Design Of Digital Module Of Neutron LWD Tool And Research On Its Software Reliability

Porosity is of substantial significance for formation evaluation.The Neutron Logging While Drilling(LWD)Tool measures porosity while drilling based on theory of radioactive well logging.As an important component of Neutron LWD Tool,Digital module is responsible for controlling modules of the tool to accomplish measurement and storage of neutron pulse,well geometry parameters and auxiliary parameters,and calculating the porosity.Besides,digital module parses and executes instruction of the control system.A stable and reliable digital module is essential for the logging work.On basis of a national research project undertaken by a logging service company,this thesis studies the software and hardware design of the digital module.And analysis of the module's software reliability is presented.The thesis first introduces the circuit architecture of Neutron LWD Tool and the functional requirements of digital module are analyzed.Hardware design scheme of digital module is proposed,which consist of control circuit,communication circuit,power conversion circuit,power monitor circuit,parameter measurement circuit and storage circuit,and the detailed design of these circuit is presented as well.Then,the requirements of software of digital module are studied.A software architecture composed of function layer and application layer is designed to improve reliability,maintainability and reusability of the software.The function layer takes function as the characteristic to build service modules such as communication service and storage service.The application layer completes the application related to logging operation based on the service provided by function layer.The detailed design of the two software layers is discussed in the thesis.Software reliability of digital module is analyzed using test data.The fault module,fault mode and fault cause of software are divided and analyzed using Failure Modes Effects and Criticality Analysis(FMECA)method,and fault modules of highest criticality are recognized,which are the targets to improve.Then,the number of residual faults of digital module software is proved based on G-O model and Delayed S-shaped model,which belong to Non-Homogeneous Poisson Process(NHPP)class of Software Reliability Growth Model(SRGM).The descriptive and perspective performance of these two models are analyzed to select the most appropriate model.In the thesis,the complete function and power consumption tests of digital module are conducted,and the analysis of the results is presented.The results show that the digital module meets the functions and performance requirements of the relevant project.