文96地下储气库结盐机理及防治措施

Mechanisms of salt precipitation and control measures:An example from Wen 96 gas storage

为了降低注采井及储层结盐给渤海湾盆地东濮凹陷文96地下储气库注采气生产带来的不利影响,保障下游管网安全平稳供气,以文96储气库储层天然岩心为研究对象,室内以干气驱替饱和岩心试验模拟注采气过程地层结盐状况,考察注采压力、生产压差、渗透率及天然气饱和水蒸汽含量等因素对地层结盐的影响,探讨地层结盐机理及规律;进而以现场实测资料模拟井筒中的温度以及压力分布,通过自制高温高压井筒模拟装置开展注采井井筒结盐影响因素研究,观察结盐过程及现象,结合多周期注采生产实践总结出注采井井筒结盐规律。研究结果表明:(1)注气过程岩心结盐表现为初始阶段、平衡阶段及缓和阶段3部分;(2)采气过程中随着岩心渗透率降低,结盐压力越低,结盐对岩心伤害的程度越大;(3)压力是影响井筒结盐的主要因素。结论认为,基于文96储气库地层及井筒结盐机理,研制出适合该储气库注采气工况条件的复合抑盐剂并开展现场试验,最终形成了一套适合文96储气库的清防盐技术措施。现场应用效果证实,该技术能有效降低结盐对储气库注采调峰的影响,可以为后期同类型储气库建设及运行提供参考。

In Wen 96 gas storage,in order to alleviate an adverse impact of salt precipitation in injection-production wells and reservoirs on gas injection and production and to guarantee both safe and smooth gas supply to downstream pipelines,several natural cores from some reservoirs were taken as objectives to study salt-precipitation mechanisms.In the laboratory,a dry-gas-displacing core-saturated experiment was carried out to simulate the precipitation in the reservoirs in the process of gas injection and production,investigate the influences of injection-production pressure,production-pressure difference,permeability,and gas-saturated water-vapor content on the precipitation,and discuss the precipitation mechanisms.Certain data measured on site was adopted to simulate the temperature-pressure distribution at wellbore and the self-made high temperature,and a high-pressure wellbore simulator was used to study the factors influencing the salt precipitation at the wellbore of injection-production wells and observe the precipitation process.And combined with multi-cycle injection and production practice,the salt-precipitation mechanisms at the wellbore were summarized.Results show that(1)the precipitation in the cores in the process of gas injection can be divided into initial,balance,and easement stages;(2)during gas production,the precipitation pressure decreases and the core damage degree by the salt increases with the decrease of core permeability;and(3)pressure is the main factor influencing the precipitation.In conclusion,based on the salt-precipitation mechanisms of Wen 96 gas storage,one combined salt inhibitor suitable for working conditions of gas injection and production in this area was developed and tested on site,and ultimately a set of salt removal and control measures available for this gas storage were made.The field application proves that these measures can effectively alleviate the salt-precipitation impact on the peak shaving of gas storage and provide reference for constructing similar gas storages.