Optimization Design Of Multiphase Flow Vessel-Type Slug Catcher For QK18-1 Platform In Boxi Oilfield

The conveying medium of pipeline between QK18-2 to QK18-1 platform in Boxi oilfield belongs to gas-liquid multiphase flow.There is a severe slug flow problem under normal transportation and pigging conditions.If it is not suppressed,it will cause harm to the downstream equipment and affect the normal production of the oil field.Slug catcher is an effective device to eliminate slug flow.And it is also one of the most mature methods at present.In order to optimize the design of a vessel-type slug catcher with good economy and high separation efficiency on the QK18-1 platform.The optimization design technology of the vessel-type slug catcher is systematically studied.The specific research contents are as follows:(1)When optimizing the vessel-type slug catcher.It is necessary to know the slug volume of the pipeline as the design data basis of the catcher.Therefore collect the basic production parameters of the Boxi oilfield from QK18-2 platform to the QK18-1 platform.The pipeline simulation model is established based on the OLGA software and the normal operating conditions of the pipeline are simulated.The simulation results show that severe slug flow has occurred in the sea pipe.It is considered that the slug volume will increase in pigging condition.The transient analysis model of pigging pipe is established by OLGA software and the numerical simulation of the transient state of the pipe is carried out.Obtaining the pigging slug quantity provides the data basis for the size calculation of the catcher and the boundary conditions.(2)After the slug is obtained,the slug catcher should be selected and the internal structure should be optimized.According to its working principle and design method,the initial size of the vessel-type slug catcher is calculated.And then considering the diameter,the length,the inclination angle of the deceleration plate and the number of the baffles,the orthogonal experimental design method is used to determine the factors and levels of the structural parameters.And the combination scheme of different structural parameters is put forward.It provides a reliable and reliable sample space for the later optimization design.(3)For the proposed design plan,we need to know the security,economy and separation efficiency of each scheme.The simulation model of the vessel-type slug catcher is set up in AN SYS Workbench.And the internal liquid level fluctuation and separation efficiency of the above design are calculated by Fluent and CFX software respectively.Then the cost input of each scheme is calculated according to the economy of the catcher.The scheme is evaluated and analyzed according to the calculation.It provides data basis for the later optimization design.(4)The combination of sample and numerical results based on MATLAB genetic algorithm is combined.With the objective of cost input and separation efficiency,the diameter of the tank,the length of the tank,the inclination angle of the deceleration plate and the number of the baffles,are used as the design variables.A multi-objective optimization function of vessel-type slug catcher is established and optimized.The optimized vessel-type slug catcher has brought some economic benefits while ensuring the safety of production:in Boxi oilfield.It is targeted to vessel-type slug catcher optimize technology research.Then the optimized structure of the vessel-type slug catcher on the QK18-1 platform of Boxi oilfield is determined.It not only effectively eliminates slug flow and reduces investment cost,but also considers the separation efficiency properly,thus reducing the downstream pipelines and equipments load.It also provides a reference for the structural size design of vessel-type slug catcher.