Marija Macenić, Tomislav Kurevija^*, Tin Herbst

Energy Engineering, Vol.123, No.1, 2026, DOI:10.32604/ee.2025.067067 - 27 December 2025

Abstract The increased interest in geothermal energy is evident, along with the exploitation of traditional hydrothermal systems, in the growing research and projects developing around the reuse of already-drilled oil, gas, and exploration wells. The Republic of Croatia has around 4000 wells, however, due to a long period since most of these wells were drilled and completed, there is uncertainty about how many are available for retrofitting as deep-borehole heat exchangers. Nevertheless, as hydrocarbon production decreases, it is expected that the number of wells available for the revitalization and exploitation of geothermal energy will increase. The… More >

Yuze Xue¹, Li Kou^2,3, Guosheng Jia^4,*, Liwen Jin⁴, Zhibin Zhang⁴, Jianke Hao⁴, Lip Huat Saw^5,*

Energy Engineering, Vol.122, No.3, pp. 1005-1024, 2025, DOI:10.32604/ee.2025.059198 - 07 March 2025

Abstract Geothermal energy, a form of renewable energy, has been extensively utilized for building heating. However, there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in building energy systems, which are essential for decision-making. Therefore, this paper presents a comparative study of the performance and economic analysis of shallow and medium-deep borehole heat exchanger heating systems. Based on the geological parameters of Xi’an, China and commonly used borehole heat exchanger structures, numerical simulation methods are employed to analyze performance and economic efficiency. The results indicate that increasing the… More > Graphic Abstract

Yijun Gao^1,2, Yong Wang^1,*, Qing Na¹, Jiawei Zhang¹, Aixiang Wu¹

FDMP-Fluid Dynamics & Materials Processing, Vol.20, No.11, pp. 2443-2458, 2024, DOI:10.32604/fdmp.2024.051385 - 28 October 2024

Abstract Filling methods in the mining industry can maximize the recovery of mineral resources and protect the underground and surface environments. In recent years, such methods have been widely used in metal mines where pipeline transportation typically plays a decisive role in the safety and stability of the entire filling system. Because the filling slurry contains a large percentage of solid coarse particles, the involved pipeline is typically eroded and often damaged during such a process. A possible solution is the so-called nesting repair technology. In the present study, nesting a 127 mm outer diameter pipeline… More >

Ali H. Tarrad^*

FDMP-Fluid Dynamics & Materials Processing, Vol.18, No.4, pp. 1111-1127, 2022, DOI:10.32604/fdmp.2022.021541 - 06 April 2022

Abstract An analytical model was built to predict the thermal resistance of a vertical double U-tube ground-coupled heat pump that operates under steady-state conditions. It included a geometry obstruction factor for heat transfer throughout the backfill medium due to the presence of the second loop. The verification of the model was achieved by the implementation of five different borehole configurations and a comparison with other correlations in the available literature. The model considered a U-tube spacing range between (2) and (4) times the U-tube outside diameter producing a geometry configuration factor range of (0.29–0.6). The results More >

Xiyuan Li¹, Peng Chu^2,3,*, Zhuang Lu^2,3, Yuanyuan Liu^2,3, Zibin Zhu^2,3, Jin Gao^2,3, Xiaoxue Liao^2,3, Tao Yang^2,3

Energy Engineering, Vol.118, No.6, pp. 1811-1825, 2021, DOI:10.32604/EE.2021.015751 - 10 September 2021

Abstract The permeability is a key factor to determine the efficiency of coalbed methane (CBM) production. The borehole enlargement technology using hydraulic and mechanical measures to cut coal is an effective method to increase the coal seam permeability and improve the efficiency of gas drainage. Reasonable design of the layout of boreholes is the prerequisite for efficient and economical gas drainage. In this paper, based on the strain-softening model, the stress and permeability model of the coal seam around the enlarged borehole was built, and based on the dual-medium model, the gas migration model in the… More >

Jingying Li¹, Tiejun Zhu¹, Fengming Li¹, Dong Wang¹, Xianbiao Bu², Lingbao Wang^2,*

Energy Engineering, Vol.118, No.3, pp. 517-534, 2021, DOI:10.32604/EE.2021.014464 - 22 March 2021

Abstract The single well geothermal heating (SWGH) technology has attracted extensive attention. To enhance heat extraction from SWGH, a mathematical model describing heat transfer is set up, and the key influence factor and heat transfer enhancement method are discussed by thermal resistance analysis. The numerical results show that the thermal resistance of rock is far greater than that of well wall and fluid. So, reducing rock thermal resistance is the most effective method for enhancing the heat extraction power. For geothermal well planning to drill: rock thermal resistance can be reduced by increasing well diameter and… More >

Chenpeng Song^1,2, Yulong Chen^3,*, Jiehao Wang^2,*

CMES-Computer Modeling in Engineering & Sciences, Vol.120, No.3, pp. 779-797, 2019, DOI:10.32604/cmes.2019.07000

Abstract Hydraulic fracturing has been applied to enhance CBM production and prevent gas dynamical hazard in underground coal mines in China. However, affected by in situ stress orientation, hydrofracture can hardly continuously propagate within coal seam but may easily extend to the adjacent roof-floor strata, causing ineffective permeability enhancement in coal seam and increasing the risk of gas transfinite during mining coal. Thus, it is very necessary to artificially control the propagation direction of hydrofracture and make it well-aligned in large scale in coal seam. In this study, a method for controlling propagation direction of hydrofracture… More >

Yi Xue^1,2,3

CMES-Computer Modeling in Engineering & Sciences, Vol.113, No.4, pp. 429-441, 2017, DOI:10.3970/cmes.2017.113.429

Abstract The lack of research on the effect of diffusion on methane extraction leads to low methane concentration and low utilization. The Comsol Multiphysics software is used to solve the numerical gas and solid coupled model which considers the diffusion of coal matrix, fracture seepage, permeability evolution and coal deformation. The simulation results reveal the effect of diffusion process on methane migration. The gas diffusion rate is relatively high in the initial stage. With the increase in time, the difference between coal fractures and coal matrix blocks becomes lower and the gas diffusion rate decreases gradually. More >

A. Tadeu¹, P. Stanak², J. Antonio¹, J. Sladek², V. Sladek²

CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.5, pp. 345-378, 2015, DOI:10.3970/cmes.2015.107.345

Abstract This paper implements a numerical method based on the mutual coupling of the boundary element method (BEM) and the meshless local Petrov-Galerkin (MLPG) method to simulate elastic wave propagation in fluid-filled boreholes. The fluid-solid interaction is solved in the frequency domain assuming longitudinally invariant geometry in the axial direction (2.5D formulation).
This model is used to assess the influence of the non-homogeneous material properties of a borehole wall that can be caused by a damaged zone, construction process or the ageing of material. The BEM is used to model propagation within the unbounded homogeneous domain… More >

Yi Xue^1,2, Feng Gao^1,2,3, Xingguang Liu⁴, Xiru Li²

CMC-Computers, Materials & Continua, Vol.47, No.2, pp. 127-141, 2015, DOI:10.3970/cmc.2015.047.127

Abstract In order to study the effect of high pressure water jet cutting technology on the permeability of single coal seam, we use the damage variable to describe the fracture distribution of coal seam, develop the 3-D finite element program based on the damage theory, and then analyze the damage distribution of coal seam after drilling and slotting. Using MTS815 rock mechanics testing system and the permeability test system, we conduct the permeability test and get the relationship between permeability and damage. Based on the damage distribution of coal seam after drilling and slotting and the More >