Abstract

An experimental simulation on the miscible displacement in fractured oil reservoir is presented. The theoretical and experimental presented. The theoretical and experimental studies are based on the ideas originally developed by Coats and Smith and recently modified by Perez-Cardenas in connection with miscible and immiscible displacements in heterogenous media which contain a double-porosity system. The proposed model considers that fluid displacement takes place through the fracture system by Convection-Dispersion process, while the matrix blocks exchange matter with the fractures mainly by hydrodynamic dispersion and molecular diffusion. To test the theory and experimental model, several displacements simulations were carried out with real field data. This paper describes application of two-dimensions simulations to miscible displacement during waterflooding operations. The first section describes a method of calculating the behavior of a water salinity tracer by use of an analytical solution for the Dispersion-Convection Equation. The second section of this work extends the analytical results in Berea sand cores. Finally, the last section covers the field simulation, thus the objective is to study the tracer evolution for frontal displacement simulation. Results are presented on calculations of salinity digital images for each evolution step at several pore volume injected and levels of mechanical dispersion-convection.

Introduction

In Mexico several millions of additional reserves have been generated through waterflooding, one of the most important methods in improving recovery from oil reservoirs. Waterflooding as a secondary oil recovery is the most ancient method used in Mexico because it is economic and easy to introduce. Waterflooding begins by injecting treated water by means of several wells for the frontal displacement technique, per example an array of seven wells. In displacements in porous media a variety of instabilities in displacement front can arise that detract from efficiency of displacements of one fluid to another. Immiscible displacement at an unfavorable mobility ratio is not well known to be unstable to viscous fingering of the water saturation into the oil. At same time, miscible displacement at a favorable mobility ratio is known to be a stable to viscous fingering of the injection water salinity into the reservoir water salinity. There have been many attempts to characterize the last phenomenon through laboratory experiments and direct simulations, but for the second phenomenon this paper represents a new attempt to characterize a reservoir. In particular for waterflooding we consider that two types of displacements say exist at same time: an immiscible displacement (oil by water) and a miscible displacement (water in situ by injected water). For immiscible displacement competition between viscous and capillary forces has a dominant effect on finger behavior, while for miscible displacement (water in-situ by injection water) a gradient of concentrations has a dominat effect on the same finger behavior too. Thus, hydrodynamical dispersion and viscous fingering are important parameters in miscible and immiscible displacements.

P. 311

This content is only available via PDF.
You can access this article if you purchase or spend a download.