Influence of the Adsorption and Absorption Performance of Oil in the Nanoporous Kerogen Particles of Shale Rock on the Oil Movability

The movable property of oil in shale is of great importance for the development of shale oil. In this work, the influence of adsorption and absorption performance of oil in the kerogen particles on the oil movability in shale cores was determined by low-field nuclear magnetic resonance (NMR) during centrifugation. The variations of movable oil contents in shale cores with centrifugal time and centrifugal force were discussed as well as the movable oil contents in macro/micro shale pores and inorganic matter/kerogen of shale cores. The results showed that 81.8% of the oil saturated into shale cores is mainly dispersed in micropores and in the states of absorbed, adsorbed, and free oil. In shale cores, the contents of absorbed oil and adsorbed oil are averaged at 40.9 and 20.5%, while the content of free oil is about 38.7%. During centrifugation, the movable contents increase with time and centrifugal force. The oil saturated in macropores is the main contribution to movable oil. The contents of movable oil in macro- and micropores are averaged at 86.7 and 8.5%, while the contributions of movable oil in macro- and micropores to total movable oil are averaged at 66.1 and 33.9%. In micropores, the contributions of movable absorbed oil and adsorbed/free oil to total movable oil in micropores are averaged at 3.9 and 4.6%. Meanwhile, the T 2 cutoff value of the shale core is much lower than that of tight sandstone. The contents of movable oil in inorganic matter and kerogen are averaged at 35.6 and 5.6%, while the contributions of movable oil in inorganic matter and kerogen to total movable oil are averaged at 67.8 and 32.2%. The contributions of movable adsorbed/free oil and absorbed oil in kerogen to total movable oil are averaged at 16.0 and 16.1%. Therefore, the movability of shale oil is greatly influenced by the presence of kerogen in shale, and how to effectively displace the adsorbed oil and absorbed oil in kerogen is significant to enhance shale oil recovery.