Modeling of heat extraction from variably fractured porous media in Enhanced Geothermal Systems

Hadgu, Teklu; Kalinina, Elena Arkadievna; Lowry, Thomas Stephen

doi:10.1016/j.geothermics.2016.01.009

Cited by 66 publications

(19 citation statements)

References 8 publications

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“…When the matrix grid is small enough, the pore pressure of the grid can be accelerated to equal the fluid pressure in the NF. 39,45 As fracturing time increases, fluid pressure in the reservoir and in NFs continues to rise. When its value is greater than the normal stress of the NF surface, tensile failure occurs to the NF, that is as follows:…”

Section: Rock Failure Criterionmentioning

confidence: 99%

Study on induced stress of hydraulic fracturing in fractured‐porous elastic media

Wang

Zhao

et al. 2020

Energy Science & Engineering

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The study on induced stress of hydraulic fracturing is an important part of hydraulic fracturing design, temporary plugging and steering fracturing design, and completion design in oil and gas development. Based on fracture continuum method (FCM), cohesive unit method, and finite volume method (FVM), the propagation behavior of multiple hydraulic fractures (HFs) in fractured‐porous media reservoir is simulated from the perspective of fluid and geological stress coupling. The influence of natural fractures (NFs) on stress distribution and stress inversion sensitive factors are studied. NFs in the model are equivalent to physical models controlled by tension and shear bonds. The proposed model can deal with any number of NFs, which greatly improves the computational efficiency of the model. Then PKN analytic solution and Abaqus software results were used to verify the correctness of our model. The results show that the NF will make the reservoir stress show strong heterogeneity after fracturing, and the prominent feature is the regional stress mutation. The sudden change of stress shows the sudden increase or decrease in stress; with the increase in the initial stress difference, the stress inversion becomes more difficult. When the stress difference exceeds 3 MPa, the stress inversion area is almost 0. The stress interference increases with the decrease in cluster spacing. The stress inversion region between HFs decreases, while the external stress inversion region increases; Biot coefficient has great influence on stress and stress inversion. With the decrease in Biot coefficient, stress inversion region will decrease obviously. When the Biot coefficient is 0.4, there is no stress inversion area in the whole reservoir. Poisson's ratio has little influence on stress inversion. When Poisson's ratio changes between 0.1 and 0.3, the change range of stress is within 1 MPa, and the stress inversion area is almost unchanged. Our results can be helpful for understanding the stress distribution after hydraulic fracturing in fractured‐porous media.

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Section: Rock Failure Criterionmentioning

confidence: 99%

Study on induced stress of hydraulic fracturing in fractured‐porous elastic media

Wang

Zhao

et al. 2020

Energy Science & Engineering

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“…Investigations into EGS for electricity production are underway in Canada and abroad, e.g. (Ferguson and Grasby, 2014;Grasby et al, 2012;Hadgu et al, 2016;Ledésert and Hébert, 2012;Limberger et al, 2018;Majorowicz and Moore, 2014). The Western Canadian Sedimentary Basin and Williston Basin in the Canadian Prairies have the potential for sedimentary geothermal energy production (Jacek and Stephen, 2010;Majorowicz and Moore, 2014;Manz, 2011;Walsh, 2013).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of NaCl and MgCl2 heat exchange fluids in a deep binary geothermal system in a sedimentary halite formation

Moore

Holländer

2020

Preprint

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Halite formations are attractive geothermal reservoirs due to their high heat conductivity, resulting in higher temperatures than other formations at similar depths. However, halite formations are highly reactive with undersaturated water. An understanding of the geochemical reactions that occur within a halite-saturated formations can inform decision making regarding well construction, prevention of well clogging, formation dissolution, and thermal short-circuiting. Numerical 1-D and 3-D flow and equilibrium reactive transport modeling were used to characterize the produced NaCl-brine in a well targeting a halite-saturated formation. The potential for inhibition of precipitation and dissolution using an MgCl2-brine and NaCl+MgCl2-brine were also investigated. Within the injection well, with heating from 60 to 120°C, the solubility of halite decreases resulting in the potential dissolution of 0.57 mol L-1 at the formation. Cooling from 120 to 100°C in the production well results in precipitation of 0.20 mol L-1 halite as well as anhydrite, brucite, carnallite, goergeyite, gypsum, halite, kieserite and polyhalite. Introduction of Mg2+ into the heat exchange brine resulted in a decreased potential for dissolution by 0.35 mol L-1 as the heat exchange fluid entered the formation and within the formation itself, as well as decreased precipitation within the production well, compared to the NaCl-brine. The NaCl-brine solubility was altered by changes in pressure up to 0.18 mol L-1. This indicates that designing and monitoring the composition of heat exchange fluids in highly saline environments is an important component in geothermal project design.

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“…The results showed that the flow rate increases with the delay of simulation time due to matrix dissolution, which again exhibits exponential grow. On the whole, increasing attention has been significantly paid to geothermal development, and many scholars are studying the exploitation of a geothermal field from different aspects . The EGS test is extremely difficult and expensive before the construction of a power plant.…”

Section: Introductionmentioning

confidence: 99%

Production capacity and mining plan optimization of fault/fracture‐controlled EGS model in Gonghe Basin

Zhang

Xie

Zhang

2019

Energy Science & Engineering

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Taking full advantage of geological conditions is beneficial to reduce the development cost and enhance the exploit of geothermal energy in the Gonghe Basin. In this paper, a thermal-hydraulic coupled model is put forward to study the heat extraction for Gonghe Basin based on local thermal nonequilibrium theory considering the natural fault. An excellent heat recovery system and reasonable combination of parameters are the premise of sustainable geothermal development. Two doublet systems are introduced to investigate the efficiency of the fault/fracture-controlled EGS model.A comparative analysis is performed from the aspect of production temperature, heat extraction ratio, flow impedance, injection pressure, thermal power, and electric power. Key parameters (injection rate, injection temperature, production pressure, number of fractures, vertical interval between the two storages, and the storage permeability) are discussed. The results show that the fault-fracture-controlled doublet model is more suitable for EGS to heat transfer than the common doublet model. The doublet model at a depth of 3300-3800 m has a temperature gradient of 0.04°C/m.For fault-fracture-controlled EGS model, the optimal values are 50 kg/s, 15 MPa, 60°C, 310 m, 4 × 10 −14 m 2 , and two for injection rate, production pressure and injection temperature, vertical interval, storage permeability, and fracture number, respectively. The best well pattern layout method for the Gonghe Basin is one injection well and two production wells. The production temperature varies from 196.8°C to 192.7°C when the heat extraction ratio is 0.13 at the end of the operation. Thus, the fault-fracture-controlled EGS model can provide a mining method and advance the development of geothermal energy for the Gonghe Basin in the future. K E Y W O R D Senhanced geothermal system, fault/fracture-controlled model, local thermal nonequilibrium, parameter optimization | 2967 ZHANG et Al.

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Modeling of heat extraction from variably fractured porous media in Enhanced Geothermal Systems

Cited by 66 publications

References 8 publications

Study on induced stress of hydraulic fracturing in fractured‐porous elastic media

Study on induced stress of hydraulic fracturing in fractured‐porous elastic media

Evaluation of NaCl and MgCl2 heat exchange fluids in a deep binary geothermal system in a sedimentary halite formation

Production capacity and mining plan optimization of fault/fracture‐controlled EGS model in Gonghe Basin

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