Nano-petrophysics study of Haynesville Shale, East Texas, USA

Abstract

As one of the most productive shale gas plays, the Haynesville Shale has a high geopressure gradient and high temperature, but with a lack of petrophysical understanding. To analyze the pore geometry and wettability related connectivity of this formation, multiple methods such as total organic carbon content (TOC), X-ray diffraction (XRD), vacuum saturation, mercury intrusion capillary pressure (MICP), contact angle, fluid imbibition, and helium pycnometry were used on 10 Haynesville Shale core samples from a single well over a vertical distance of 123 ft. The results from those tests show that the Haynesville Shale is calcareous shale with 2.26~5.28% of TOC. The porosities range from 3 to 8%, and the pore-throat sizes are concentrated at the nanoscale (2.8~50 nm). Moreover, the permeability and effective tortuosity of the pore network controlled by 2.8 to 50 nm pore-throat size are 3.7 to 23.4 nD and 1413 to 3433, respectively. All ten samples show strong oil-wet characteristics and only three samples exhibit mixed wettability (both oil-wet and water-wet). In general oil-wet samples show higher pore connectivity when they imbibe hydrophobic (a mixture of n-decane:toluene at 2:1, as an oil analog) than hydrophilic (deionized water) fluids.