Polymer Structure and Its Relationship to the Dilute Solution Properties of High Molecular Weight Polyacrylamide

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the 49th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Texas, Oct. 6–9, 1974. Permission to copy is restricted to an abstract of not more than 300 words. illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract The anomalous viscosity behavior of high molecular weight polyacrylamide (PAA) has been studied on the basis of macromolecular structure and referenced to more classical rheological studies. Specialized electron microscope techniques were developed to study the super-molecular structure of PAA and allow the direct measurement of its molecular weight (MW) and MW distribution. Supermolecular structures that are MW dependent characterized the morphology of PAA in dilute aqueous solutions. Variations in the properties of dilute PAA solutions following properties of dilute PAA solutions following controlled degradation were found to be reflected in the gross alteration of the observed super-molecular structure. The ability to relate the dilute solution properties of PAA to a physical base has been properties of PAA to a physical base has been helpful in advancing our understanding of the unusual properties of this polymer as well as allowing us to more effectively utilize this unique material in secondary oil recovery processes. processes Introduction The unusually high solution viscosity observed for very dilute solutions of polyacrylamide (PAA) has made this synthetic water polyacrylamide (PAA) has made this synthetic water soluble polymer of interest in secondary oil recovery operations. A unique property of dilute solutions of PAA of molecular weight greater than 1 × 10 is the anomalous viscosity observed when these dilute polymer solutions pass through porous media. Pye and co-workers have reported that viscosities calculated from Darcy's equation for flow through porous media gave viscosities for PAA solutions 5 to 20 times greater than those PAA solutions 5 to 20 times greater than those determined for the same concentration of polymer solution using classical rheological procedures. This anomalous viscosity effect has become known as the "resistance factor." Subsequent studies have confirmed much of this early work and established the anomalous viscosity behavior of PAA as a distinctly unique property of the polymer in dilute aqueous solution. polymer in dilute aqueous solution. Although classical studies of polymer rheology and characterization have been useful in the practical exploitation of the "resistance" practical exploitation of the "resistance" phenomenon, a clear understanding at the fundamental phenomenon, a clear understanding at the fundamental level has not been satisfactorily achieved. In the final analysis it is the size, shape, and chemical functionality of the polymer molecules in solution and their interaction with the solvent and one another that is responsible for the cumulative properties of a dilute polymer solution.