增强型地热系统的多区域多物理场耦合三维数值模拟
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摘要
增强型地热系统(EGS)研究对发展地热发电具有重要意义。由于EGS通常涉及多区域多物理场耦合,且井内流动处于湍流状态,在EGS数值模拟中需要正确处理区域耦合、合理模拟井内湍流,并达到足够的计算精度和效率。基于多区域多物理场耦合三维有限元模型,系统研究EGS渗流与传热过程。计算结果表明:1)通过施加正确的连接条件能够实现在EGS不同区域之间的压力场、速度场和温度场的自然耦合; 2)多种湍流模型模拟井内流动给出基本一致的压力变化,并且预测井内湍流压降约为层流压降的4倍,但比注水井与生产井之间的总压降小3个量级,因而井内湍流对EGS采热过程总体影响不显著; 3)在EGS结构和物性垂向变化、储层中自然对流、井内湍流效应均可忽略的条件下,EGS以水平方向渗流和水平方向对流传热占主导,从而可采用两维模型近似模拟。
Studies on enhanced geothermal system( EGS) are important for developing geothermal power generation. As an EGS typically involves multi-regional and multi-physical coupling and the in-well flows are turbulent,it is necessary in EGS numerical simulation to handle regional coupling correctly,represent in-well turbulence reasonably,and achieve sufficient computational accuracy and efficiency. In this study,the processes of porous flow and heat transfer associated with EGS are systematically investigated based on a multi-region and multi-physics coupled 3D finite element model. The obtained results are given as follows. 1) The natural coupling of temperature,pressure,and velocity fields between different EGS regions can be successfully realized in terms of correctly posed connection conditions. 2) Different turbulence models for in-well flows predict essentially consistent in-well pressure variation. The turbulence pressure drop across the well depth is predicted to be about 4 times as large as the laminar pressure drop but 3 orders of magnitude smaller than the overall pressure drop from the injection well to the production well,resulting in insignificant influence of in-well turbulence on the EGS heat extraction process. 3) With the vertical variations of EGS structure and thermophysical properties,the natural convection inside the reservoir,and the effects of in-well turbulence all being negligible,an EGS is dominated by horizontal porous flow and horizontal convective heat transfer,and thus may be approximately simulated by 2D modeling.
Studies on enhanced geothermal system( EGS) are important for developing geothermal power generation. As an EGS typically involves multi-regional and multi-physical coupling and the in-well flows are turbulent,it is necessary in EGS numerical simulation to handle regional coupling correctly,represent in-well turbulence reasonably,and achieve sufficient computational accuracy and efficiency. In this study,the processes of porous flow and heat transfer associated with EGS are systematically investigated based on a multi-region and multi-physics coupled 3D finite element model. The obtained results are given as follows. 1) The natural coupling of temperature,pressure,and velocity fields between different EGS regions can be successfully realized in terms of correctly posed connection conditions. 2) Different turbulence models for in-well flows predict essentially consistent in-well pressure variation. The turbulence pressure drop across the well depth is predicted to be about 4 times as large as the laminar pressure drop but 3 orders of magnitude smaller than the overall pressure drop from the injection well to the production well,resulting in insignificant influence of in-well turbulence on the EGS heat extraction process. 3) With the vertical variations of EGS structure and thermophysical properties,the natural convection inside the reservoir,and the effects of in-well turbulence all being negligible,an EGS is dominated by horizontal porous flow and horizontal convective heat transfer,and thus may be approximately simulated by 2D modeling.
引文
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[13] Gong B,Liang H,Xin S,et al. Effect of water injection on reservoir temperature during power generation in oil fields[C]∥Proceedings of 36th Workshop on Geothermal Reservoir Engineering. Stanford, California, USA:Uneriversity Stanford,2011.
[14] BatailléA,Genthon P,Rabinowicz M,et al. Modeling the coupling between free and forced convection in a vertical permeable slot:Implications for the heat production of an enhanced geothermal system[J]. Geothermics, 2006, 35(5):654-682.
