| The crude oil transported by A-S pipeline in an oil field in the northeast of China is waxy crude oil with high viscosity and easy to coagulate,which is mainly transported by heating.With the increase of oilfield development years and the decrease of production year by year,A-S pipeline is about to face the problem of low throughput operation,which may stop flow at any time,increase of pipeline energy consumption,damage of equipment,pipeline overpressure,etc.,seriously affecting the safe and stable operation and production of Oilfield Pipeline.Firstly,according to the heat transfer mechanism of the pipeline and the actual production and operation data,considering the phenomenon of oil flow friction heat generation,the specific calculation method of the total heat transfer coefficient of the pipeline is studied,and the total heat transfer coefficient K value is modified by the inverse calculation interpolation method,based on which the thermal calculation model of the pipeline is established.In terms of pipeline pressure drop calculation model,Darcy formula and various pressure drop models embedded in PIPEPHASE software are used to simulate the pressure drop of horizontal pipeline,and the optimal pressure drop model is determined by comparison.On this basis,the simulation results are compared with the test results,and the error analysis is carried out,and the least square method is used to modify,and the pressure drop model of the external oil pipeline is established.It is verified that the relative errors of hydraulic and thermal models are all within 5%,which meets the expected model accuracy,and has practical significance for reducing energy loss of oil field.Secondly,using the established hydraulic and thermal models,combined with the actual operation characteristics of the pipeline,the research on the minimum hydraulic and thermal safety capacity of the pipeline is carried out,and the safe operation boundary of the pipeline is defined.According to the sensitivity analysis of the minimum safe transmission capacity of the pipeline,the oil temperature at the outlet of the pipeline is determined to be the most important control factor of the safe transmission capacity of the pipeline.Based on this,the calculation software of the minimum safe transmission capacity of A-S external oil pipeline,which is convenient for the visual operation of the oil field,is developed to provide the theoretical basis for the safe and stable operation of the crude oil under the low transmission capacity.At last,according to the current situation of the low capacity operation of the pipeline,taking the determined safe capacity of the pipeline as the boundary,three kinds of pipeline safety assurance schemes suitable for the oilfield are analyzed and designed.By using the established hydraulic and thermal models,the scheme is numerically simulated to determine the optimal water mixing transportation,adding the intermediate heating station and the positive and negative transportation schemes.Finally,through economic comparison,the finalpipeline safety assurance scheme is determined to ensure the safe and economic operation of the pipeline.The relevant research results of this paper can modify the hydraulic and thermal models,increase the accuracy of the model,and develop the pipeline safety assurance scheme under the condition of low throughput based on the analysis and calculation of the minimum safe throughput of the pipeline,so as to provide guarantee and technical support for the safe operation of the pipeline. |
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