A NEW PYROLYSIS TECHNIQUE USING A DIAMOND-ANVIL CELL - IN-SITU VISUALIZATION OF KEROGEN TRANSFORMATION

A pyrolysis technique has been developed to study hydrocarbon source r ock potential by in situ visualization of kerogen transformation in a diamond anvil cell under a microscope (white and UV-light) using a CCD video monitoring system. The technique enables us to observe directly the processes and timing (or temperature) of kerogen transformation d uring pyrolysis in open or closed systems (either anhydrous or hydrous ). It has been used to study a Green River kerogen and a lignite sampl e at heating rates similar to Rock-Eval pyrolysis under several pyroly sis conditions. The study has revealed: (1) the solid kerogen yields m obile oily liquids and solid residues and continues to evolve into gas es. Most gases are generated later than oily liquids, probably from cr acking of liquid. (2) The kerogen transformation is not significantly retarded in a closed system or at higher water pressure relative to an open system. (3) The neoformed oily liquid is immiscible with aqueous fluid at high pressure (8 kbar), but dissolves in the fluid at lower pressure (3 kbar). This confirms that the solubility of oily liquids i n hydrothermal water decreases significantly with increasing pressure. The dissolved oily liquid can survive without cracking into gas at hi gher temperatures than the immiscible oily liquids. (4) An aqueous sol ution containing oxalic acid (which decomposes into CO2 and H-2 at run conditions) dramatically retards the kerogen transformation. (5) Fluo rescence of the total sample (kerogen with pyrolysate), which increase s dramatically during transformation, may be used to follow quantitati vely the rate of the reaction. (6) The preliminary results in an open, anhydrous system using a lignite sample with low hydrogen index (HI) show the decomposition of lignite into gases without the oily liquid p recursor. Copyright (C) 1996 Elsevier Science Ltd