摘要： 砾岩储层结构特征差异显著,其中砾石的存在不仅导致砾岩的强非均质性,也对砾岩的力学性质和裂缝发育产生重要影响.目前,针对砾石不同粒径的组成对砾岩力学性质和裂缝发育的影响规律尚不清楚.本文引用土力学中级配的概念来表征砾石不同粒径的组成,并将曲率系数Cc和不均匀系数Cu作为级配参数对级配特征进行量化,建立了基于颗粒流PFC2D数值模拟软件的砾岩数值模型,根据应力—应变曲线、抗压强度、弹性模量和裂缝的发育状况,分析了砾石级配参数对砾岩力学性质和裂缝扩展规律的影响.结果表明:砾岩的抗压强度主要受不均匀系数Cu和砾石平均粒径的影响,抗压强度与Cu呈负相关关系.砾岩的弹性模量与砾石平均粒径相关.裂缝数目受曲率系数Cc和砾石平均粒径的影响,其中裂缝数目与Cc呈负相关关系.裂缝数目与裂缝的复杂程度呈正相关关系.研究结果为探究砾岩储层力学性质和裂缝扩展规律提供了新思路.

关键词: 砾岩, 砾石级配, 力学性质, 裂缝扩展, 数值模拟

Abstract: There are significant differences in the structural characteristics of conglomerate reservoirs,among which the presence of gravel not only leads to strong heterogeneity of conglomerate,but also has a significant impact on the mechanical properties and fracture development of conglomerate.At present,the influence of the composition of different particle sizes of gravel on the mechanical properties and crack development of conglomerate is still unclear.This article cites the concept of inter-mediate gradation in soil mechanics to characterize the composition of different particle sizes of gravel,and quantifies the grading characteristics using the curvature coefficient Cc and non-uniformity coefficient Cu as grading parameters.A numerical model of conglomerate based on particle flow PFC2D simulation software is established.The influence of gravel gradation parameters on the mechanical properties and crack propagation of conglomerate is investigated by analyzing the stress-strain curve,compressive strength,elastic modulus,and crack development status.The findings reveal that the compressive strength of conglomerates is primarily influenced by the non-uniformity coefficient Cu and the average particle size of gravel,exhibiting a negative correlation with Cu.Similarly,the elastic modulus of conglomerates correlates with the average particle size of gravel.The number of cracks is affected by both the curvature coefficient Cc and the average particle size of gravel,demonstrating a negative correlation with Cc.Conversely,the number of cracks positively correlates with the complexity of the fractures.These research findings offer novel insights into exploring the mechanical properties and fracture propagation patterns of conglomerate reservoirs.

Key words: conglomerates, gravel grading, mechanical properties, crack propagation, numerical simulation

中图分类号: 

• TE357.1 P642.3