漂浮下套管技术在浅层页岩气水平井中的应用及优化

Application and optimization of floating casing running technology in shallow shale gas horizontal wells

较之于深层页岩气水平井,浅层页岩气水平井虽然钻井投资成本较低、钻井周期较短,但是浅层页岩气井的水垂比较大、井身轨迹复杂,使得套管难以下入,导致水平段长度受限,对页岩气单井控制储量造成了不利的影响。为此,在昭通国家级页岩气示范区叙永—古蔺地区的太阳—大寨区块采用了漂浮下套管技术,并且在13口井的现场应用实践中不断分析、总结、优化,进而形成了一套适用于浅层页岩气的漂浮下套管技术系列。研究结果表明:(1)浅层页岩气水平井采用漂浮下套管技术可以明显增加套管下入能力,并且能够防止套管遇阻遇卡等复杂情况发生;(2)常规破裂式(玻璃板)漂浮接箍其破裂盘正常打开时存在着破碎不彻底、易导致固井胶塞遇阻的缺点,同时其破裂盘承压能力低、抗疲劳能力差,遭遇狗腿度变化较大的井段,有可能造成破裂盘径向受力,容易使漂浮接箍提前打开;(3)通过优选漂浮接箍装置,由常规破裂盘漂浮接箍优化为全通径漂浮接箍,有效地保证了下套管施工作业的安全及固井质量。结论认为,采用全通径漂浮接箍可以有效地避免常规破裂式(玻璃板)漂浮接箍存在的缺陷,该技术应用效果良好、适合进一步推广使用。

Compared with deep shale gas horizontal wells,shallow shale gas horizontal wells have lower drilling investment cost and shorter drilling cycle,but the horizontal vertical ratio of shallow shale gas wells is large,and the well trajectory is complex,which makes it difficult to run the casing,resulting in the limited length of horizontal section,which has an adverse impact on the controlled reserves of single shale gas well.Therefore,in Taiyang-Dazhai block of Xuyong-Gulin area,Zhaotong national shale gas demonstration area,the floating casing technology has been adopted,and has been continuously analyzed,summarized and optimized in the field application practice of 13 wells,thus forming a series of floating casing technology suitable for shallow shale gas.The results show that:(1)the floating casing running technology can significantly increase the casing running ability of shallow shale gas horizontal wells,and prevent the casing from being stuck;(2)the conventional fractured(glass plate)floating coupling has the disadvantages of incomplete fracture and easy to cause the cementing plug to be blocked when the fracture disc is opened normally.At the same time,the fracture disc has low pressure bearing capacity and poor fatigue resistance.When encountering the well section with large dogleg degree change,it may cause radial stress on the fracture disc and easy to open the floating coupling in advance;(3)by optimizing the floating coupling device,the conventional fracture disc floating coupling is optimized to full diameter floating coupling,which effectively ensures the safety of casing operation and cementing quality.The conclusion is that using full diameter floating coupling can effectively avoid the defects of conventional broken(glass plate)floating coupling,and the technology has good application effect and is suitable for further promotion.