ABSTRACT

ABSTRACT:

The X-ray computed tomography (CT) technique was used to characterize a variable aperture sandstone rock fracture. The introduced relative fracture aperture measurement method from demountable mechanical strain gauge (DEMEC) eliminated some of the drawbacks in previously proposed calibration techniques. Moreover, instead of one calibration curve, different calibration curves were developed for each position of the fracture. It increased the accuracy and reduced the effects of beam hardening in aperture calculation. An experimental setup was fabricated to conduct single phase flow tests in fractured rock sample and the hydraulic aperture of the fracture was estimated. The measured hydraulic aperture was compared with the calculated average aperture from the CT data. The DNAPL invasion of the variable aperture sandstone fracture was numerically simulated under varying capillary pressures, assuming small sub regions of the fracture as parallel plates. The capillary pressure curve and the phase distribution were derived from the numerical results.

1 INTRODUCTION

The analysis of multiphase flow process in rough walled rock fractures is essential to understand various phenomena in different fields such as hydrogeology, petroleum engineering and geomechanical engineering. The migration of Dense Non-Aqueous Phase Liquids (DNAPL), a critical ground water contaminant in many industrialized cities, in fractured aquifers is the main concern of this study. Hence, a correct estimation of DNAPL migration and distribution is essential to design an efficient remediation scheme. DNAPL migration in fractured bedrock aquifer is rather different from their migration behavior in sand or granular aquifers. The fracture aperture, the pattern of fracture connections, DNAPL pool height and the physical properties of DNAPL determine the migration and distribution process (Pankow & Cherry 1995). DNAPLs enter into a fracture once it overcomes its entry pressure and then the migration is controlled by the capillary forces between water and DNAPL.

This content is only available via PDF.
You can access this article if you purchase or spend a download.