Molecular structure characterization and interaction of a polymer blend of xanthan gum-polyacrylamide to improve mobility-control on a mature polymer flood

According to the strategy to search alternative products which can replace (partially) the use of expensive polymers in polymer-flood projects, this work helps to find the optimum combination between polymer and xanthan-gum to develop a mixture that generates viscosity in good economical and rheological conditions. The aim of this work is the characterization of the mixture of a biopolymer (xanthan gum) and a synthetic polyacrylamide in specific proportions and reservoir conditions. Both polymers are suitable for polymer flood injection, but they have weaknesses on their own: the polyacrylamide is very susceptible to saline environments and mechanical degradation, while biopolymers as xanthan gum exceed these reservoir conditions but are highly degraded by some bacteria. A polymer blend of mother solutions was prepared by mechanical mixing. It is proved that a blend improves the desirable properties of mobility control if the polymers show miscibility. Several techniques were used to evidence possible interaction between the polymers. A series of tests were performed to provide complementary data regarding molecule structure, miscibility, interaction and stability of the xanthan gum-polyacrylamide mixture at 35/65 proportion in a 16,000 ppm TDS reservoir synthetic brine. The polymer mother solutions and the mixture were lyophilized in order to determine thermal events by Differential Scanning Calorimetry (DSC), Differential Thermal Analysis (DTA) and Thermo Gravimetric Analysis (TGA). Also Fourier Transform Infrared (FTIR) spectroscopic studies and Proton Nuclear Magnetic Resonance (1H NMR) were performed to obtain distinctive molecular fingerprint; and Scanning Electron Microscopy (SEM) so as to complete the morphological studies. This work shows detailed techniques of the characterization and the conclusions achieved that confirm the molecular interaction of the blend. DSC analysis at low temperatures evidence similar vitric transitions for xanthan gum and polyacrylamide mother solutions. Vitric transition ...