低渗致密气藏压裂水平井产能预测新方法

水平井分段压裂是低渗致密气藏增产改造的关键手段,压裂水平井的产能预测和影响因素分析对气藏的高效开发具有重要指导意义。基于气体流动中的压降分析,通过对地层段、裂缝段、射孔孔眼段和井筒段的压降进行耦合,综合考虑裂缝应力敏感性、孔眼周围气体汇聚效应和井斜角的影响,建立了压裂水平井产能预测新模型,并分析了速度系数、井斜角、应力敏感系数等因素对产能的影响。实例计算表明新模型预测精度较高,便于工程应用。垂直裂缝产量沿井筒呈中部低、端部高的"倒钟形"分布,且跟端方向裂缝产量略高于趾端方向。随速度系数减小,气井产量先增加后稳定不变,增加幅度随裂缝条数增加而加大;气井产量随井斜角增加而增加,且增加幅度随水平段长度增加而加大;生产后期,裂缝应力敏感会显著降低气井产量,应力敏感系数越大,产量越低。

A NEW METHOD OF THE PRODUCTIVITY PREDICTION FOR THE FRACTURED HORIZONTAL WELLS IN LOW-PERMEABILITY TIGHT GAS RESERVOIRS

The staged fracturing of the horizontal well is the key method to stimulate the production of low-permeability tight gas reservoirs.The productivity prediction and influencing factor analysis possess important significances for the high-efficiency development of the reservoirs.Based on the pressure drop analysis in the gas flow,through the interval integration among the formations,fractures,perforated holes and horizontal wellbore,a novel model for the productivity prediction of the fractured horizontal wells was established comprehensively considering the stress sensitivity,gas convergence effect near the perforated holes and influence of the well deviation angle,and moreover the influences of the velocity coefficient,well deviation angle,stress sensitivity coefficient on the productivity are figured out.The case calculation shows that the new model is characterized by high precision and ease to the engineering operation.The production distribution of the vertical fractures presents the mode of " inverted bell",namely the fracture production is lower in the middle wellbore section and higher in the end wellbore section.And moreover,the fracture production in the heel end direction is slightly higher than that in the toe end direction.With the decrease of the velocity coefficient,the well production increases firstly and then stabilizes,the more the facture number is,the bigger the increase amplitude will be,so will be the inclination angle and horizontal section length;at the late production stage,the fracture stress sensitivity can significantly reduce the well production,and furthermore the bigger the stress sensitivity coefficient is,the lower the production will be.