【摘要】 体积压裂后在压裂区内形成形态异常复杂的缝网,常规建立在欧几里得几何基础上渗流模型难以准确反映多重强非均质性介质内的流动特点。基于分形和反常扩散理论,考虑体积压裂区2个方向的流动,建立了水平井复合三线性流反常扩散的理论模型,并用分数阶微分进行数值求解,通过与欧几里得空间的模型对比,验证了新模型的正确性。采用新模型计算分析了体积压裂水平井压力动态响应及特殊流动特征的影响因素,结果表明:与常规三线性流模型相比,新模型拟压力导数曲线上窜流特征出现的时间更早,说明气体在考虑双向流动的裂缝区流动更迅速;反常扩散效应增加了流动阻力并造成特征流动阶段出现时间延迟,反常扩散指数越大,气体流动孔道的连通性越差,压降越大;天然裂缝分形维数影响井筒储存之后的所有流动阶段,而基质分形维数的效应只出现在裂缝和基质窜流之后的阶段。新模型能准确描述体积压裂改造区渗流的复杂性,有助于完善体积压裂水平井试井解释模型和提高生产动态分析精度。更多还原

【Abstract】 Complicated network is formed in the stimulated reservoir volume, the conventional percolating model on the basis of Euclidean geometry cannot accurately reflect the multiple flow characteristics of the strong heterogeneity within the medium. Based on the fractal and anomalous diffusion theory, considering the flow in the two directions of the volume fractured zone, the theoretical model of the anomalous diffusion was established for the horizontal well with composite three linear flow and solved numerically by fractional order derivative, compared with Euclidean space model, the correctness of the new model was verified, the pressure dynamic response and influencing factors of the special flow characteristics for the SRV horizontal well were analyzed with the help of the new model. The results show that compared with the conventional three linear flow model, the upper interporosity flow characteristics appear more earlier on the pseudo-pressure derivative curve of the new model, this indicates that the gas flows more faster in the fracture zone considering the bidirectional flow; the anomalous diffusion effect increases the flow resistance and causes the characteristic flow stage delayed, the larger the anomalous diffusion index is, the worse the connectivity of the gas flow channel and the greater the pressure drop will be; the fractal dimension of the natural fracture affects all flow stages after the wellbore storage, while the effect of the matrix fractal dimension only appears at the stage after the interporosity flow between the fracture and matrix. The new model can accurately describe the complexity of the percolation in the volumetric fractured zone, and help to improve the SRV horizontal well test interpreting model and enhance the precision of the production performance analysis.更多还原