西非某深海天然气管道投产方案研究及应用

Research on deepwater natural gas pipeline commissioning scheme for project in West Africa

某深海天然气管道由内径为10 in柔性立管及12 in刚性管通过海底管汇终端连接组成,常规的海底天然气管道投产需要经历排水、干燥、惰化、天然气置换氮气、通气投产等步骤。为了节省费用和时间,该项目创新采用淡水置换海水、天然气置换淡水和变径球隔离乙二醇干燥的试运投产方案。对天然气串漏量、水合物生成、变径清管球、清管列车组合等进行了数值模拟研究。模拟研究及投产实践表明:通过合理设置清管列车组合可以避免形成爆炸混合物;只要清管列车组合和MEG剂量选择合适,高压、低温工况下局部夹水通气方案可以避免产生水合物;大变径清管球应用于海底管道系统切实可行。

The deepwater natural gas pipeline consists of10inch flexible riser and12inch steel pipeline which are connected by PLET.When coming to commissioning,the subsea pipeline will conventionally be dewatered,dried and purged with nitrogen before the nature gas goes into the pipeline.For saving money and time,the proposal is taken by using fresh water to displace seawater,using natural gas to displace fresh water and drying with MEG which separated by multi-diameter pigs.The numerical simulation of gas throughout quantity,hydrate formation,multi-diameter pigs and pig train is carried out.The results of the study indicate that explosive mixed gases can not be formed by using suitable pig train;hydrates can not be formed in the high pressure and low temperature conditions by using suitable pig train and MEG quantity;multi-diameter pigs are applicable for deepwater pipelines.