Factors Influencing the Efficiency of Miscible Displacement

Abstract

Published in Petroleum Transactions, AIME, Volume 217, 1959, pages 1–8. Abstract This paper presents results of an experimental investigation of factors that control the efficiency with which oil is displaced from porous media by a miscible fluid. The study was made to elucidate the relevant processes both on microscopic level (within individual or between neighboring pore spaces) and on macroscopic level (within a large sand body). Mixing of miscible fluids on the microscopic level was studied in sand-packed tubes. It was found that molecular diffusion is the dominant dispersion mechanism for reservoir conditions of rate, length and pore sizes. Macroscopic channeling was studied for various mobility ratios in reservoir models-scaled to relate viscous gravitational, and diffusional forces. The formation of channels was due to viscous fingering, gravity segregation and variations in permeability. With adverse mobility ratios, it was found for reservoirs of realistic widths that diffusion will not be effective in preventing the formation and growth of fingers, even in homogeneous sands. At sufficiently low rates channeling was eliminated by gravity segregation in tilted reservoirs. The dependence of recovery on mobility ratio, length-to-width ratio, flow rate and angle of dip is presented. Introduction Oil recovery by solvent flooding is finding increasing application in the field. while the process promises high recoveries from the region swept by solvent, under adverse conditions only a small fraction of the reservoir volume may be swept at the time solvent breaks through to the producing well. Further, the high cost of the solvent encourages its use only as a bank whose size must be kept at a minimum. Thus, two important questions arise:what fraction of the reservoir can be swept, practically, by solvent? andwhat is the minimum size solvent bank that can be used to carry out the displacement? The answers to these questions require knowledge of both macroscopic channeling processes and microscopic mixing processes. The studies described here were carried out to gain this knowledge. Microscopic mechanisms which cause mixing will be discussed first, because an understanding of these mechanisms is necessary for proper interpretation of the experimental work on channeling described later.

Major carbon 14 anomaly in a regional carbonate aquifer: Possible evidence for megascale channeling, South Central Great Basin

“…The term channeling, borrowed from the petroleum engineering literature on macroscopic displacement phenomena (see, for example, Blackwell et al [1959] and Koval [1963]), refers to the uneven intrusion or fingering of one fluid into another with which it is miscible. Channeling, during water flooding operations, for example, can be caused by (1) permeability stratification, (2) segregation of fluids by gravity, and (3) segregation of fluids by differences in their viscosity [Blackwell et al, 1959]. The relationship between longitudinal dispersion and channeling was succinctly summarized by Koval [1963].…”

Glass micromodel study of bacterial dispersion in spatially periodic porous networks

“…The comparison between these systems was not meant to be exact, but rather to compare the relative order of magnitude of the dispersion coecients. In Figure 7, the micromodel dispersion coecients at various Peclet numbers were compared to those determined for granular repacked beds and were found to quantitatively agree (Blackwell and Rayne, 1959;Carberry and Bretton, 1958;Ebach and White, 1958; Gunn and Pryce, (Eidsath, 1983) and the experiments by Gunn and Pryce (1969) suggest that spatially periodic systems would have higher dispersion coecients than randomly packed three-dimensional systems. The dispersion coecients for the two-dimensional micromodel networks are similar to those for the three-dimensional packed columns.…”

Horizontal ethanol floods in clean, uniform, and layered sand packs under confined conditions

“…Craig et al [1957] conducted horizontal floods in uniform rectilinear models with unconsolidated sands with water and glycerol solutions to quantify gravity effects on frontal stability. Blackwell et al [1959] evaluated the stabilizing effects of gravity forces in rectilinear models using mobility ratios between 5 and 40, darcy velocities of 0.15 to 15.2 rn d -•, and density differences between 0.1 and 0.28 g cm -3 at dip angles of 4 ø to 90 ø. Hawthorne [1960] conducted floods in uniform rectilinear models with unconsolidated sands using solvents and oils in a downflow mode at a 45 ø dip angle.…”