Hydrophilic and Hydrophobic Characteristics of Reservoir Rocks Quantified by Nuclear Magnetic Resonance-Detected Water Isotherms

Accurate determination of rock wettability is crucial for evaluating petroleum reserves and optimizing oil production. Reservoir rocks, formations that contain accumulations of oil or gas, often comprise a large collection of mineral types and a wide range of pore sizes. This heterogeneity makes it difficult to measure the wettability of reservoir rocks by conventional techniques, such as contact angle measurement. Here, we resolve this problem by applying an in situ nuclear magnetic resonance (NMR) adsorption isotherm technique. Investigations of glass bead phantoms demonstrate that NMR-detected isotherms are capable of distinguishing between hydrophilic and hydrophobic surfaces within the pore network. This NMR-based isotherm methodology is further applied to reservoir rocks. Water isotherms of the pristine rocks provide information on two important rock properties-wettability and pore-size distribution. Such information can be used, among other things, to model the wettability of the formation and to maximize waterflood recovery efficiency.