scholarly journals The Influence of the Injected Water on the Underground Coalbed Methane Extraction

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1151
Author(s):  
Yanbao Liu ◽  
Zhigang Zhang ◽  
Wei Xiong ◽  
Kai Shen ◽  
Quanbin Ba
Keyword(s):  
Hydraulic Fracturing ◽  
Coalbed Methane ◽  
Gas Flow ◽  
Critical Time ◽  
Shanxi Province ◽  
Coal Bed ◽  
Hydraulic Pressure ◽  
Intrinsic Permeability ◽  
Permeability Evolution ◽  
Two Phase

The increasing demand on coal production has led to the gradually increase of mining depth and more high methane mines, which bring difficulties in terms of coalbed methane (CBM) extraction. Hydraulic fracturing is widely applied to improve the production of CBM, control mine gas, and prevent gas outbursts. It improves coal bed permeability and accelerate desorption and migration of CBM. Even though the impacts of hydraulic fracturing treatment on the coal reservoirs are rare, negative effects could not be totally ignored. To defend this defect, the presented work aims to study the influence of water filtration on coal body deformation and permeability evolution. For this purpose, a simulation based finite element method was developed to build a solid-fluid coupled two-phase flow model using commercial software (COMSOL Multiphysics 5.4). The model was verified using production data from a long strike borehole from Wangpo coal mine in Shanxi Province, China. Several simulation scenarios were designed to investigate the adverse impacts of hydraulic fracturing on gas flow behaviors. The mechanisms of both relative and intrinsic permeability evolutions were analyzed, and simulation results were presented. Results show that the intrinsic permeability of the fracture system increases in the water injection process. The impacts of water imitation were addressed that a critical time was observed beyond which water cannot go further and also a critical pressure exists above which the hydraulic pressure would impair the gas flow. Sensitivity analysis also showed that a suitable time and pressure combination could be observed to maximize gas extraction. This work provides an efficient approach to guide the coal bed methane exploitation and other unconventional gas reservoirs.

Topology Analysis and Optimization Design of Coal Bed Methane Gathering System in China

2014 ◽  
Author(s):  
Jun Zhou ◽  
XiaoPing Li ◽  
Mengya Cheng ◽  
Tao Deng ◽  
Jing Gong
Keyword(s):  
System Design ◽  
Topological Structure ◽  
Coalbed Methane ◽  
Optimization Design ◽  
Processing System ◽  
Shanxi Province ◽  
Coal Bed ◽  
Pipe Network ◽  
Gas Field ◽  
Optimal Position

China is abundant in coalbed methane (CBM) resource. The unconventional natural gas reserves has reached 36.81*1012 m3. The Qinshui Basin in Shanxi Province is the largest gas field among CBM gas fields in China which are commercially exploited since the year 2003. In order to solve some typical problems in CBM production, this article considered the geographical characteristics of the fields, introduced and analyzed the low pressure gathering and transporting process and facilities, as well as the important techniques. Respectively, this article introduced the surface gathering and transporting procedure, analyzed the characteristics and topological structure; it also proposed the optimization scheme of combining steel pipes with PE pipes in processing system. The gathering and transporting processes of remote areas should be flexible and able to solve the problems during gas recovery from both largely exploited CBM blocks and remote blocks with low production. Thus a more reasonable system design should be proposed. To carry out the scheme, it first defined the topological structure of the system with graph theory, then established the economic model of the combined scheme. The article calculated the critical length of pipeline between two methods and defined the concept of “remote” well area. With the analysis of the actual conditions in a certain block in Qinshui Shanxi, the conclusion shows that: the scheme of laying pipelines can make more profit, which is consistent with the actual field situation., At the same time, we chose a phased optimization method, which divided the optimization of entire system into several sub-problems, including well group division, nodes connection relationship, determination of plant’s optimal position, and optimization of pipe diameter. Then we established optimization model that takes the investment costs of each stage as objective functions. The example shows that compared with the artificial design result, the total length of pipeline was reduced by 4.576 km, pipeline investment by 7.35×104 US$, with the respective rates of returns of 19.57% and 4.89%. The number of valve sets in the system fell from 16 to 11 (31%). By analyzing the investment and construction scale of the existing pipe network and optimal pipe network we have proved that the method has an ideal optimization effect. These techniques and schemes can give reasonable instructions in CBM surface gathering system design, powerfully promoting the development of the Chinese CBM industry.

