通道压裂中纤维辅助携砂机理研究

发布时间：2018-01-10 12:21

本文关键词：通道压裂中纤维辅助携砂机理研究　出处：《西南石油大学》2017年博士论文　论文类型：学位论文

【摘要】：通道压裂技术(Channel Fracturing)是通过交替泵注含支撑剂和不含支撑剂脉冲段,在裂缝中形成不连续支撑剂团状铺置的新型压裂技术;较于常规压裂技术,该技术能有效降低支撑剂用量、提高改造效果。现场实践和室内实验表明纤维能提高支撑剂团稳定性、降低支撑剂沉降速度,是实现通道压裂的关键。目前,对于纤维辅助携砂机理研究处于初期,对纤维作用下支撑剂输送机理认识不清,导致施工参数无法定量优化。因此,本文在纤维基本物理性质及其对压裂液流变性影响研究的基础上,进一步开展了压裂液-支撑剂-纤维三相耦合流动的数值模拟研究,并通过纤维作用下支撑剂大尺度输送实验进行验证,最终对通道压裂施工参数进行了优化。通过纤维分散性实验和稳定性实验,对纤维基本物理性质进行了分析;在此基础上,通过压裂液流变实验和电镜扫描实验,研究了纤维对压裂液基液和冻胶压裂液微观结构、表观粘度以及粘弹性的影响规律。实验结果表明:纤维具有大长径比、均匀分散、化学稳定的特征,在压裂液中以固相形态存在,纤维之间相互接触少;纤维能促进胍胶分子链网络结构形成,使得压裂液基液表观粘度明显增加,其增量受到纤维浓度、稠化剂浓度、剪切速率以及温度的影响;冻胶压裂液胍胶分子链网络结构本身强度较高,纤维对冻胶压裂液表观粘度的影响较小,但会一定程度提高其弹性模量。基于离散元方法(DEM),考虑压裂液曳力、浮力以及支撑剂与纤维之间的相互作用力,分别建立纤维运动模型和支撑剂运动模型;基于计算流体力学(CFD),考虑支撑剂和纤维对压裂液流动的影响,建立三相耦合的压裂液流动模型;耦合上述三个模型,得到压裂液-支撑剂-纤维三相耦合流动模型。分别采用相耦合的SIMPLE算法、显示差分法对液相、固相运动方程进行求解,通过纤维压裂液中颗粒沉降实验验证了该模型的正确性。采用建立的压裂液-支撑剂-纤维三相耦合流动模型,开展单支撑剂和单纤维、单支撑剂和多纤维以及支撑剂团沉降模拟,研究了纤维辅助机理。模拟结果表明,纤维通过与支撑剂的物理碰撞约束支撑剂的运动,该约束作用受到碰撞位置、纤维取向、纤维浓度和长度的影响。碰撞使得纤维发生运动,纤维之间相互作用增强、接触数量增多,多根纤维相互接触形成网状结构,大大降低支撑剂运动速度。纤维通过与支撑剂以及纤维之间的碰撞,将支撑剂团外围支撑剂受到的压裂液曳力,传递给内部其他支撑剂,使得支撑剂之间速度差异减小,提高支撑剂团的稳定性。开展了纤维作用下支撑剂大尺度输送实验,结合压裂液流变实验结果和纤维辅助携砂机理分析结果,验证了工程条件下纤维对支撑剂团输送的作用机理,并进一步对通道压裂施工参数优化开展了研究。实验结果表明,纤维、压裂液、泵注参数是通道压裂支撑剂输送形态的关键控制因素。对比分析支撑剂输送形态和通道特征,确定了最优脉冲单元注入参数区间,建立了施工排量和脉冲时间优化图版,为通道压裂施工参数优化提供了指导。本文揭示了纤维辅助携砂机理,可为通道压裂工艺参数优化、压裂液、支撑剂和纤维优选提供有效指导。
[Abstract]:Channel (Channel Fracturing) fracturing technology by alternating injection pump containing proppant and without proppant fracturing technology to form a new type of pulse, discontinuous proppant slug laid in cracks; compared with the conventional fracturing technology, this technology can effectively reduce the amount of proppant, improve the modification effect. The field practice and indoor experiment show that the fiber can improve the proppant mass stability, reduce the proppant settling velocity is a key channel for fracturing. At present, fiber assisted sand carrying mechanism research in the early stage, the fiber under the action of proppant transport mechanism is unclear, leading to quantitative optimization of construction parameters. Therefore, based on the basic physical properties of fracturing and fiber effects of fluid rheology on the basis of the further development of the proppant fracturing fluid - - fiber three-phase coupling flow numerical simulation research, and through the fiber under the action of supporting large scale transport agent Send the experimental verification, the final parameters of channel fracturing were optimized. Experiment and stability experiment of fiber fiber dispersion, basic physical properties are analyzed; on this basis, the fracturing fluid rheology experiment and scanning electron microscopy experiments, effects of fiber on fracturing fluid base fluid and fracturing fluid micro structure, table influence of viscosity and viscoelasticity. The experimental results show that the fiber has a high aspect ratio, uniform dispersion, stable chemical characteristics, with solid morphology in fracturing fluid, contact between fibers; fiber can promote the formation of guar gum molecular chain network structure, make the fracturing fluid liquid apparent viscosity increased significantly and the increment by fiber concentration, thickener concentration, shear rate and temperature effects; frozen guar gum fracturing fluid high molecular chain network structure strength, fiber to freeze the apparent viscosity of gum fracturing fluid Little effect, but will be increased to a certain extent. The elastic modulus of the discrete element method (DEM), based on the consideration of the fracturing fluid drag, buoyancy and interaction between proppant and fiber, respectively establish fiber motion model and proppant motion model; based on computational fluid dynamics (CFD), considering the influence of fiber on the proppant and fracturing fluid the flow of fracturing fluid flow model of three-phase coupling; coupling of the above three models, get the proppant fracturing fluid - - fiber three-phase coupling flow model. Using SIMPLE coupling algorithm, display difference method of liquid phase, solid phase flow equations are solved by experiment of particle deposition in the fracturing fluid to verify the fiber the model is established. Using the proppant fracturing fluid - - fiber coupling three-phase flow model, carry out single proppant and single fiber, single and multi fiber proppant and proppant sedimentation simulation research group, fiber Dimensional auxiliary mechanism. The simulation results show that the fiber with physical collision proppant constrained proppant movement, collision position, the constraint is affected by fiber orientation, fiber density and length. The fiber collision motion, and enhanced the interaction between fibers, contact number, a plurality of fibers in contact with each other to form a network structure, greatly reduce the proppant velocity. The collision between the fiber and fiber with proppant, will support the fracturing fluid drag agent by peripheral supporting agent, transfer to other internal supporting agent, makes the speed difference between the proppant decrease, improve the stability of proppant group. Carried out under the action of large scale fiber proppant transport experiment according to the experimental results, the analysis results of fracturing fluid rheology and fiber assisted sand carrying mechanism, to verify the mechanism of fiber proppant transport group engineering conditions, and a Step on channel fracturing parameter optimization was studied. The experimental results show that the fiber, fracturing fluid, injection parameter is fracturing proppant transport channel form the key control factors. Comparative analysis of proppant transport form and channel characteristics, to determine the optimal injection parameters of unit pulse interval, established construction displacement and pulse time optimization chart provide guidance for the optimization of construction parameters of fracturing channel. This paper reveals the fiber assisted sand carrying mechanism, optimization, channel fracturing parameter of fracturing fluid, proppant and fibers preferably provide effective guidance.

【学位授予单位】：西南石油大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TE357

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