Investigation Into The Fracturing Treatment For Shale Formation With Large Dip Angle In Northeast Of Chongqing

The shale formation with large dip angle is under strong tectonic stress in northeast of Chongqing.Uncertainty of hydraulic fracture propagation due to inclined bedding planemakes it difficult to take fracturing treatment in this area.Based on the characteristic analysis of Lu Jiaping shale formation,the difficulties of fracturing are pointed out.Using numerical and physical simulation method,the effects of various geological(vertical stress bias,dip angle and cement strength of bedding planes)and engineering factors(pump rate and fracturing fluid viscosity)on frature propagation rules are studied.Taking Y1 well as representative,the fracturing parameters of the shale reservoirs with large dip angle are optimized.The results show that the geometry of fracture becomes more complex due to the existance of inclined bedding planes.The interaction between hydraulic fracture and bedding planes,(cross,diversion or offset)makes the propagation path uncertain.Limited bedding planes are apt to be opened but extend further under lower vertical stress bias(≤5MPa);while hydraulic fracture propagates in vertical plane under higher vertical stress bias(≥10MPa),which can improve the stimulated formation thickness.In those formations where bedding planes are developing,high pump rate is of little significance to enhance the connection in reservoir thickness direction.Fracturing fluid with high viscosity may be more helpful for hydraulic fracture to breakthrough the bedding plane.Information under inverse faulting mechanisms(σv<σh<σH),the number of perforation clusters should be increased and the distance between perforation clusters should be reduced appropriately.In the meanwhile,it’s benefitial to improve the proportion of fluid with high viscosity in pad.In formation under strike slip faulting mechanisms(σh<σv<σH),it should be prevented that hydraulic fracture extends out from the reservoir in vertical direction.While more fracturing fluid with low viscosity should be used to enhance the lateral extension of bedding palnes in formation.The research results have certain significance for the fracturing treatment for shale formation with large dip angle in northeast of Chongqing.