裂缝宽度预测的有限元数值模拟  

PREDICTING FRACTURE WIDTH BY FINITE ELEMENT NUMERICAL SIMULATION

作　　者：练章华[1] 康毅力[1] 徐进[2] 徐兴华[2] 

机构地区：[1]西南石油学院 [2]中国新星石油公司西南石油局

出　　处：《天然气工业》2001年第3期47-50,共4页Natural Gas Industry

基　　金："九五"国家重点科技攻关项目"川西定向钻井致密气层保护技术研究"!(99- 110- 0 2- 0 6 )

摘　　要：用断裂力学有限元法 ,建立了裂缝宽度预测的有限元模型 ,研究了川西定向井致密气层中裂缝宽度、裂缝长度及裂缝周围应力变化与液柱压力的关系。用弹塑性断裂力学有限元法来确定裂缝的宽度以及裂缝尖端处的应力强度因子 ,同时研究裂缝周围的应力变化 ,目的是通过大量的计算机模拟 ,找出裂缝宽度变化与井筒压力的关系 ,最终建立裂缝宽度与井筒压力、地层岩石力学特性参数及裂缝长度的预测模型。结果表明 ,同一井筒压力作用下 ,总能找到某一临界裂缝长度 ,使得应力强度因子达到最大 ,超过这一临界裂缝长度时 ,裂缝的开裂能力减弱 ,要使裂缝继续扩展 ,则必须提高应力强度因子。文章研究方法为预测裂缝宽度。A finite element model of predicting fracture width was set up by use of the finite element method of fracture mechanics, by which the relation between the liquid column pressure and the fracture width, fracture length and change of stress around fractures were studied by the authors. The objective of determining the fracture width and the stress strength factor at the tips of fractures as well as the change of stress around fractures by the finite element method of elastic-plastic fracture mechanics is to find out the relation between the fracture width and the wellbore pressure, through computer simulation for many times, to set up the prediction model expressing the relation between the fracture width and the wellbore pressure, rock mechanical characteristic parameters and fracture length finally. The result shows that under the same wellbore pressure a certain critical fracure length can be eventually found to make the stress strength factor up to the maximum;when the critical fracture length is exceeded, the opening capacity of the fractures will be decreased;and it is necessary to raise the stress strength factor in order to extend the fracture width continually. Some theoretical data are provided for predicting the fracture width and fracture strike by this method introduced in the paper.

关 键 词：定向井 裂缝宽度 断裂力学 有限元 致密气藏 预测 川西地区 

分 类 号：TE311[石油与天然气工程—油气田开发工程]