中浅层水平井钻柱振动分析及加压方案研究

Drill string vibration analysis and pressurization scheme for medium-shallow horizontal wells

中浅层油气储层埋深浅、物性差、自然产能低,为较难动用的致密砂岩油藏,这会给水平井钻井带来巨大挑战,其中钻柱振动、拖压和摩阻问题是中浅层水平井急需解决的难题。因此,对于钻柱振动和摩阻的模拟非常重要。以鄂尔多斯地区水平井为例,基于三向耦合振动模型,从轴向力、钻柱横向位移和摩擦扭矩三个方面描述了鄂尔多斯地区两种不同井深结构的中浅层水平井钻柱的动力学特性,并和中深井做了对比。探讨了在使用加重钻杆、水力振荡器解决拖压问题过程中,不同加重钻杆根数、尺寸,水力振荡器脉冲力及安装位置对钻柱动力学特性及疲劳寿命的影响。结果显示:相较于中深层水平井,中浅层水平井钻压波动量仅为中深井的1/8,但是在造斜段,尤其是中和点附近的轴向力波动量却很大,达到20 kN,是中深井的1/3,因此造斜段中和点附近钻柱的振动是中浅井关注的重点。针对托压问题,在直井段末端至井斜25°~35°井段增加10~12根或者18~20根?114 mm或?127 mm加重钻杆,既能够保证较小的钻压波动量和摩阻,又能够保证造斜段钻柱较高的疲劳寿命。该结论在现场得到了应用。此外,可配合使用水力振荡器进一步降低摩阻,推荐水力振荡器安装在距钻头40 m处,脉冲力选用21 kN。

Medium and shallow oil and gas reservoirs are characterized by shallow buried depth,poor physical properties and low natural productivity,they are tight sandstone oil reservoirs and difficult to produce,they bring great challenges to horizontal well drilling.Among them,problems of drill string vibration,drag pressure and friction are urgent ones to be solved.Therefore,the simulation of drill string vibration and friction is very important.Here,taking the horizontal well in Ordos area as an example,based on the 3-D coupled vibration model,dynamic characteristics of drill string of two different well depth structures in Ordos area were described from 3 aspects of axial force,horizontal displacement of drill string and friction torque,and compared with those of medium-deep wells.In the process of using heavy weight drill pipe(HWDP)and hydraulic oscillator to solve the drag pressure problem,effects of number and size of HWDP,pulse force of hydraulic oscillator and installation position on dynamic characteristics and fatigue life of drill string were discussed.Results showed that compared with medium-deep horizontal wells,the WOB fluctuation of medium-shallow horizontal wells is only 1/8 of that of medium-deep wells,but the axial force fluctuation in oblique segment,especially,near neutral point is very large and reaches 20 kN,it is 1/3 of that of medium-deep wells,so drill string vibrations in oblique segment and near neutral point receive much attention;to solve the problem of supporting pressure,adding 10-12 or 18-20?114 mm or?127 mm HWDPs at place from the end of vertical segment to 25°-35°deviation segment can not only ensure smaller WOB fluctuation and friction,but also ensure high fatigue life of drill string in oblique segment.The conclusion was applied in site.In addition,a hydraulic oscillator was used together to further reduce friction.It was recommended that the hydraulic oscillator should be installed at 40 m away from the drill bit,and the pulse force should be 21 kN.