Casing load creep test under gypsum formation and its numerical simulation analysis

Key words:  gypsum formation  casing failure  casing load  creep rule  numerical simulation

Abstract:

In the gypsum formation, 65 percent of wells appear casing failure, which shows that gypsum creep is an important reason for casing failure in Zhongyuan Oilfield. The creep experiments were carried out using six cores under simulated for-mation condition to find the casing failure mechanism in gypsum formation. The creep rule and the characteristic parameters of the gypsum formation were obtained from the experiments. According to the test results，the finite element model for casings load calculation was established，and the calculation software was also compiled. Using the software，the casing load of one well was calculated in gypsum formation. The results show that the casing radical load has a relationship with phase angle and creep time, and the maximum load is 10% greater than the stress in situ.