The Study Of Conglomerate Rock Mechanical Properties Based On Laboratory Test And Particle Flow Code Discrete Element

The conglomerate is rich in reserves and is now gradually becoming a key oil reservoir in China.Hydraulic fracturing is currently an effective means to increase production and transform conglomerate reservoirs.In the conglomerate rock body,the fractures may show an expansion pattern through and around the gravel during hydraulic fracturing.At present,the study of these fracture propagation models is mostly based on simplified models,while ignoring the effect of the reservoir conglomerate microstructure on the fracture propagation model.In this paper,firstly 10 sets of uniaxial compression experiments were carried out.Combining component analysis experiments,the relationship between reservoir conglomerate composition and uniaxial strength was discussed.In this paper,three-point bending experiments were conducted on 10 groups of semicircular conglomerate specimens with prefabricated fractures,combined with CT technology to reconstruct the mesoscopic structure of reservoir conglomerate samples in three dimensions,and summarized the mesoscopic characteristics of reservoir conglomerate.The influence mechanism of the destruction mode.Secondly,this paper uses PFC2D software to carry out the numerical simulation of uniaxial compression,combined with the results of the uniaxial compression physical experiment,analyzes the effect of the mesoscopic structure of the conglomerate on the uniaxial experimental results;numerical simulation of fracture toughness,combined with CT scanning and 3D reconstruction results,further analyzing the influence of mesoparameters and meso-structure on the experimental results.Physical experiment results show that the compressive strength range is: 8.20 ～53.84MPa;the elastic modulus range: 2.02 ～ 18.94GPa;the components are mainly quartz minerals,feldspar minerals,clay minerals;the fracture toughness range: 0.10 ～0.41 MPa · m0.5.The numerical simulation results show that there are two ways of conglomerate failure modes: through-conglomerate and conglomerate,and the mechanism of the influence of conglomerate mesoscopic characteristics on rock failure mode is verified.Finally,a comprehensive analysis of the results of macro mechanics experiments and mesoscopic numerical simulations results in the following conclusions:1.In conglomerate,the relationship between strength and stiffness values and clay mineral content is positively correlated.Clay minerals play a role in cementing gravel particles in conglomerate,so as the content of clay minerals increases,a complex mesostructure will be formed inside the conglomerate,which will affect the mechanical behavior of conglomerate.2.A hypothetical research unit is proposed,and the meso-structure inside the unit has a significant effect on the formation of failure forms such as perforated gravel and winding gravel.When loaded,the interaction between the element and the whole will affect the direction of crack propagation and the delineation of the new element.3.The particle flow discrete element numerical simulation of the uniaxial experiment verified the effect of the clay mineral cementation on the strength and rigidity of the conglomerate;the fracture toughness simulation verified that the proposed research unit was reasonable during the crack propagation process.Its meso-structure has a significant effect on the formation of perforated gravel and orbital gravel.