Study On Reservoir Seepage And Productivity Characteristics Caused By Reorientation Fracture

In the field of petroleum industry,hydraulic fracturing is an essential production enhancement technique for oilfield production.If the initial propagating direction of fracture skews the direction of the maximum principal stress of the formation during the hydraulic fracturing process,the fracture may orientate.Some studies pointed out that reorientation fracture have a potential of increasing oil production.In order to study the effect of reorientation fracture on the seepage characteristics of the reservoir and its production enhancement effect,in this study,a two-dimensional productivity model of the vertical reorientation fracture in the permeability anisotropic reservoir was first developed and the seepage characteristics were analyzed.The calculation results show that reorientation fracture can increase the productivity by 1 to 1.5 times compared with the conventional plate-like fracture in the reservoir with higher value of permeability anisotropy.Furthermore,in order to consider more parameters,a three-dimensional numerical model was developed.The sensitive parameter analysis based on the threedimensional numerical model shows that: the production enhancement effect is better,if there is a reorientation fracture with small inclination angle in the reservoir where the value of horizontal permeability anisotropy is very large;the increase of the number of reorientation fracture sometimes may not provide a significant increase of production;when the ratio of the height of the reorientation fracture to the height of the payzone is around 0.6,the production enhancement effect of reorientation fracture is not obvious;the parameter of vertical permeability anisotropy has limited influence on the productivity of fracture.The mechanism for the production enhancement effect of reorientation fracture can be explained as: reorientation fracture has a complex geometry of its surface.Compared with the conventional plate-like fracture,the reorientation fracture can communicate more reservoir fluid seepage area and directions;the higher value of permeability anisotropy,the curved surface shape of the reorientation fracture can better exert its advantages of communicating preferred flow direction and region.The sensitive parameter analysis shows that the changes of the production enhancement effect of reorientation fracture is not monotonic as the change of those parameters in most cases,but has some local extreme or maximum values.This indicates that when conducting an oil filed project,these extreme values or maximum values and economic evaluations should be comprehensively combined and considered in order to obtain an optimal solution.