Abstract：Along with the exploration of oil-field in the medium and late terms，the problem of the casing damage which is resulted from the reservoir of loose sandstone is becoming the focus of the study. The sand production has become a serious problem that influences well productivity and damaging production equipment. According to real properties of oil field，the sand production mechanism of the reservoir of the loose sandstone is discussed and 3D finite element model of casing-cement sheath-formation is established. An elasto-plastic constitutive model is utilized on the basis of Mohr-Coulomb yield surface. The model，based on the finite element method，is used to discuss the changing of the sand production position and its surroundings，and the changing of the casing stress where the perforated wellbore is located when the sand production changes under the given parameters. The results indicate that the casing stress condition changes greatly with well depth and the sand production quantity. The study provides the basis for the research of the casing failure mechanism and controlling measure of the loosen sandstone reservoirs.
