单管输送模式开发深水气田水合物的防治措施分析

Prevention and remediation of hydrate in deep-water gas field development with single pipe transportation mode

以单管输送模式开发深水气田,水合物堵塞后解堵困难,存在气田无法继续生产的风险,对水合物防治提出了更高要求。基于水合物相平衡方程,利用OLGA软件,对气田不同阶段的水合物生成进行预测,提出预防措施,并采用双侧降压法开展解堵分析。结果表明,预调试阶段,需对外输管道实施排水干燥;开井启动和正常生产阶段,均存在水合物生成风险;开井启动阶段,需要在油嘴上游注入甲醇,前2 h注入流量为45 m^(3)/d,随后可调整至10 m^(3)/d,共注入10 h;正常生产阶段,需要在油嘴下游连续注入乙二醇,注入流量为85 m^(3)/d;气田停产阶段,无水合物生成风险。管汇间管道发生水合物堵塞,可通过降压方式解堵;外输管道发生堵塞,若堵塞前水中乙二醇质量分数大于33%,则可通过降压方式解堵,否则难以解堵。

It’s difficult to remedy the hydrate blockage in the development of deep-water gas field with single pipe transportation mode, and there is a risk that the gas field cannot continue to produce, which puts forward higher requirements for hydrate prevention and remediation. Based on the hydrate phase equilibrium equation, OLGA software was used to predict the hydrate formation at different stages of the gas field and propose preventive measures, and use the dual side pressure relief method to carry out unblocking analysis. The results show that in the pre-commissioning stage, it is necessary to drain and dry the export pipeline. Hydrate formation risk exists during well startup and normal production. In the well startup stage, methanol needs to be injected upstream of the choke,the injection flow is 45 m^(3)/d in the first two hours, and then it can be adjusted to 10 m^(3)/d for a total of 10 hours. In the normal production stage, ethylene glycol needs to be continuously injected downstream of the choke, with the injection ffow of 85 m^(3)/d.In the shutdown stage, there is no risk of hydrate formation. Hydrate blockage of pipelines between manifolds can be removed by pressure relief. When the export pipeline is blocked, if the mass fraction of ethylene glycol in the water is more than 33% before the blockage, the blockage can be removed by pressure relief, otherwise it is difficult to remove the blockage.