基于CFD的裸眼水平井投球滑套球座冲蚀模拟

发布时间：2019-05-30 01:34

【摘要】：分段压裂是水平井的关键配套技术之一,此技术可在较短的时间内将多个储层一次性地压裂,能最大程度地减少对储层的负面影响,从而实现多层合采、提升单井产量、最大限度提升储层采收率等的目的。裸眼水平井分段压裂技术是段提高油气藏产能较为成熟的技术之一,该工艺可操作性好、可靠性高,能较好改造低孔、低渗透油气藏,是目前国内主流的一种提升油气井产能的技术。封隔器和投球滑套是裸眼水平井分段压裂管柱中的重要组成部分,是保证裸眼水平井分段压裂技术可靠性和安全性能的关键,其密封性能甚至可决定压裂施工的成败。归纳了国内外普遍认可的冲蚀理论模型,根据其优缺点和适用范围,结合压裂管柱内携砂流体实际工况,进一步研究了投球滑套球座受颗粒冲刷磨损的机理及数值模拟的理论模型。从外界环境因素、颗粒性能、靶材属性等方面总结了影响球座冲蚀的因素。本文参照现场压裂施工的实际工况,经考虑携砂流体高含砂比的情况,构建了液固两相欧拉双流体模型,同时利用UDF对球座的入口紊流速度进行了修正。利用用计算流体力学(CFD)的理论,分析了投球滑套球座因携砂液冲刷磨损而造成的密封失效问题,并利用ANSYS-FLUENT软件对球座冲蚀磨损进行模拟。通过对滑套的冲蚀破损分析,构建了一套适用于球座冲蚀磨损程度的评价指标；模拟发现球座与低密度球的坐封点冲蚀破损最为严重,这为球座流道优化设计奠定了基础。同时分析研究了各种现场因素对球座冲蚀的影响及在某小段地层压裂时其上游各球座的冲蚀分布规律,并计算整个井位压裂完成后各球座被剥蚀掉的材料体积,解决了球座因冲蚀而存在连续失效的问题。为了有效避免球座在压裂过程中冲蚀失效,改进了双角度前锥面球座和角度+球面密封球座。这两种球座通过改变传统球座流道的结构设计对传统球座进行了耐冲蚀优化,但它们依旧适用于原压裂管柱。研究结果表明,双角度前锥面球座能极大地提高前锥面的耐冲蚀能力,并且角度+球面密封球座不仅能有效提升球座的密封性能,还可避免球座流道冲蚀最为严重的部位与坐封点重合；分析不同携砂液排量、支撑剂颗粒粒径、携砂液含砂比等因素影响两种球座冲蚀的规律,研究发现携砂液排量对双角度前锥面球座的影响最为突出。通过对投球滑套球座冲蚀行为及提升抗冲蚀磨损能力的研究,为解决投球滑套球座冲蚀失效问题提供了合理思路,同时也为现场压裂施工提供了理论指导,因此具有较强的参考价值。
[Abstract]:Segmented fracturing is one of the key supporting technologies of horizontal wells. This technology can fracturing multiple reservoirs at one time in a relatively short period of time, which can minimize the negative impact on the reservoir, so as to achieve multi-layer combined production and increase the production of single well. The purpose of maximizing reservoir recovery and so on. The piecewise fracturing technology of open hole horizontal well is one of the more mature technologies to improve the production and energy of oil and gas reservoirs. The process has good maneuverability, high reliability and can be used to transform low porosity and low permeability reservoirs. At present, it is a mainstream technology to improve the productivity of oil and gas wells in China. Packer and ball slip sleeve are important components of segmented fracturing string in open hole horizontal wells, and they are the key to ensure the reliability and safety performance of segmented fracturing technology in open hole horizontal wells, and their sealing performance can even determine the success or failure of fracturing operation. The erosion theoretical model, which is widely accepted at home and abroad, is summarized. According to its advantages, disadvantages and applicable scope, combined with the actual working conditions of sand carrying fluid in the fracturing pipe string, The mechanism of particle erosion and wear of pitching sliding sleeve ball seat and the theoretical model of numerical simulation are further studied. The factors affecting the erosion of ball pedestal are summarized from the aspects of external environmental factors, particle properties and target properties. In this paper, according to the actual working conditions of field fracturing construction, the liquid-solid two-phase Euler two-fluid model is constructed by considering the high sand content ratio of sand carrying fluid, and the turbulent velocity at the entrance of the ball seat is modified by UDF. Based on the theory of computational fluid dynamics (CFD), the sealing failure of ball seat caused by sand carrying fluid scour and wear is analyzed, and the erosion wear of ball seat is simulated by ANSYS-FLUENT software. Based on the analysis of erosion damage of sliding sleeve, a set of evaluation indexes suitable for the erosion wear degree of ball seat is constructed, and it is found that the erosion damage of seat and low density ball is the most serious, which lays a foundation for the optimal design of ball seat channel. At the same time, the influence of various field factors on the erosion of ball pedestal and the erosion distribution of each ball pedestal upstream of a small formation during fracturing are analyzed and studied, and the material volume of each ball pedestal denudated after the completion of fracturing in the whole well position is calculated. The problem of continuous failure of ball seat due to erosion is solved. In order to effectively avoid the erosion failure of the ball seat in the process of fracturing, the double angle front conical ball seat and the angle spherical sealing ball seat are improved. The erosion resistance of the traditional ball seat is optimized by changing the structure design of the traditional ball seat channel, but they are still suitable for the original fracturing pipe string. The results show that the double angle front conical ball seat can greatly improve the erosion resistance of the front cone, and the angle spherical sealing ball seat can not only effectively improve the sealing performance of the ball seat. It can also avoid the most serious erosion of the ball seat channel and the coincidence of the sitting sealing point. The erosion laws of two kinds of ball pedestal are analyzed, such as different sand carrying liquid discharge, propelling particle size and sand content ratio of sand carrying liquid. It is found that the influence of sand carrying liquid discharge on double angle front conical ball seat is the most prominent. Through the study of the erosion behavior of the pitching sliding sleeve pedestal and the improvement of the erosion wear resistance, this paper provides a reasonable idea for solving the erosion failure problem of the pitching sliding sleeve pedestal, and also provides theoretical guidance for the field fracturing construction. Therefore, it has a strong reference value.
【学位授予单位】：长江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TE983

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