Abstract: Oil reservoirs with high formation saturation pressure difference are usually characterized by medium porosity, mid-to-high permeability and wide variation of reservoir pressure, and stress sensitivity is a common problem in the development of such reservoirs. In view of the stress sensitivity of oil reservoirs with high formation saturation pressure difference, taking Kenli Oilfield as an example, the experiment for gas logging permeability of natural core in net confining stress was conducted to obtain the change rule of effective stress and permeability of the core in single and multiple times of pressure rise and fall, and a new stress sensitivity coefficient was defined to develop a power-based stress sensitivity quantitative characterization method for such oil reservoirs. The results showed that the maximum permeability loss of 30, 100, 300 mD cores during single pressure rise and fall was 35%, 27% and 15%, respectively. The change trend of core permeability of multiple times of pressure rise and fall is similar to that of single time of pressure rise and fall. The permeability loss increases with the increase of pressure rise and fall times. When the reservoir permeability is lower than 100 mD, the maximum permeability loss can be up to more than 30%. The study on change rule and characterization method of stress sensitivity is of great important guidance for the formulation of reasonable working system, reasonable productivity and reservoir protection scheme design for oil reservoir with high formation saturation pressure difference.

Key words: high formation saturation pressure difference, medium porosity and medium permeability, stress sensitivity, characterization method, Kenli Oilfield