摘要
脆性评价是页岩气钻井以及压裂工艺设计的重要环节.然而,现今对于脆性的定义十分模糊,且脆性评价的方法没有成熟的理论作为支撑.本文以岩石应力应变关系为基础,采用能量法来进行储层岩石脆性评价.根据断裂力学裂纹尖端的非线性场理论,以前端区作为尖端特殊的屏蔽构型,来描述储层岩石在断裂过程中能量的耗散.通过计算本征内聚力与前端区稳态阻力比值来表征储层岩石的脆性指数.研究表明,能量耗散相对越大,岩石的脆性指数越低,其塑性特征表现得越明显.基于能量耗散的储层岩石脆性评价是分析岩石力学特性的重要内容,也为压裂选层提供了重要依据.
Brittleness evaluation plays an important role in both shale drilling and fracturing design. However, the definition of brittleness is unclear and the method for brittleness evaluation has no reliable theory to support. Based on stress-strain relationship, this paper uses energy method to evaluate rock brittleness. According to nonlinear crack-tip field theory in fracture mechanics, considering frontal zones as special shielding configurations of crack tip to describe energy dissipation during the process of fracturing. The ratio between the intrinsic cohesion energy and the steady-state resistance of frontal zones can be used as rock brittleness index. The study indicates that the more the energy dissipates,the lower the value of rock brittleness, and the plastic property will become even more obvious. This rock brittleness evaluation based on energy dissipation is essential in analyzing rock mechanics and selecting fracturing section.
出处
《力学学报》
EI
CSCD
北大核心
2015年第6期984-993,共10页
Chinese Journal of Theoretical and Applied Mechanics
基金
国家杰出青年科学基金(51325402)
国家自然科学基金(51490651,51234006)和国家自然科学基金创新研究群体科学基金(51221003)资助项目~~
关键词
脆性评价
能量耗散
应力应变关系
断裂力学
brittleness evaluation
energy dissipation
stress-strain relationship
fracture mechanics
