基于细观数值试验的水平井多裂纹间距确定

STUDY OF THE MULTIPLE HYDRAULIC FRACTURES SPACING IN HORIZONTAL WELL FOR HETEROGENEITY ROCK BASED ON MESO-NUMERICAL EXPERIMENT

Stress shadow效应是影响水平井压裂多裂缝设计、提高储层体积压裂效果的关键因素,当水平井中的水力裂纹数量增多并且间距减少时,裂缝间相互作用的stress shadow效应尤为显著。本研究从岩石细观非均质性的特点出发,基于渗流-应力-损伤模型,对不同井孔间距内应力场的相互作用及对裂纹发展形态的影响进行研究,以优化水平井多裂纹射孔间距。研究结果表明,当井孔间距小于某临界长度时,井孔间的相互作用较强,容易形成孔间连通的水力裂纹;由stress shadow效应影响的井孔临界间距受岩石非均质的影响,当岩石的非均质性较强时,影响间距较大,当岩石的非均质性较弱时,影响间距较小;随着岩石均质度的提高,stress shadow效应对尖端"应力伞"的影响变弱,裂纹尖端应力伞面积变小。通过这一研究,可以为水平井多裂纹射孔间距优化提供一定的理论依据。

The stress shadow effect is the key factor influencing the multiple fracture design in horizontal well and improvement of the stimulated reservoir volume.When the spacing of fractures in horizontal become smaller and the number gets more,interaction between the fractures is much evident.Based on the characteristics of rock meso-heterogeneity and the percolation–stress–damage model,this study studied the interaction of stress field in different well spacing and its influence on the crack development pattern,so as to optimize the perforation spacing of multiple cracks in horizontal Wells.The experimental results show that:(1)When the spacing gets less than the critical correlation length,interaction between injection wells are much more obvious,and orthogonal fractures appears between the injection point.(2)The magnitude of the correlation length depends on the degree of heterogeneity of the rock,the critical spacing gets larger with increasing of heterogeneity,vice versa.(3)With the increase of reservoir homogeneity,area of stress umbrella caused by stress shadow deceases.Through this research,it can provide certain theatrical basis for horizontal well multiple perforations spacing optimization.