Laboratory Characterization of Shale Oil Storage Behavior: A Comprehensive Review

Shale oil has become an important oil resource over the past decade. The oil storage behavior, including the adsorbed oil and free oil, is one of the most important controlling factors for shale oil production. Because the shale oil storage behavior is largely determined by the fluid and solid interactions, this review first evaluates the shale mineralogy, pore structure, and oil properties. Then, the experimental methods to characterize the free oil and adsorbed oil are reviewed. The relationship between the oil storage behavior and shale and oil properties are then discussed. It is concluded from the literature work that the organic matter has the highest adsorption capacity for oil, followed by clay minerals, quartz, and calcite. While it is well-known that heavier oil components are adsorbed more than the lighter components, a relationship between the ratio of pore size to oil molecular size and the ratio of free oil to adsorbed oil is suggested and plotted. Finally, it is found from the literature that accurate experimental methods and theoretical models on free oil and adsorbed oil characterization are still missing; therefore, these topics require attention in future researches on shale oil.