深水井控中地层呼吸效应的识别与处理探讨

在海洋深水海域,由于其沉积环境的特殊性而使得地层比较脆弱,表现为地层孔隙压力和破裂压力之间的窗口比较窄,在实施钻探作业过程中当循环当量钻井液密度接近于地层破裂压力而超过井周地层的闭合钻井液密度当量,就会形成地层呼吸效应,即正常钻进保持循环时部分钻井液进入井眼附近地层,在接立柱停止循环时这部分钻井液回吐而观察到溢流,从表象上难以判断是地层回吐还是真正发生了溢流,需要频繁使用司钻法循环出溢流来确认,这给井控作业增加额外时间和风险.此文分析了深水地层呼吸效应的形成机理,阐述在深水钻井中如何识别与判断地层呼吸,提出相应的技术措施,为深水钻井作业提供参考.

Discussion on Identifying and Handling of Formation Ballooning in Deep Water Well Control

Ballooning is a term often used to describe the physical phenomena where drilling fluid is lost while circulating and then regained when the pumps are shut down. In deep water drilling, due to the narrow window between pore pressure and fracture pres- sure of formation, and weakness, when equivalent circulating mud density is close to the formation fracture pressure, more than equivalent mud density of closing induced or in-situ micro fractures, formation ballooning can be observed. It is difficult to deter- mine formation ballooning, or real kick, should circulate out the bottoms to confirm it by the driller＇s method, which adds additional time and risk in well control operation. In this paper, the mechanism of formation ballooning has been analyzed, and the methods to identify a formation ballooning has been discussed, and the measures for dealing with this problem have been put forward, which can provide reference for deep water drilling.