Quantifying Hydrophilic and Hydrophobic Pore Networks of the Bakken Shale

Abstract

Yuxiang Zhang; Qinhong Hu; Troy J. Barber; Md Golam Kibria

Understanding rock wettability behavior from micrometer to nanometer scale is of great significance to in-situ hydrocarbon volume calculation and oil recovery improvement in tight-rock reservoirs. In this study, comprehensive rock-fluid experiments were performed to investigate wettability of three members of the Bakken Formation. The contact angle of selected specimens was measured by applying four types of hydrophilic and hydrophobic fluids (i.e., DI water, API brine, IPA isopropyl alcohol, and n-decane) to observe rock wettability in millimeter scale. Then through a spontaneous imbibition test, different fluid flow behaviors in the shale were compared. As capillary-pressure greatly controls fluid migration in micro- and nano-pores, mercury injection capillary pressure (MICP) analysis, using non-wetting fluid mercury, was conducted to obtain pore system characteristics with multiple connected pore networks at the pore-throat size ranging in mm-nm scale. Furthermore, the wettability at nano-pore scale was qualified through a small-angle neutron scattering technique, by comparing the volume fraction of intruded fluids. The results suggest a distinct difference in the rock wettability between the upper/lower Bakken and middle Bakken, which is mainly caused by mineralogical composition and organic matter content. Multiple and complementary approaches enable us to quantify the proportion, and size distribution, of hydrophilic vs. hydrophobic pore networks in the Bakken Shale.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018