Novel Associative Copolymer with Favorable Properties in Polymer Flooding Applications

摘要

New thickeners based on associative properties are discussed. The new thickeners are anionic, water- soluble copolymers with pendant associative groups. These associative groups are based on a novel, patented chemistry. The viscosity of the new copolymer shows superior behavior at elevated temperature especially in presence of salt and divalent ions. For example a viscosity of 40 mPas was measured with the new copolymer at 60°C in a brine containing 20% total dissolved salt including a high amount of hardness and a copolymer concentration of 2000 ppm. A standard, partially hydrolysed polyacrylamide (PHPA) with high molecular weight showed a value of only 9 mPas under these conditions. Moreover, compared to standard material the new polymer technology exhibits high shear stability, which can be explained by the associative polymer superstructure. The filtration properties of the new copolymer were evaluated in detail. Filtration properties had been tested in comparison to existing polymer flooding technologies with a variety of polycarbonate filter membranes with filter sizes ranging from 5 μm down to 1.2 μm. It turned out that the new copolymers could be filtered through all these membranes with good filtration ratios. Data on injectivity and rheological behavior of the new associative copolymer from a core flood test are presented. While common high molecular weight copolymers like PHPA or AMPS/acrylamide copolymers exhibit a shear-thickening behavior at high shear rates, the new thickeners are shear-thinning under these conditions. Good injectivity into a 0.2D as well as into a 2D core is given. The new polymer technology presented, shows favorable properties, which can offer advantages over current polymer flooding technologies.