[15] Blcher M,Zimmermann G,Moeck I,et al. 3D numerical modeling of hydrothermal processes during the lifetime of a deep geothermal reservoir[J]. Geofluids,2010,10(3):406-421.
[16] Zhou L,Hou M Z. A new numerical 3D-model for simulation of hydraulic fracturing in consideration of hydro-mechanical coupling effects[J]. International Journal of Rock Mechanics and Mining Sciences,2013,60(2):370-380.
[17] Jiang F,Luo L,Chen J. A novel three-dimensional transient model for subsurface heat exchange in enhanced geothermal systems[J]. International Communications in Heat and Mass Transfer,2013,41:57-62.
[18] Jiang F,Chen J,Huang W,et al. A three-dimensional transient model for EGS subsurface thermo-hydraulic process[J]. Energy,2014,72:300-310.
[19] Chen J,Jiang F. Designing multi-well layout for enhanced geothermal system to better exploit hot dry rock geothermal energy[J]. Renewable Energy,2015,74:37-48.
[20] Cao W,Huang W,Jiang F. A novel thermal-hydraulicmechanical model for the enhanced geothermal system heat extraction[J]. International Journal of Heat and Mass Transfer,2016,100:661-671.
[21] Luo F,Xu R,Jiang P. Numerical investigation of fluid flow and heat transfer in a doublet enhanced geothermal system with CO2as the working fluid(CO2-EGS)[J]. Energy,2014,64:307-322.
[22] Li X,Jiang P,Xu R,et al. Experimental investigation on the natural convection heat transfer in the vertical annulus of a CO2injection well under steady-state conditions[J].International Journal of Greenhouse Gas Control,2016,52:387-400.
[23] Jiang P, Li X, Xu R, et al. Heat extraction of novel underground well pattern systems for geothermal energy exploitation[J]. Renewable Energy,2016,90:83-94.
[24] Zeng Y, Su Z, Wu N. Numerical simulation of heat production potential from hot dry rock by water circulating through two horizontal wells at Desert Peak geothermal field[J]. Energy,2013,56:92-107.
[25] Zeng Y,Wu N,Su Z,et al. Numerical simulation of heat production potential from hot dry rock by water circulating through a novel single vertical fracture at Desert Peak geothermal field[J]. Energy,2013,56(63):268-282.
[26] Zeng Y,Zhan J,Wu N,et al. Numerical investigation of electricity generation potential from fractured granite reservoir through a single vertical well at Yangbajing geothermal field[J]. Energy,2016,114(1):24-39.
[27] Pruess K. Enhanced geothermal systems(EGS)using CO2as working fluid:a novel approach for generating renewable energy with simultaneous sequestration of carbon[J].Geothermics,2006,35(4):351-367.
[28] Pruess K. On production behavior of enhanced geothermal systems with CO2as working fluid[J]. Energy Conversion and Management,2008,49(6):1 446-1 454.
[29] Saeid S,Al-Khoury R,Barends F. An efficient computational model for deep low-enthalpy geothermal systems[J].Computers and Geosciences,2013,51:400-409.
[30] Saeid S,Al-Khoury R,Nick H,Barends F. Experimentalnumerical study of heat flow in deep low-enthalpy geothermal conditions[J]. Renewable Energy,2014,62:716-730.
[31] Saeid S,Al-Khoury R,Nick H,et al. A prototype design model for deep low-enthalpy hydrothermal systems[J].Renewable Energy,2015,77:408-422.
[32] Huang X,Zhu J,Li J. On wellbore heat transfer and fluid flow in the doublet of enhanced geothermal system[J]. Energy Procedia,2015,75:946-955.
[33] Wilcox D C. Turbulence model for CFD[M]. California,USA:DCW Industries Inc,1994.
[34] Driver D M, Seegmiller H L. Features of a reattaching turbulent shear layer in divergent channel flow[J]. AIAA Journal,1985,23(2):163-171.
[35] Menter F R. Two-equation eddy-viscosity turbulence models for engineering applications[J]. AIAA Journal,1994,32(8):1 598-1 605.
[36] Nield D A,Adrian B. Convection in porous media[M].Berlin:Springer,2013.
