Resarch On Fracture Propagation Of Horizontal Well With Segmented Multiple Cluster Fracturing In Low Permeability Reservoir

Low-permeability reservoirs with lower permeability,more difficult to exploit and more abundant reserves have attracted more and more attention in the energy field.In recent years,multi-cluster fracturing technology for horizontal wells with low permeability reservoirs has developed rapidly,and the mechanism behind it is also the focus of research by scholars.Firstly,this paper investigates the research status and existing problems of low permeability reservoir development and hydraulic fracturing numerical simulation at home and abroad and then elaborates the stress distribution near the horizontal wellbore and the theory of porous media.According to the effective stress principle,the fluid-solid coupling equation of stress field and seepage field in low permeability reservoir is established.The basic theory of the cohesive pore pressure model is introduced.On this basis,this paper uses the finite element software ABAQUS to establish a 2D and a 3D single-cluster model,and a 3D staged multi-cluster fracturing models of horizontal wells without considering cavity interference was also established.The simulation results of single cluster fracture show that when the direction of the horizontal wellbore is perpendicular to the direction of horizontal maximum principal stress,fractures are more likely to initiate and extend,and the extension distance is the longest.At the end of fracture propagation,an elliptical hydraulic fracture with high pressure inside the fracture is formed,and the pore pressure around the fracture decreases step by step with the fracture as the center.Horizontal principal stress difference and rock tensile strength ratio are negatively correlated with fracture initiation pressure and elongation pressure while fracturing fluid displacement and rock elastic modulus are positively correlated with fracture elongation pressure.The rock elastic modulus,horizontal principal stress difference,and tensile strength ratio are positively correlated with fracture length and negatively correlated with fracture width,while the fracturing fluid displacement and horizontal principal stress difference are positively correlated with fracture length and fracture width.The tensile strength ratio is the key factor to control the fracture height.When the tensile strength ratio is less than 3/10,the fracture is controlled to extend in the reservoir interval.The simulation results of multi-cluster fracture propagation show that the internal cavity interference phenomenon exists in each stage of multicluster fracture propagation,and the internal fracture interference phenomenon with an odd number of fractures is more serious than that with an even number of fractures.Generally,the length of the middle fracture is inhibited,and it is difficult to form effective fractures.Expansion of fracture cluster spacing,optimization of fracture number,increase of fracturing fluid displacement and increase of horizontal principal stress difference can reduce the intensity of internal fracture interference,improve the hydraulic fracturing effect,and achieve the purpose of effective reconstruction of low permeability reservoir.In this paper,multiple factors such as in-situ stress distribution,rock mechanics parameters,construction displacement,fracture cluster number,and fracture cluster spacing are taken into consideration comprehensively,which provides a theoretical basis for the optimization of field construction parameters and the reduction of internal fracture interference intensity for multicluster fracturing of horizontal Wells.