Gelled polymer systems for permeability modification in petroleum reservoirs

The research program described in this report was conducted to improve the performance and predictability of in situ gelation processes designed to increase volumetric sweep efficiency of fluid displacement processes. A principal objective of this research was to develop procedures for design and evaluation of permeability modification processes. Research was conducted in three broad areas: (1) Physical and Chemical Characterization of Gelling Systems (2) In situ Gelation and (3) Mathematical Modeling of In Site Gelation. Gelling systems used chromium as the crosslinking agent. Polyacrylamide and polysaccharides gelling systems were studied. Research was conducted on the chemical structure of polymer/metal ion complexes, kinetics of the reduction of Cr(6) to Cr(3) by thiourea, kinetics of oligomerization and uptake of chromium by polyacrylamide and rheology of chromium/polysaccharide gelling systems. Studies of polymer/metal ion complexes were conducted using solutions of pure monomer, dimer and trimer forms of chromium. A mathematical model was developed to examine the kinetics of Cr(3) oligomerization and uptake of chromium by polyacrylamide. Rheological studies were completed on chromium/polysaccharide gels. In situ gelation experiments were conducted using a bis-ethylenediamine chromium complex and chromium(3) polyacrylamide gelling systems in sandpacks. A numerical model of in situ gelation of chromium/polyacrylamide systems was developed for linear displacement in a sandpack. The numerical model is based on filtration mechanisms and is consistent with experimental data and models developed in this research program. 103 figs., 21 tabs