盐穴储气库井筒泄漏监测室内模拟实验

Laboratory simulation experiment of well-leak monitoring of salt-cavern gas storage

由于盐穴储气库注采井井筒管柱和胶结水泥石长期受到交变温度及应力的影响,容易发生漏失,为了保障储气库平稳安全运行,结合光纤分布式声波传感系统(DAS)进行了井筒泄漏监测的室内模拟实验。实验模拟盐穴储气库选用Ø177.8 mm和Ø244.5 mm的油套管柱组合,内管注气、环空注液、设置中间丝扣为泄露点,通过注氮气控制内外压差为0~12 MPa,结合光纤分布式声波传感系统(DAS)及噪声测井技术进行模拟分析。实验结果明确了分布式振动光纤泄漏监测系统的泄漏特征为DAS瀑布图、DAS频谱图均有异常显示,系统的精度为±1 m以内,泄露测量下限为0.83 L/min;系统能有效判别并实时监测气体在注采运行过程中是否发生泄漏,为盐穴储气库井筒泄漏监测技术提供参考和技术支持。

The injection/production well of salt-cavern underground gas storage tends to suffer leak due to long-term influence of alternate temperature and stress on pipe string and set cement.In order to ensure the smooth and safe operation of salt-cavern underground gas storages,laboratory simulation experiment of well-leak monitoring was carried out based on optical-fiber distributed acoustic sensing system(DAS).In the experiment,the tubing-casing string combination ofØ177.8 mm andØ244.5 mm was selected to simulate a salt-cavern underground gas storage,gas was injected into the internal pipe,liquid was injected into the annulus,the middle thread was set as the leak point,and the internal-external pressure difference was controlled in the range of 0-12 MPa by virtue of nitrogen injection.The simulation was conducted by means of DAS and noise logging technology.It is determined that the leak characteristics of the distributed vibration fiber based leak monitoring system are abnormal shows on DAS waterfall plot and DAS spectrum map.Its accuracy is within±1 m and lower limit of leak measurement is 0.83 L/min.This system can perform effective discrimination and real-time monitoring of gas leak in the process of injection and production and provide the technical support for developing a kind of technology suitable for monitoring the well-leak of salt-cavern underground gas storage.