Study On The Law Of Fracture Propagation On Multi-well At Different Time Considering To Stress Interference

Under the operation mode of"well factory"of shale oil reservoirs,the stress disturbance between wells will affect the fracture propagation pattern and fracturing effect,resulting in certain errors between the reservoir transformation results and the design scheme.Accurately analyzing and determining the fracture propagation law under the action of inter-well stress disturbance is an urgent problem to be solved.In this thesis,taking two-wellbore as research object,a three-dimensional multi-well hydraulic fracturing fracture propagation fluid-structure interaction model is established based on the discrete element method,and the effects of horizontal principal stress difference,well spacing,fracturing fluid displacement,injection time,cluster spacing,fracturing fluid viscosity and natural fractures on the fracture propagation law of multi-well fracturing are analyzed.The following conclusions are obtained.(1)Affected by the original in-situ stress and the change of surrounding in-situ stress caused by the opening of the wellbore first,The tip of the hydraulic fracture of the No.2 wellbore(No.1 and No.3 hydraulic fracture)on the side close to the No.1 wellbore is deflected,which is easy to form a complex fracture network and increase the volume of reservoir transformation.(2)In the numerical model,when the cumulative value of the height difference between the hydraulic fractures of each hydraulic fracture along the upper and lower parts of the wellbore is small,and the propagation of each hydraulic fracture will be relatively balanced;on the contrary,the propagation will be unbalanced.When the horizontal principal stress difference is less than 6 MPa,the well spacing is greater than 80 m,the injection time is less than 800 s,the fracturing fluid displacement is less than 0.2 m~3/s,the cluster spacing is 30 m,and the fracturing fluid viscosity is less than 0.04 Pa·s,the stress interference is less affected and the fracture propagation is more balanced.(3)When the natural fracture angle is 45°,the natural fracture strength is 0.1 MPa,the horizontal principal stress difference is 0 MPa,the fracturing fluid displacement is 0.3 m~3/s,and the fracturing fluid viscosity is 0.01 Pa·s,the number of activated and communicated with natural fractures in each wellbore increases,and the complexity of the fracture network is high.(4)When the horizontal principal stress difference is small,the interaction between hydraulic fracture and natural fracture produces a complex fracture network parallel to the direction of the minimum horizontal principal stress,which makes the extension length of hydraulic fracture poor.when the horizontal principal stress difference is large,the hydraulic fractures tend to pass through the natural fractures near the wellbore and communicate with the natural fracture at the farther distance of the wellbore,which lead to that the hydraulic fracture extends for a longer length.(5)The increase of fracturing fluid displacement has a greater impact on the total area and total volume of hydraulic fractures.High fracturing fluid displacement can significantly increase the volume of reservoir stimulation,but it will lead to channeling between hydraulic fractures in adjacent wells.It is unfavorable to on-site construction.The study in this paper can provide a reference for optimizing the multi-well fracturing process measures and fracture pattern prediction in horizontal well,and has important reference significance for improving the recovery rate of shale oil reservoirs.