非常规超深井井身结构在LG61井的应用

Application of unconventional ultra-deep wellbore configuration in the well LG61

四川盆地北部LG西区地质情况复杂,以二叠系为目的层的井深度一般都在6000m以上,地层压力高,钻井液密度均在2.00g/cm3以上,喷漏显示频繁。为了解决这一难题,提出LG61井采用非常规的超深井6开制井身结构,LG61井设计井深6690m。主要采用了如下的钻井工艺技术措施:①小井眼采用特殊小接头88.9mm钻杆,以提高强度;②在小井眼井段,采用了PDC钻头,保持适当的钻压和转速,严格控制扭矩;③在确保井控安全的前提下,尽量降低钻井液密度;④219.1mm、168.3mm、114.3mm套管均采用高强度耐腐蚀无接箍套管(尾管悬挂),小间隙防气窜固井技术;模拟套管刚度特殊通井,经比较套管与钻柱刚度与外形尺寸,摸索出一套非常规井身结构的通井钻具组合,确保套管在小间隙情况下,顺利下至预定井深。该套成功的钻井技术为同类非常规超深井井身结构的设计和施工提供了借供了借鉴与参考。

In the western LG area,the wells targeted at Permian strata are generally deeper than 6000 m with high strata pressure,the densities of the drilling fluids in use are all over 2.00 g/cm3,and drilling accidents occurred frequently,such as blowing out and lost circulation.In order to solve these problems,this paper puts forward the application of unconventional six-open ultra-deep well structure in the well LG61 with the designed depth of 6690 m.The main technologies and measures are summarized as follows:①The 88.9 mm drilling pipe with special small joints was adopted in slim hole drilling to improve the strength.②In the slim-hole interval,the PDC drilling bit was used with proper rotary speed and weight on bit (WOB),and strictly controlled torque.③The density of drilling fluid was made as low as possible,subject to the safety of well control.④High-strength and corrosion-resistant 219.1 mm,168.3 mm and 114.3 mm flush casings (with the liner hung),and small gapping anti-gas channeling cementing technology were utilized.Special drifting has been carried out via simulation of casing stiffness.By comparison in stiffness and physical dimension between the casing and the drilling string,a set of drifting tools for unconventional well structure have been obtained to ensure the casing to reach the settled well depth in the case of small annular space.The drilling technologies successfully used in the well LG61 have laid a foundation for the well design and operation of similar wells.