Changes in the cross-link density of Paris Basin Toarcian kerogen during maturation

The volumetric swelling of three Paris Basin Toarcian kerogens by a set of 20 organic solvents was measured. There is no evidence of specific interactions (e.g. hydrogen bonds) between the kerogens and the liquids. Their interaction thermodynamics is described reasonably well by Regular Solution Theory. The cross-link density of the three kerogens is too high to permit accurate calculation of the number average molecular weight between cross links. Qualitatively, the swelling data demonstrate that the cross-link density increases with increasing maturation. Surprisingly, the solubility parameter (δ) of the kerogen is constant for the three samples of different maturity. Kerogen extractabilites have been measured and parallel the magnitude of solvent swelling, as expected.