Understanding water uptake and drainage in shales has important implications for both hydrocarbon extraction and hydraulic fracturing fluid disposal. This study reports gravimetric water sorption isotherms and kinetics of water transport in shales. Moisture mass transport profiles during water uptake and drainage processes were numerically simulated. Quantitative parameters characterizing the water transport properties were calculated and their dependences on water saturation were analyzed. An approach was proposed to evaluate the permeability of shales using dynamic water sorption. The reliability of the estimated results was verified by the experimental values using gas permeability measurements.The apparent diffusion coefficients of water sorption on shales were found to be between 1.0 × 10⁻¹² and 1.5 × 10⁻¹¹ m²/s. The apparent diffusion coefficient first increases with water saturation and remains stable at a moderately saturated condition. However, this coefficient decreases for shales with high water saturation. Apparent diffusion coefficients for the sorption process are almost equal to those for the desorption process, except at the moderate saturation condition. Liquid water (including adsorbed water) contributes more than 80% to the water transport, whereas water vapor mainly contributes to shales with low water saturation. The liquid water permeability determined by water sorption is consistent with the crushed‐rock permeability measured by gas expansion. A further reasonable agreement is achieved between the analytical gas permeability, as a function of water saturation, and the experimental gas phase permeability. Water sorption kinetics provide an indirect method for assessing the water transport properties as a function of water saturation when direct measurements are not available.

Using a seismic database from the Qiongdongnan Basin in the South China Sea, this study demonstrates that shelf-edge trajectories and stratal stacking patterns are reliable, but understated, predictors of deep-water sedimentation styles and volumes of deep-water sand deposits, assisting greatly in locating sand-rich environments and in developing a more predictive and dynamic stratigraphy. Three main types of shelf-edge trajectories and their associated stratal stacking patterns were recognized: (1) flat to slightly falling trajectories with negative trajectory angles (Tse) (−2° to 0°) and negative shelf-edge aggradation to progradation ratios (dy/dx) (−0.04 to 0) and associated progradational and downstepping stacking patterns with low clinoform relief (Rc) (150–550 m [492–1804 ft]) and negative differential sedimentation on the shelf and basin (As/Ab) (−0.6 to 0); (2) slightly rising trajectories with moderate Tse (0°–2°) and medium dy/dx (0–0.04), and associated progradational and aggradational stacking patterns with intermediate Rc (250–400 m [820–1312 ft]) and intermediate As/Ab (0–0.6); and (3) steeply rising trajectories with high Tse (2°–6°) and high dy/dx (0.04–0.10) and associated dominantly aggradational stacking patterns with high Rc (350–650 m [1148–2132 ft]) and high As/Ab (1–2). Each trajectory regime represents a specific stratal stacking patterns, providing new tools to define a model-independent methodology for sequence stratigraphy. Flat to slightly falling shelf-edge trajectories and progradational and downstepping stacking patterns are empirically related to large-scale, sand-rich gravity flows and associated bigger and thicker sand-rich submarine fan systems. Slightly rising shelf-edge trajectories and progradational and aggradational stacking patterns are associated with mixed sand/mud gravity flows and moderate-scale slope-sand deposits. Steeply rising shelf-edge trajectories and dominantly aggradational stacking patterns are fronted by large-scale mass-wasting processes and associated areally extensive mass-transport systems. Therefore, given a constant sediment supply, then Tse, dy/dx, Rc, and As/Ab are all proportional to intensity of mass-wasting processes and to amounts of mass-transport deposits, and are inversely proportional to the intensity of sand-rich gravity flows and to amounts of deep-water sandstone. These relationships can be employed to relate quantitative characteristics of shelf-edge trajectories and stratal stacking patterns to deep-water sedimentation styles.

Organic-inorganic interactions of clay minerals and organic matter: Action mechanism and analysis techniques