Oil generation kinetics determined by DAC-FS/IR pyrolysis: technique development and preliminary results

Nonconventional diamond anvil cell (DAC) pyrolysis techniques are being developed to monitor in situ kerogen transformations using fluorescence (FS), and infrared (IR) spectroscopy. Results show that for an oil-prone lacustrine source rock, the temperature range of fluorescence brightening during pyrolysis corresponds to that of the petroleum generation window measured by FID. First-order kinetic parameters calculated from five heating rates revealed a single activation energy and a frequency factor, which are very close to those determined by the conventional Pyromat pyrolysis. These results suggest that the DAC-IR/FS pyrolysis technique may be used to determine the kinetic parameters for oil generation from source rocks. For marine and coaly sources, fluorescence brightening occurs at temperatures higher than those of petroleum generation as monitored by FID. The absorption of early-generated liquid in the samples plus early generation of nonfluorescing petroleum, most likely gases, is a possible explanation. The results of the DAC-IR experiments have confirmed the capabilities of the in situ technique for examining the reaction pathways, the timing and the rate of the organic transformation, in particular, the progressive change of functionality of atomic groups in samples during the transformation. Several major reaction pathways found in this study are consistent with those widely observed in natural kerogen samples with increasing burial depths. The DAC-IR technique can also be a tool for studying the timing of gas generation from source rocks.