Abstract
Abstract In order to prevent well leakage in high temperature and high pressure (HTHP) wells, pressure test is a very important leak prevention operation that causes artificial high-pressure environment in wellbore. However, failure of wellbore equipment due to harsh condition is a common problem that brings great economic losses. Ram blowout preventer (BOP) is an important component of wellbore integrity, which is subjected to heavy loads from the test gas and the push rod during the pressure test. Therefore, the serious stress concentration of ram BOP induced by heavy loads and complex geometry is a major reason of fracture. Hence, the focus is to find out the fracture mechanism of ram BOP with experimental method and finite elements (FE) model in this paper. A series of damage inspection and strength test of ram BOP is carried out to find out the fracture characteristics. Based on detection information, FE analysis is conducted to analysis stress distribution and fracture reason of ram BOP. The results show that the maximum stress exceeds the yield strength (705 MPa) of the material under the actual working condition. Serious stress concentration at the notch root of the ram BOP can be easily caused by test pressure (from test gas) and contact pressure (from push rod). Both experimental method and FE analysis show the characteristics of ductile fracture obviously. Stress concentration at notch root is very sensitive to the test pressure. The work presented in this paper can provide basis and reference for preventing failure of ram BOP and improve efficiency and production.
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