NOVELTY - The process involves characterizing organic carbon-rich substrates, microbial organisms and inorganic mineralogy in subterranean formation. An injectate-water chemistry is determined to promote biogas generation. Injectate-water properties are geochemical modeled in the formation. Generated biogas is geochemical modeled in the formation. The injectate-water chemistry is optimized to promote biogas generation. Injectate-water with the optimized injectate-water chemistry is injected into the formation. Biogas production and changes are monitored in the produced-water chemistry.    USE - Process for geochemical modeling of biogas generation from sub-surface organic matter-rich formations such as man made formations e.g. landfills and subsurface bioreactors, and natural formations such as shale, coal, oil sands, bitumen, tar, oil, sandstone and limestone with organic debris, in subterranean formation.    ADVANTAGE - The process enables lyophilizing cells produced from enrichments or fermenter for storage and transport to a well site in the presence of reducing agents to protect methanogens and other obligate anaerobes from oxidation during storage and injection. The method enables analyzing oxygen scavengers to identify risks including oxygen removal, inhibitions of anaerobic microbial growth and sulfur contamination, so that the production water process is reviewed for potential oxygen contamination. The method enables optimizing injectate-water process to reduce or avoid risks during biogas generation.    DETAILED DESCRIPTION - The injectate-water chemistry includes pH, salinity, nutrient concentrations, sodium, potassium, magnesium, sodium chloride, potassium chloride, ammonia, phosphate, sulfate, chloride, trace elements, iron, manganese, tungsten, tungstate, cobalt, zinc, copper, boron, borate, molybdenum, molybdate, selenium, nickel, vitamins, sodium-nitrilotriacetate, p-aminobenzoate, biotin, cobalamins, cyanocobalamin, methylcobalamin, hydroxycobalamin, folic acid, lipoic acid, nicotinic acid, pyridoxine, thiamine, riboflavin, pantothenic acid, amino acids, dietary minerals, fatty acids, carotenoids, tocopherols, riboflavins, phylloquinones, niacins, citric acid, ascorbic acid and cholecalciferol. INDEPENDENT CLAIMS are also included for the following:    (1) a process for reducing risk during biogas generation from sub-surface organic matter-rich formations    (2) a process for modeling biogenic gas formation in vitro.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow diagram illustrating a process for creating optimized nutrient and microbial compositions.