The oil-gas gathering and transportation station is the key to the oil and gas gathering and transportation in the whole onshore oil and gas field, and also the high risk. Therefore, it is very important to evaluate the risk of oil and gas gathering and transportation station and take corresponding measures according to the result. Based on the bowtie model, the left-wing is replaced by Bayesian network, and the uncertainty factor is considered. In the process of Bayesian network to the right event tree, the bowtie barrier is added to construct the Net-bowtie improved model. The dynamic change model is used to consider the real-time changes of basic events into Bayesian networks. Based on the improved compression algorithm, the conditional probability table is encoded and compressed so as to store the data. Finally, the practical application of the dehydration and degassing station of the Net-bowtie model is given, and the data storage space saving of the improved compression algorithm is validated. This model has been used in the field of dehydration and degassing stations of the DND Gas Field and the corrosion reliability of the northeastern Sichuan gas mine.
K E Y W O R D Scompression algorithm, dehydration and hydrocarbon removal station, net-bowtie, qualitative analysis, risk assessment
INTRODUCTIONOnshore oil and gas gathering station is for storing and preliminarily processing the crude oil and natural gas produced by the oil wells in onshore oil and gas fields, and the gathering station is the key to the oil and gas accumulation of the entire onshore oil and gas field, and also the place with high risk. Many equipment in the station are with high concentration and in continuous production operations. Once the leakage occurs due to corrosion, operation mistakes, equipment failure, and other causes, it is quite easy to cause major accidents such as fire explosion. 1 One of the most typical accidents happened on January 20, 2006, when the pipeline explosion occurred at the gas station of China oil and gas field branch of CNPC in Renshou County of Sichuan province, causing 10 deaths, three seriously injured, and 47 injured. 2Oil and gas gathering station is a high-risk place where any mistakes cannot be made in the process of production operation, which may otherwise will bring serious consequences, resulting in losses of people's life and property, and hence it is extremely important to do the risk assessment on oil and gas gathering stations and take corresponding measures according to the results.In risk assessment, risk level is a parameter to measure the risks, which is mainly calculated based on the probability of occurrence and the severity of consequences. According to different risk assessment methods, they can be divided into qualitative risk assessment and quantitative risk assessment. 3 However, the risk assessment of the gathering stations is quite a tough task. The failure modes and consequences of each equipment in the production process are uncertain.