Research And Application Of Reliability Test Method For Safety Control System Of Shale Gas Well Site

The frequent change of working conditions and well logistics parameters in shale gas wellhead,in the long-term production process,makes the safety control system form a series of problems,such as the accuracy of pressure detection elements decreases,the setting value is not accurate,system sensitivity is poor,and so on.In order to ensure the reliability of the safety control system,it is necessary to test and analyze the reliability of the safety control system so as to realize the safety and efficient production for shale gas well site.In this paper,the reliability test method for safety control system of shale gas field is studied,and the reliability test platform for safety control system of well site is designed and built,the field application of the research results has been completed by relying on PS1 shale gas well site.The main research work is as follows:(1)The present situation of safety control system for shale gas well site in China and abroad,application of related new test technology,new method and new equipment in control system is researched.Meanwhile,the basic data of well site technology,the operation parameters of the equipment facilities and control system in PS1 well site is collected.(2)The reliability test method of safety control system for shale gas well site is studied,and the reliability test flow of high-low-pressure truncation control system and outbound emergency truncation system is put forward,to test the actual shutdown value,response time and shutdown time of the truncation system,so to evaluate the sensitivity,reliability and the effectiveness of interlock function of the safety control system.(3)The reliability test platform of shale gas field safety control system is designed,and the overall structure of the test platform is put forward.The high-low voltage output test unit based on servo valve control system is designed,which controls high and low pressure analog signal adjustment to output.The variable slope pressure output test unit is designed,whose controlling core adopts a three-loop servo control system,to feedback adjusts the pressure to output the analog signal according to the fixed slope.The design of time detection unit composed of sensor,data acquisition system and computer terminal is completed.(4)Based on the reliability test platform of shale gas well site safety control system,the reliability of high-low-pressure truncation control system in PS1 shale gas well site is tested and analyzed,the reasonable truncation parameter setting value is recommended.There are three measures to improve the reliability of well site safety control system by setting fast discharge valve outlet of the hydraulic valve,increasing the diameter of hydraulic loop and replacing hydraulic oil.(5)The actual shutdown value,response time and shutdown time of the emergency truncation valve at PS1 well site are tested,the reliability of the emergency truncation system at different pressure drop rates is analyzed,and the effectiveness of the pressure drop rate interlocking function of the truncation valve is evaluated.(6)The leakage model of shale gas well site is established,and the influence of pipeline leakage aperture size,leakage point position and operating pressure on the pressure drop of emergency truncation valve is analyzed,and a general threshold setting method of cut-off valve pressure drop rate is formed.It is recommended that the threshold value of pressure drop rate of outbound truncation valve of PS1 well site be set.(7)Following to the relevant requirements of test specifications and standard,"the reliability test code for safety control system in shale gas well site" is compiled,which consists of the test contents that need to be completed,the recommended test platform,the test methods used and the test reports formed.