页岩气水平井卡钻主要原因及预防对策

Main reasons and preventive countermeasures for pipe sticking in shale-gas horizontal wells

四川盆地长宁—威远国家级页岩气示范区目前已经实现了埋深3500m以浅海相页岩气的规模化、效益化开发,但随着该区页岩气水平井段长度的延伸,管柱下入过程中摩擦阻力、扭矩增大,易造成频繁遇阻、卡钻等现象。为此,在分析卡钻原因的基础上,从预防钻井过程中井眼力学变形的角度出发,以提高页岩长水平井井段的钻井液封堵性能为重点,协同优化影响井眼轨迹和井眼环空岩屑浓度的钻具组合与钻井参数,通过优化井身结构、井眼轨迹、钻井液性能等技术措施,配套降摩减阻及提速配套工具,制订了页岩气水平井防卡钻技术措施,并进行了现场应用。研究及应用结果表明:(1)对于水基钻井液采用加入适量复合盐抑制剂的方式并配合固控设备的应用,可有效控制钻井液中的有害固相含量,而对于油基钻井液则采用提高油水比、增加乳化剂等方式以增强其稳定性;(2)井眼轨道设计优化为三维轨道二维化后,钻柱最大摩阻较之于优化前降低了20%;(3)高效随钻震击器的钻具组合,配合以合理的钻井参数控制机械钻速,可以达到满足井眼环空携岩要求的岩屑浓度,减少岩屑床的厚度;(4)现场12井次的应用效果表明,水平井段阻、卡等复杂事故时率由2.3%降低至0.92%。结论认为,该研究成果为解决页岩气长水平段卡钻难题提供了有效的技术途径。

So far,shale gas of neritic facies above3500m in the Changning–Weiyuan National Shale Gas Demonstration Area of the Sichuan Basin has been developed beneficially on a large scale.With the extension of horizontal sections of shale-gas horizontal wells in this area,however,frictional drag and torque increase during the tripping in of pipe strings,which results in frequent hindering and sticking.In this paper,the reasons for sticking were analyzed.Then,bottom hole assembly(BHA)and drilling parameters influencing the wellbore trajectory and the concentration of cuttings in hole annulus were optimized from the point of view of preventing mechanical deformation of borehole during drilling and with the improvement of sealing performance of drilling fluid in the long horizontal sections of shale-gas horizontal wells as focus.Finally,the anti-sticking technologies and measures for shale-gas horizontal wells were formulated by optimizing casing program,wellbore trajectory and drilling fluid properties,combined with friction drag reduction and rate of penetration(ROP)improvement tools,and field application was conducted.And the following research results were obtained.First,the content of hazardous solid in water-based drilling fluid can be controlled effectively by adding an appropriate amount of composite salt inhibitor into it,combined with the application of solid control equipment.And the stability of oil-based drilling fluid can be enhanced by improving the oil–water ratio and increasing the quantity of emulsifier.Second,the maximum friction drag on drilling strings is decreased by20%after the three-dimensional hole track design is optimized to be two dimensional.Third,based on the BHA with efficient bumper while drilling,combined with reasonable drilling parameters to control ROP,the cutting concentration satisfying the cutting carrying requirement of hole annulus can be reached and the thickness of cutting bed is reduced.Fourth,on-site application by12well times indicates that the time efficiency of complex accidents in horizontal sections(e.g.pipe hindering and sticking)decreases from2.3%to0.92%.In conclusion,the research results provide an important technological approach to solving the sticking in the long horizontal sections of shale gas horizontal wells.