Study On Numerical Simulation Of Hydraulic Multi-cracks Initiation And Propagation Under The Influence Of Stress Shadow

Horizontal well Volume-fracturing technology is one of an important means of modern oil and gas exploration,for tight and unconventional reservoirs,using multi-stage and multi-cluster perforation,multi-fracturing one time,the exited fracturing will make a difference to the subsequent cracks of the initiation pressure and propagation direction.The existed fracturing will improve the pressure and propagation direction of the subsequent cracks especially within a certain distance,and this is the stress shadow effect.Understand how the stress shadow mechanism effects will effectively reduce initiation pressure or avoid the maximum fracturing pressure,control the fracturing propagation trend,increase the valid fracturing volume or form complex fracture networks and is also of great significance to improve the reservoir producing degree.This paper uses ABAQUS finite element simulation platform,considers fluid-solid coupling effect and rock fracturing transient effect when processing,establishes multi-cracks initiation and propagation mechanics model and finite element model,By cohesive element technology,based on the maximum circumferential tensile stress criterion to calculate the subsequent crack initiation pressure under the influence of stress shadow and validated the wells.The calculation and test error of the field well is 5.2%,verify the feasibility and correctness of the numerical simulation and theoretical analysis.On this basis,analysis influence on multiple fracturing pressure of stress type,initial stress,crack distance,displacement,fracture height,elastic modulus and Poisson’s ratio.The result shows that: Under the influence of initial geostress difference,displacement,elastic modulus and Poisson’s ratio,normal fault horizontal well fracturing pressure increased.Under the influence of displacement,elastic modulus and Poisson’s ratio,reverse fault horizontal well fracturing pressure increased,but reduced with initial geostress difference,when the difference is larger than 4.8MPa,stress shadow can promote fracturing.By three-dimensional extended finite element method establish the extended horizontal well multi-cracks fracture extension finite element model,fracturing fluid injects into the perforation eye ongoing,tracking expansion form of multiple fractures dynamically,obtain the mutual influence and expansion of multiple fractures.Numerical simulation results show that the crack propagation is affected by crackdistance,initial stress,displacement,elastic modulus and Poisson’s ratio are less affected.When present horizontal stress difference is under 2MPa,new cracks can be activated.The above research results provide a theoretical basis for the application of stress shadow effect in tight or unconventional reservoirs,and have certain guiding significance for practical production.