The occurrence state of shale oil affects both its mobility and recoverability.In order to quantitatively evaluate the shale oil contents in different occurrence states (adsorbed and free) and their ratios

a series of mathematical models and a theoretical framework for quantitative evaluation of adsorbed and free shale oil were established.They can be used to evaluate:①the contents of adsorbed and free single-component hydrocarbons under unsaturated adsorption conditions (0

<

p/p

0

<

1);②the contents of adsorbed and free single-component hydrocarbons and mixed hydrocarbons (remaining oil) and their ratios under saturated adsorption conditions (p/p

0

≥ 1).The models have comprehensively taken into account the microscopic occurrence characteristics of shale oil (density of adsorbed and free phases

thickness of adsorbed phase)

microscopic structure of shale pores (morphology

size

pore volume

specific surface area) and physical properties of shale reservoir (porosity

oil saturation

apparent density).According to the models and the target area of lacustrine shale oil in eastern China (a case study of Dongying sag)

the microscopic occurrence mechanisms of shale oil are preliminarily revealed and the following understandings are obtained:① the contents of adsorbed and free oil and their ratios are jointly controlled by multiple influential parameters;② the impact of pore size is significant when the pore size is less than 50 nm or so

while when the pore diameter is larger than 50 nm or so

the impact is relatively weak

and the content of free oil depends on the volume of oil-bearing pores.