EFFECT OF PRESSURE ON THE KINETICS OF KEROGEN PYROLYSIS

Laboratory experiments on three different source rock samples indicate that pressure effects on generation kinetics are measurable but minor. Pressure effects are quantified in terms of an activated volume which is analogous to the use of activation energy to quantify temperature effects. Although the three shales had slightly different activated volumes, a value of 27 cm3/mol is recommended as typical for the activated volume of the transformation of kerogen to products. With this activated volume, a 1380 bar pressure corresponds to about a 7-degrees-C increase in generation temperature. Since generation commonly occurs at pressures less than 1380 bar, the effects of pressure on generation timing appear minor and well within the range of uncertainty from other causes.