Oil shale has been processed to produce hydrocarbon oils since the middle of the 19th century. Large scale production has usually involved mining the shale and retorting it under anaerobic conditions at atmospheric pressure, at temperatures near 500°C, for times on the order of an hour. More recently, methods have been proposed in which the shale is heated in the ground (in-situ) via boreholes. Proposed temperatures are in the range 300–350°C and processing times are days to months. The pressure at which gases and vaporizable liquids are extracted is another variable that can be used to optimize the process for oil and gas yield and quality. In order to analyze the results of field tests, and to specify optimal oil shale pyrolysis process conditions, kinetic models that describe the transformation of kerogen into oil and gas are required. This work describes experiments performed to provide the data required to construct those models.
Numerous studies of Green River oil shale pyrolysis have been published over the years. Most of these have focused on the richest interval, the Mahogany, and have been performed in either open (atmospheric pressure) or closed (bomb) conditions. The new elements of this work are
samples were taken from the deepest of the kerogen-rich layers of the Green River Formation, the R1 and
experiments were performed under semi-open (controlled pressure) conditions. The data generated are therefore appropriate inputs to models used in conjunction with in-situ controlled-pressure production tests of R1 shale.
In agreement with previous work, this investigation finds that processing shale at relatively low temperatures, for longer times, and at moderately elevated pressures, reduces yields but improves product quality relative to surface retort methods. Produced oil has a generally uniform composition throughout the maturation process and is predominantly composed of saturates and light aromatics, which are desirable for refinery operations. Produced gas is rich in natural gas liquids.