计算射孔井产率比的三维有限元新方法

A NEW 3D FINITE ELEMENT METHOD FOR CALCULATING THE PRODUCTIVITY RATIO OF A PERFORATED WELL

  • 摘要: 为了更精确更全面地计算射孔井的产率比, 该文建立了一种射孔井的三维无量纲稳态渗流模型, 推导了模型的三维有限元求解方程, 采用高密度四面体网格并使用并行计算, 获得了模型的数值解. 与传统计算射孔井产率比方法的对比发现:Karakas方法的精度要明显高于Hagoort方法, 但Karakas方法在一些参数下存在一定误差且不能计算特定条件下的产率比;该文提供的有限元方法在相位角、污染区影响等方面更具普适性. 分析了射孔几何结构、井周污染区、射孔压实区和储层渗透率各向异性等因素对射孔井产率比的影响, 结果表明:增加射孔长度能不断地提高产能;射孔密度和相位角均存在一个最优值;射穿污染区是减小污染区影响产能的有效手段;射孔压实区和低垂向渗透率都会严重降低射孔井的产能. 该研究为射孔井的完井设计、产能预测提供理论指导.

     

    Abstract: In order to get more accurate and comprehensive productivity ratios, this paper presents a 3D steady dimensionless porous flow model for perforated wells. A new 3D finite element modeling method is developed. The numerical solution is obtained using fine tetrahedral meshes and a parallel computing method. By comparing the calculated results with the results of the traditional methods, it shows that precision of Karakas method is higher than that of Hagoort method. However, the Karakas method still has some variable-dependent errors, meaning that it cannot be used under certain conditions and with specific values of some parameters. The proposed finite element method is more useful than the Karakas method in calculating the productivity ratios of certain perforated wells with specific phase angles or impacts from pollution. The effects of actual perforation geometry, formation damaged zones, perforation compacted zones, and reservoir permeability anisotropy on productivity ratios were also analyzed, and the results show that increasing perforation length tends to increase productivity. Additionally, there are optimal values for both perforation density and perforation phase angle, and shooting through the formation damaged zone around the wellbore is the most effective way to reduce the effect of damaged zones on productivity. Perforation compacted zones and those with low vertical permeability dramatically reduce productivity. This study provides theoretical guidance to improve the completion design and predict the productivity of perforated wells.

     

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