深水不保温海底管道蜡沉积预测及清管研究

Study on Wax Deposition Prediction and Pigging of Deep Water Uninsulated Subsea Pipeline

含蜡原油管道的蜡沉积会导致管道运行参数出现剧烈变化,给管道的安全运行造成严重威胁。为研究深水不保温海底管道的蜡沉积规律并提出相应的清管策略,利用多相流模拟软件(OLGA),对南海某油田深水不保温回接管道的蜡沉积和清管过程进行模拟。研究表明:海底管道输送原油属于轻质低黏、低凝含蜡原油,但由于海底环境温度较低,海底管道未进行保温设计,导致管道的蜡沉积问题严重。针对不保温输油管道,综合考虑管道内最大蜡沉积厚度达到2 mm和清管过程中清除的蜡量不能超过10 m3作为清管周期制定依据,确定投产初期海底管道的清管周期为5天;常规清蜡清管器无法实现该条海底管道的在线清蜡作业,建议改用旁通清管器进行在线清蜡作业,旁通清管器的旁通率确定为1.5%~2.0%。

The wax deposition of waxy crude oil pipeline will lead to drastic changes of pipeline opera-tion parameters,which will seriously threaten the safe operation of pipelines.In order to study the law of wax deposition of uninsulated subsea pipelines in deep water and put forward the corresponding pig-ging strategy,the wax deposition and pigging process of uninsulated tieback pipelines in a deep-water oil field in South China Sea is simulated by using multiphase flow simulation software(OLGA).The results show that the crude oil transported by subsea pipeline is light,low viscosity and low condensa-tion waxy crude oil.However,due to the low seabed ambient temperature,the pipeline is not de-signed for heat preservation,which leads to the serious wax deposition problem.For uninsulated subsea pipelines,considering that the maximum wax deposition thickness in the pipeline reaches 2 mm and the amount of wax removed during pigging should not exceed 10 m3 as the basis for pigging cycle formula-tion,the pigging cycle of subsea pipelines is determined to be 5 days in the early stage of production.Conventional wax pigging could not be carried out online for this subsea pipeline,so it is suggested to use bypass pigging for online wax removal.The bypass rate of bypass pig is determined to be 1.5%~2.0%.