BEHAVIOR OF OXIDIZED TYPE-II KEROGEN DURING ARTIFICIAL MATURATION

A series of artificially oxidized type II kerogens (ventilated oven, 140-degrees-C, 8-256 h) from the Paris Basin (France) has been pyrolyzed in cold-seal autoclaves at temperatures ranging between 250 and 450-degrees-C for 24 h at 100 MPa. Oxidates and pyrolysates have been characterized by C-13 solid-state NMR, FTIR spectroscopy, Rock-Eval pyrolysis, elemental analysis, and CHCl3 extraction. Results indicate that oxidation is responsible for an important decrease of the petroleum potential and for the increase of different oxygen-bearing functions' (carbonyl, carboxyl, esters, ethers) concentration. The behavior of the different oxidates during artificial maturation is characterized by two distinct stages: oxygen removal (250-300-degrees-C) and hydrocarbon production (300-450-degrees-C). It is shown that oxidation induces an important decrease of the hydrocarbon yield during maturation and that no regeneration of petroleum potential can be observed. Comparison of the most oxidized kerogen (256 h) with an unoxidized type III coal of similar initial elemental composition has also been carried out.