Pyrolysis experiments on kerogen (Estonian Kukersite) were conducted in a confined system (gold capsules) in the presence and absence of water and various minerals, i.e., kaolinite, montmorillonite, calcite, and dolomite, respectively, at a fixed pressure of 50 MPa and in the temperature range 240-400 degrees C. For the four experiments in the presence of minerals and a large amount of deionized water (OC/mineral/water 1:24:7-10), the ratios of isobutane/n-butane and isopentane/n-pentane generally increase with temperature and mineral acidity. As to the two experiments for kerogen alone and kerogen plus a small amount of water (OC/water 1: 1.5), these two ratios are relatively high at low temperature (280-320 degrees C) and substantially low at high temperature (320-400 degrees C) in comparison with the experiments in the presence of minerals and a large amount of deionized water. The ratios of ethene/ethane and propene/propane generally decrease with increasing temperature. At the same temperature, these two ratios increase with an increasing amount of water and decrease with increasing mineral acidity. Pyrolysis experiments on this Kukersite kerogen with various OC/water ratios (0-15) further demonstrated that the ratios of ethene/ethane, propene/propane, isobutane/n-butane, and isopentane/n-pentane increased with increasing water/OC ratio. In addition, the amount of the gas hydrocarbons varied significantly with water/OC ratio, i.e., from 83.20 to 109.70 mg/g of OC at 350 degrees C and from 271.50 to 340.07 mg/g of OC at 450 degrees C, with the water/OC ratio increasing from 0 to 15. The amount Of CO2 produced also increases substantially and consistently with that of gas hydrocarbons with water/OC ratio. The amount of oxygen in the generated CO2 exceeds the oxygen in the initial kerogen in the experiments with water/OC ratios of 10 and 14.5 at 450 degrees C, indicating that water derived hydrogen and oxygen have been incorporated into gas hydrocarbons and CO2.