A New Workflow to Study the Impact of Artificial Maturations on the Petrophysical Properties of Unconventional Shale Rocks

Abstract

Abstract Multiple challenges are associated with the characterization and development of unconventional shale reservoirs. The petrophysical properties play significant roles in hydrocarbon production from unconventional reservoirs. Several techniques can be used to determine the petrophysical properties such as routine core analysis, nuclear magnetic resonance (NMR), and dielectric techniques. This study presents an effective workflow to characterize the petrophysical properties of unconventional shales at different maturation stages. In this study, the conducted measurements are X-ray diffraction (XRD) analysis, Rock-Eval pyrolysis, helium porosity, NMR, and dielectric experiments. The rock samples were prepared for the measurements by drying the samples under a vacuum. In addition, the samples were artificially maturated using a muffle furnace at different temperatures and heating times. The impact of shale maturation on the petrophysical properties was captured by evaluating the rock properties after each maturation stage. Results show that the shale samples have a TOC of 17.5 wt.% on average, and a hydrogen index (HI) of 809, indicating that the samples are belonging to kerogen type I. The mineralogical analysis indicates that the used shale samples have a calcite percentage of around 59.9%. Moreover, the artificial maturation led to reducing the total organic content, due to the conversion of organic matter into hydrocarbon fluids. NMR and dielectric measurements showed that the shale porosity system was altered due to artificial maturation. The real dielectric constant was reduced indicating a reduction in the kerogen percentages. The cumulative probability density was increased after the maturation, revealing the shale porosity was increased which could be attributed to the dissolution of kerogen during the maturation process. Ultimately, this study improves our understanding of characterizing unconventional shale formations. Also, a reliable workflow is proposed for a better characterization of the unconventional formations by integrating routine core analysis, Rock-Eval, NMR, and dielectric techniques. Such workflow can pave the way to introduce a downhole technique to characterize unconventional resources more effectively.