井底涡旋器设计的理论与试验研究

【作者】 杜君；

【导师】 陈平； 熊友全；

【作者基本信息】 西南石油学院 ， 油气井工程， 2005， 博士

【摘要】 国内外研究表明,井底压差是影响机械钻速的主要因素,随着压差的增大,机械钻速几乎呈指数规律下降。为降低井底压差对机械钻速的影响,钻井技术工作者提出了近平衡钻井技术;为完全消除井底压差对机械钻速的影响,又提出了欠平衡钻井技术,近平衡、欠平衡钻井技术的应用不仅有效地提高了机械钻速,而且有利于发现和保护油气层。就提高机械钻速而言,欠平衡钻井技术在复杂地区的应用仍存在一定的安全隐患,本文的研究工作是开发出一种新技术,其应用能实现井底附近局部压力的降低,而井筒的绝大部压力处于近平衡状态,这样既保证了井下安全,又可有效地降低井底压差、提高机械钻速、及时发现油气藏。 借助于现代流体力学的涡旋理论,本文提出了降低井底附近局部压力的涡旋器设计思路。这种涡旋器安装在钻头上,在钻柱旋转带动下,通过其上喷嘴喷出的射流在环空中产生涡旋流,使涡旋器上方环空中的钻井液柱压力不能完全传递到井底,导致井底压力的局部降低。在提出了涡旋器设计的物理模型后,本文建立了描述涡旋器工作状况的流体力学模型,模型包含了钻头喷嘴射流产生的流场对涡旋器流场的影响。采用标准的k—ε紊流模型,运用时均法推导并建立相应的紊流模式,求解方法具有以下特点: 1.可对在井底产生的淹没射流流场进行三维数值模拟,直观地看到井底附近井壁压力的变化情况。 2.可考虑钻柱、钻头旋转对井底附近流场的影响,通过调整涡旋器的结构参数和水力参数,随时掌握井底附近流场、压力场的变化情况。 理论计算研究表明: 1.流量在0.024m~3/s、0.026m~3/s、0.028m~3/s、0.030m~3/s、0.032m~3/s的情况下,流量 越大,钻头的压力损失也越大,并呈线性递增的关系;流量增大,井底与井底涡旋器顶部的压力差呈现线性递增的趋势;流量增大,导致高速射流引起的环空旋流的旋转速度增加,同时井底部分流场也参与旋转,最终导致井底压力降低。 2.侧喷嘴倾斜角度在0度、30度、45度和60度情况下,由于井底涡旋器的旋流作用,导致井底产生旋转,对钻头喷嘴射流产生了影响,以致在45度时出现压力损失最小的情况;在0度时,出现了明显的正压状况,而在30～60度都出现了明显的负压,其中45度左右时,负压力差最大。说明在设计井底涡旋器时,最好不要采用0度喷嘴,优选45度喷嘴。 3.在5mm、6mm、7mm和8mm四种不同直径下的侧喷嘴情况下,侧喷嘴直径越小,压力损失越大;直径越小,喷嘴射出的钻井液速度越大,旋转力也相应增大,从而导致井底的液杜压力降低。 为证实井底涡旋器能有效地降低井底附近的压力,提高钻井速度,根据涡旋器设计理论设计制造了两种规格的井底涡旋器,开展了实验测试和现场试验的研究工作,实验研究表明井底涡旋器可有效地降低井底附近的压力。在中原油田新文72-189井和文269-6井进行的现场试验,机械钻速平均提高20%以上。更多还原

