pressure ◽  
Water Production ◽  
Permeability Heterogeneity ◽  
Vertical Permeability ◽  
Water Production Rate

Because geologic sedimentation and hydrofracturing processes are not homogeneous, the reservoirs of enhanced geothermal systems (EGSs) are also heterogeneous; this has a significant influence on the electricity generation performance of EGS. Presently, there are a lack of systematic and profound studies on the effect of vertical permeability heterogeneity in stratified formation on the electricity generation performance of EGS. In order to uncover the effect of vertical permeability heterogeneity on electricity generation performance of EGS, in this work we analyzed the influence of vertical permeability heterogeneity on electricity generation performance of EGS through a numerical method based on geological data at the Yangbajing geothermal field. The results indicate that when the average permeability of stratified formations is constant for a homogeneous reservoir, the system attains maximum water production rate, maximum electric power, minimum reservoir impedance and maximum pump power; with the increasing of the vertical permeability heterogeneity, the water production rate gradually decreases, the electric power gradually declines, the reservoir impedance gradually increases and the pump power gradually declines. When the average permeability of stratified formations is constant, with the increasing of the vertical permeability heterogeneity, the injection pressure and energy efficiency only changes very slightly; this indicates that the vertical permeability heterogeneity is not the main factor affecting the system injection pressure and energy efficiency.

scholarly journals Numerical simulation on heat extraction performance of enhanced geothermal system under the different well layout

2019 ◽  
Vol 38 (1) ◽  
pp. 274-297 ◽  
Author(s):  
Yuanyuan Ma ◽  
Shibin Li ◽  
Ligang Zhang ◽  
Hao Li ◽  
Zhaoyi Liu
Keyword(s):  
Life Span ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Electricity Generation ◽  
Heat Extraction ◽  
Geothermal System ◽  
Enhanced Geothermal System ◽  
Water Wells ◽  
Extraction Performance

China has hundreds of thousands of oil and water wells, about 30% of which have been abandoned currently. If we can convert abandoned wells into geothermal wells, it will save lots of money and reduce drilling and completion time greatly. In this paper, six enhanced geothermal system (EGS) well layout schemes are proposed based on the utilization of abandoned oil–water wells and common oilfield well pattern. Here six common injection-production well patterns in oilfield are combined to hot dry rock (HDR) production and the heat extraction performance is simulated. The results show that the injection well number and the location of injection wells have critical influence on the heat extraction performance. Under the same total injection mass flow rate, the injection well number is the key factor and the fracture area is the secondary factor on heat extraction when the HDR energy is enough. For electricity generation, the life span is 20.2, 19.2, 19.0, 19.2, 18.2 and 13.9 years, and the heat extraction ratio is 65.83, 57.35, 65.96, 62.79, 59.30 and 43.09% from case 1 to case 6, respectively. For heating demand, the life span is 30.0, 30.0, 29.9, 30.0, 29.8, and 27.7 years, the heat extraction ratio is 78.91, 69.63, 77.02, 75.92, 72.27 and 58.94% from case 1 to case 6, respectively. The total injection mass flow rate and injection temperature also have a negative effect on the heat extraction performance. Case 1 (row parallel well layout), Case 3 (four-spot well layout) and Case 4 (five-spot well layout) are a good choice both for electricity generation and heating demand. This study provides good guidance for the selection and optimization of different EGS well layout.

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