SEM and CT X-ray imaging were used to quantify the surface geometries of sandstone pore and throat networks of the oil-bearing Stanley Sandstone of the Eutaw Formation of Jasper County, Mississippi, both in dry samples and in samples that had undergone laboratory simulations of Microbial Permeability Profile Modification (MPPM) oil-recovery technology. The goal of the study was to acquire some quantified understanding of the way induced bacterial activity affected the surface geometries and impacted the porosity and permeability of the oil-bearing Stanley Sandstone. Visible porosity remained high, but significant permeability modification occurred ubiquitously with pore and throat spaces of 10 ìm – 20 μm diameter. Based upon quantitative analysis of photomicrographs, biofilm did not completely fill porosity but did clog pore throats, thus significantly impacting permeability.