Abstract:
Objective The post-accident analysis of major hazards is a very complicated research work in oil field drilling site. The key parameters of the accident and its influence rule are studied by numerical simulation.
Methods The fuzzy boundary condition is solved by the boundary condition hypothesis and trial calculation method on the premise that the specific parameters cannot be obtained. This paper mainly uses the well loss calculation model and field data to invert the well loss process to determine the leading parameters required for kick simulation, and studies the change law of bottom hole pressure when the string is falling.
Results The downhole drilling string of a certain well is 4 500 meters long, generating more than 20 MPa surge pressure, and the cumulative loss for 7-8 minutes can reach more than 20 m3, which has a great impact on field operations and a short response time. The falling of short drill pipe produces less surge pressure and lower risk. The
Results show that under the condition of large fracture (more than 10 mm), the large surge pressure can instantly produce more than tens of cubic meters of leakage, which can not be controlled. In the case of narrow fracture (1 mm), the accumulated leakage amount reaches 20 m3 in about 6 minutes. In the case of micro-fracture (0.25 mm), the accumulated loss in 10 hours is only 20 m3.
Conclusions The long drill string drop produces a larger surge pressure, which is the main sensitive parameter of loss and the main reason of blowout. The well shut-in measures should be taken as soon as possible.
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