Research from this paper provides insight into the physical and chemical consequences of steam-assisted recovery of heavy oils and bitumens from sedimentary-rock reservoirs and reveals that geological and geochemical context is an essential consideration. To study mineral effects on gas production, the authors of the complete paper studied a well-characterized oil-containing core and the isolated crude oil from that core. The samples were run at 250 to 300 degrees C in the continued presence of liquid water for 24 hours. The reaction products of all experiments include gases, oil flotate, oil sinkate, water-soluble products, and water-insoluble residues. All reaction products were studied with a variety of analytical techniques, including Fourier-transform infrared spectroscopy, chromatographic fractionation [saturate, resin, and asphaltene (SARA) analysis], gas chromatography mass spectrometry (GCMS), pyrolysis GCMS, and gas chromatography (GC) flame photometric detectors (FPDs)/thermal-conductivity detectors. These techniques were applied to whole oil, maltenes, and asphaltene fractions. Physical properties, including viscosity and density, were also measured.