Computed Tomography Studies of 3-D Miscible Displacement Behavior in a Laboratory Five-Spot Model

Abstract

ABSTRACT This paper presents the results of computed tomography (CT) studies of three-dimensional (3-D) miscible displacements in a laboratory five-spot model. In the field, gravity forces resulting from a density difference between a miscible agent (solvent) and a reservoir oil may cause segregation and result in an overriding solvent tongue. The laboratory model used in these experiments is a one-quarter of a five-spot pattern (20 cm × 20 cm × 15 cm) with a porous medium constructed of spherical glass beads. Viscous and gravity forces are scaled within certain limits to represent conditions applicable to the field. Displacements are conducted at mobility ratios of 7.5 and 22.4 over a range (approximately 2 to 23) of viscous-to-gravity force ratios (Rv/g). Previous five-spot recovery correlations, based on a combination of 2-D areal and 2-D vertical sweepout, are found to overestimate recovery for the 3-D displacements. At one pore volume injected, for example, recoveries range from approximately 10% to 30% lower than those indicated by earlier correlations. In contrast with 2-D behavior, recovery efficiency increases continuously with greater Rv/g. The displacement characteristics for 2-D flow typically show a single overriding solvent tongue; the 3-D displacement characteristics observed here typically include an overriding tongue with secondary fingers. These results provide new experimental data in true 3-D geometry, and reinforce concerns with extending previous 2-D concepts to flow in 3-D five-spot patterns.