Research On All-electric Control System For Subsea Tree

There are rich oil and gas resources below global ocean,they have become the key exploitation object for huge reserves.The research of relative equipment and technology has been paid high attention by every country which involved in ocean oil exploitation.Subsea Christmas tree is one of the most important equipment of subsea production system,which is an indispensable high-end equipment during ocean oil exploitation.And subsea all-electric Christmas tree is the most cutting-edge and has the most development potential of global subsea production system,until now,there is only American Cameron has mastered the design and manufacturing method of subsea all-electric Christmas tree,but it's production is in the stage of testing.Therefore,this paper studies the control system of subsea all-electric Christmas tree,and realized full-electric intelligent control and real-time fault diagnosis of the Christmas tree.The author developed a hardware system of the control system of subsea all-electric Christmas tree,including master control station,overwater power and communication unit,subsea power and communication unit and subsea control module.And designed redundancy underwater controller,redundancy power supply and redundancy electric actuator.A high pressure cabin suits 1500 meters' depth is designed.To ensure its requirement for strength and seal,modeling,simulation and analysis have been done on shell,foundation and O shaped seal ring by finite element software such as Ansys,Abaqus.The author developed a software system of the control system of subsea all-electric Christmas tree.By analyzing control function and monitoring function of the control system of Christmas tree,the author designed technological process of production circuit,annulus circuit and agent injection circuit of the Christmas tree system,and finally obtained the scheme of subsea full-electric Christmas tree system.A PMAC controller program is compiled to complete the logical control and real-time monitor on each circuit.VB is adopted to complete the Christmas tree's monitor interface,which realizes function of oil production,monitor control,failure warning and so on.Aiming at transient failure and interval failure of subsea all-electric Christmas tree control system,the author put forward a fault diagnosis method based on dynamic Bayesian network,and its task is to identify the fault component and different kinds of failure,known as transient failure,interval failure and permanent failure.And transition relation among four states,no failure,transient failure,interval failure and permanent failure,is simulated by utilizing Markov chain.A dynamic degradation model of subsea full-electric Christmas tree control system is created by utilizing dynamic Bayesian network.Judge rules of fault diagnosis are established according to engineering experience.Finally,four fault diagnosis cases of subsea full-electric Christmas tree control system are studied to prove the feasibility of the method.