【作者】 张佐刚；

【导师】 赵明鹏；

【作者基本信息】 辽宁工程技术大学 ， 工程力学， 2006， 博士

【摘要】 磨粒射流处理近井地层技术是近年来发展起来的修复和改善近井地层渗透性能、增产增注和提高原油采收率的一项高新技术。我校已经先后在大庆、胜利、辽河、河南等油田的200多口井进行了现场实验和应用,取得了良好效果,本文是对磨料射流近井地层处理技术中的几个主要科学问题进行的理论研究。首先,对由于钻井、完井、井下作业和长期采油和注水过程中流体污染,固体颗粒、碎屑沉淀的堵塞,引起井周地层应力重新分布,使得井周地层应力升高、孔隙度减小,造成了近井地层的损伤。将应力重新分布、孔隙度减小的问题分别视为可动边界和可压缩骨架的渗流问题进行了分析,得到了近井地层渗透率的变化规律以及影响的范围。为制定磨料射流处理近井地层改善其渗透性能的施工工艺提供理论依据。磨粒射流系固—液两相流射流。在磨料射流处理近井地层技术采用的磨料射流中,砂质量比一般为5%,容积比约为3%,同体积内颗粒的质量和容积远小于水的质量和容积,因而可以忽略颗粒对流体的作用以及颗粒与颗粒之间的作用力,而将砂、水固液两相流简化为等效的单相流体按普通单相流体力学方法进行求解。由于忽略了颗粒与颗粒之间的相互作用力,所以将固体颗粒伪流体视为理想流体,水视为牛顿粘性流体,考虑到射流速度高(一般为紊流流动),采用涡粘性模型,忽略重力,将流体流动视为不可压缩的稳态流动,得到了在所述假设条件下的稳态等效紊流微分方程,并按照普遍流体力学原理,采用奇异摄动法,得到了等效流体即两相流体圆孔自由紊流的射流边界层微分方程即圆孔自由紊流磨料射流的微分方程。分别采用相似性解法和动量积分法对上述磨料射流微分方程进行求解,得到了该射流断面上轴向流速沿轴线的变化规律和射流半径沿轴线的变化规律,为分析磨料射流对材料表面上的冲击作用提供了基础。研究表明,套管在磨料射流作用下的破坏主要是磨料射流对材料断续的高速冲击施加的脉冲载荷,而水流的连续冲击只在材料继续破坏过程中发挥作用。因而得以大幅度降低射流工作压力进行切割。材料表面受到颗粒冲击产生的接触压力形成接触剪应力,以及在接触边界上产生径向拉应力。岩层在射流作用下的破坏是射流向岩层接触受阻突然截止,产生水击压力,以波的形式向岩层传播,成为加载波。当水击压力瞬间消失时,又产生卸载波,岩层在应力卸载波作用下产生拉应力而破坏。作用于金属套管内表面上的射流可以视为自由淹没射流。磨料颗粒以等效流体射流相同的速度冲击金属套管。金属材料一般抗拉、抗压强度相等,远高于抗剪强度。因而磨料颗粒撞击金属套管时,与套管表面接触形成的接触剪应力超过接触剪切强度而产生破坏,按照弹性力学接触问题的理论,建立含有水力参数、磨料参数、切割参数及套管材料参数在内的金属套管磨料射流切割方程式,可用以研究各参数变化对磨料射流切割金属套管的影响,确定磨料射流处理近井岩层损伤的切割工艺参数。对于其它金属材料,磨料射流切割也有一定的参考意义。在井下,对岩石切割是磨料射流在金属套管切割形成的缝中以及在已切割形成的岩层缝中继续对岩石进行冲击。射流流动不仅要受金属套管切口的影响,而且射流在底部和两侧又受到岩层固壁的影响,因而不能视为自由射流。在此条件下建立了磨料射流流体流动的微分方程,采用量纲分析方法进行求解,得到了射流最大轴向流速沿射流方向的变化规律及射流半宽沿射流方向的分布规律。由岩石力学可知岩石的抗拉能力远小于抗压、抗剪能力,同时根据弹塑性动力学中应力波理论求得了卸载波产生的最大拉应力。当卸载波产生的最大拉应力超过岩石的抗拉强度而发生破坏,同时建立了水力参数、磨料参数、切割参数和岩石物理性质在内的磨料射流切割岩石的方程式,可用以研究各参数对磨料射流对岩石进行切割的影响。为处理近井地层,确定切割工艺参数提供依据。根据对磨料射流近井处理进行的地面模拟实验,实验结果与本文所建立的理论计算结果基本相符,因此本文所建立的理论可用于工程实际。最后,根据本文建立的磨料射流切割金属套管和岩层的理论计算公式结合地面模拟试验,对近井地层处理作业时,磨料射流切割工艺参数的选择和确定进行了论述。更多还原

