纤维控制支撑剂回流机理研究

发布时间：2018-07-23 15:42

【摘要】：目前,水平井分段压裂因其自身优势成为有效开发低渗致密储层的关键手段。但是,在压裂液返排和气井生产过程中,由于该压裂技术规模大、排液时间长、气体产量大、流速高等特点,导致支撑剂容易发生回流。大量调研发现,在我国的川西、苏里格、新疆、大庆等气田,支撑剂回流都是影响压裂效果的重要问题之一。为控制该现象,形成了以覆膜支撑剂和尾追纤维为主要手段的防回流技术,纤维以其使用简单灵活、适用范围广、成本低等优势成为应用最广泛的控制方法。但是,由于有关该技术的机理研究不深入,实际操作时缺乏可靠的理论指导,因而工程上关于纤维参数的选择多依靠经验决定,正是该问题的存在引发了本文的研究动机。基于以上问题,本文采用数学建模与实验评价相结合的方法,开展了如下研究：(1)对现有支撑剂预测模型作了修正,建立了考虑砂体自身强度的支撑剂回流表征新模型,为针对性研究回流控制技术作用原理及其应用效果奠定了基础。(2)以砂体抗剪强度为主、抗拉强度为辅,建立了纤维增强砂体强度的数学模型,为研究纤维作用机理及相关参数优化提供了定量计算依据。(3)利用室内实验对纤维的分散性能、悬砂性能及其对导流能力的影响作了评价,为进一步优化纤维的综合性能提供实验依据。(4)综合实验与数学模型计算结果,在保证纤维控制作用的前提下兼顾纤维综合效果,形成了工艺参数优化建议。(5)将本文研究成果用于指导现场施工,并就施工效果进行了评价。通过上述研究,取得了如下突破：(1)建立了考虑支撑剂砂体强度的回流预测模型,模型结果显示,当缝宽比很高时,充填层自身强度尚能抵御部分流体拖曳作用,并非如前人所述一旦有流体流动支撑剂就会发生回流。(2)通过本文建立的纤维增强作用模型,可以实现对相关工艺参数的优化,解决当前现场施工参数选取经验化的问题。(3)本文开展的实验验证了强度模型计算可靠性,通过大尺寸裂缝模拟可视装置观察纤维对支撑剂铺砂形态的影响发现,当掺入长度较短的纤维时,砂堤中将形成有利于流体流通的孔隙通道,有助于提高充填层导流能力；当纤维长度较长时,悬砂和稳砂效果更显著。
[Abstract]:At present, segmental fracturing of horizontal wells has become a key means to develop low permeability tight reservoirs effectively because of its own advantages. However, in the process of fracturing fluid backflow and gas well production, the proppant is prone to backflow because of its large scale, long drainage time, large gas production and high velocity of flow. A large number of investigations show that in western Sichuan, Sulige, Xinjiang, Daqing and other gas fields, proppant reflux is one of the important problems affecting fracturing effect. In order to control this phenomenon, a backflow prevention technique is formed, which is mainly made up of film mulching proppant and tail chasing fiber. The fiber has become the most widely used control method because of its advantages of simple and flexible use, wide application range and low cost. However, due to the lack of deep research on the mechanism of the technology and the lack of reliable theoretical guidance in practical operation, the selection of fiber parameters in engineering depends on experience, and it is the existence of this problem that leads to the research motive of this paper. Based on the above problems, the methods of mathematical modeling and experimental evaluation are used in this paper. The following studies are carried out: (1) the existing proppant prediction model is modified, and a new model of reflux characterization of proppant considering the strength of sand body is established. It lays a foundation for the study of the principle of reflux control technology and its application effect. (2) the mathematical model of fiber reinforced sand body strength is established, in which the shear strength of sand body is the main factor, and the tensile strength is supplemented by the shear strength of sand body. It provides a quantitative calculation basis for studying the mechanism of fiber action and the optimization of related parameters. (3) the dispersion properties, suspended sand properties and their effects on the flow conductivity of the fibers are evaluated by laboratory experiments. It provides the experimental basis for further optimizing the comprehensive properties of the fiber. (4) Comprehensive experiment and mathematical model calculation results, under the premise of ensuring the fiber control function, the comprehensive effect of the fiber is taken into account. The optimization suggestion of process parameters is formed. (5) the research results of this paper are used to guide the field construction and the construction effect is evaluated. Through the above research, the following breakthroughs have been achieved: (1) the backflow prediction model considering the strength of proppant sand body has been established. The results show that when the ratio of fracture to width is very high, the strength of the filling layer can still resist the drag of some fluids. It is not reflux once there is fluid flow proppant, as mentioned before. (2) through the fiber reinforcement model established in this paper, we can optimize the relevant process parameters. To solve the problem of empirical selection of construction parameters at present. (3) the reliability of strength model calculation is verified by the experiments carried out in this paper, and the influence of fiber on the sand form of proppant is observed through large scale crack simulation visual device. When the short fiber is added into the sand embankment, the pore passage will be formed in favor of fluid flow, which will help to improve the conductivity of the filling layer, and when the fiber length is longer, the effect of suspended sand and sand stabilization will be more obvious.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE357.12

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