非均质性对水平井产能的影响

Impacts of permeability heterogeneity on horizontal well productivity

基于Joshi等的假设,将水平井的三维流动问题变换为2个相互联系的二维流动问题,通过保角变换求解。将非均质储集层的水平渗透率和垂直渗透率按几何平均、算术平均和调和平均方法分别处理,根据电模拟原理,建立了9种非均质储集层水平井产能计算模型,评价非均质性对水平井产能的影响。评价结果,非均质性越强、储集层厚度越大产能越低,但厚度超过一定界限时产能降低不再明显;用算术平均方法处理渗透率建立的模型会低估非均质性对产能的影响;用几何平均和调和平均方法处理渗透率建立的模型评价,薄油层非均质性越强,产能越高。

Based on Joshi et al’s assumption,a 3-D drainage problem was reduced to two 2-D solution problems,the 9 productivity formulae for horizontal wells in heterogeneous reservoirs is presented by using geometric,arithmetic and harmonic average to modify the horizontal and vertical permeability in the mapped equations. The impacts of permeability heterogeneity on the productivity of horizontal wells were analyzed. The results show that horizontal well productivity generally decreases with increase in the ratio of horizontal to vertical permeability and reservoir thickness. However,its impact on horizontal well productivity is not very efficient if the reservoir thickness exceeds a certain limit. Furthermore,oil production is usually under-predicted by the model developed by arithmetic average and the models of vertical permeability modified by geometric and harmonic average can explain why horizontal well productivity increases apparently with increase in the ratio of horizontal to vertical permeability in thin oil formation.