钻井法凿井气举反循环多相排渣运移规律及其洗井参数优化试验研究

Experimental study on transport law of multiphase slag discharge and optimization of well washing parameters in gas lift reverse circulation of drilling shaft sinking

针对西部地区侏罗系地层煤矿立井钻井法施工中出现的气举反循环洗井排渣效率低问题,以可可盖煤矿中央回风立井ϕ4.2 m超前钻井为工程背景,采用相似模型试验和PIV(粒子图像测速法)测试技术相结合的方法,研究了井底及排渣管内液固气多相耦合运移规律;基于模型试验结果,分析了洗井排渣效果主要影响因素,并提出了高效洗井排渣工艺参数.研究结果表明:自主研发的煤矿立井气举反循环排渣试验装置,可实现钻井法井底及排渣管内流体运移特性的可视化试验研究;岩渣在井底做“积聚—悬浮—吸附—补充—再积聚”动态循环运动,排渣管内液固区段流体呈上下螺旋往复运动,液固气区段呈上下交替的振荡运动,上返速度分布均具有强烈的脉动现象;井底流体的运动主要以水平流动为主,流体的垂直上返仅存在于吸渣口附近,且上返速度与泥浆循环量呈正相关,增大刀盘转速或泥浆循环量可提高井底环流和径向流速;排渣效果影响因素显著性依次为刀盘转速、注气流量、风管沉没比和泥浆黏度;基于工程背景和试验结果,满足井底清洁高效洗井排渣相关钻进参数为刀盘转速11.5 r/min,注气流量3500 m^(3)/h.研究结果可为破解侏罗系地层深大立井钻井法洗井排渣效率低下技术难题,提供有益的理论参考.

Based on the engineering background of ϕ4.2 m advanced drilling of central return air shaft in Kekegai Coal Mine,the problem of low efficiency of air-lifting reverse circulation well washing in the construction of vertical shaft drilling method in Jurassic strata in western China was studied.The law of multi-phase coupling migration of liquid,solid and gas in bottom hole and slag discharge pipe was studied by using similar model test and PIV(Particle Image Velocimetry)testing technology.Based on the model test results,the main influencing factors of well washing were analyzed,and the technological parameters of efficient well washing were put forward.The results show that the self-developed coal mine vertical shaft air-lifting reverse circulation slag discharge test device can realize the visual experimental study on the fluid migration characteristics of the bottom hole and slag discharge pipe of drilling method.The rock slag moves in a dynamic cycle of“accumulation—suspension—adsorption—replenishment—re-accumulation”at the bottom of the well.The fluid in the liquid-solid section in the slag discharge pipe moves up and down spirally,while the liquid-solid section oscillates up and down alternately,and the upward velocity distribution has a strong pulsation phenomenon.The movement of the bottom hole fluid is mainly horizontal flow,the vertical upward return of the fluid only exists near the slag suction,and the upward return velocity is positively correlated with the mud circulation,increasing the cutter head speed or mud circulation can increase the bottom hole circulation and radial velocity.The significant influencing factors of slag discharge effect are cutter head speed,gas injection flow rate,air duct sinking ratio and mud viscosity.Based on the engineering background and test results,the drilling parameters related to bottom hole cleaning and slag discharge are cutter head speed 11.5 r/min and gas injection flow rate 3500 m^(3)/h.The research results can provide useful theoretical reference for solving the technical problem of low efficiency of well washing and slag discharge in deep and large vertical shaft drilling in Jurassic strata.