MONITORING THE CHANGES IN THE MICROSTRUCTURE, AND THE ELASTIC AND TRANSPORT PROPERTIES OF EAGLE FORD MARL DURING MATURATION

Organic-rich marl is one of the best unconventional reservoirs because of its high calcite and low clay content leading to relatively high permeability and frackability. However, how its stiff pores and relatively high permeability affect the changes in its microstructure and elastic and transport properties during maturation remains a research interest. We induced ex-situ maturation of organic-rich marl core plugs by conducting confined pyrolysis in fine-steps across the maturity windows from immature through the early-peak oil, late oil, wet gas, and finally the dry gas window. This was performed under both high and low confining pressures on different samples in order to investigate the role of confining pressure during maturation. After each pyrolysis, we monitored the changes in microstructure, porosity, velocity, permeability, and geochemical properties. The results show increasing porosity, decreasing velocity, and increasing permeability as the maturation progresses. The time-lapse scanning electr...