To overcome the shortcomings of conventional, near-wellbore profile modification methods, a microbial profile modification (MPM) method with spores was investigated. A halotolerant, spore-forming mesophile was isolated and characterized. These biopolymer-producing spores propagate easily in Berea cores with permeabilities more than about 500 md. With a specifically formulated nutrient package, they are readily germinated and produce biofilm, which reduces the permeability of the rock. The depth of penetration and the degree of permeability reduction can be controlled by varying injection schemes.