ABSTRACT:

Modeling fluid flow through a single rough walled fracture is complex due to the tortuous paths followed by the fluid particles and presence of rough walls. This effect is conventionally taken into fluid flow formulae using JRC values. However, it is argued that JRC is a subjective method and hence may not be suitable to be used for quantitative characterization of profile roughness. In this paper, this concept is further investigated by analyzing the fluid flow response of JRC profiles under laminar flow regime using 2D computational fluid dynamics numerical code (CFD). Number of synthetic profiles were analysed first to verify the numerical results. Analysis of JRC profiles showed in general a positive correlation between pressure drop and JRC values (i.e. profile roughness) but fluctuations were observed in some JRC profiles which are believed to be due to the subjective nature of these exemplar profiles.

1 INTRODUCTION

Simulation of fluid flow in natural fracture networks is important in many fields such as hydrogeology, geology, mining and petroleum engineering. Natural fractures are generally rough and irregular with uneven walls which usually make contact at several discrete points. Accordingly, a good understanding of fluid flow in a single fracture is essential before studying a complicated case of fracture network. It is well known that surface roughness has a great impact on fluid flow characteristics through a single rough walled fracture, e.g. transmissibility (Zimmerman& Yeo 2000). Almost commonly used parameter to characterize roughness is JRC comparative approach introduced by Barton and Chouby (1977). However, JRC is a subjective method based on observational comparison of real rock surface with 10 standard exemplar profiles and enough care is to be made when it is used to determine surface roughness (Beer et al., 2002; Asadi et al., 2009).

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