Abstract

A series of experiments were performed in order to study the applicability of polymer gels, polymer enhanced foams and foamed gels in environments that are relevant to Western Canadian reservoirs. The problem of plugging fractures in tight gas reservoirs was tackled first. Three commercial technologies were evaluated and two gave spectacular results for carbonate core from Western Alberta. The testing experience led to the conclusion that chemical compositions and operating parameters are reservoir specific and need to be developed by the design team. The exercise further demonstrated that the design team should never rely on the service company alone to perform a test. On site viscosity and gelation tests must be performed to ensure that the injected product has the desired properties. This will lead to considerable savings in capital spending. In the second part of this work, a wide variety of surfactants were screened using Berea core, high pressure, moderate temperature and high salinity solutions. Polymer enhanced foams were created in various combinations. The design team had to tackle problems of adsorption versus optimum concentration, compatibility of reagents and presence of oil. Foamed gels are faced with the problem of controlling gelation while maintaining a low cost for chemicals.

Introduction

The possibility of enhancing reservoir conformance by utilizing polymer gels and aqueous foams have been two areas of significant importance in the petroleum engineering literature for the past twenty-five years. Recently, the idea of combining the two technologies for the same purpose has also been given some consideration. The term Foamed Gels (FGs) and Polymer-Enhanced Foams (PEFs) are used in the literature to describe such combinations of gels and foams. The foam is generated by mixing a gas with a surfactant solution. The gel is created through the in-situ cross-linking of a polymer in the presence of a catalytic agent. Foamed gels are simply a polymer cross-linking solution containing a surfactant which is foamed using a gas. A foamed gel can be created by means similar to those used in regular aqueous foam generation. The major difference between foamed gels and aqueous foams is that after some time, the external phase of the foamed gel cross-links thereby greatly enhancing the mechanical stability of the foam system. Aqueous foams, whose interfaces are stabilized by surfactants alone, collapse if surfactant-free water flows through them. Ideally, the polymer gel foaming solution will not gel during the injection of a foam into the porous matrix. Thus, a foamed gel system behaves like a foam during injection, and after gelation, it behaves similarly to a gel. This work deals with testing the applicability of polymer gels and polymer enhanced foams in Canadian oil and gas reservoirs. A series of experiments were conducted to illustrate such potential.

RECENT LITERATURE

A tremendous amount of work has been published on gels, foamed gels and polymer enhanced foam. The following is a brief selection of some recent papers. According to Miller and Foglerl, foamed gels offer greater control over permeability reduction than do commonly used bulk gels.

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