Pore Geometry Characteristics And Fluid-Rock Interaction In The Haynesville Shale, East Texas, United States

Since 2007, the Upper Jurassic marine Haynesville Formation has become one of the leading shale gas plays and is currently the third most prolific producer in the United States. A detailed study has been performed to understand the pore geometry and fluid-rock interactions in the Haynesville organic-rich shale using 10 core samples covering a vertical profile of 123 ft in a well located in San Augustine, TX. Several complementary analyses were integrated, including well logs, petrographic microscopy, total organic carbon, X-ray diffraction, pyrolysis, mercury intrusion porosimetry (MIP), nitrogen physisorption, fluid immersion porosimetry (FIP) after vacuum saturation, contact angle measurement, and spontaneous imbibition (SI). The porosity from MIP of the marine Haynesville Shale samples ranges from 2.84 to 7.31%, greater than many other shales in North America. The shale samples analyzed here have a pore system dominated by pores with throat diameters in the 2.8-50 nm range, with associated pore volumes accounting for 69-92% of the total porosity. The results of contact angle, SI, and FIP with several fluids (aqueous and hydrocarbon) indicate that samples uptake oil preferentially. A new wettability scheme with nine categories suggests that Haynesville Shale samples vary from (i) strongly oil-wet and intermediately water-wet, (ii) intermittently mixed-wet, (iii) strongly mixed-wet, and (iv) strongly water-wet. Moreover, this integrated study of the nanoscale petrophysics provides a reasonable explanation of fracturing fluid loss and steep production decline in the Haynesville Shale.