Application of SQP Algorithm to Optimize Perforation in Horizontal Wells
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摘要: 射孔孔眼沿水平井井筒合理分布能提高其开发效果,达到稳油控水的目的。考虑钻井污染和射孔损害对油藏渗流的影响及摩擦损失和加速损失对水平井井筒内压降的影响,建立了油藏渗流和水平井井筒内流体流动耦合模型,扩展了Landman的油藏-井筒稳态渗流耦合模型。基于射孔位置分布对水平井产能和流入剖面的影响,建立了以孔眼位置分布为决策变量、沿井筒流入剖面为约束条件,水平井产量为目标函数的射孔水平井产能优化模型。采用序列二次规划算法对该优化模型进行了求解,得到射孔孔眼沿水平井井筒的最优分布。优化结果表明,射孔孔眼沿水平井井筒存在最佳分布:为得到最大产量,水平井跟部和趾部的射孔孔密较大,中部最小;要使沿井筒入流剖面均匀,射孔孔密沿跟部到趾部方向先增大后减小,约在井筒长度的3/4位置处取得最大值。Abstract: Optimal distribution of perforations on a horizontal well can assist in enhancing effective exploitation,stabilizing well productivity and controlling water cut.Considering the effect of drilling and perforation damage on the seepage in reservoir and the effect of friction and acceleration losses on the pressure drop in wellbore,a steady-state model is presented which couples the Darcy flow into perforations from the reservoir with the frictional and accelerated flow in wellbore.The model described here extends the perforated wellbore model developed by Landman.Based on the effect of perforation distribution on productivity and the inflow profile of a horizontal well,an optimization model is developed,in which the production of the horizontal well is taken as an objective function,the perforation distribution as decision-making variables and the inflow profile as constraints.SQP algorithm is applied to establish an optimization model of the perforated horizontal well to get the optimal perforation distribution.The results indicate that an optimal position distribution of perforations exists along the wellbore,which can effectively improve the profile of inflow rate along the wellbore and the production of the well.The perforation is denser at heel and toe,and the lowest density should be in the middle of the horizontal section,which can lead to maximum production.Under the constraint of uniform inflow flux,the perforation density should be increased from heel to the toe of wellbore,reaching maximum at the location 3/4 length of the wellbore.This research provides a new guideline for optimization of perforation parameters for horizontal wells.
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Keywords:
- horizontal well /
- perforation distribution /
- optimization model /
- SQP algorithm
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