A maturation series of a Type II kerogen from the Williston Basin (Bakken Shale) has been studied. The macromolecular structure of this kerogen is compared ot that of another Type II kerogen (Toarcian Shale, Paris Basin) and a Type I kerogen (Green River Shale, Uinta Basin) using solvent swelling measurements. The swelling of Type I and II kerogens roughly follow Regular Solution Theory and show no specific solvent interactions. Immature Type I kerogen is much less cross-linked than is immature Type II kerogen. Both Type I and II kerogens become more cross-linked during maturation as evidenced by a decrease in maximum swelling. It appears that during maturation, groups fragment off of the kerogen and the kerogen undergoes a polymerization reaction.
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