年間 12 号発行
ISSN 印刷: 1091-028X
ISSN オンライン: 1934-0508
Indexed in
USE OF FRACTURE AS A PLANAR SOURCE OF FLOW TO DETERMINE THE EFFECT OF A STAGNANT ZONE ON THE DILUTION OF A FRONT
要約
Transport of solute through fracture is important in several aspects of oil recovery. The presence of a stagnant zone within the fracture as well as the porous matrix affects the transport process significantly, and is investigated here. This paper describes experiments with potassium iodide (KI) as a solute in brine flowing through a fractured slab of Berea sandstone. A step change in concentration at the fracture inlet was tracked at the outlet. A similar experiment was performed in smooth replica of a fracture with saw-cut face of Berea rock forming the wall. The responses were also simulated using theoretical models, accounting for (a) diffusion into the stagnant zone inside the fracture and (b) diffusion into the stagnant zone that, in turn, is open for diffusive transport into the brine in the adjoining matrix. The laboratory model of the fracture used in the experiment allowed for a controlled flow of injected solution into the matrix in addition to flow through the fracture. The control of such flow is a novel approach to establish in the laboratory the flow in a fracture that is entirely surrounded by a porous matrix. The mathematical model developed in this paper suggests that uniform penetration into the matrix throughout the entire length of the fracture requires a thin, wide, and (preferably) low-permeability slab. In one of the experiments with unidirectional flow through the fracture, some of the injected KI solution flowed into the matrix prior to flow through the fracture outlet. The concentrations, recorded at the fracture outlet, provided further insight to the transport of solute when the fluid from the stagnant zones had been dispelled into the matrix. Porous media, beyond a distance equal to a few fracture apertures does not contribute to the dilution of the solution front for the flow velocity and timeframe in this experiment.