Changing Law of Flow-Field at Wellhead Under Hard Shut-In Procedure

Abstract

In view of the application status and disadvantages of well shut-in methods commonly adopted in the oil field of China, the pressure and flow velocity at wellhead under the hard shut-in procedure were simulated by finite element method. The effects of blowout preventer opening, inlet velocity and gas content on the wellhead pressure and flow velocity were investigated. The results show that the pressure at the blowout preventer is increasing significantly with decreasing of the opening, inlet velocity and gas content and the maximum pressure appears at the 10 % opening. The velocity at the blowout preventer is increasing significantly with decreasing of the blowout preventer opening and the inlet velocity, which will cause erosion destruction under long time using. The velocity at blowout preventer is decreasing with the increasing of gas content and the maximum velocity appears at the gas content of 9 %. Determining overflow in the well bottom and shutting down the blowout preventer earlier to prevent too much gas from invading into the hole and avoid causing flow velocity increase can decrease shock load on the blowout preventer effectively. Also, the shock load on blowout preventer can be decreased by shutting down the blowout preventer with adopting “fast first and slow last” shut-in procedure, which would provide guidance for the field operation.