Prediction of restarting pressure of shut-down offshore pipe for heavy oil-water mixed transportation
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Abstract:
To ensure the safe shutdown and smooth start-up of heavy oil gathering and transportation subsea pipeline, taking LD heavy oil as the research object, the rheological characteristics and mechanical response characteristics of restart for heavy oil and its emulsion were analyzed by Anton Paar Rheolab QC rheometer. The orthogonal start-up experimental data were analyzed by SPSS software, and a start-up stress model with four parameters and seven coefficients was established. An indoor loop restart experimental device was developed to analyze the variation of the start-up pressure of the shutdown pipeline under different working conditions. The predicted value of restart pressure based on the start-up stress model is compared with the measured value to evaluate the reliability of the prediction. The results show that the changes of initial start-up stress of heavy oil emulsion with time can be divided into three stages, including rising stage, declining stage and equilibrium stage. The average absolute relative error between the predicted value and the measured value of the restart pressure is 16.38%. The restart pressure decreases with the increase of temperature and increases with the increase of start-up flow rate. And with the increase of flow rate properly can shorten the start-up time, but also can enlarge the restart pressure at the same time.
