Heteropolysaccharide preparation and use thereof as a mobility control agent in enhanced oil recovery

A variant strain of Agrobacter radiobacter has been found to produce a unique heteropolysaccharide containing D-galactose, D-glucose and pyruvic acid in approximate molar ratios of 2:15:2 in a seventeen member repeat unit having the structure shown below, wherein Glc represents D-glucose, Gal represents D-galactose and Pyr represents pyruvic acid, with the numerals indicating the positions of linkage in these ring structures. The heteropolysaccharide is useful in mobility control in oil reservoir formations, especially when crosslinked with trivalent metal cations (Cr3+, Al3+, Fe3+ or Ti3+) to form a gel which preferentially fills high permeability zones in such reservoirs.