Abstract

The effect of the bedding structure on the mechanical properties of layered shale was studied by means of experiment and numerical simulation. Based on continuum damage theory and discrete fracture network modeling method (D-DFN), a finite element model describing structural discontinuity and mechanical anisotropy of shale is established. In this model, the degradation process of stiffness and strength of shale after failure is described based on the stress-displacement relationship of elements. In order to distinguish the mechanical properties between the bedding and the matrix, a nonzero initial damage variable is set in bedding elements to show initial lower elastic modulus and strength of bedding elements compared with initially nondamaged matrix elements. The calibration of model parameters is discussed, and the simulation results are compared with the experimental results. The results show that the D-DFN method can effectively simulate the anisotropic characteristics of shale deformation and strength, which verifies the effectiveness of the method.

Highlights

  • As an energy source, oil and gas resources are superior to coal in many aspects such as transportation, heating value, and environmental protection

  • The problem of resource recovery and reducing environmental pollution during the mining process [1] has been the focus of attention by scholars, and in-depth research has been conducted on the problem of improving recovery, such as carbon dioxide storage [2, 3] and adding nanoparticles to the polymer [4, 5]

  • (2) The shale bedding structure is described by the discrete fracture network (DFN) modeling method

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Summary

Introduction

Oil and gas resources are superior to coal in many aspects such as transportation, heating value, and environmental protection. Since the 20th century, the proportion of oil and gas in the world energy structure has gradually increased. It is usually used as a strategic material to evaluate, plan, and manage and to formulate special policies and strategies for its development and utilization. An indepth understanding of the mechanical properties of rocks plays an important role in improving the recovery of oil and gas resources in tight reservoirs. During long-term diagenesis, shales develop a large number of discontinuities such as bedding, joints, and cracks through deposition and compaction, leading to structural discontinuity and mechanical anisotropy [8,9,10]. A lot of experiments and theoretical studies have been done by former researchers [12, 13]

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