海底高压输气管道泄压分析与研究

Pressure relief of subsea high-pressure gas pipeline

渤海某气田采取间歇式注气开采的方式,当停止注气后管道内高压气体需要泄放以保证海管安全。一种泄放方式是将高压气体泄放到另外一条低压输气海底管道,另一种泄放方式是在平台上通过火炬放空。利用OLGA动态模拟软件进行方案比选,结果表明:将高压气体泄放到另外一条低压输气海底管道,冬季泄压会造成高压海底管道温度低于其设计温度,因此推荐在夏季进行泄放;当泄放阀开度达到10%时,泄放最大流量与开度100%时接近,而低压海管入口流体温度升高到-12.9℃,有效降低了泄放时产生的低温对下游低压海底管道输气的影响。至于泄压至平台火炬系统,因泄压阀上下游压差过大,造成火炬管网需要超低温设计。因此最终推荐采取泄压至低压输气海底管道的方案。

A gas field in the Bohai Sea is developed by intermittent gas injection. When the gas injection is stopped, the high-pressure gas in the pipelines needs to be discharged for the safety of subsea pipelines. One way is to discharge the high-pressure gas into another subsea low-pressure gas pipeline, and the other is to discharge it on the platform through flare. The dynamic simulation software OLGA is employed for scheme comparison. The results show that if the high-pressure gas is discharged into another subsea low-pressure gas pipeline, the temperature of the high-pressure pipeline will be lower than its design temperature in winter. Therefore, the gas is recommended to be discharged in summer. When the opening of the relief valve reaches 10%, the maximum discharge is close to that when the opening is 100%. Additionally, the fluid temperature at the inlet of the low-pressure pipeline rises to-12.9 ℃, which effectively reduces the impact of the low temperature generated during the discharge on the gas transportation of the downstream lowpressure pipeline. As for the pressure relief to the platform flare system, the pressure difference between the upstream and downstream of the relief valve is too large, resulting in the need for an ultra-low temperature design of the flare network. Therefore, the scheme of pressure relief for low-pressure gas pipelines is recommended finally.