【Abstract】 The technology of abrasive jet deposing near well stratum is a new and high technology which was developed in recent years to restore and improve the permeability near well stratum, increase production and injection and raise the oil output. We have performed the experiment on the spot and applied this technology on 200 more wells in Daqing, Shengli, Liaohe, Henan oil field and so on, and have achieved the good results. This thesis does theoretical research on the main scientific problems in the technology.First, the block caused by fluid production, solid particles and plastic precipitation which are produced in the process of drilling, completion, silo operating, long-term oil production and injection water increases the stratum stress around the wells, leads it to redistribute, reduces the pore slit and destroys the near well stratum. Stress redistribution and the slit reducing can be respectively viewed as the effluent seepage of movable boundary and compressive frame. We can get the changeable law and influence scope of permeability near well stratum which provides a theoretical basis for construction technology.Abrasive jet is solid-liquid two-phase fluid. In the constitution of abrasive jet, the quality of sand is 5%, and volume is 3%comparing with the same quality and volume water, particles are far less than it. Thus the interaction between particles and fluid and between particles can be ignored, so sand and water, the two-phase fluid can be simplified as the equivalent one-phase fluid to find solutions according to the ordinary one-phase fluid mechanics. Since the particles interaction can be ignored, solid as Newtonian viscosity fluid. Considering the speed of jet is high (generally is turbulence flow) by applying slip-stick model, ignoring the gravity, and regarding fluid flow as incompressible stationary flow, we get the stationary equivalent turbulence differential equation under the hypothesis conditions as remarked above. According to the principle of common fluid mechanics, we can find the solutions of equivalent fluid by using singular perturbation. That is, the differential equation of free turbulence jet boundary layer of two-phase fluid pore or differential equation of pore free turbulence abrasive jet.By using similarity solution and momentum integral method to find the solution of differential equation of abrasive jet as mentioned above, we can conclude the law that axial flow speed and the jet radius change along the axial line which provides a basis for analyzing that abrasive jet impacts on material and the surface of target.The research shows, the destruction of adapting pipes influenced by abrasive jet is mainly that abrasive jet imposes pulse loading on materials by continual rapid impact, but the continual impact of water plays the role in the process of material destruction. So jet stress is able to be reduced significantly for cutting. Contact force generated by particles imposing on the surface of material can form contact shear stress and radial tensile stress. Under the influence of jet, rock layer’s destruction is the abrupt cut-off of block which is produced by jet when it contacts with rock layer, with the production of hydraulic pressure which spreads to rock layer in the form of wave named loading waves. When hydraulic pressure instantly disappears, unloading waves, because of producing tensile stress, the rock layer is destructed.The jet which plays a role on the internal surface of metal adapting pipe can be seen as free submerged jet. Abrasive particles impact on the metal adapting pipe at the same rate of the equivalent fluid jet. Generally, metal material’s pull-resistant strength is the equal to the compressive strength, but both of them are far stronger than shear strength. So contact shear stress generated by abrasive particles impacting on the surface of the pipes is stronger than contact shear strength and results to destruction. According to the contact theory of Elastic Mechanics, establish the cutting formulation of abrasive jet of metal adapting pipe. Containing hydraulic, abrasive, cutting and adapting pipe material parameters which can be used to study the parameter changes which influence the abrasive jet cutting the pipes and confirm the injury cutting technology parameter. Abrasive jet cutting has certain reference significance for other metal materials.Under wells, rock cutting continues to impact the rocks in the slits which are formed in the process of abrasive jet cutting the metal adapting pipes and in the slits of having cut rock layer. Influenced not only by the notch of metal adapting pipes, but also by the wall of rock layer on its bottom and both sides, efflux flow can not be seen as free jet. Under that condition, we can establish the differential equation of abrasive fluid flow by using dimensional analysis method to find the solutions, we can get the changeable law that the largest axial-oriented flow speed of jet change along the jet orientation and the law of distribution that jet half width is along jet-orientation. According to Rock Mechanics, the rock’s pull resistant strength is far less than compressive strength and shear strength, at the same time, according to the theory of stress waves in Elastic Plastic Mechanics, we can know the largest pull stress produced by unloading waves. When the largest pull stress exceeds the rock’s pull-resistant strength, the rocks will be damaged, at the same time, we can get the equation of abrasive jet cutting rocks including hydraulic, abrasive, and cutting parameters and the physical qualities of rocks. By using the equation, the parameter’s influence on the cutting can be shown. The equation also provides the basis to determine the parameters of cutting technology for depositing near well stratum.According to the ground imitative tests of the abrasive jet disposing near well stratum, we can find the results of the tests conform to the theoretical computational results established by this thesis, which can be utilized in practical project. Finally, the thesis discusses the selection and confirmation of cutting technology parameter of abrasive jet on the basis of established computational formulation of abrasive jet cutting metal adapting pipe and rock theory and the ground imitative tests.更多还原