[37] Turcotte D L,Schubert G. Geodynamics[M]. Cambridge:Cambridge University Press,2014.
[38] Ignat L,Pelletier D,Ilinca F. A universal formulation of twoequation models for adaptive computation of turbulent flows[J]. Computer Methods in Applied Mechanics and Engineering,2000,189(4):1 119-1 139.
[39] Abe K,Kondoh T,Nagano Y. A new turbulence model for predicting fluid flow and heat transfer in separating and reattaching flows—I. Flow field calculations[J]. International Journal of Heat and Mass Transfer,1994,37(37):139-151.
[40] Lundgren T S. Slow flow through stationary random beds and suspensions of spheres[J]. Journal of Fluid Mechanics,1972,51:273-299.
[41] COMSOL. COMSOL multiphysics programming reference mannual[CP]. 2016.
[2] Zhang Y,Li Z,Guo L,et al. Electricity generation from enhanced geothermal systems by oilfield produced water circulating through reservoir stimulated by staged fracturing technology for horizontal wells:a case study in Xujiaweizi area in Daqing Oilfield,China[J]. Energy,2014,78:788-805.
[3] Huang X,Zhu J,Niu C,et al. Heat extraction and power production forecast of a prospective enhanced geothermal system site in Songliao Basin,China[J]. Energy,2014,75:360-370.
[4]庞忠和,胡圣标,汪集旸.中国地热能发展路线图[J].科技导报,2012,30(32):18-24.
[5]王晓星,吴能友,苏正,等.增强型地热系统开发技术研究进展[J].地球物理学进展,2012,27(1):355-362.
[6] Huang S. Geothermal energy in China[J]. Nature Climate Change,2012,2(8):557-560.
[7]汪集旸,胡圣标,庞忠和,等.中国大陆干热岩地热资源潜力评估[J].科技导报,2012,30(32):25-31.
[8] Jelacic A,Fortuna R,La Sala R,et al. An evaluation of enhanced geothermal systems technology[R]. Geothermal Technologies Program,US Department of Energy,2008.
[9]许天福,张延军,曾昭发,等.增强型地热系统(干热岩)开发技术进展[J].科技导报,2012,30(32):42-45.
[10] Llanos E M,Zarrouk S J,Hogarth R A. Numerical model of the Habanero geothermal reservoir, Australia[J].Geothermics,2015,53:308-319.
[11]李强,于红侠.潜山油田地热发电试验工程及应用前景[J].煤气与热力,2012,32(6):20-23.
[12] Gong B,Liang H,Xin S,et al. Numerical studies on power generation from co-produced geothermal resources in oil fields and change in reservoir temperature[J]. Renewable Energy,2013,50:722-731.
[13] Gong B,Liang H,Xin S,et al. Effect of water injection on reservoir temperature during power generation in oil fields[C]∥Proceedings of 36th Workshop on Geothermal Reservoir Engineering. Stanford, California, USA:Uneriversity Stanford,2011.
[14] BatailléA,Genthon P,Rabinowicz M,et al. Modeling the coupling between free and forced convection in a vertical permeable slot:Implications for the heat production of an enhanced geothermal system[J]. Geothermics, 2006, 35(5):654-682.
[15] Blcher M,Zimmermann G,Moeck I,et al. 3D numerical modeling of hydrothermal processes during the lifetime of a deep geothermal reservoir[J]. Geofluids,2010,10(3):406-421.
[16] Zhou L,Hou M Z. A new numerical 3D-model for simulation of hydraulic fracturing in consideration of hydro-mechanical coupling effects[J]. International Journal of Rock Mechanics and Mining Sciences,2013,60(2):370-380.
[17] Jiang F,Luo L,Chen J. A novel three-dimensional transient model for subsurface heat exchange in enhanced geothermal systems[J]. International Communications in Heat and Mass Transfer,2013,41:57-62.
[18] Jiang F,Chen J,Huang W,et al. A three-dimensional transient model for EGS subsurface thermo-hydraulic process[J]. Energy,2014,72:300-310.
