页岩气井生产管柱优选研究与应用

Research on and application of production string optimization in shale gas wells

页岩气井开发初期产量高,大部分井直接采用空套管投产,可有效带液生产。在放压放产生产制度下,井口压力快速降到输压,然后出现带液生产异常,井筒积液,甚至水淹停产,造成气井生命周期急剧缩短。为此,必须下入生产管柱并实施后续排水采气工艺。开发初期并未形成明确的生产管柱下入技术指导现场生产,因此在页岩气规模上产时无法做到在科学合理的计划下有步骤高效地推进实施生产管柱下入。立足页岩气井后期生产低压、小产、长水平段等特点,通过开展最大产气量、井筒压力损失、抗气体冲蚀能力计算,井筒流动规律、携液能力分析,并从辅助后期排水采气工艺实施考虑,结合大量现场应用分析,提出了生产管柱的油管尺寸、下入时机、管柱结构及下入深度、配套工具等优选生产管柱技术要求。明确优选生产管柱技术,指导现场高效推进实施,应用规模呈逐年增长的趋势。应用效果表明,该技术有效降低了气井递减率,为后续排水采气措施的及时实施及维护气井产能提供了技术基础。

In the early stage of shale gas well development,the production is high and most of the wells are directly put into production with hollow casing,which can effectively enhance production with liquid.Under the production system of releasing pressure,the wellhead pressure quickly drops to transmission pressure,and then there are abnormal production with liquid,wellbore liquid accumulates,production shutdown by floods,which causes dramatic drop to the life cycle of gas wells.For this purpose,it is necessary to lower the production string and implement the follow-up drainage and gas recovery process.No clear string lowering technology has been developed to guide field production in the early stage,so it is impossible to promote the implementation in a systematic and efficient manner under a scientific and reasonable plan when shale gas production is on a large scale.Based on the characteristics of shale gas wells production in late stage,such as low pressure,long horizontal section,etc.,through the analysis on maximum gas production,wellbore pressure loss,gas erosion resistance calculation,wellbore flow law,liquid carrying capacity,and assisting drainage & gas recovery in late stage,combined with a large number of field application analysis,technical requirements are put forward for optimizing string such as lowering timing,tubing size,string structure and lowering depth,etc.The application results show that this technology can effectively reduce the decline rate of gas wells and provide a technical basis for the timely implementation of subsequent drainage & gas recovery measures and maintenance of gas well productivity.