水平井限流压裂对射孔孔眼冲蚀的影响

Effect of Limited Entry Fracturing for Horizontal Wells on Perforation Erosion

水平井限流压裂中存在携砂液冲蚀射孔孔眼现象,导致段内多簇改造不均衡,不利于地质储量的充分动用,亟需认识清楚孔眼冲蚀过程。基于孔眼摩阻公式,推导了段内多簇多孔的孔眼冲蚀模型,考虑初始孔径差异和簇间应力差,采用孔径、流量分配和孔眼摩阻的变化来量化分析孔眼冲蚀规律。研究结果表明,平均初始孔径较大、应力较小的射孔簇易产生过度冲蚀;随着孔径的增大,孔眼摩阻迅速减小,限流作用减弱,不利于缝控储量均衡动用;单纯地提升排量并不能明显减小簇间的孔眼冲蚀差异;在相对较低的携砂液浓度下,簇间孔眼冲蚀和流量分配更均匀。这说明初始孔径差异和簇间应力差是导致孔眼冲蚀不均匀的主要因素,在限流压裂设计中可通过采用等孔径射孔工艺、适当增加前置液量、优化布孔位置和数量等方法,改善施工段携砂液分配。本研究为优化水平井限流压裂设计提供了支撑。

Perforation erosion of sand-carrying fluid exists in limited entry fracturing of horizontal well,which leads to uneven stimulation of clusters in segment and the inadequate use of geological reserves.Therefore,it is desiderated to understand the perforation erosion process.Based on the perforation friction equation,the perforation erosion model with multiple clusters of holes in the section was deduced considering the initial hole diameter differences and stress difference between clusters.The variation of entry hole diameter,flow distribution and perforation friction were used to quantitatively analyze the perforation erosion rule.The research results indicate that perforation clusters with larger average initial hole diameter and smaller stress tend to produce excessive erosion perforation clusters.With the increase of entry hole diameter,the hole friction decreases rapidly leading to the hole limiting effect weakens,which is not conducive to the balanced utilization of fracture-controlled reserves.Simply lifting the pump rate cannot significantly reduce the difference of perforation erosion among clusters.In addition,relatively lower slurry concentration can drive more uniform perforation erosion and flow rate distribution between clusters.It is concluded that the difference of initial hole diameter and stress difference between clusters are the main factors leading to uneven hole erosion.In the design of limited entry fracturing,the distribution of sand carrying fluid can be improved by adopting equal aperture perforating process,appropriately increasing the pre-liquid volume,and optimizing the location and quantity of holes.This study provides support for the optimization of limited entry fracturing design of horizontal wells.