Research On Reliability Of Subsea BOP Stacks For The Depth Of 3000 Meters

Deepwater drilling is the key of offshore oil and gas exploration and development. Deepwater BOP system is the key equipments which ensure safety in drilling operation.When drilling in deepwater, once the Subsea BOP system breakdown, the BOP and riser must be pulled to the surface and cause great economic loss.If accident of blowout out of control occurs caused by equipment fault,it may cause disastrous consequences and Incalculable loss.From this point, reliability study is absolutely necessary in the process of BOP system designing.Reliability study includes two aspects:reliability analysis and calculation.Either analysis or calculation should be based on accurate and effective reliability data. Faced with severe lack of historical data problem, searched numerous related literature at home and abroad and processed them with appropriate methods.According to preliminary design for the 3000 meters subsea BOP, analysed its structure, function and working environment to provide a basis for the reliability model.Comprehensive used FMECA and FTA methods, searched for all the possible failure modes of system andequipments. Calculated the criticality of failure modes qualitatively or quantitatively, then scheduled and find the most critical failure modes. Find out all the fault reasons and their combinations. Summarized fault reasons in several ways and drew conclusions, and made recommendations for improvement targeted.According to the structure and function of the system, built reliability allocation model and simplified. By using Analytic Hierarchy Process for several times, distributed the system reliability index to various equipment. Then completed reliability prediction by using FTA. According to calculation result, the preliminary design for the 3000 meters subsea BOP met the requirements well. Finally, completed a software which according to the reliability distribution and prediction work of deepwater BOPs.