岩石力学参数影响断背斜内张裂缝发育带的概念模型

Analysis of conceptual models for the influence of rock mechanics on tensile zone in faulted anticlines

在对库车坳陷克拉苏构造带内断背斜的构造裂缝研究中,发现断背斜内转折端发育张裂缝发育带,且张裂缝发育带的单井测试产量高,是断背斜内的油气高产区,深化研究张裂缝发育带及其影响因素对于油气勘探开发具有重要意义。前期工作发现张裂缝发育带受背斜"中和面"的控制,而岩石力学参数对断背斜内张裂缝发育带的影响还不清楚。因此,以库车坳陷克拉苏构造带内断背斜为背景,通过有限元数值模拟方法,建立了不同岩石力学参数的二维力学概念模型,分析了杨氏模量、泊松比和粘度比对张裂缝发育带的影响。结果表明:在杨氏模量大于70 GPa时,最大应变值随着杨氏模量增大而快速增大;随着杨氏模量的增加,张裂缝发育带的宽度和厚度总体上呈现线性增加的特征。在杨氏模量大于40 GPa条件下,随着泊松比增加,最大应变值和张裂缝发育带的宽度总体上缓慢增加。在粘度比小于25的情况下,最大应变值为0,不存在张裂缝发育带的宽度和张裂缝发育带的厚度;在粘度比大于25的情况下,最大应变值开始大于0且逐渐增大,张裂缝发育带的宽度和张裂缝发育带的厚度都随着粘度比的增加而增加。

The study on the structural fracture development in the faulted anticline in Kelasu tectonic zone,Kuqa Depression,reveals a tensile fracture zone developed in the hinge zone of the faulted anticline.And the flow rate from single-well test in the tensile fracture zone is high,indicating a prolific zone.Therefore,it is of great significance to oil/gas exploration and development to make an in-depth study on the tension fracture zone and its controlling factors.Our previous study reveals that the tensile fracture zone is controlled by neutral surfaces,but the influence of rock mechanics on the zone remains unclear.Then,we build several 2D mechanical conceptual models with different rock mechanical parameters through finite numerical modeling,for analyzing the influence of Young’s modulus,Poisson ratio and viscosity ratio on the tensile fracture zone.The results show that:(1)when the Young’s modulus is greater than 70 GPa,the maximum strain value grows rapidly with the increasing Young’s modulus;both the width and thickness of the zone feature an overall linear growth with the increasing Young’s modulus;(2)when the Young’s modulus is greater than 40 GPa,the maximum strain value and width of the zone grow progressively with the increasing Poisson ratio;(3)when the viscosity ratio is less than 25,the maximum strain value comes to zero,and the width or thickness of the tensile fracture zone can be neglected;while when the viscosity ratio is greater than 25,the maximum strain value grows greater than zero and increases gradually,and so do the width and thickness of the zone.