scholarly journals Reservoir Permeability Evolution during the Process of CO2-Enhanced Coalbed Methane Recovery

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2996 ◽  
Author(s):  
Gang Wang ◽  
Ke Wang ◽  
Yujing Jiang ◽  
Shugang Wang
Keyword(s):  
Effective Stress ◽  
Coalbed Methane ◽  
Volumetric Strain ◽  
Fracture Aperture ◽  
Permeability Evolution ◽  
Methane Recovery ◽  
Permeability Model ◽  
Reservoir Permeability ◽  
Stress Changes ◽  
Enhanced Coalbed Methane

In this study, we have built a dual porosity/permeability model through accurately expressing the volumetric strain of matrix and fracture from a three-dimensional method which aims to reveal the reservoir permeability evolution during the process of CO2-enhanced coalbed methane (CO2-ECBM) recovery. This model has accommodated the key competing processes of mechanical deformation and adsorption/desorption induced swelling/shrinkage, and it also considered the effect of fracture aperture and effective stress difference between each medium (fracture and matrix). We then numerically solve the permeability model using a group of multi-field coupling equations with the finite element method (FEM) to understand how permeability evolves temporally and spatially. We further conduct multifaceted analyses to reveal that permeability evolution near the wells is the most dramatic. This study shows that the farther away from the well, the gentler the evolution of permeability. The evolution of reservoir permeability near the injection well (IW) and the production well (PW) are very different, due to the combined effects of effective stress changes and gas adsorption and desorption. Furthermore, adsorption is the main controlling factor for the change of permeability for regions near the IW, while the change in effective stress is the main cause for the change in permeability near the PW. Increasing the injection pressure of CO2 will cause the reservoir permeability to evolve more quickly and dynamically.

scholarly journals A Thermo-Hydro-Mechanical-Chemical Coupling Model and Its Application in Acid Fracturing Enhanced Coalbed Methane Recovery Simulation

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 626 ◽  
Author(s):  
Chaojun Fan ◽  
Mingkun Luo ◽  
Sheng Li ◽  
Haohao Zhang ◽  
Zhenhua Yang ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coalbed Methane ◽  
Coupled Model ◽  
Coupling Model ◽  
Gas Production ◽  
Methane Recovery ◽  
Acid Fracturing ◽  
Enhanced Coalbed Methane Recovery ◽  
Reservoir Permeability ◽  
Enhanced Coalbed Methane

The reservoir permeability dominates the transport of gas and water in coal seam. However, coal seams rich in gas usually contain various pores and fractures blocked by a large amount of minerals, which leads to an ultra-low permeability and gas extraction rate, and thus an increase of drilling workload. We first propose a thermo-hydro-mechanical-chemical coupled model (THMC) for the acid fracturing enhanced coalbed methane recovery (AF-ECBM). Then, this model is applied to simulate the variation of key parameters during AF-ECBM using a 2D geometry. The effect of different extraction schedules are comparatively analyzed to give an insight into these complex coupling responses in coal seam. Result confirms that the AF-ECBM is an effective way to increase the reservoir permeability and improve the gas production using the proposed model. The range of permeability increment zone increases most dramatically in the way of acid fracturing, followed by none-acid fracturing and acidizing over time. The gas production in order is: acid fracturing (AF-ECBM) > fracturing (F-ECBM) > acidification (A-ECBM)> direct extraction (D-CBM).

scholarly journals A dynamic evolution model of coal permeability during enhanced coalbed methane recovery by N2 injection: experimental observations and numerical simulation

RSC Advances ◽  
2021 ◽  
Vol 11 (28) ◽  
pp. 17249-17258
Author(s):  
Bo Li ◽  
Junxiang Zhang ◽  
Zhiben Ding ◽  
Bo Wang ◽  
Peng Li
Keyword(s):  
Numerical Simulation ◽  
Effective Stress ◽  
Coalbed Methane ◽  
Evolution Model ◽  
Dynamic Evolution ◽  
Combined Effects ◽  
Methane Recovery ◽  
Coal Permeability ◽  
Enhanced Coalbed Methane Recovery ◽  
Enhanced Coalbed Methane

A dynamic evolution model of coal permeability during CH4 displacement by N2 injection was proposed, considering the combined effects of matrix swelling/shrinkage and effective stress, for providing a reference on N2-ECBM.

scholarly journals Evolution of Coal Permeability during Gas Injection—From Initial to Ultimate Equilibrium

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2800 ◽  
Author(s):  
Xingxing Liu ◽  
Jinchang Sheng ◽  
Jishan Liu ◽  
Yunjin Hu
Keyword(s):  
Effective Stress ◽  
Local Equilibrium ◽  
Fracture Aperture ◽  
Permeability Evolution ◽  
Full Spectrum ◽  
Coal Permeability ◽  
Fracture Pressure ◽  
Permeability Changes ◽  
Apparent Equilibrium ◽  
Non Equilibrium

The evolution of coal permeability is vitally important for the effective extraction of coal seam gas. A broad variety of permeability models have been developed under the assumption of local equilibrium, i.e., that the fracture pressure is in equilibrium with the matrix pressure. These models have so far failed to explain observations of coal permeability evolution that are available. This study explores the evolution of coal permeability as a non-equilibrium process. A displacement-based model is developed to define the evolution of permeability as a function of fracture aperture. Permeability evolution is tracked for the full spectrum of response from an initial apparent-equilibrium to an ultimate and final equilibrium. This approach is applied to explain why coal permeability changes even under a constant global effective stress, as reported in the literature. Model results clearly demonstrate that coal permeability changes even if conditions of constant effective stress are maintained for the fracture system during the non-equilibrium period, and that the duration of the transient period, from initial apparent-equilibrium to final equilibrium is primarily determined by both the fracture pressure and gas transport in the coal matrix. Based on these findings, it is concluded that the current assumption of local equilibrium in measurements of coal permeability may not be valid.

scholarly journals Influence and Sensitivity Study of Matrix Shrinkage and Swelling on Enhanced Coalbed Methane Production and CO2 Sequestration with Mixed Gas Injection

2011 ◽  
Vol 29 (6) ◽  
pp. 759-775 ◽  
Author(s):  
Fengde Zhou ◽  
Guangqing Yao ◽  
Zhonghua Tang ◽  
Oyinkepreye D. Orodu
Keyword(s):  
Methane Production ◽  
Coalbed Methane ◽  
Net Present Value ◽  
Sensitivity Study ◽  
Mixed Gas ◽  
Methane Recovery ◽  
Matrix Shrinkage ◽  
Enhanced Coalbed Methane Recovery ◽  
Shrinkage And Swelling ◽  
Enhanced Coalbed Methane

Matrix compressibility, shrinkage and swelling can cause profound changes in porosity and permeability of coalbed during gas sorption and desorption. These factors affect the distribution of pressure, methane production and CO2 sequestration. This paper compares the effects of cleat compression and matrix shrinkage and swelling models with the injection of different compositional gas mixtures (CO2 and N2). It shows that well performance, pressure distribution and properties of the seam are strongly affected by matrix shrinkage and swelling. Matrix shrinkage and swelling also affects net present value of the enhanced coalbed methane recovery scheme. In order to select the best enhanced coalbed methane recovery schemes, economic evaluation and sensitivity studies are necessary.

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