Study On Hydraulic Fracture Propagation In Lamianted Shale Oil Stratums

Unconventional oil and gas is an important oil and gas resource in China.As a kind of unconventional oil and gas resource,shale oil is often developed by hydraulic fracturing in order to improve reservoir recovery.But when reservoir reconstruction lamiantion,the presence of natural fracture and the interference between seam problem caused by the complexity of the fracture is higher,so the law of the hydraulic fracture mechanics mechanism and rational shale,revealing the lamianted influence on hydraulic fracture extension rule and current limiting fracturing regularity of cracks under the condition of multiple clusters competitive layer for rational shale oil reservoir fracturing optimization design is of prime importance.In this paper,the typical shale oil reservoir structure and rock mechanical properties are characterized by laboratory experiments.On this basis,a three-dimensional finite element numerical model is established to carry out the parameter law analysis of the lamianted fracture on the competitive expansion of multi-cluster fractures under hydraulic fracturing and flow limiting fracturing conditions.The mechanism and regularity of the study are expected to provide theoretical reference for the optimization of shale oil reservoir fracturing.The microscopic structure of shale was studied by scanning electron microscope,and its mechanical properties were analyzed by uniaxial and triaxial compression,Brazilian splitting and half disk three-point bending experiments.The fracability of shale was evaluated by different brittleness index evaluation methods.The results show that the shale has high brittleness,high strength and good fracability.The rock is easy to be destroyed along the lamiantion when crushed under pressure.Based on the mechanism of shale hydraulic fracture propagation,a numerical simulation method suitable for this problem is obtained.A three-dimensional finite element model was established by ABAQUS software to study the law of shale fracture propagation,and the formation properties and construction parameters that affect the behavior of fracture steering,slippage and layer penetration were analyzed,and the action mechanism and influence law of each parameter on the morphology of fracture propagation were obtained.Studies have shown that poor ground stress,the strength of the lamianted surface friction coefficient and increasing affects lamiantion tangential method of relative displacement and the effect on the bedding to the effective principal stress makes hydraulic fracture form wear layer seam,construction parameters change will affect the process of interaction between hydraulic fracture and lamiantion,but for the fracture morphology of the impact is not obvious.According to the brittleness index of shale obtained from experiments,a corresponding fluid-solid coupling model was established to simulate the fracture propagation process of multi-cluster limited fracturing in shale oil reservoir,and the influences of different cluster spacing,perforation friction,perforation diameter,different construction displacement,fracturing fluid viscosity and total volume on fracture interference were studied.The study shows that increasing the cluster spacing,perforation friction resistance,construction displacement,fracturing fluid viscosity and total injection amount in hydraulic fracturing can improve the uniformity of multi-cluster fracture synchronous propagation,increase the total area of fracture discharge,and improve the reservoir reconstruction effect.