Boundary Effect on Pore Pressure and Coal Seam Deformation during CO2 Sequestration in Coal Seam

 

Li Zhu

Ph. D. student
School of Mechanics & Civil Engineering, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China
e-mail: heng-carlos@126.com

Weiqun Liu *

State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, 221008, China
School of Mechanics & Civil Engineering, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China
*Corresponding author: e-mail: wqliu@cumt.edu.cn

Zhiqiang Shen

School of Mechanics & Civil Engineering, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China

Zhengfeng Yi

School of Mechanics & Civil Engineering, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China

 

 ABSTRACT

A mathematical model built for CO2 permeating through coal seam in finite boundary condition is solved by using Laplace transformation and Residue calculation method with the purpose to study the influence of boundary conditions on pore pressure in coal seam during injection. Compared with the result in infinite boundary condition, further research shows that boundary conditions make a difference on the distribution of coal seam deformation. The following results can be obtained from this study: (1) Displayed from the pore pressure distribution of the both, boundary conditions have little effect on pore pressure in the initial stage of CO2 injection. When the gas permeates to the model boundary, the figures are no longer similar. (2) The pore pressure near the wellbore increases sharply and the pore pressure gradient turns out to be rather huge in the preliminary stage. As time goes by, the pore pressure increases continuously, while the pressure gradient decreases and finally approaches the level. (3) Vertical deformation equation can be acquired based on Langmuir equation and the aeolotropy of coal adsorption swelling. (4) Comparison of coal seam deformation distribution in finite and infinite boundary conditions shows that boundary conditions do not affect the distribution of deformation in the initial stage, and these two kind of distribution differ from one and another when CO2 permeates to the boundary.

Keywords: CCS; CO2 sequestration in coal seam; boundary effect; pore pressure distribution; coal seam deformation

Get the entire paper (pdf)    Go back to the TOC