A Laboratory Study of Water Immobilization for Improved Oil Recovery
Authors: Meehan D.N. , Crichlow D.E. , Crichlow H.B. 
Published: December 2007

Introduction

In most oil reservoirs, injected water follows the paths taken by previously injected water. If some water-swept paths could be immobilized, continued waterflooding paths could be immobilized, continued waterflooding might sweep new paths and yield more oil than traditional waterflooding. Laboratory experiments were conducted in which vertical sand packs were waterflooded to breakthrough. Various fractions of the water-swept volume then were immobilized. An additional waterflood was conducted to determine how much additional oil could be recovered by this technique. Data were gathered that indicated improved microscopic displacement efficiency and oil recovery. Results indicated that the magnitude of additional oil recovery using this technique was small and increased with the degree of immobilization. Increases in flooding pressures of three- to fivefold were required to flood after immobilization. Favorable alterations in the water-oil relative permeability ratio and fractional flow curves were found also.

Several methods have been proposed to divert injected water into previously unswept paths. Polymers and polymerizing monomers are perhaps the most notable polymerizing monomers are perhaps the most notable solutions to date. One possible mechanism for improved oil recovery by polymer injection is the migration of polymers to block the more permeable paths. Injected polymers to block the more permeable paths. Injected water then would be forced into previously unswept paths. Immobilization of an injected fluid might serve a paths. Immobilization of an injected fluid might serve a similar purpose.

Consider the problem of what benefits will result from immobilization, that is, physically plugging water-swept flow paths and diverting injected water into unswept paths. The answer depends on the distribution of unswept paths. The answer depends on the distribution of unswept oil after waterflooding. Applications of this technique might be most helpful in heterogeneous systems. This investigation sought to identify any beneficial effects by using relatively uniform properties for the flooded reservoir.

The increased displacement efficiency, the magnitude of incremental oil recovery by such a process, and other information was obtained in this study. This included the increase in pressures required to flood after immobilization, the alteration of the water-oil relative permeability, and be relationship of increased oil recovery permeability, and be relationship of increased oil recovery to the fraction of the swept paths immobilized. The study also investigated the effects of successively injecting stages of immobilizing material and waterflooding.

A series of waterfloods was conducted in vertical sand packs. Waterflood results are presented for six packs. Waterflood results are presented for six experiments, each of which involved two complete floods. The first flood consisted of water injection until no additional oil was recoverable. After resaturating the core with oil, a second flood was conducted that involved a waterflood to water breakthrough, injection of a fluid that became immobile, and a subsequent waterflood. Various fractions of the water-swept pore volume at breakthrough were immobilized in these experiments.

JPT

P. 205