Study on the Full-Range Pore Size Distribution and the Movable Oil Distribution in Glutenite

The pore size distribution (PSD) and fluid mobility parameters are vital parameters for predicting rock properties and the reservoir quality classification. Because of the characteristics of strong heterogeneity, a complex pore-throat structure, and a wide PSD of glutenite, it is more difficult to acquire the full-range PSD and fluid occurrence states of glutenite. This paper investigates the full-range PSD, the distribution, and the controlling factors of the movable oil in glutenite based on various experiments. X-ray diffraction, casting thin sections, scanning electron microscopy (SEM), low-temperature nitrogen adsorption (LTNA), high-pressure mercury intrusion, and nuclear magnetic resonance (NMR)-centrifugation experiments were conducted on 18 glutenite samples from the Mahu Sag, Junggar Basin, China. A new method for characterizing the full range PSD of glutenite was proposed by integrating LTNA and NMR-centrifugation experiments, and the full-range PSD is in good agreement with the casting thin sections and SEM images. Moreover, in terms of the distribution patterns of the T-2 spectra under the n-dodecane saturation condition, the glutenite samples are divided into four categories (i.e., type-I, type-II, type-III, and type-IV). From type-I to type-IV, both the pore size and the movable oil saturation of glutenite samples show a gradually decreasing trend. In addition, the movable oil mainly occurs in the pore-throat configurations of type-A, type-B, and type-C in glutenite. The development of the different types of pore-throat configurations is controlled jointly by the sedimentary compositions and mineral compositions. For higher quartz clastic and feldspar mineral contents and lower calcite and clay mineral contents, glutenite is more developed in type-A, type-B, and type-C pore-throat configurations. The above findings will provide intellectual support for identifying high-quality glutenite reservoirs and improving the productivity of glutenite oil reservoirs.