双台阶水平井不稳定渗流耦合模型及求解

Transient Fluid Flow Coupling Model and its Solution About Two-stepped Horizontal Well

针对国内外对双台阶水平井渗流规律及产能分析研究相对欠缺的情况,以水平井不稳定渗流模型为基础,根据势叠加原理,采用半解析方法建立了双台阶水平井不稳定渗流模型,同时考虑了井筒内变质量流动压降损失影响,给出了定压生产条件下耦合模型解法。通过实例计算,结果表明双台阶水平井比产能指数沿井筒长度不是均匀分布的,大致呈非对称"U"型分布,且跟端的比产能指数略高于趾端;井筒沿程压差分布曲线明显有一个台阶,说明压降损失主要集中在中间夹层连接段处,主要为重力压降损失。该成果为双台阶水平井井身结构设计,及合理利用双台阶水平井进行开发方案设计、计算开发指标、制订开发调整方案等提供理论依据,从而合理、高效地开发我国复杂油气田。

The study of percolation theory and deliverability analysis for two-stepped horizontal well is imperfect at home and abroad. Based on the horizontal well unstable flow model and the potential superposition principle,the two-stepped horizontal well unstable flow model is established by using a semi-analytical method and by considering the variable mass flow within the wellbore pressure loss,the solution of the coupling model is presented under the bottomhole constant pressure. The research results of the real examples show that the productivity index distribution along the borehole is non-uniform,which is the asymmetric“U”shaped pattern. The productivity index at the heel is slightly higher than that at the toe. There is an obvious step on the curve of pressure difference distribution along the wellbore,which shows that the pressure loss at the connection section is larger. The results are meaningful and provide a theoretical basis for the two-stepped horizontal well casing design,and for designing the field development project,computing development indicators,formulating development adjustment programs, and therefore,to efficiently develop the complex oil and gas fields.