Transient Pressure Analysis of a Multiple Fractured Well in a Stress-Sensitive Coal Seam Gas Reservoir

Zuhao Kou,Haitao Wang

doi:10.3390/en13153849

Abstract

This paper investigates the bottom-hole pressure (BHP) performance of a fractured well with multiple radial fracture wings in a coalbed methane (CBM) reservoir with consideration of stress sensitivity. The fluid flow in the matrix simultaneously considers adsorption–desorption and diffusion, whereas fluid flow in the natural fracture system and the induced fracture network obeys Darcy’s law. The continuous line-source function in the CBM reservoir associated with the discretization method is employed in the Laplace domain. With the aid of Stehfest numerical inversion technology and Gauss elimination, the transient BHP responses are determined and analyzed. It is found that the main flow regimes for the proposed model in the CBM reservoir are as follows: linear flow between adjacent radial fracture wings, pseudo-radial flow in the inner region or Stimulated Reservoir Volume (SRV), and radial flow in outer region (un-stimulated region). The effects of permeability modulus, radius of SRV, ratio of permeability in SRV to that in un-stimulated region, properties of radial fracture wings, storativity ratio of the un-stimulated region, inter-porosity flow parameter, and adsorption–desorption constant on the transient BHP responses are discussed. The results obtained in this study will be of great significance for the quantitative analyzing of the transient performances of the wells with multiple radial fractures in CBM reservoirs.

Highlights

Coalbed methane (CBM) has played an increasingly important role in the energy consumption market
Researchers have focused on utilizing valid stimulation treatment, hydraulic fracturing technology, to effectively develop coalbed methane (CBM) in reservoirs, which usually consists of two components: (1) small-diameter pores, providing storage space for CBM and (2) natural fractures, acting as storage space, and connecting pores in matrix and providing flow channels for fluid, which can be described by the double-porosity system [1,2]
The generated fracture network close to the wellbore in unconventional hydrocarbon reservoirs caused by stimulation treatment are generally termed as study is considered as an isinner region near wellbore, the multi-wing artificial in this study considered as antheinner regionwhich near includes the wellbore, which includes the fractures and the induced fracture network

Summary

Introduction

Coalbed methane (CBM) has played an increasingly important role in the energy consumption market. Researchers have focused on utilizing valid stimulation treatment, hydraulic fracturing technology, to effectively develop CBM in reservoirs, which usually consists of two components: (1) small-diameter pores, providing storage space for CBM and (2) natural fractures, acting as storage space, and connecting pores in matrix and providing flow channels for fluid, which can be described by the double-porosity system [1,2]. Gradually decreasing pore pressure results in increasing effective stress, which further leads to decreasing permeability [3,4,5,6]. The stress sensitivity needs to be considered when modeling gas seepage in porous media during production. Pedrosa [7] creatively presented the definition of permeability modulus to characterize the relationship between permeability and pore pressure. Zhang and Ambastha [8] derived a numerical solution to determine the pressure responses in stress-sensitive reservoirs. Chen et al [9]

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Results

Conclusion