[19] Chen J,Jiang F. Designing multi-well layout for enhanced geothermal system to better exploit hot dry rock geothermal energy[J]. Renewable Energy,2015,74:37-48.
[20] Cao W,Huang W,Jiang F. A novel thermal-hydraulicmechanical model for the enhanced geothermal system heat extraction[J]. International Journal of Heat and Mass Transfer,2016,100:661-671.
[21] Luo F,Xu R,Jiang P. Numerical investigation of fluid flow and heat transfer in a doublet enhanced geothermal system with CO2as the working fluid(CO2-EGS)[J]. Energy,2014,64:307-322.
[22] Li X,Jiang P,Xu R,et al. Experimental investigation on the natural convection heat transfer in the vertical annulus of a CO2injection well under steady-state conditions[J].International Journal of Greenhouse Gas Control,2016,52:387-400.
[23] Jiang P, Li X, Xu R, et al. Heat extraction of novel underground well pattern systems for geothermal energy exploitation[J]. Renewable Energy,2016,90:83-94.
[24] Zeng Y, Su Z, Wu N. Numerical simulation of heat production potential from hot dry rock by water circulating through two horizontal wells at Desert Peak geothermal field[J]. Energy,2013,56:92-107.
[25] Zeng Y,Wu N,Su Z,et al. Numerical simulation of heat production potential from hot dry rock by water circulating through a novel single vertical fracture at Desert Peak geothermal field[J]. Energy,2013,56(63):268-282.
[26] Zeng Y,Zhan J,Wu N,et al. Numerical investigation of electricity generation potential from fractured granite reservoir through a single vertical well at Yangbajing geothermal field[J]. Energy,2016,114(1):24-39.
[27] Pruess K. Enhanced geothermal systems(EGS)using CO2as working fluid:a novel approach for generating renewable energy with simultaneous sequestration of carbon[J].Geothermics,2006,35(4):351-367.
[28] Pruess K. On production behavior of enhanced geothermal systems with CO2as working fluid[J]. Energy Conversion and Management,2008,49(6):1 446-1 454.
[29] Saeid S,Al-Khoury R,Barends F. An efficient computational model for deep low-enthalpy geothermal systems[J].Computers and Geosciences,2013,51:400-409.
[30] Saeid S,Al-Khoury R,Nick H,Barends F. Experimentalnumerical study of heat flow in deep low-enthalpy geothermal conditions[J]. Renewable Energy,2014,62:716-730.
[31] Saeid S,Al-Khoury R,Nick H,et al. A prototype design model for deep low-enthalpy hydrothermal systems[J].Renewable Energy,2015,77:408-422.
[32] Huang X,Zhu J,Li J. On wellbore heat transfer and fluid flow in the doublet of enhanced geothermal system[J]. Energy Procedia,2015,75:946-955.
[33] Wilcox D C. Turbulence model for CFD[M]. California,USA:DCW Industries Inc,1994.
[34] Driver D M, Seegmiller H L. Features of a reattaching turbulent shear layer in divergent channel flow[J]. AIAA Journal,1985,23(2):163-171.
[35] Menter F R. Two-equation eddy-viscosity turbulence models for engineering applications[J]. AIAA Journal,1994,32(8):1 598-1 605.
[36] Nield D A,Adrian B. Convection in porous media[M].Berlin:Springer,2013.
[37] Turcotte D L,Schubert G. Geodynamics[M]. Cambridge:Cambridge University Press,2014.
[38] Ignat L,Pelletier D,Ilinca F. A universal formulation of twoequation models for adaptive computation of turbulent flows[J]. Computer Methods in Applied Mechanics and Engineering,2000,189(4):1 119-1 139.
[39] Abe K,Kondoh T,Nagano Y. A new turbulence model for predicting fluid flow and heat transfer in separating and reattaching flows—I. Flow field calculations[J]. International Journal of Heat and Mass Transfer,1994,37(37):139-151.
[40] Lundgren T S. Slow flow through stationary random beds and suspensions of spheres[J]. Journal of Fluid Mechanics,1972,51:273-299.
[41] COMSOL. COMSOL multiphysics programming reference mannual[CP]. 2016.
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