GSA 2020 Connects Online

Paper No. 217-14
Presentation Time: 4:15 PM

QUANTIFYING OIL- AND WATER-WETTABLE PORE NETWORKS OF THE BAKKEN, MANCOS, AND UTICA-POINT PLEASANT SHALES


QINHONG, Hu1, ZHANG, Yuxiang1, WANG, Qiming1, ZHAO, Chen1, BLEUEL, Markus2 and LITTRELL, Kenneth3, (1)Department of Earth and Environmental Sciences, The University of Texas at Arlington, 500 Yates Street, Arlington, TX 76019, (2)Center for Neutron Research at National Institute of Standards and Technology, 100 Bureau Dr, Gaithersburg, MD 20899, (3)Oak Ridge National Laboratory, Neutron Sciences Directorate, Oak Ridge, TN 37831

Microscopic pore structure (both geometry and connectivity) characteristics control fluid flow and hydrocarbon movement in mudrocks. Considering the uniquely wide spectrum of pore sizes (nm to sub-mm), microscale mixed wettability, as well as the interplay of pore structure and wettability in organic-rich mudrocks, this work presents various approaches to quantifying the oil- and water-wettable pore networks for three leading American tight oil formations (Bakken, Mancos, and Utica-Point Pleasant) with a range of maturation and mineral compositions. The approaches include the utility of different wetting fluids (deionized water or API brine, n-decane and/or toluene, isopropyl alcohol or tetrahydrofuran or dimethylformamide), fluid pycnometry, fluid immersion porosimetry after vacuum saturation, mercury intrusion porosimetry, low-pressure gas physisorption isotherm, nuclear magnetic resonance, and field emission-scanning electron microscopy. In particular, (ultra-) small angle neutron scattering techniques, (U)SANS, are used to quantify the total (both edge-accessible and isolated) porosity and characterize pore size distribution in a pore length size from 1 nm to 10 mm; in addition, the employment of contrast matching technique of (U)SANS enables the discrimination of accessible (open) pores and inaccessible (closed) pores to a particular liquid fluid. Our results show that the Bakken samples have a relatively high total porosity (8.87-12.95%) with no more than 30% of the pores are accessible from sample surface, and are not preferentially wet by oil or water, while the Utica/Point Pleasant samples have a total porosity of 6.70-9.65% with over 80% of the pores are accessible ones and tend to be more oil-wet than water-wet.

Acknowledgements: Access to SANS NG7-30 and USANS BT5 instruments was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under agreement No. DMR-1508249. A portion of this research used the USANS BL-1A resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.