Orthogonal Test Analysis on Conditions Affecting Electricity Generation Performance of an Enhanced Geothermal System at Yangbajing Geothermal Field

Yuchao Zeng,Yifei Cao,Liansheng Tang,Nengyou Wu,Jing Song

doi:10.3390/en10122015

Abstract

The main conditions affecting electricity generation performance of an enhanced geothermal system (EGS) include reservoir porosity, reservoir permeability, rock heat conductivity, water production rate and injection temperature. Presently there is lack of systematic research the relative importance of the five aforementioned conditions. The orthogonal test method is a statistical approach to analyze multi-factor and multi-level influence on system performance. In this work, based on the geological data at Yangbajing geothermal field, we analyzed the five conditions affecting the electricity generation performance of EGS, and ranked the relative importance of the five factors. The results show that the order of the relative importance of the conditions on electric power is water production rate > injection temperature > reservoir porosity > rock heat conductivity > reservoir permeability; the order of the relative importance of the conditions on reservoir impedance is reservoir permeability > injection temperature > water production rate > reservoir porosity > rock heat conductivity; the order of the relative importance of the conditions on pump power is water production rate > reservoir permeability > injection temperature > reservoir porosity > rock heat conductivity, and; the order of the relative importance of the conditions on energy efficiency is water production rate > reservoir permeability > reservoir porosity > injection temperature > rock heat conductivity. The construction of an EGS reservoir should be located at a formation with higher reservoir porosity or rock heat conductivity, while the determination of reservoir permeability, water production rate and injection temperature should be based on the comprehensive target.

Highlights

Zeng et al employed the equivalent porous media (EPM) method to investigate the electricity generation potential through a single horizontal well [6], multiple vertical wells [7], multiple horizontal wells [8], and a single vertical well [9] at Yangbajing geothermal field, and the results show that the horizontal well system has better electricity generation performance under the same conditions
hot dry rock (HDR) geothermal energy, and the results enable a detailed analysis on the effects of well layout on enhanced geothermal system (EGS) heat extraction performance [15]
Zeng et al investigated the main factors influencing the electricity generation performance of EGS, and the results demonstrate that the main factors affecting the performance are reservoir permeability, water production rate and injection temperature [19]

Summary

Introduction

Under the pressure of energy shortages and environmental pollution, developing renewable and clean energy is of great strategic significance [1]. As a clean and renewable energy, the development and utilization of geothermal energy has received worldwide attention [1]. Geothermal energy can be divided into three categories according to depth and resource temperature. If the depth is shallower than 200 m and the resource temperature is less than 90 ◦ C, this type is the shallow geothermal resource and is mainly used for heat supply or refrigeration. If the depth is Energies 2017, 10, 2015; doi:10.3390/en10122015 www.mdpi.com/journal/energies

Methods

Results

Conclusion