Application of lean six-sigma methodology to reduce the failure rate of valves at oil field

there are mainly two types of valves used in oil fields: isolation and control valves. Choke valve is an example of control valves. A choke valve is used mainly to adjust the production rates for every individual oil or water well. There are 240 choke valves at the Field under study. Several failures have been reported for these choke valves including: cage damage, seat damage, plug damage or actuator failure. A total of 37 failed choke valves have been reported that affect the availability of the production wells and causing deviation from the production targets. The objective of this study is to make recommendations to reduce the failure rate of choke valves by applying lean six sigma approach aiming to increase availability of production wells as well as meeting production targets for producing wells. The procedure follows the framework: define, measure, analyze, improve and control DMAIC phases. The project started with problem definition through statistical analysis of the current performance and quantification of failed choke valves for certain period of time. This involves using the supplier-input-process-output-customer SIPOC diagram. The process also involved brainstorming session to identify potential root causes of the problem. Classifying and rating these causes were achieved by use of the several tools: a "fishbone" diagram, cause-and-effect matrix, and failure mode and effect analysis (FMEA). This was followed by the root cause analysis technique using five (5) whys concept. Finally implementation plan was generated that's incorporating all of the process improvement recommendations including: approach material specialists and check for proper material selection, upgrade the choke valve material based on feedback received from specialists, ensure availability of spare parts for choke valves, emphasize on proper rig cleaning activities, study the feasibility of installing strainer upstream the choke valve to avoid foreign particles, review existing preventive maintenance procedure and update accordingly and review the design pressure for the choke valve.