【Abstract】 The domestic and international research express that the well bottom pressure is the main factor to affect the machine’s drilling velocity, along with pressure increasing, the penetration rate present the index number regulation to descend soon and almost. For lowering effect of the well bottom pressure-drop to the penetration rate, the underbanlanced drilling technique the worker put forward the (near equilibrium artesian well) technique; In order to cancel well bottom pressure-drop’s influence to the penetration rate, and then put forward to underbanlanced drilling and near balance drilling, these techniques not only raises the machine to drill availably soon, but also is advantageous to discover and protect the reservoir. In regard to the exaltation machine drill soon , underbanlanced drilling apply in the complicated region still unsafe , it is applied and the nearby and partial pressure of the well bottom can be lowed, but a pressure of the wellbore be placed in the near equilibrium, thus can guaranteed the well’s safety, and then can lower the well bottom pressure, enhance the penetration rate and discover the reservoir soon and in time .With the help from the vortex theories of the modern hydrodynamics, this text puts forward to, vortex machine design way of thinking of lower the well bottom pressure of the nearby and partial pressure. This kind of vortex machine installs on the bit, under the drill string ’motivation, spray the shoot of the nozzle to flow through its top to produce the vortex to flow in the annulus, make the drilling fluid column pressure in the annulus above the vortex machine cant deliver to the well bottom completely, causing the part of the well bottom pressure lower. After putting forward physics model of the whirlpool machine design, this text built up the fluid mechanics model of the description whirlpool machine work condition, the model includes the bit to spray the influence that the mouth shoots to flow to flow the field to flow the field to the vortex machine outputly.Adopt the standard k-e turbulent model, deduces and builds up the turbulent flow model adopt with it by time average method, to this mode, solving the method have the following characteristics:1. Can directly perceived through the senses of drown to shoot to flow the field to carry on three dimension digital simulation in the well bottom, keep the view ground see the well bottom nearby well face pressure of variety circumstance.2. Consider the drill stem and bit to revolve the influence that flows the field to the well bottom neighborhood, adjust the structure parameter and the water power parameters of the whirlpool machines, can control the variety circumstance that the well bottom neighborhood flows the field, the pressure field.The theory calculation studies the enunciation:1. When flow rate is 0.024m3/s、0.026 m3/s、 0.028 m3/s、 0.030 m3/s and 0.032 m3/s, thegreater the flow rate is, the greater the pressure loss on the bit is, which increases linearly; the pressure differential between bottom hole and top of vortex device tends to increase linearly as flow rate rises; the increase of rotating speed of the annular eddying flow generated by the high velocity jet is resulted from the increase of flow rate, at the same time, partial bottom hole flow field is also involved in the rotation, eventually leading to reduction of bottom hole pressure.2. When the inclination angle of a side nozzle is 0, 30,45 and 60 degrees, the eddying flow of the bottom hole vortex device will cause rotation at the bottom hole, affecting on the jet from bit nozzles. As a result, a minimum pressure drop is reached at an inclination angle of 45 degrees, obvious positive pressure is created at 0 degree while obvious negative pressure is created at 30 - 60 degrees, including a maximum negative pressure differential occurred at about 45 degrees. From this fact, it can be shown that it is better not to select 0 degree nozzle and 45 degree nozzle is preferred.3. Among four sizes of side nozzle: 5, 6, 7 & 8 mm, the smaller the nozzle diameter is, the greater the pressure loss is; the smaller the diameter is, the higher the velocity of the drilling fluid jetted from the nozzle is and the greater the rotation energy is, leading to reduction of the hydrostatic pressure of liquid column at bottom hole.In order to confirm that the well bottom vortex machine can lower the pressure of the well bottom neighborhood availably, the exaltation drilling speed, designed the theories design to make two kinds of wells of specification bottom vortex machine according to the vortex machine, open the exhibition the experiment test and the research work that the spot experiment, experiment the research enunciation well bottom whirlpool machine and can lower the pressure of the well bottom neighborhood availably .At ZhongYuan oil filed new text of 72-189 well and 269-6 well carry on experiment, the penetration rate raise by 15% in average.This text sets out from the basic theories of the hydrodynamics, put forward the well bottom whirlpool machine design, and the digital simulation, the indoor experiment tests to system research .The research confirmed that the well bottom vortex machine can lower partial pressure of the well bottom neighborhood.更多还原