An Evaluation of Water-Soluble Polymers For Secondary Oil Recovery - Parts 1 and 2

Viscosity-building properties of 34 polymers, representing 12 chemicallydifferent molecular structures or functional groups and a great variation inmolecular weights, were determined. Wide ranges of salinity (NaCl), polymerconcentration, and shear rate were used. The stability of polymers polymerconcentration, and shear rate were used. The stability of polymers in causticsolutions also was studied. The degree of shear degradation of individualpolymers is compared.

Introduction

The increasing use of water-soluble polymers in secondary and tertiary oilrecovery has resulted in the writing of more than 100 technical papers in thepast decade. Most of these papers have covered some special aspect of polymerapplication, but little comparative data about performance of differentpolymers under identical performance of different polymers under identicalconditions were published.

Mungan studied viscosity behavior for a wide range of shear rates, but thenumber of polymers and range of salinities was limited. Although Nouri et al.and Ferre extended the number of polymers to almost 12 and provided somecomparative data, a comprehensive provided some comparative data, acomprehensive comparison of the rheological performance of polymers for variousconditions was lacking. Hill et al. and Tinker and Bowman comparedfilterability and shear degradation of a partially hydrolyzed polyacrylamide(HPAM) and a biopolymer. Maerker studied the shear degradation of an HPAM for avariety of conditions.

Norton and Falk investigated the synergism between a variety of polymers andlater the possible use of various cellulose derivatives in the Maraflood TMprocess. Szabo published some data on polymers relating process. Szabopublished some data on polymers relating to polymer-sulfonate interactions.

However, a comprehensive study was needed to enlarge the type and number ofpolymers investigated and to compare systematically the viscosity-buildingproperties of these polymers under various conditions. properties of thesepolymers under various conditions. Additionally, a comparison of caustic withshear-resistance properties also was deemed important. This paper provides theresults of such a study. These rheological studies were further extended in anevaluation of flow behavior in porous media." Observations from Parts 1 and2 provide adequate information to screen polymer candidates initially forsecondary or tertiary oil-recovery projects.

Solution Viscosities and Cost Evaluations Procedure Procedure Solutions ofall dry polymers were prepared the same way. Polymer was added slowly to theupper two-thirds of the vortex of a solvent being stirred with a magneticstirrer. Solutions of liquid polymers (106, Q-41-F, VX-92, and Cynatrol TMproducts) were prepared as recommended by the suppliers. All solutions werestirred overnight to ensure full hydration.

Viscosities of the polymer solutions were determined on a Brookfield LVTviscometer at each available rpm (60 through 0.3). The UL adaptor was used forsolutions in 0. 1, 2, and 10% NaCl brines. Those in distilled water weredetermined with the small sample adaptor. The viscometer was checkedperiodically for accuracy with the mineral oil standards supplied by itsmanufacturer. All viscosity measurements were performed at 25 deg. C on freshlyprepared solutions. No biocides or oxygen scavengers were used.