Numerical Simulation On Fracture Extension Of Hydraulic Fracturing

With low permeability and ultra-low permeability reservoir exploration and development of unconventional reservoirs and oil field development entered the later period,increase the reservoir reconstruction of artificial control method has become the main direction of oil and gas field development.In recent years,along with the development of the technology of horizontal well,horizontal well segmented clusters fracturing has become a more increased volume of main reservoir artificial control method,but due to the complexity of multiple clusters of fracturing fracture morphology and affected by many factors,so the construction is difficult or fracture morphology is difficult to control.For this,this article selects multiple clusters of fracturing horizontal well and vertical well repeated fracturing as the research object,in order to research the different reservoir parameters(elastic modulus,poisson's ratio and reservoir in-situ stress)and different artificial control parameters(displacement and viscosity of fracturing fluid,perforating parameters)to increase the influence of reservoir reconstruction volume fracture morphology.The numerical results show that stress distribution at crack tip and perforation root present high singularity because of stress singularity and fluid injection in multi-cluster staged fracking for horizontal.The crack induce stress tend to reduce principle stress difference.With distance increasing between research point and horizontal well,the induce stress field influence less.The shorter cluster space the induce stress influence less,the change of in-situ stress is fewer and show a symmetrical stress distribution with middle point axis when there exit 2 clusters.The induce stress generated by middle crack influence obviously when 3 clusters are designed.In that case,principle difference will decrease as the distance apart from the middle crack wall and the direction of max principle will change near the side crack.distance between clusters and principal difference can influence fracture morphology obviously.As the crack length increasing,the degree influence on fracture morphology of induced stress field gradually strength.The cluster space and horizontal stress difference rise can lead a drop on induced stress field.Fracturing sequence can change the distribution of induced stress field evidently.If the sequence can be optimized reasonable,crack length will extend further.Based on the model results,two horizontal wells have been optimized and compared to adjacent wells.Two optimized wells show higher yield compare to adjacent wells,which prove the correctness and feasibility of this model indirectly.Due to the initial crack and the change of pore pressure in the process of production,the direction and size of the original stress field change a lot in re-fracturing,which lead a stress field redirection;Reservoir and rock physical mechanical parameters bring a significantly change of reservoir stress field distribution;with the difference of horizontal stress,rock elastic modulus and oil field production time increasing,induced stress effect and stress redirection area decrease;the greater of poisson's ratio,the induced stress effect and redirection area is smaller.