Numerical simulation of a coupled gas flow and geomechanics process in fractured coalbed methane reservoirs

Abstract

The pores and throats of coal seam are narrow, and the permeability is very low. It is a porous medium with complicated deformation mechanism. In the process of gas production, the change of stress, pore pressure, gas adsorption and desorption will lead to the change of grains, pore volume, and the seepage capacity of coal seam. Based on the theory of poroelastic and seepage mechanics, a physical model of fractured horizontal well and a coupled mathematic model of coal deformation and gas flow are established. The dynamic change model of permeability is deduced too. The development characteristics and laws of coalbed methane are numerically simulated by using numerical analysis software Comsol Multiphysics. Finally, the sensitivity of the key parameters in the model and the influence of the fracture parameters are analyzed. The results show that the application of fractured horizontal well is an effective measure to increase production of coalbed reservoirs; with the increase of Langmuir volumetric strain constant, fracture half‐length, and the numbers of fracture, the production of coalbed methane is increasing. In the case of constant total fracture length, number, and spacing, when fracture half‐lengths are long and short interlaced distribution, the production is the highest and it is the best fracture distribution pattern. The study provides a theoretical basis for the further study of coalbed deformation, gas migration, efficient, and rational development of coalbed methane reservoirs.

Impact factors and contributions of commingled production in multiple coal seams

“…As far as hydraulic fracturing is concerned, the half length of fracture and permeability after fracturing are positively correlated with gas production, indicating that the influence of reservoir characteristics on productivity after fracturing is greater than that of in situ reservoir conditions. This is consistent with the results obtained by Zhang et al 47 through the physical and numerical simulation of hydraulic fracturing; that is, the increase in the half-length and number of fractures will promote an increase in CBM production. In the case of a small difference in geological conditions, there is a significant correlation between the fracturing effect and gas production (Figure 10A,B).…”

Analysis of the Causes of Altered Coal Seam Permeability Based on On‐Site Directional Long‐Drill Hydraulic Fracturing Tests

“…Therefore, many scholars have carried out multi-dimensional research on this problem. They mainly focus on the construction of mathematical model of coal seam fracture and extension, [5,6] numerical simulation of hydraulic fracturing, [7][8][9][10] and the evolution law and change characteristics of coal pore and fracture, [11] etc. In 1960, hydraulic fracturing technology was firstly adopted in coal mines in the former Soviet Union.…”

Experimental study on stress sensitivity of high‐temperature and high‐pressure sandstone gas reservoirs in Yingqiong Basin

“…[29][30][31][32][33][34][35] A new stress-sensitive permeability analysis model was proposed by Zhu et al 36 And Zhu et al 37 thought the permeability performance under reservoir condition was divided into two stages through a semi-analytical model. The relationship between stress and permeability was studied through numerical simulation by Zhang et al 38 and Zhao et al 39,40 In addition, some scholars [41][42][43] have studied the changing of permeability in the production process.…”