Abstract: Oil viscosity affecting the mechanical characteristics of sandstone around the oil wellbore plays a significant role on oil extraction with the more viscous oil reservoir development. Based on cylindrical coordinate system, a numerical model using 3-dimensional particle flow code (PFC3D) of the perforation test is forward to simulate the oil extraction. For the numerical model, different viscous fluids are considered to simulate the mechanical response to practically reflect the process of the sand production. The macro stress curves indicate that under the same fluid flowing, the increasing fluid viscosity increases the tangential stress and deviatoric stress of the sand, and it also increases the shear failure probability so as to make the sand yielded more easily and have more sand production. And also, bond stress indicates that the largest stress is close to the inner oil, and the increasing fluid viscosity increases the tensile stress as localization and also increases the shear stress as globalization with obvious variation trend; the particle rotation also indicates that the increasing viscosity makes the particle rotated more strongly, and increases the probability of the dislodged particles from the sand to become the sand production. The above results agree with the practical response of the sand during oil extracting, and indicate that under the same conditions, more viscous fluid has greater influence on the mechanical response of the sand and has more obvious sand production. Therefore, the achievement will provide an important base for using effective sand control methods for different viscous oils.

Key words: 3-dimensional particle flow code, sandstone around the oil wellbore, mechanical response, different viscosities