Research On Well Control Manifold Using Ultrasonic Testing And Safety Assessment Methods

Well control manifold is a vital part of well control equipment, which has direct influence on oil field drilling operation. Based on the metallographic analysis of well control pipeline, flat valve and S elbow pipe, a conprehensive evaluation on its safety is conducted. Fristly, a fault tree concerns well control manifold invalidation is built. By finding out the minimal cut set and itspobability of ocurrence, an conclusion is drawn that the erosion of pipeline wall caused by medium has the highest risk probability, which is 0.0298. Secondly, hierarchical analysis and fuzzy comprehensive evaluation are conducted to caculate the weight of potential risks. Though hierarchical analysis, it is found that abrasion and crack are of the highest weights, which are 0.3146 and 0.1546. And according to the fuzzy comprehensive evaluation, the safety score of the assessed well control manifold is 86.616~76.489. Comparing with safety rating chart, the safe level of the assessed well control manifold is between medium and good, which means the manifold is in good condition.Based on the results of comprehensive safety evaluation, suitable detection technology needs to be adopted to conduct further test on well control pipelines. According to the abrasion and crack situation, regular inspection period is arranged to study the influence these deficiency have on well control pipeline. By comparing nomally used non-destructive testing methods, ultrasonic testing technology is selected to inspect well control manifold since it has advantage when testing big thickness equipment. Considering the complex structure of well control manifold, ultrasonic testing probes are designed according to different parts and materials of manifold. According to different materials of manifold, a 5MHz ultrasonic testing probe is designed to inspect flat valve and pipeline, while a 2.5MHz one to inspect S elbow pipe. Both probe use PZT-5 as piezoelectric chip, which thickness is 14 mm. Matching circuits, protective film and damping block are designed according to the structure characteristics of well control pipeline, as well as sound field analysis of the disk source. Through the above research and analysis, two ultrasonic probes are made, which model numbers are 5P14 Z and 2.5P14 Z. By using trapezoidal block to examine the probes, we found that the detection precision of the probes is 0.1mm and fulfills the need of testing. A fixed bracket of manifold pipelines detecting probe is designed. And by conducting laboratory test, it is proved that the bracket is capable of fixing more than one probe when testing well control pipeline. Thus, the efficiency of ultrasonic testing is improved.Lastly, a UT system is used to conduct inspection on well control pipeline in a certain oil field in Dongying. The system is consist of ultrasonic reflectoscope, specificlly designed probes and a fixed bracket. From the experiment, it is found that ultrasonic reflectoscope can output effective test waveforms, which are further analysised to confirm the defeciency of the manifold. Therefore, the field testing showed that the UT system is capable of conduct thickness detection of the manifold with highi degree of accuracy. Combination the comprehensive safety evaluation with UT, a synthetical assessment is given on the service condition of well control manifold to ensure its safety.