Rock characterization of Fayetteville shale gas plays

摘要

Multiple techniques were used to characterize the petrophysical properties of the rock samples from the Fayetteville shale gas play, including clay mineralogy, wettability, organic matter and their maturation, submicron pore structure, and 3-D pore structure. X-ray diffraction (XRD) mineralogy analysis showed high quartz and low clay content in the Fayetteville shale. Wettability tests revealed that the shale surface is originally intermediate-wet and the additives used in hydraulic fracturing fluids can alter shale gas surfaces toward water-wet conditions. The kerogen analysis suggested kerogen type IV and a high level of maturation in the tested samples. Three types of pores were observed through SEM images and the majority of the pores in organic matters were submicron sized (5-100 nm). A three-dimensional pore structure model was reconstructed from 200 two-dimensional SEM/F1B images, and the rock petrophysical properties, including porosity, permeability, and tortuosity, were calculated from the model. In addition, a good agreement was found between the total organic carbon (TOC) computed from SEM images and the TOC measured in the laboratory.