scholarly journals The pilot appraisal of acid fracturing of coalbed methane reservoir in southeast Qinshui Basin, China

2016 ◽  
Vol 20 (4) ◽  
pp. 1 ◽  
Author(s):  
Yu Yang ◽  
Chengwei Zhang ◽  
Huijun Tian ◽  
Wangang Chen ◽  
Xiadong Peng ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Coalbed Methane ◽  
Mining Area ◽  
Coal Bed ◽  
Coal Seams ◽  
Acid Sensitivity ◽  
Qinshui Basin ◽  
Acid Fracturing ◽  
Well Production ◽  
Macro Scale

The reserves of Coalbed Methane (CBM) in Qinshui Basin are quite promising, but the outputs from CBM wells are quite small even after massive hydraulic fracturing. Herein the fracture system with #3 and #15 coal seams in Qinshui basin was analyzed, and it was found that both of the macro-scale fractures and micro-scale fractures are filled with clay and carbonate minerals, which explains the low productivity of CBM wells after conventional hydraulic fracturing. Acid fracturing has long been an effective method for carbonate gas reservoir to improve the gas well production. However, there were few reports about the application of acid fracturing in coal bed methane field. Based on the mineral identification and acid sensitivity test, the feasibility of acid fracturing demonstrated that the acid does more help than damage to increase the permeability of coal seams in Qinshui basin. Onsite operations have shown that acid fracturing is applicable for the CBM wells in Jincheng Mining Area. It was also observed from the microseismic survey that when applying the acid fracturing treatment, the stimulated reservoir area depends on the acid volume pumped in the first stage, which is crucial to the success of the stimulation. Evaluación piloto de fractura ácida en depósitos de gas metano de carbón en el suroeste de la cuenca Qinshui, China  ResumenLas reservas de gas metano de carbón (CBM, del inglés Coalbed Methane) en la cuenca Qinshui son más que prometedoras, pero la producción en los pozos es muy pequeña, incluso después de fracturas hidráulicas masivas. En este trabajo se analizaron los sistemas de fractura de las vetas de carbón #3 y #15 de la cuenca Qinshui y se encontró que tanto las fracturas a macroescala como aquellas a microescala están cubiertas con arcillas y minerales carbonatos, lo que explica la baja productividad de los pozos de gas metano de carbón después de la fractura hidráulica convencional. La fractura ácida ha sido un método efectivo en los depósitos de gas carbonato para mejorar la producción en el pozo de gas. Sin embargo, existen pocos informes sobre la aplicación de la fractura ácida en el campo del gas metano de carbón. De acuerdo con la identificación mineral y las pruebas de sensibilidad ácida, la factibilidad de la fractura ácida demostró que el ácido es reparador en el incremento de la permeabilidad en las vetas de carbón de la cuenca Qinshui. Las operaciones in situ han demostrado que la fractura ácida es aplicable para los pozos de gas metano de carbón en el área minera de Jincheng. También se observó en el sondeo microsísmico que cuando se aplica un tratamiento de fractura ácida, el área del depósito estimulada depende del volumen de ácido bombeado en primera instancia, lo que es determinante en el éxito de la estimulación.

scholarly journals A Calculation Model of the Net Pressure for Forming Map Cracking in Coalbed with Cleats During Hydraulic Fracturing Process

2015 ◽  
Vol 8 (1) ◽  
pp. 193-197
Author(s):  
Li Yuwei ◽  
Ai Chi ◽  
Liu Yazhen
Keyword(s):  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Coalbed Methane ◽  
Maximum Principal Stress ◽  
Calculation Model ◽  
Coal Bed ◽  
Minimum Principal Stress ◽  
Fracturing Process ◽  
The Face ◽  
Net Pressure

An important prerequisite for achieving efficient exploitation of coalbed methane wells is through forming map cracking by hydraulic fracturing. In order to analyze the mechanical mechanism for forming map cracking of the coal bed with cleats, the mechanical conditions for forming map cracking during hydraulic fracturing process of coal bed was proposed using extensional faulting in elastic mechanics and the shear damage criterion, and the minimum net pressure calculation model for forming map cracking was established when the butt cleat and face cleat in coal opened at the same time. It can be concluded through using the calculation model that the net pressure value that needed for forming map cracking first decreased and then increased with the increasing of the angle between the face cleat and the direction of horizontal minimum principal stress. The cleats and fissures developed along the horizontal maximum principal stress were easy to open and extend under the effect of hydraulic fracturing. The variation of the internal friction coefficient variation of the face cleat had little effect on the minimum net pressure that was needed for forming map fracturing after the angle between the direction of face cleat and horizontal minimum principal stress is determined.

