NATURAL FRACTURE CHARACTERIZATION IN THE HAYNESVILLE SHALE, EAST TEXAS

The Haynesville Shale in East Texas and Northwest Louisiana is one of the most studied and explored shale-gas plays in the United States today. With new horizontal drilling and completion strategies, energy companies have been able to produce hydrocarbons straight from the source rock making the Haynesville Shale an attractive resource. A key component of enhanced hydrocarbon production is the presence of natural fractures. In the case of the Haynesville, little is known about the occurrence of natural fractures and their effect on hydrocarbon production (Hammes et al., 2011). In this study, natural fractures present in 160 feet of Haynesville Shale are imaged and characterized using the commercial software Avizo® Fire and petrographical analysis. The purpose of this study is to characterize natural fractures in the Haynesville Shale by identifying fracture orientation, fracture fill and how these features correlate with the mineralogy. Other research goals are to see if the presence of anhydrite in the Haynesville results in overpressure and fracturing and the effect that natural fractures have on absolute permeability in the Haynesville Shale. A popular method for characterizing permeability and porosity in rocks is to use high-resolution x-ray computed tomography (CT). Computed tomography provides nondestructive three-dimensional visualization and characterization, creating images that map the variation of X-ray attenuation within objects, which relates closely to density (Ketcham and Carlson, 2001). CT scans through the Haynesville Shale are used to characterize fractures and permeability in Avizo® Fire. The CT scans provide fracture density, fracture orientation and density of the matrix. Optical microscopy, cathodoluminescence (CL), SEM and XRD are then used to provide petrographical analysis of the Haynesville core. Optical microscopy reveals the general mineralogy and fabric of the rock, CL reveals features that may not be observed with optical microscopy such as fractures, and SEM and XRD are used to determine the mineralogy of the core. The petrographic analysis can be used to make a potential correlation between mineralogy, specifically clay, calcite and TOC, with fracture density. Fracturing is evident throughout the length of the core as well as an abundance of sedimentary structures.