A Structured Approach of Reliability Demonstration Test in the Developmentof Electromechanical Remotely Operated Downhole Control Device forIncreased Operations Efficiency

摘要

The remotely operated electromechanical control device(ECD)is coupled to an open-close valve that wouldnormally require hydraulic lines from surface.With each function of the valve,an intervention is eliminated,which increases operational efficiency and saves rig time.As these devices are permanently installed insevere downhole environments,design-in reliability is paramount.Reliability demonstration test(RDT)isa key element of the design-for-reliability process to verify that the product satisfies the system reliabilitytarget.This paper presents a structured RDT approach to demonstrate the reliability of a remotely operatedECD in a cost-and time-efficient manner.The reliability target of the ECD was established based on the tasks requirements(open-close functions),well conditions,and mission life.Key subassemblies of the ECD were identified,and a system reliabilitytarget was allocated to the subsystem level using a weight factor-based approach.A test-to-successmethodology was used to design the RDT of individual subassemblies by identifying the underlying failuremechanism,applicable test stresses,and acceleration factors.A parametric cumulative binomial test designmodel was used to optimize the test parameters,such as sample size,test time,and number of valve open-close functions.Conducting a system reliability test is often cost prohibitive.Therefore,performing a reliability test atthe subsystem level is an alternative approach of verifying system reliability.Reliability allocation weightfactors are determined based on the cost,time,and relative difficulty in testing the design feature.Agingparameters were found to be the number of valve open-close functions based on the underlying tasks,operating time,and well environment(temperature).This paper highlights the structured methodology and application requirements of RDT to meet themission reliability target of a remotely operated ECD.A comprehensive reliability target was establishedbased on the underlying tasks,operating time,and well environment.A combination of overstress(temperature)and use-rate accelerations was used in the test design.An optimum value assessment of testdesign parameters was performed for developing a cost-effective test design.The approach and benefits ofstructured reliability test design are discussed in the paper.