scholarly journals Meshless method simulation and experimental investigation of crack propagation of CBM hydraulic fracturing

2018 ◽  
Vol 73 ◽  
pp. 72 ◽  
Author(s):  
Guojun Wen ◽  
Haojie Liu ◽  
Hongbo Huang ◽  
Yudan Wang ◽  
Xinyu Shi
Keyword(s):  
Numerical Simulation ◽  
Hydraulic Fracturing ◽  
Mathematical Models ◽  
Meshless Method ◽  
Coalbed Methane ◽  
Physical Simulation ◽  
Rock Sample ◽  
Crack Opening ◽  
Hydraulic Pressure ◽  
Coal Rock

For simulating CoalBed Methane (CBM) hydraulic fracturing using 3-D meshless method, this paper analyzed the hydraulic fracturing mechanism and cracking form for coal rock and established the geometric and mathematical models of hydraulic fracturing propagation in coal rock in terms of the Hillerborg model on crack opening displacement theory. With the theoretical basis of hydromechanics, the formulas for calculating hydraulic pressure inside the fracture by numerical simulation were deduced from the analysis on this fluid-structure interaction problem. The geometric and mathematical models established above were described by 3-D meshless Galerkin (EFG, Element-Free Galerkin) method and compiled into the numerical simulation program using VB and FORTRAN programming language to simulate the fracture propagation for an actual coal rock sample with a drilling hole as an example. Then the physical simulation experiment of hydraulic fracturing propagation of coal seam was conducted on the same coal rock sample. Through the direct observation with naked eyes and detection by advanced instruments of ESEM and Micro-CT, the shape and parameters of cracks on the surface of and inside the coal rock sample were achieved, which indicated that experimental results are reasonably consistent with numerical simulation results.

scholarly journals Route Optimization of Pipeline in Gas-Liquid Two-Phase Flow Based on Genetic Algorithm

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Jun Zhou ◽  
Guangchuan Liang ◽  
Tao Deng ◽  
Jing Gong
Keyword(s):  
Genetic Algorithm ◽  
Coalbed Methane ◽  
Hydraulic Properties ◽  
Optimization Theory ◽  
Route Optimization ◽  
Hydraulic Calculation ◽  
Shanxi Province ◽  
Phase Flow ◽  
Optimal Route ◽  
Two Phase

This paper describes the problems in route optimization of two-phase pipelines. Combining the hydraulic calculation with route optimization theory, this paper establishes an automatic route optimization model and adopts the general genetic algorithm (gGA) and steady-state genetic algorithm (ssGA) to solve the model, respectively, gets the optimal route, and discusses the influence of parameters setting to the result. This algorithm was applied in determining pipelines routes in coalbed methane gathering and transporting system in Shanxi Province, China. The result shows that the algorithm is feasible, which improves the hydraulic properties by reducing the pressure drop along the line while the pipeline length is still acceptable.

scholarly journals A fully coupled thermo-hydro-mechanical model associated with inertia and slip effects

2017 ◽  
Vol 21 (suppl. 1) ◽  
pp. 259-266 ◽  
Author(s):  
Yi Xue ◽  
Zheng-Zheng Cao ◽  
Cheng-Zheng Cai ◽  
Fa-Ning Dang ◽  
Peng Hou ◽  
...  
Keyword(s):  
Coal Seam ◽  
Mechanical Model ◽  
Coalbed Methane ◽  
Gas Flow ◽  
Gas Adsorption ◽  
Coal Bed ◽  
Klinkenberg Effect ◽  
Numerical Result ◽  
Slip Effects ◽  
Fully Coupled

The inertia and slip effects have a significant impact on the coal seam gas extraction. A fully coupled thermo-hydro-mechanical model is established in this study, which takes into account the influence of non-Darcy gas flow and Klinkenberg effect on the coal seam deformation and coalbed methane migration. The numerical result shows that the coalbed methane migration and transport evolution coal bed methane reservoir is not only dependent on the coal matrix deformation, gas pressure and gas adsorption, but also closely related to inertia effect and slip effect.

