Research On The Security Assessment For CO₂ Injection And Acquisition System

The technology of injecting CO₂ to improve recovery has been widely used in recent years,however,there are also some security risks,especially CO₂ corrosion.Currently,there is no complete safety evaluation process for the system in both China and abroad.In this paper,based on the research of CO₂ injection and acquisition system,we formed a safety evaluation process composed of risk assessment,corrosion monitoring and detection,strength evaluation and life evaluation.We take a CO₂ injection and production system in the the oil field as an example,and carry out the safety evaluation in combination with the field process.The risk assessment in this paper is based on the probabilistic analysis and consequence analysis method recommended by API581.We combine the two factors into the risk matrix to obtain an order of the risk value,then detect and monitor the selected high-risk equipment accordingly.Through the investigation of the detection and monitoring method of corrosion defects,we get the comparison of advantages and disadvantages as well as the scope of application,and through the comparison and analysis of the process flow and the technical parameters of the equipment,the method which is suitable for the the detection and monitoring of the system is selected.Then analyze the effectiveness of the detection method.The process provides a proof for the selection of the detection method.Test results based safety evaluation includes strength evaluation and life evaluation.For the strength evaluation,this paper adopts the recommended method of strength evaluation in API579.The first and second evaluation methods are often used in enterprises because of the simple realization,but the method is too conservative.In this paper,the finite element method is used to evaluated the strength of the tubing and the gathering pipelines in Tahe oil field,to determine whether they meet the strength requirements and get the minimum residual wall thickness.Life evaluation is based on the prediction of corrosion rate.We introduce the measurement of corrosion rate of CO₂injection system by laboratory coupon method and obtain the remaining life span based on the corrosion rate and the minimum residual wall thickness which the system demanded.In this paper,we summarized the evaluation method of CO₂ injection and acquisition system and formed a complete evaluation process,which can be used as a reference for the safety evaluation of CO₂ injection and acquisition system.