CONNECTED PORE SYSTEMS OF SHALE CORE, CHEMICALLY-TREATED SHALE SAMPLES, AND BULK MINERALS

Nearly two decades of the American experience in shale hydrocarbon exploration and production point out a low total recovery of tight oil at 5 %–10 % and shale gas at 12 %–30 %. One of the key obstacles to the workable advance of shale resources, specifically the pore structure (connectivity and geometry) of the nanopores for storing and transporting hydrocarbons, is seldom examined, though the country is counting shale gas as a transition energy resources for shifting energy industry from dirty fuel to cleaner energy. For this study, we collected samples from a diverse of principal oil-gas producing shale formations (basin) in the US (Barnett, Bakken, Niobrara). These geologic formations have different geologic characteristics and ages (e.g., porosity, permeability, mineralogy, tortuosity, wettability). We examined those samples mineralogical composition, pore structure, imbibition, and wettability. We use the following set of complementary tests: X-ray diffraction, mercury intrusion capillary pressure (MICP), different fluid and tracer imbibition( n-decane, acetone, DI water and API brine) into primarily dry shale and wettability test with various liquids. One batch of samples we treated with water for seven days, and another with acetone for 4-5 hours to run for MICP analysis to examine the potential change on pore systems. We also run common shale rock-forming bulk minerals (quartz, calcite, and feldspar) and clay minerals (illite, chlorite, montmorillonite, kaolinite), based on our XRD data, in MICP and examine how the pore structure results compare with the bulk shale rock samples. Overall results from the above correlation approaches will answer the distribution and evolution of connected pore systems, and its relationship to compositions of shales. This can bridge the gap between fluid behavior studies, pore structure and mineralogical composition of different shales, which in general affect the migration of hydrocarbon molecules from the shale matrix into the stimulated fractures for recovery.