考虑射孔摩阻的水平井段内多裂缝流量均衡分配规律研究

Multi-fracture flow balanced distribution law in horizontal well sections considering perforation friction

水平井分段多簇压裂过程中,簇间应力阴影将引起多裂缝进液差异。页岩气藏生产测井数据表明,超过40%的射孔簇对油气产量无贡献。为揭示多裂缝非均匀扩展机制,建立了考虑多孔介质流固耦合的多裂缝竞争扩展有限元模型,构建了井筒流动模型,并对压裂液流动压降进行了简化表征,设计引入了管流单元和流体连接单元,有效模拟了井筒与孔眼处的流量动态分配,研究了射孔摩阻对多裂缝进液分配比例的影响规律。结果表明:当射孔摩阻增大到特定阈值时,多裂缝流量分配比例将由簇间应力阴影转变为射孔摩阻控制,合理布置低孔密、孔数可有效增大射孔摩阻,促进多裂缝均衡扩展;利用该模型对西南某区块X水平井射孔方案进行优化,当簇间距为15 m、孔径为0.015 m、总孔数由50降至32时,单簇平均进液量提高了0.125 m^(3)/min,各簇进液差异系数为3.9%;非均匀布孔时,单簇平均进液量提高了0.101 m^(3)/min,各簇进液差异系数为4.1%。该研究为水平井多裂缝均匀扩展提供了理论方法和参考依据。

In the process of staged multi-cluster fracturing of horizontal wells,the inter-cluster stress shadow will cause the difference of multi-fracture fluid injection.The production logging data of shale gas reservoir shows that more than 40%of perforation clusters have no contribution to oil and gas production.In order to reveal the mechanism of multi-fracture nonuniform propagation,a finite element model of multi-fracture competitive propagation considering the fluid-solid coupling of porous media was established,the wellbore flow model was established and the fracturing fluid flow pressure drop was simply represented,the pipe flow unit and fluid connection unit were designed and introduced to effectively simulate the dynamic distribution of flow between the wellbore and the perforation hole,and the law of the perforation friction on the distribution ratio of multi-fracture fluid injection was studied.The results show that when the perforation friction increases to a specific threshold,the proportion of multi-fracture flow distribution will change from inter-cluster stress shadow to perforation friction dominance.Reasonably arranging low perforation density and the number of perforation can effectively increase perforation friction and promote balanced propagation of multi-fractures;Using this model to optimize the perforation plan of southwest horizontal well X,when the cluster spacing is 15 m,the perforation diameter is 0.015 m,and the total number of perforation is reduced from 50 to 32,the average fluid inflow of a single cluster is increased by 0.125 m^(3)/min,and the difference coefficient of fluid inflow for each cluster is 3.9%;When the perforations are distributed unevenly,the average fluid inflow of a single cluster increases by 0.101 m^(3)/min,and the difference coefficient of fluid inflow of each cluster is decreased to 4.1%.This study provides a theoretical method and reference basis for multi-fracture uniform propagation in horizontal wells.