【作者】 于鸿春；

【导师】 管志川；

【作者基本信息】 中国石油大学 ， 油气井工程， 2007， 博士

【摘要】 井下磨料射流割缝技术是一项油井增产、水井增注、提高原油采收率的高新技术。已在大庆、胜利、辽河等油田推广使用,效果良好。本文是对磨料射流割缝机理及力学模型进行研究,从而建立油(水)井磨料射流割缝理论,为该项技术不断改进及工艺参数选择提供理论支撑。井下割缝需要对金属和岩层两类不同性质材料进行切割,因而本项研究对于普遍的磨料射流切割也有指导意义和参考价值。磨料射流是少量磨料颗粒与水组成的混合物形成的射流,根据磨料颗粒粒径小、质量及容积浓度低、均匀分布、水流速高、磨料颗粒能随水一道流动的特点,可以视为平衡稀疏流的固液两相流。采用连续介质双流体模型,在建立了固液两相流基本微分方程的基础上,得到了与固液两相流等效的单相流体的基本方程组。从而可以应用单相流体力学原理和方法研究固液两相流体流动问题。本文采用了极坐标、时间平均方法建立紊流方程。通过量级比较法,将紊流方程简化为相应边界层方程,即紊动圆形断面的自由磨料射流微分方程。求得了磨料圆形紊流自由射流的微分方程相似解和动量积分解,得到了圆形自由磨料射流流速分布,轴线上轴向流速和断面面积沿程变化规律。根据地面模拟试验研究和理论分析,磨料射流对金属套管的切割,主要是由磨料射流中的磨料颗粒,与金属套管内表面接触,产生的作用力而实现的。由于磨料颗粒与金属套管接触面积很小,即使产生作用力不大,在接触区域内产生的接触应力将很大,由于套管是金属材料,当接触剪应力超过材料接触剪强度,接触区材料破坏,从母体上剥落形成凹陷,材料表面在大量磨料颗粒连续不断地作用下,凹陷不断产生,积累形成割缝,因而磨料射流对金属套管的切割是磨料颗粒高速与套管接触产生的剪应力作用的结果。实质上是弹性力学理论中的接触问题,从而建立了磨料射流切割金属套管的力学模型。在磨料射流通过被切开的缝隙对岩层进行切割的过程中,受缝隙底部及缝隙两侧的限制,被卷吸进入射流中的周围流体大幅度减少,因而射流流速降低减缓。因而考虑了其固壁摩擦阻力建立了磨料射流运动的微分方程,通过微分方程相似解和量纲分析解相结合,得到了通过缝隙的磨料射流轴线上轴向速度沿程变化规律。岩层是脆性物质,其抗拉强度仅为抗剪强度的几分之一,更是为抗压强度的十几分之一,因此岩层是在射流中大量磨料颗粒高速连续冲击岩层表面时,卸载引起的拉伸波作用下破坏,产生碎粒不断从岩层表面剥落而被切割。在岩石动力学、流体力学、波传播理论的基础上建立了磨料射流切割岩层力学模型。与磨料射流切割套管力学模型构成了油井磨料射流割缝理论。并进行了实例计算,计算结果与地面模拟割缝试验进行对比基本吻合,可以在工程中应用。最后对割缝增产的机理及磨料射流割缝工艺参数的选择进行了分析。更多还原

【Abstract】 Oil well downhole abrasive jet slotting technology is a highly new technology for oil well production increasing, injection increasing of water injector and improving oilfield recovery which has been used in Daqing Oilfield, Shengli Oilfield and Liaohe Oilfield, etc. with very good results. Mechanism and mechanical model of abrasive jet slotting are studied in the paper so that theory of abrasive jet slotting for oil (water) well is established and theoretical support is provided for continuous improving and technical parameter selection of the technology. In downhole slotting, two kinds of materials with different properties of metal and rock need to be slotted, so this research is also suitable for common abrasive jet slotting.Abrasive jet is a jet formed by the mixer of a small amount of abrasive particles and water. In view of small grain diameter, low mass and volumetric concentration, even distribution and high flow rate and flowing with water for abrasive particles, it can be regarded as solid-liquid two phase flow of balanced sparse flow. Based on basic differential equation of solid-liquid two phase, basic equations for equivalent monophasic fluid of solid-liquid two phase flow are obtained with continuous medium dual fluid model so that solid-liquid two phase fluid flowing can be studied with mechanism and method for monophasic fluid mechanics. Turbulent equations are established with methods of polar coordinates and averaging time and turbulent equation is simplified as correspondent boundary layer equation, that is, free abrasive jet differential equation of turbulent circular section through magnitude comparison. Similar solution and momentum integral solution for differential equation of free jet of abrasive circular turbulent are derived and flow rate distribution for circular free abrasive jet, axial flow rate on axial line and on way variation for cross section are obtained.According to surface simulation test and theoretical analysis, slotting of metallic casing by abrasive jet is realized by the acting force caused by contact of abrasive particles in abrasive jet and internal surface of metallic casing. As contacting area for abrasive particles and metallic casing is small, even the acting force is not large, contacting stress formed in contacting region is still large. Since casing is made of metallics, as contacting stress exceeds contact shear strength, material in contacting region is damaged and scaled to form depression. Depressed areas are formed continuously by the action of a large amount of abrasive particles on the material surface to form slots. Therefore, metallic casing is slotted by abrasive jet when shear stress formed by contact of high-speed of abrasive particles and casing is damaged. As a matter of fact, mechanical model for slotting of metallic casing by abrasive jet is established due to contacting problem in elastic mechanics.Rock is slotted by abrasive jet through slots. Restricted by the bottom and two sides of slots, surrounding fluid indrafted into the jet is reduced greatly, so flow rate of the jet slows down. Differential equation for abrasive jet motion is established by considering solid-wall frictional resistance and on way variation of axial speed on axial line for abrasive jet through slots is obtained by combination of similar solution of differential equation and dimensional analytical solution. Rock is fragile material with tensile strength only one fraction of shear strength and compressive strength. So rock is damaged by tensile wave caused by unloading of a large amount of abrasive particles which impact rock surface continuously at a high speed and slotted by debris scaled from rock surface. Mechanical model of rock slotting by abrasive jet is established on the basis of rock dynamics, fluid mechanics and wave propagation theory. And oil well abrasive jet slotting theory is formed by combination of mechanical model of rock slotting by abrasive jet and mechanical model of casing slotting by abrasive jet. Calculation of the example is similar to surface simulation slotting test which can be applied in engineering. Finally, mechanism of slotting simulation and selection of technical parameters for abrasive jet slotting are analyzed.更多还原