Investigation of the Contamination of Fractured Formations by Non-Newtonian Oil Pollutants

Abstract

In many practical applications, non-aqueous phase liquid (NAPL) pollutants exhibiting a clearly non-Newtonian rheological behavior (e.g. crude oil, suspensions of engine oils, asphalt, creosote, etc.) may migrate through fractured formations and contaminate aquifers. The present work is the ®rst step toward the development of non-Darcian models concerning the non-linear NAPL¯ow in single fractures, and determination of the coupled eects of non-Newtonian NAPL rheology and¯ow rate on the transient immiscible displacement of an aqueous phase by a NAPL. Initially, a protocol is developed for the preparation and rheological characterization of synthetic non-Newtonian NAPLs, which are based on waxy oils. Then, an arti®cial transparent glass-etched single fracture of controlled morphology is fabricated and used for the measurement of the non-linear pressure gradientÐsuper®cial velocity relationship for the¯ow of NAPL of varying rheology. Pore network simulations and eective medium approximation (EMA) are used for the interpretation of the experimental results and derivation of an analytic non-Darcian one-phase¯ow model. Visualization experiments of the immiscible displacement of an aqueous phase by Newtonian and non-Newtonian NAPLs are performed on the arti®cial fracture under controlled values of the viscosity ratio and capillary number (ratio of viscous to capillary forces). Comparative study of the Newtonian and non-Newtonian NAPL¯ow patterns allows us to evaluate the interactive eects of NAPL rheology,¯ow rates and fracture morphology on the spatial and temporal distribution of such liquid pollutants within single fractures.# 2001 AEHS

Experimental study of turbulent unconfined groundwater flow in a single fracture

“…Our finding supports several recent simulation studies such as Schedl (1992), Mourzenko et al (1995), Brown et al (1995), Choi et al (1997), Oron andBerkowitz (1998), Baker (2000), Kolditz (2001), andBerkowitz (2002), and experimental studies such as Lloyd et al (1996) and Theodoropoulou et al (2001) which indicated that the LCL assumption might be inaccurate in many cases of fracture flow, but disagrees with those that employed the laminar flow and LCL assumptions such as Louis (1969), and Witherspoon et al (1980).…”

“…Kohl et al (1997) has reported non-Darcian flow in natural rocks in two independent multirate flow experiments in the hot dry rock (HDR) test site at Soultz of France. Non-Darcian flow behavior was observed for realistic fractures with rough surfaces by many other studies such as Schedl (1992), Lloyd et al (1996), Choi et al (1997), Oron andBerkowitz (1998), Baker (2000), Kolditz (2001), Theodoropoulou et al (2001), andBerkowitz (2002).…”

Correlation of the two-phase flow coefficients of porous media with the rheology of shear-thinning fluids

“…The shear viscosity of NWP was measured as a function of the shear stress with a Dynamic Stress Rheometer (SR-200, Rheometrics Inc.) and was fitted to the mixed Meter-andpower-law fluid model [6,22] (Table 1, Fig. 1) given by…”

“…In addition, drainage [22] and imbibition [36] experiments with a shear-thinning non-wetting fluid have revealed that the pore-scale mechanisms and transient flow pattern are affected significantly by the non-Newtonian rheology, as well. The question is whether and how the capillary pressure and relative permeability curves, estimated from unsteady-state experiments are correlated with the fluid rheology, or equivalently, with the rate-dependent shear viscosities of non-Newtonian fluids.…”

“…porosity ω orientation angle of pores with respect to the mean flow direction a Newtonian wetting fluid by a shear-thinning non-wetting one [22], and having set the non-Darcian model governing the flow of shear-thinning fluids in porous media [6], the effects of non-Newtonian fluid rheology on capillary pressure and relative permeability curves are to be determined. The effective multiphase transport coefficients of natural porous media (e.g.…”