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水力压裂能使油井周围地层形成对称的垂直裂缝面,是有效的增产措施。垂直裂缝井采液时诱发地层中的平面二维椭圆渗流,形成以裂缝端点为焦点的共轭等压椭圆和双曲线流线族。基于扰动椭圆的概念和等价的发展矩形的思想,建立了具有启动压力梯度的油水两相非达西椭圆二维渗流数学模型。这种模型属于具有活动边界的非线性问题,分别用特征线法和有限差分法求解,得到了含水饱和度分布和活动边界的变化规律。还基于非活塞驱替理论,导出垂直裂缝井注水水开发低渗透油田时的产油量、压差及井排见水时间的计算公式,并进行实例计算分析,认为在此情况下,启动压力梯度和注入率对含水率、含水上升速率、含水饱和度分布、活动边界变化规律影响较大,对产油量、压差随时间变化规律及井排见水时间的影响也较大;还认为,低渗透非达西流条件下存在可获得最经济开发指标的最佳注入率。为垂直裂缝井注水开发低渗透油田的研究提供了数值模拟的模型和动态分析及预测的理论依据。图4表1参8(王孝陵摘)
Hydraulic fracturing can make the formation around the well symmetrical vertical fracture surface, is an effective stimulation measures. The vertical fractured well induces planar two-dimensional elliptical seepage in the formation during fluid production, forming a conjugate isobaric elliptic and hyperbolic streamline family with the fracture endpoint as focal point. Based on the concept of perturbed ellipse and the equivalent developmental rectangle, a mathematical model of two-phase non-Darcy ellipse oil and water two-dimensional seepage with initial pressure gradient was established. The model belongs to a nonlinear problem with active boundary. The model is solved by the method of characteristic line and the finite difference method respectively. The variation of water saturation distribution and active boundary are obtained. Based on the theory of non-piston displacement, the formulas of oil production, pressure difference and water breakthrough time of low-permeability oilfield with vertical well fractured well are deduced and the example calculation and analysis are carried out. It is considered that in this case, the starting pressure Gradient and injection rate have a great influence on the variation of water cut, water cut-off rate, water saturation distribution and active boundary, but also affect the law of oil production and pressure drop with time and water breakthrough time. , There is the best injection rate to get the most economical development index under the condition of low-permeability non-Darcy flow. This study provides a numerical simulation model and a theoretical basis for dynamic analysis and prediction for the research on the development of low permeability oilfields by injecting water into vertical fracture wells. Figure 4 Table 1 Reference 8 (Wang Xiaoling Abstract)