scholarly journals Numerical Simulation Research on Hydraulic Fracturing Promoting Coalbed Methane Extraction

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Fan Yongpeng ◽  
Shu Longyong ◽  
Huo Zhonggang ◽  
Hao Jinwei ◽  
Yang Li
Keyword(s):  
Numerical Simulation ◽  
Hydraulic Fracturing ◽  
Production Rate ◽  
Coalbed Methane ◽  
Coupled Model ◽  
Research Process ◽  
Extraction Process ◽  
Methane Pressure ◽  
Two Phase ◽  
Fracture Length

Although hydraulic fracturing technology has been comprehensively investigated, few scholars have studied the influence of hydraulic fracturing on the effect of coalbed methane (CBM) extraction, and few considered the interaction between water and CBM in the research process, which is not conducive to guiding the engineering design of hydraulic fracturing wells. In this work, a hydraulic-mechanical-thermal coupled model for CBM extraction in hydraulic fracturing well is established; it combines gas-liquid two-phase infiltration, where nonisothermal adsorption is also considered. The COMSOL Multiphysics software is used to carry out the numerical simulation study of the CBM extraction process in hydraulic fracturing well and analyze the influence of coalbed permeability, initial methane pressure, and fracture length on CBM extraction in hydraulic fracturing well, and the results show that the hydraulic-mechanical-thermal coupled model for CBM extraction can be used for CBM extraction research in hydraulic fracturing well. The initial coalbed permeability, initial gas pressure, and fracture length all affect the migration speed of CBM to surface well in different ways and have a greater impact on the CBM production rate of hydraulic fracturing well. The greater the initial coalbed permeability and methane pressure are, the longer the fracture length is and the greater the CMB production rate of hydraulic fracturing well is. The change trend of coalbed permeability during the extraction process of surface fracturing well is directly related to the state of the reservoir. The factors of stress, temperature, and CBM desorption jointly determine the increase or decrease of coal seam permeability.

The influence of the Stokes and Archimedes forces on the stability of a two-phase flow

2003 ◽  
Vol 3 ◽  
pp. 266-270
Author(s):  
B.H. Khudjuyerov ◽  
I.A. Chuliev
Keyword(s):  
Spectral Method ◽  
Stability Region ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Solid Phase ◽  
Stability Characteristic ◽  
Phase Flow ◽  
Two Phase ◽  
The Stability

The problem of the stability of a two-phase flow is considered. The solution of the stability equations is performed by the spectral method using polynomials of Chebyshev. A decrease in the stability region gas flow with the addition of particles of the solid phase. The analysis influence on the stability characteristic of Stokes and Archimedes forces.

Simulation of mechanically stirred two-phase liquid-gas flow

1986 ◽  
Vol 51 (5) ◽  
pp. 1001-1015 ◽  
Author(s):  
Ivan Fořt ◽  
Vladimír Rogalewicz ◽  
Miroslav Richter
Keyword(s):  
Spatial Distribution ◽  
Velocity Field ◽  
Gas Flow ◽  
Liquid Velocity ◽  
Model Parameters ◽  
Two Phase ◽  
Mean Velocity ◽  
Rushton Turbine ◽  
Low Viscosity ◽  
Volumetric Gas Flow Rate

The study describes simulation of the motion of bubbles in gas, dispersed by a mechanical impeller in a turbulent low-viscosity liquid flow. The model employs the Monte Carlo method and it is based both on the knowledge of the mean velocity field of mixed liquid (mean motion) and of the spatial distribution of turbulence intensity ( fluctuating motion) in the investigated system - a cylindrical tank with radial baffles at the wall and with a standard (Rushton) turbine impeller in the vessel axis. Motion of the liquid is then superimposed with that of the bubbles in a still environment (ascending motion). The computation of the simulation includes determination of the spatial distribution of the gas holds-up (volumetric concentrations) in the agitated charge as well as of the total gas hold-up system depending on the impeller size and its frequency of revolutions, on the volumetric gas flow rate and the physical properties of gas and liquid. As model parameters, both liquid velocity field and normal gas bubbles distribution characteristics are considered, assuming that the bubbles in the system do not coalesce.

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